robotics

2016-04-14T11:12:00.000-07:00

ESP 8266 Series:

Latest Addition

Short Description of ESP8266 Series Features:

1. ESP-01: PCB antenna, through matching, open about 400 m distance to do, easy to use.

2. ESP-02: SMD package for submission limit, the antenna can be drawn with the IPX header casing.

3. ESP-03: SMD package, built-in ceramic antenna technology, all available IO leads.

4. ESP-04: SMD package, customers can customize the type of antenna, flexible design, all the IO leads.

5. ESP-05: SMD package, only leads to serial and RST pin, small external antenna.

6. ESP-06: Bottom mount technology, all the IO port leads with metal shielding shell can be too FCC CE certification, it is recommended to use.

7. ESP-07: Semi-hole chip technology, all IO leads, with metal shielding shell can be too FCC CE certification, IPX can be an external antenna, built-in ceramic antenna can also be used.

8. ESP-08: with the ESP-07, the different forms that customers can define their own antenna.

9. ESP-09: Ultra-small size package, only 10 * 10 mm, four-layer board technology 1M byte!.

10. ESP-10: SMD interface, narrow-body design, 10 mm wide, suitable for light with controller.

11. ESP-11: SMD interface, ceramic antenna, small size.

12. ESP-12: very stable, easy to use.

Stable ESP 8266-12

2016-04-14T10:52:00.000-07:00

ESP 8266 -01 wifi Module Pinout

2016-04-12T12:24:00.000-07:00

ESP 8266- 01

This board is from Ai-Thinker Technology Co. Ltd.

What is this ESP8266-01

It's a wireless SOC
It has GPIO, I2C, ADC, SPI, PWM and some more
It's running at 80MHz
64KBytes of instruction RAM
96KBytes of data RAM
64KBytes boot ROM
It has a Winbond W25Q40BVNIG SPI flash
It's a RISC architecture
The core is a 106micro Diamond Standard core (LX3) made by Tensilica
The ESP8266 chip is made by Espressif
Modules bearing this chip are made by various manufacturers

Features:

802.11 b/g/n protocol
Wi-Fi 2.4 GHz, support WPA/WPA2
Super small module size (11.5mm x 11.5mm)
Integrated 10-bit ADC
Integrated TCP/IP protocol stack (ipv4 only at the moment)
Integrated TR switch, balun, LNA, power amplifier and matching network Integrated PLL, regulators, and power management units
+20dBm output power in 802.11b mode
Supports antenna diversity
Deep sleep power <10uA, Power down leakage current < 5uA
Integrated low power 32-bit MCU
SDIO 2.0, SPI, UART, I2C
STBC, 1x1 MIMO, 2x1 MIMO
A-MPDU & A-MSDU aggregation & 0.4µs guard interval
Wake up and transmit packets in < 2ms
Standby power consumption of < 1.0mW (DTIM3)
Operating temperature range -40C ~ 125C
Specification
802.11 b/g/n
Wi-Fi Direct (P2P), soft-AP
Integrated TCP/IP protocol stack
Integrated TR switch, balun, LNA, power amplifier and matching network
Integrated PLLs, regulators, DCXO and power management units
+19.5dBm output power in 802.11b mode
Power down leakage current of <10uA
Integrated low power 32-bit CPU could be used as application processor
SDIO 1.1/2.0, SPI, UART
STBC, 1×1 MIMO, 2×1 MIMO
A-MPDU & A-MSDU aggregation & 0.4ms guard interval
Wake up and transmit packets in < 2ms
Standby power consumption of < 1.0mW (DTIM3)

Description:

ESP-01 ESP-8266 is an ideal choice for hobbyist to start experimenting with IOT. The dimension of this module is 25mm x 15mm, with simple pin connections (standard 2×4 pin headers), using serial TX/RX to send and receive Ethernet buffers, and similarly, using serial commands to query and change configurations of the WiFi module.

ESP8266 ESP-01 Serial WIFI Transceiver Module is a cheap and easy way to connect to internet via WIFI to any microcontroller platforms like Arduino. You can use AT commands to connect to WiFi networks and open TCP/IP connections (without need to have TCP/IP stack running in microcontroller).

The module(ESP-01) can work with AT command when used with Arduino, USB to TTL adaptor (FTDI USB module is recommended). Additional power supply might be needed to power up the board.With GCC toochain and SDK availability opportunities with ESP8266 as a IOT device is endless.

2014-09-30T10:18:00.003-07:00

About Devolopment Board

1.AVR Development board with All ICs
2.Microcontrollers: Atmega16, Atmega8
3.LCD 16x2
4. Seven Segments 4 numbers
5. RTC battery
6. Buzzer
7. Two Relays
8. Eight DIP Switch
9. Eight 5mm LEDs
10. 4 x 4 Keypad
11. Two Serial Ports
12. Temperature Sensor LM35
13. Power adapter 12V, 1A
14. Single pin female connectors: 20
15. Serial Cable
16. USB Cable
17. AVR USB Programmer

2014-08-31T08:16:00.000-07:00

DC MOTOR CONTROL By IR-Remote using PWM AtMega8

Note:-click to-AtMega 8 datasheet

Introduction

To control the speed of DC motor where precision and protection are essence, we use a technique called PWM (pulse width modulation) to control the speed of DC motor.We can achieve speed control of DC motor using mechanical or electrical techniques but they require large size hardware to implement but Micro controller based system provides easy way to control the speed of DC motor.We will use ATmega8 controller to produce PWM wave. By varying the width of this PWM wave, we can control the speed of DC motor. In ATmega8 controller, timer1 and timer2 have PWM mode.

PWM Based DC Motor Speed Control using Microcontroller Circuit Principle:

The heart of this project is ATmega8 controller. These controllers

consist of 2 PWM modes. Now we will see how to generate

PWM wave using timer2 PWM mode.

Before writing the program to the PWM mode we need to know

the register description of all the registers that are used for PWM mode.

TCCR2 (Timer Counter Control Register):

In Timer 2, we have different modes like CTC mode, normal mode,

phase correct PWM mode, Fast PWM

mode,etc.Among all of these modes, we have to select FastPWM mode.

From the above figure, it is clear that

For Fast PWM mode,

WGM21=1 WGM20=1

To select PWM mode

TCCR2 |= (1<<WGM21)| (1<<WGM20);

Again in PWM mode we have two modes one INVERTING and

other is NON – INVERTING.

To select non-inverting mode,

COM21=1 COM20=0

TCCR2 |= (1<<COM21);

To select inverting mode,

COM21=1, COM20=1

TCCR2 |= (1<<COM21)| (1<<COM20);

After that we have to select prescaler value.

CS22 CS21 CS20 Description

0 0 0 No clock source

0 0 1 clk/1

0 1 0 clk/8

0 1 1 clk/32

1 0 0 clk/64

1 0 1 clk/128

1 1 0 clk/256

1 1 0 clk/1024

To set the prescaler to 8,

CS22=0 CS21=1 CS20=0
TCCR2|= (1<<CS21);

OCR2 (Output Compare Register):

OCR2 register contains an 8 bit value that is continuously compared with counter value.

PWM Program:

//********************************************************

// *********** PWM DC MOTOR CONTROL with IR *************

//********************************************************

//Controller: ATmega8 (1MHz internal Crystal)

//Compiler: ICCAVR

//Author: bidyut das, Chennai

//Date: FEB 2013

//********************************************************

//this program uses two of the three PWM channels (OC1A & OC1B)

//of the ATmega8, for controlling speed & direction of DC motor

//The remote of Sony TV was used for sending IR codes

#include <iom8v.h>

#include <macros.h>

#include "PWM_main.h"

//*********************************************************************

// Initializing functions for ports, timer0 & timer1

//*********************************************************************

void port_init(void)

{

PORTB = 0x00;

DDRB = 0x06; //PWM pins OC1A & OC1B defined as outputs

PORTC = 0x00;

DDRC = 0x20; //LED for IR detection indication

PORTD = 0x00;

DDRD = 0x01; //LED, for testing purpose

}

//timer0 init

void timer0_init(void)

{

//8-bit timer for measuring delay between IR pulses

TCCR0 = 0x03; //CLK / 64

TCNT0 = 0; //reset the timer

}

//TIMER1 initialize - prescale:1

//PWM Frequency: 1KHz

void timer1_init(void)

{

TCCR1B = 0x00; //stop

TCNT1H = 0xFC; //setup

TCNT1L = 0x18;

OCR1A = COUNTER_LOWER_LIMIT;

OCR1B = COUNTER_LOWER_LIMIT;

ICR1H = 0x03;

ICR1L = 0xE8;

}

/**************************************************************************

* Interrupt Service Routine for INT0

* Executed whenever a remote code is detected

**************************************************************************/

#pragma interrupt_handler int0_isr:2

void int0_isr(void)

{

unsigned char count, code, address;

unsigned int IR_input;

TCNT0 = 0;

while(!(PIND & 0x04));

count = TCNT0;

if(count < 30) //to verify start pulse (2.4 ms long)

{

delay_ms(20);

ENABLE_INT0;

return;

}

PORTC |= 0x20;

IR_input = read_IR ();

code = (unsigned char) ((IR_input & 0xff00) >> 8);

address = (unsigned char) (IR_input & 0x00ff);

motorControl ( code, address );

PORTC &= ~0x20;

delay_ms(250);

}

//*********************************************************************

//Function to read IR message from the detector

//Return value contains code in upper byte and address in lower byte

//*********************************************************************

unsigned int read_IR (void)

{

unsigned char pulseCount=0, code = 0, address = 0, timerCount;

unsigned int IR_input;

while(pulseCount < 7)

{

while(PIND & 0x04);

TCNT0 = 0;

while(!(PIND & 0x04));

pulseCount++;

timerCount = TCNT0;

if(timerCount > 14)

code = code | (1 << (pulseCount-1));

else

code = code & ~(1 << (pulseCount-1));

}

pulseCount = 0;

while(pulseCount < 5)

{

while(PIND & 0x04);

TCNT0 = 0;

while(!(PIND & 0x04));

pulseCount++;

timerCount = TCNT0;

if(timerCount > 14)

address = address | (1 << (pulseCount-1));

else

address = address & ~(1 << (pulseCount-1));

}

IR_input = (((unsigned int)code) << 8) | address;

return(IR_input);

}

//****************************************************************************

//Function to control motor speed & direction depending onthe IR code rceived

//Argumets are the code and address values received from IR detector

//****************************************************************************

void motorControl (unsigned char code, unsigned char address)

{

static unsigned char counter, dir, dir1;

if (address != 1) //detect only TV remote, other signals rejected

return;

if((code == 16) || (code == 17)) //Channel+ or Channel- button is pressed

{

if(code == 16) //Channel+

dir = 0;

else //Channel-

dir = 1;

if(dir != dir1) //change direction

{

STOP_MOTOR;

delay_ms(500);

if(dir == 0)

set_FORWARD;

else

set_REVERSE;

START_MOTOR;

dir1 = dir;

}

if(code == 18) //Volume- button pressed

{

if(counter >= COUNTER_UPPER_LIMIT) //if speed is already maximum, don't do anything

counter = COUNTER_UPPER_LIMIT;

else

counter += STEP_SIZE; //increase speed by a fixed step

OCR1A = counter;

OCR1B = counter;

}

if(code == 19) //Volume+ button pressed

{

if(counter <= COUNTER_LOWER_LIMIT) //if speed is already minimum, don't do anything

counter = COUNTER_LOWER_LIMIT;

else

counter -= STEP_SIZE; //reduce speed by a fixed step

OCR1A = counter;

OCR1B = counter;

}

if(code == 9) //'0' button pressed

{

OCR1A = COUNTER_LOWER_LIMIT;

OCR1B = COUNTER_LOWER_LIMIT;

STOP_MOTOR;

}

if(code == 0) //'1' button pressed

{

OCR1A = COUNTER_LOWER_LIMIT;

OCR1B = COUNTER_LOWER_LIMIT;

TCCR1A = 0x81;

START_MOTOR;

}

//************************************************************

//*** call this routine to initialize all peripherals

//************************************************************

void init_devices(void)

{

//stop errant interrupts until set up

CLI(); //disable all interrupts

port_init();

timer0_init();

timer1_init();

MCUCR = 0x02;

GICR = 0x40;

TIMSK = 0x00; //timer interrupt sources

SEI(); //re-enable interrupts

//all peripherals are now initialized

}

//************************************************************

//***** FUNCTION FOR SOFTWARE DELAY OF 1 mSEC (appx.) *******

//************************************************************

void delay_ms(int miliSec) //for 1 Mhz crystal

{

int i,j;

for(i=0;i<miliSec;i++)

for(j=0;j<100;j++)

{

asm("nop");

}

//*******************************************************

// ************ MAIN FUNCTION *************

//*******************************************************

void main(void)

{

init_devices();

while(1); //infinite loop, waiting for interrups from IR detector

}

//****************************** END ***************************************

Circuit Diagram:

Model Car

Some Experiments with the help of Multimeter

2014-07-06T01:28:00.006-07:00

LED when exposed to light,it generate DC voltage:-

Now switch multimeter to the lowest DC voltage range available, and touch the meter's test probes to the terminals (wire leads) of the light-emitting diode (LED). An LED is designed to produce light when powered by a small amount of electricity, but LEDs also happen to generate DC voltage when exposed to light, somewhat like a solar cell. Point the LED toward a bright source of light with your multimeter connected to it, and note the meter's indication.

Motor Acts As Generator:-

Another source of voltage through energy conversion a generator. The small electric motor specified in the "Parts and Materials" list functions as an electrical generator if its shaft is turned by a mechanical force. Connect voltmeter (multimeter, set to the "volt" function) to the motor's terminals just as connected it to the LED's terminals, and spin the shaft with fingers. The meter should indicate voltage by means of needle deflection (analog) or numerical readout (digital).

If it difficult to maintain both meter test probes in connection with the motor's terminals while simultaneously spinning the shaft with fingers, one may use alligator clip "jumper" wires.

Multimeter fuse checking:-

One may test the condition of a multimeter's fuse by switching it to the resistance mode and measuring continuity through the test leads (and through the fuse). On a meter where the same test lead jacks are used for both resistance and current measurement, simply leave the test lead plugs where they are and touch the two probes together. On a meter where different jacks are used, this is how one insert the test lead plugs to check the fuse.

Bread board continuity:-

Although multimeter is capable of providing quantitative values of measured resistance, it is also useful for qualitative tests of continuity: whether or not there is a continuous electrical connection from one point to another. For instance, test the continuity of a piece of wire by connecting the meter probes to opposite ends of the wire and checking to see the the needle moves full-scale. What would we say about a piece of wire if the ohmmeter needle didn't move at all when the probes were connected to opposite ends?

Use meter to determine continuity between the holes on a breadboard: a device used for temporary construction of circuits, where component terminals are inserted into holes on a plastic grid, metal spring clips underneath each hole connecting certain holes to others. Use small pieces of 22-gauge solid copper wire, inserted into the holes of the breadboard, to connect the meter to these spring clips so that one can test for continuity.

How to use a MultiMeter

2014-07-03T05:45:00.003-07:00

Usage of Multimeter

Note: Multimeter being used to measure the varies quantities such as Voltage ,Resistance, Current.Apart from this it is also used in continuity test, diode check etc.

Multimeter

Description:

A multimeter is an electrical instrument capable of measuring voltage, current, & resistance.Digital multimeter have numerical displays, like digital clocks, for indicating the quantities. Analog Multimeter indicate these quantities by means of a moving pointer over a printed scale.

Some digital multimeters are autoranging. An autoranging meter has only a few selector switch (dial) positions. Manual-ranging meters have several different selector positions for each basic quantity: several for voltage, several for current, and several for resistance. Autoranging is usually found on only the more expensive digital meters.

Set multimeter's selector switch to the highest-value "DC volt" position available. Autoranging multimeters may only have a single position for DC voltage, in which case need to set the switch to that one position. Touch the red test probe to the positive (+) side of a battery, and the black test probe to the negative (-) side of the same battery. The meter should now provide with some sort of indication. Reverse the test probe connections to the battery if the meter's indication is negative (on an analog meter, a negative value is indicated by the pointer deflecting left instead of right).

If meter is a manual-range type, and the selector switch has been set to a high-range position, the indication will be small. Move the selector switch to the next lower DC voltage range setting and reconnect to the battery. The indication should be stronger now, as indicated by a greater deflection of the analog meter pointer (needle), or more active digits on the digital meter display. For the best results, move the selector switch to the lowest-range setting that does not "over-range" the meter. An over-ranged analog meter is said to be "pegged," as the needle will be forced all the way to the right-hand side of the scale, past the full-range scale value. An over-ranged digital meter sometimes displays the letters "OL", or a series of dashed lines. This indication is manufacturer-specific.

ILLUSTRATION

Voltage:

Voltage is the measurement of electrical “push” ready to motivate electrons to move through a conductor.It is the specific energy per unit charge,defined as joules per coulomb. It is analogous to pressure in a fluid system: the force that moves fluid through a pipe, and is measured in the unit of the Volt (V).

INSTRUCTION

To measure voltage, follow these steps:

Plug black and red probes into the appropriate sockets (also referred to as "ports") on multimeter. For most multimeters, the black probe should be plugged into the socket labeled "COM," and the red probe into the socket labeled with a "V" (it might also have some other symbols).
Choose the appropriate voltage setting on multimeter's dial. Remember that most battery-powered circuits will have direct current.. If working with a manual-ranging multimeter, estimate the range need based on the battery (or batteries) powering your circuit. For example, if circuit is powered by a single 9V battery, it probably doesn't make sense to select the setting for 200V, and 2V would be too low. If available, would want to select 20V.
Touch the probe tips to your circuit in parallel with the element you want to measure voltage across. For example, Figure shows how to measure the voltage drop across a light bulb powered by the battery. Be sure to use the red probe on the side connected to the positive battery terminal, and the black probe on the side connected to the negative battery terminal (nothing will be harmed if one get this backwards, but voltage reading will be negative).

Figure. Measuring voltage across a lightbulb by attaching the multimeter probes in parallel. Current flow

is represented by the yellow arrows. In voltage-measurement mode, the multimeter's resistance is very high,

so almost all of the current flows through the lightbulb, and the multimeter does not have a big impact on

the circuit. Notice how the knob has been set to measure DC voltage (DCV) and the red probe is plugged

into the correct port for measuring voltage (labeled "VΩ" because it is also used to measure resistance).

If multimeter is not auto-ranging, one might need to adjust the range. If multimeter's screen just reads "0," then the range you have selected is probably too high. If the screen reads "OVER," "OL," or "1" (these are different ways of saying "overload"), then the range you have selected is too low. If this happens, adjust range up or down as necessary.

Resistance:

Resistance is the measure of electrical "friction" as electrons move through a conductor. It is measured in the unit of the "Ohm," that unit symbolized by the capital Greek letter omega (Ω).

INSTRUCTIONS

Set your multimeter to the highest resistance range available. The resistance function is usually denoted by the unit symbol for resistance: the Greek letter omega (Ω), or sometimes by the word "ohms." Touch the two test probes of meter together. Then, the meter should register 0 ohms of resistance. If one using an analog meter, will notice the needle deflect full-scale when the probes are touched together, and return to its resting position when the probes are pulled apart. The resistance scale on an analog multimeter is reverse-printed from the other scales: zero resistance in indicated at the far right-hand side of the scale, and infinite resistance is indicated at the far left-hand side. There should also be a small adjustment knob or "wheel" on the analog multimeter to calibrate it for "zero" ohms of resistance. Touch the test probes together and move this adjustment until the needle exactly points to zero at the right-hand end of the scale.

Although your multimeter is capable of providing quantitative values of measured resistance, it is also useful for qualitative tests of continuity: whether or not there is a continuous electrical connection from one point to another. One can, for instance, test the continuity of a piece of wire by connecting the meter probes to opposite ends of the wire and checking to see the the needle moves full-scale. What would we say about a piece of wire if the ohmmeter needle didn't move at all when the probes were connected to opposite ends?

Digital multimeters set to the "resistance" mode indicate non-continuity by displaying some non-numerical indication on the display. Some models say "OL" (Open-Loop), while others display dashed lines.Connect the meter's test probes across the resistor as such, and note its indication on the resistance scale:

The needle points very close to zero, you need to select a lower resistance range on the meter, just as you needed to select an appropriate voltage range when reading the voltage of a battery.

If one using a digital multimeter, should see a numerical figure close to 10 shown on the display, with a small "k" symbol on the right-hand side denoting the metric prefix for "kilo" (thousand). Some digital meters are manually-ranged, and require appropriate range selection just as the analog meter. If yours is like this, experiment with different range switch positions and see which one gives you the best indication.

Note ....When touch the meter probes to the resistor terminals, try not to touch both probe tips to fingers. If one do, he will be measuring the parallel combination of the resistor and your own body, which will tend to make the meter indication lower than it should be! When measuring a 10 kΩ resistor, this error will be minimal, but it may be more severe when measuring other values of resistor.

You may safely measure the resistance of your own body by holding one probe tip with the fingers of one hand, and the other probe tip with the fingers of the other hand.

Current

Current is the measure of the rate of electron "flow" in a circuit. It is measured in the unit of the Ampere, simply called "Amp," (A).

INSTRUCTIONS

OR.............................................................................

The most common way to measure current in a circuit is to break the circuit open and insert an "ammeter" in series (in-line) with the circuit so that all electrons flowing through the circuit also have to go through the meter. Because measuring current in this manner requires the meter be made part of the circuit, it is a more difficult type of measurement to make than either voltage or resistance.

Some digital meters, like the unit shown in the illustration, have a separate jack to insert the red test lead plug when measuring current. Other meters, like most inexpensive analog meters, use the same jacks for measuring voltage, resistance, and current.

When an ammeter is placed in series with a circuit, it ideally drops no voltage as current goes through it. In other words, it acts very much like a piece of wire, with very little resistance from one test probe to the other. Consequently, an ammeter will act as a short circuit if placed in parallel (across the terminals of) a substantial source of voltage. If this is done, a surge in current will result, potentially damaging the meter:

Caution:

Ammeters are generally protected from excessive current by means of a small fuse located inside the meter housing. If the ammeter is accidently connected across a substantial voltage source, the resultant surge in current will “blow” the fuse & render the meter incapable of measuring current until the fuse is replaced. Be very careful to avoid this scenario!

Conclusion (while measuring Voltage & Current Of a Circuit).....

L298 MOTOR Driver

2014-07-02T23:47:00.004-07:00

L298 IC:

Description:

A very popular and reasonably priced all-in-one H-bridge motor driver is the L298. It can control two motors, not just one. It can handle 2 amps per motor, though to get the maximum current be sure to add a heat sink. The L298 has a large cooling flange with a hole in it, making it easy to attach a homebrew metal heat sink to it.If there’s a downside to the L298 it’s that it comes in a special “Multiwatt 15” package, with 15 offset pins that don’t match the standard 0.100" spacing of breadboards. But with care, the pins can be rebent as needed. Or you may prefer to simply get a breakout board for the L298, which is a small circuit board with holes drilled in it to accept the chip. You then plug the breakout board into your breadboard. Problem solved.The schematic below shows a basic connection diagram for controlling two motors using the L298 motor bridge IC. There are three input pins for each motor: Input1, Input2, and Enable1 controls Motor1. Input3, Input4, and Enable2 controls Motor2. The motors connect to Output1/Output2 and Output3/Output4, as shown.

The L298 uses two different supply voltages. The voltage on pin 9 powers the chip itself and should be 5 volts. The voltage on pin 4 supplies the motors, and it can be up to 46 volts.

Let’s look at how to control just one of the motors, Motor1. In order to activate the motor, the Enable1 line must be HIGH. You then control the motor and its direction by applying a LOW or HIGH signal to the Input1 and Input2 lines, as shown in this table.

Input1	Input2	Action
LOW	LOW	Motor breaks and stops*
HIGH	LOW	Motor turns forward
LOW	HIGH	Motor turns backward
HIGH	HIGH	Motor breaks and stops*

* To coast a motor to a slower stop, apply a LOW signal to the Enable1 line.

The L298 does not have built-in protection diodes, so you’ll need to add those. The datasheet for the L298 specifies “fast recovery” 1-amp diodes; an inexpensive selection is the 1N4933, available from most online electronic parts outlets.

L298 based Motor Driver

Fig. of Motor Driver

Features

· Maximum motor supply voltage: 46V

· Maximum motor supply current: 2A per motor

· Current Sense for each motor

· Heat sink for better performance

· Power-On LED indicator

Using the board to drive motor

Motor driving is extremely simple with the board. The board has two ChannelsA and B. It has 2 inputs and 2 corresponding outputs for each Channel. Each channel also has an enable pin and a sense pin. The Input pins are the labelled as INP A and INP B. The enable pin is labeled As EN A and EN B, and the sense pin is labelled as SNS A and SNS B.To drive a DC motor in a particular channel, the enable pin of the Channel has to be supplied with a logic high (+5V) signal. Then, a logic high signal has to be supplied to the input pins to control the direction of the motor. Supplying logic high to any one of the input pins will drive the DC Motor in one direction. On supply logic high to the other Input pin, the motor will run in the opposite direction. Supplying logic high to both input pins will brake the rotation of the motor and Supplying a logic low (0V or Gnd) signal to both the input pins will allow the DC motor to rotate freely.The sense pin can be used to sense and limit the amount of current the motor in corresponding channel is consuming. By default this option is not enabled on the board and the sense pin is directly connected to GND through a jumper.

Internal and external logic supply for the board

The L298 requires an input voltage of 5V for its operation. The board has an on board 5 V regulator (LM7805) for the same. It takes the motor input voltage and regulates it to 5V. The regulated voltage can also be supplied to external circuits and can be tapped through the 5V and Gnd header

The on board voltage regulator can work on a maximum input voltage of 35 V. If you wish to drive motors with voltages greater than 35 V, you will have to supply external 5 V for the board, and cut of the input supply to the on board regulator. This will prevent it from getting damaged due to a high input voltage. You can do this by de-soldering the jumper on the bottom side of the board between Pin 1 of the voltage regulator and the+ve Input Voltage pin.

Advantages of L298 over L293

2014-07-01T10:24:00.001-07:00

Reason of Choosing L298 Motor Driver

The L298 chip is the bigger brother to the L293 chip (a popular small-motor driver IC), but the L298 handles more current, and more voltage - just what you need for those robots that need more power!

One of the first realizations in robotics is that making something move isn’t an easy task. There are many ways to strengthen (”buffer”) a signal so it’s strong enough to drive a large load like a motor. Transistor H bridge circuits, buffer chips, and dedicated motor driving chips are all suitable candidates, with their own benefits and

limitations.

We’re using the well-proven L298 for this design, as it has practically all the features that r need in a good motor driver, including thermal-shutdown, meaning that it will slow down and stop if overloaded (rather than melting down in a catastrophic manner!).

Adding a low-drop out regulator lets you tap off 5V for any other circuitry you may want to drive, and the indicator LEDs are always very useful when monitoring the behaviors of circuit.

Tech Spec:-

L298 has current capacity of 2A per channel @ 45V compared to 0.6 A @ 36 V of a L293D. L293D’s package is not suitable for attaching a good heat sink, practically you can’t use it above 16V without frying it. L298 on the other hand works happily at 16V without a heat sink, though it is always better to use one.

There are several versions of the 16 pin L293s.

The 293D is a 600 ma. 16 pin DIP that has on chip suppressor diodes.

The 293B is a 1 amp 16 pin DIP that does not have on chip diodes.

For ease of circuit use the L293 is much easier to use due to is dip package, and the L298 is a right bugger of a package to route the pins out from, but it is a bigger driver and will handle more current. it also works very well when used with the L297 chip.

L293D MOTOR DriVER

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L293D DIP16 Package

Description:-

L293D is a typical Motor driver or Motor Driver IC which allows DC motor to drive on either direction. L293D is a 16-pin IC which can control a set of two DC motors simultaneously in any direction. It means that you can control two DC motor with a single L293D IC. Dual H-bridge Motor Driver integrated circuit (IC).The l293d can drive small and quiet big motors as well

capable of driving high voltage motors using TTL 5V logic levels. They can drive 4.5V up to 36V at 1A continuous output current!

L293D Connections

L293D is a 16 pin IC which comes in a DIP Package. Its pin configuration is shown below.

L293D Pin Configuration

Now let’s have a look at its connections for bidirectional motor control.

L293D Based Motor Driver

In this way, we can have bidirectional control over two motor. Let’s have a summary of connections:

o There are two enable (EN) pins, pin 1 and pin 9. Pin 1 EN enables the motor M1 whereas pin 9 EN enables motor M2.

o Connect motor M1 across OUTPUT1 and OUTPUT2 i.e. across pins 3 and 6.

o Connect motor M2 across OUTPUT3 and OUTPUT4 i.e. across pins 11 and 14.

o The inputs for motor M1 is given across INPUT1 and INPUT2 i.e. across pins 2 and 7.

o The inputs for motor M2 is given across INPUT3 and INPUT4 i.e. across pins 10 and 15.

o Connect GROUND pins 4, 5, 12 and 13 to ground.

o Connect pin 16 to Vcc (=5V) and pin 8 to Vs (battery, 4.5V~36V).

As per the diagram, the inputs of motor M1 are M1-A and M1-B, whereas inputs of motor M2 are M2-A and M2-B.

Now consider the following cases for motor M1:

o M1-A = 1 and M1-B = 0 → M1 moves clockwise (say). Then

o M1-A = 0 and M1-B = 1 → M1 moves counter-clockwise.

o M1-A = 0 and M1-B = 0 → M1 stops.

o M1-A = 1 and M1-B = 1 → M1 stops.

Similar cases can arise for motor M2:

o M2-A = 1 and M2-B = 0 → M2 moves clockwise (say). Then

o M2-A = 0 and M2-B = 1 → M2 moves counter-clockwise.

o M2-A = 0 and M2-B = 0 → M2 stops.

o M2-A = 1 and M2-B = 1 → M2 stops.

Suppose if you need to control only one motor at a time, you need to enable that particular EN pin. Enabling both pins at the same time will drain your battery unnecessarily.

Concept

It works on the concept of H-bridge. H-bridge is a circuit which allows the voltage to be flown in either direction. As you know voltage need to change its direction for being able to rotate the motor in clockwise or anticlockwise direction, Hence H-bridge IC are ideal for driving a DC motor.

In a single l293d chip there two h-Bridge circuit inside the IC which can rotate two dc motor independently. Due its size it is very much used in robotic application for controlling DC motors. Given below is the pin diagram of a L293D motor controller.

There are two Enable pins on l293d. Pin 1 and pin 9, for being able to drive the motor, the pin 1 and 9 need to be high. For driving the motor with left H-bridge you need to enable pin 1 to high. And for right H-Bridge you need to make the pin 9 to high. If anyone of the either pin1 or pin9 goes low then the motor in the corresponding section will suspend working. It’s like a switch.

Working of L293D

The there 4 input pins for this l293d, pin 2,7 on the left and pin 15 ,10 on the right as shown on the pin diagram. Left input pins will regulate the rotation of motor connected across left side and right input for motor on the right hand side. The motors are rotated on the basis of the inputs provided across the input pins as LOGIC 0 or LOGIC 1.

In simple you need to provide Logic 0 or 1 across the input pins for rotating the motor.

L293D Logic Table

Lets consider a Motor connected on left side output pins (pin 3,6). For rotating the motor in clockwise direction the input pins has to be provided with Logic 1 and Logic 0.

• Pin 2 = Logic 1 and Pin 7 = Logic 0 | Clockwise Direction

• Pin 2 = Logic 0 and Pin 7 = Logic 1 | Anticlockwise Direction

• Pin 2 = Logic 0 and Pin 7 = Logic 0 | Idle [No rotation] [Hi-Impedance state]

• Pin 2 = Logic 1 and Pin 7 = Logic 1 | Idle [No rotation]

In a very similar way the motor can also operated across input pin 15,10 for motor on the right hand side.

MOTOR DRIVER Pt-2

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Note: see motor driver H bridge "blog" for basic concept

Use of motor driver-

In the above block diagram, we can see that there is a micro controller (MCU). Now, this MCU may/may not take in inputs (inputs as in from sensors, other digital inputs, etc). Next, as per our programming, the MCU will generate control signals. Please note that the MCU will generate signals in form of HIGH (Vcc = 5v) or LOW (zero). But this voltage is insufficient to drive a motor. That’s why we need to use a Motor Driver.

A motor driver always has a battery input Vs (which depends upon the rating of the motor). In simple terms, what a motor driver does is that it directs the Vs voltage to the motors connected (or in fact, the output pins) to it. Thus, the motors behave as per the control signals generated using the MCU with the excitation from the external battery voltage.

The most commonly used motor driver is the L293D, which is a driver IC. Apart from this we have other motor driver such as L298 ,which has some advance features over L293D. Discussed separately both driver ICs.

Motor Driver H-BRIDGE Concept Pt-1

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H-BRIDGE:

The H-Bridge is designed to drive a motor clockwise and anticlockwise. To reverse a motor, the supply must be reversed and this is what the H-Bridge does. An H-Bridge can be made with SWITCHES, RELAYS, TRANSISTORS or MOSFETS.

H-Bridge with switches:

Do not make circuit "A." It can easily create a SHORT-CIRCUIT. It is only a demonstration circuit.

Switch A and D will make the motor rotate clockwise.
Switch B and C will make the motor rotate anti-clockwise.
Switch A and B will create a BRAKE.
Do not close switch A and C at the same time.
Do not close switch B and D at the same time.

An improved design is shown in Circuit C. It does not create any short-circuit:

H-bridge Motor Control

So how does it work?. The four transistors are connected together in a “H-bridge” configuration with the motor connected in the middle. To make the motor rotate in the forward direction, a high (logic “1″ or +5V) signal is applied to the forward input, while no signal is applied to the reverse input (applying a voltage to both inputs at the same time is not allowed). The speed of the motor is controlled by using the pulse width modulating signal as before. Transistors TR1 and TR4 conduct. Current flows from terminal A through to terminal B (left-to-right direction) of the motor. To reverse the motor’s direction a high signal is applied to the reverse input and transistors TR3 and TR2 conduct, allowing current to pass through the motor in the opposite direction from terminal B through to terminal A (right-to-left direction). The flywheel diodes, D1 to D4 across the transistors of the H-bridge motor control circuit help to protect the transistors from any induced back emf generated by the motor during braking. Any suitable PNP or NPN transistor can be used other than the ones above, but all the transistors should have high power ratings, if not use heatsinks.While it is possible to construct the H-bridge motor control circuit from scratch using individual components, there are lots of IC’s and “black boxes” available off-the-shelf to make motor speed control and design far easier and usually cheaper. Two H-bridge motor control IC’s that are popular and easy to connect are the National Semiconductors LMD18200 and the Texas Instruments L293D motor-driver chips. Both are easy to use with in-built diodes, shorted circuit protection and are TTL and CMOS compatible.

WORKING OF IR SENSORS

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IR SENSORS

An IR (Infrared) sensor is used to detect obstacles in front of the robot. Whenever an obstacle is detected it gives out a signal.

Applications of the IR sensor:

IR sensors are mostly used in robotic applications for the following:

1. Proximity sensing: Detecting whether an obstacle is present within a pre-specified distance or not.

2. Color sensing: The main application is the line follower. It is used to differentiate between black and white surfaces.

3. Mapping and localization : Making a map of the surrounding and finding the position of the robot with respect to the surroundings.

WORKING OF THE IR SENSORS:

The IR sensors basically work using infrared rays. Infrared rays are a part of light spectrum that human can’t see but can be detected using special electronic gadgets. All objects in this universe emit infrared radiation including humans. The radiations emitted by different objects differ significantly. The IR sensor detects changes in the IR radiation when different objects fall on it.

The IR sensor is essentially composed of two parts:

1. Emitter

2. The detector

The emitter generates infrared rays of a particular type. The detector continuously monitors the environment for any traces of IR light of the same type as the emitter. Whenever an obstacle comes in front of the IR sensor, the IR light emitted by the emitter gets reflected to the detector. The detector detects this light and gives out a signal.

The picture shown is very simple black box model of the IR sensor. The sensor emits IR light and gives a signal when it detects the reflected light.

Now suppose we want to use our IR sensor outdoors in sunlight. Sunlight also has an IR component. This causes our sensors to wrongly assume that there is an obstacle in front of it so how do we get around this? We use an essential property of sunlight – it is continuous. So instead of sending out the ir signal continuously from the emitter, we send it pulses. This type of IR sensor is called a TSOP- thin small outline package.

The IR light is emitted in pulses. The frequency is the inverse of Time period.

CHOOSING THE CORRECT IR SENSOR:

Choosing an IR SENSOR with TSOP for indoor purposes is redundant. Hence it is important to use the right sensor, keeping in mind the following:

Usage conditions: whether the sensor will be used indoors or outdoors.

Cost: TSOPs are immune to sunlight but it is not the right choice for indoor applications simply because it is costly.

Advanced reading – IR sensor:

An IR sensor consists of an emitter, detector and associated circuitry. The emitter is simply an IR led and the detector is simply an IR photodiode which is sensitive to IR light of the same wavelength as that emitted by the IR led .whenever light falls on the photodiode, its resistance decreases and this allows more current to flow through it. Now if a resistance is connected in series with the photo diode, the increase in current through it causes the voltage across the resistance to increase. This is because

V= IR

Where,

V= voltage across the resistor

I= current flowing through the resistor

R=resistance of the resistor

As it apparent from the above relation, the voltage increases with increase in current. Now if we compare this voltage with a preset voltage, we can know when IR light is falling on the detector, i.e., when there is an obstacle in front of the robot. The current that does this is called an operation amplifier.

It has three terminals: a +ve terminal, a –ve terminal and an output terminal. If the voltage at the +ve terminal is more than the voltage at the –ve terminal the output is a HIGH (+5V) and if the voltage at the –ve terminal is more than the voltage at the +ve terminal the output is low (0) volt. Now if we connect the –ve terminal to a preset voltage and the +ve terminal to the photo diode resistor junction, we can get an output indicating whether an obstacle is present or not.

HERE HOW IT HAPPENS:

1. When the IR emitter is powered it begins to emit IR light .this cannot be seen with the naked eye. However it can be seen with naked eyes .However it can be seen through the lens of a camera.

2. The resistance and hence the output voltage of the IR receiver keeps changing as the intensity of the ir light incident on it is changed. When less IR light is incident (when there is no obstacle), the output voltage and vice versa.

3. This output voltage is connected to the non inverting pin of the op amp.

4. The output of the potentiometer is connected to the inverting voltage pin of the op amp.

5. Recall that the non inverting voltage of the op amp is greater than the inverting voltage, the output of the op amp is HIGH (5V) and when the non inverting voltage of the op amp is greater than the inverting voltage, the output of the op amp is HIGH (5V).

6. An LED is usually connected to the output of the op amp.

7 . When there is no obstacle in front of the sensor, the output voltage of the receiver is higher than the output of the potentiometer.

8. Hence, non inverting voltage of the op amp is greater than its inverting voltage and correspondingly the output of the op amp id HIGH and the LED glows.

9. When there is an obstacle in front of the sensor, the output voltage of the receiver decreases and goes below that of the potentiometer.

10. Hence the non inverting voltage of the op amp is lesser than its inverting voltage and its output becomes LOW (0V). Hence the LED stops glowing

CALIBRATING AN IR SENSOR

By changing the resistance of the potentiometer, the reference or the inverting voltage of the op amp is changed. This is very useful in order to make the IR sensor work in different lightning conditions. Doing this changes the range of the IR sensor.

Sunlight and some artificial lights have a significant components of IR light .This IR light adds to and in some cases replaces the light of the IR emitter. Hence the receiver continuously receives IR light irrespective of the presence and absence of an obstacle. Therefore a conventional IR sensor does not work in presence of sunlight or alight with a significant component of IR light.

how to install the software required for programming and how to program an AtMega16 micro-controller

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Note: 1st see main components of programming a micro controller "blog" for better understanding

Installation of Software and Programming

This tutorial will show you how to install the software required for programming and how to program an At Mega 16 micro-controller.

Installing the Required Software and Drivers:

The contents of the programmer support CD include the following:

1) USBasp Driver (Programmer device driver S/W)

2) At Mega 16 Datasheet

3) Installation and Programming Tutorials

4) Make File

5) WINAVR Installation File (Programming S/W)

Contents of the support CD

Once we have written our C code, programming a micro-controller involves two discreet steps.

1) The code in high level C language must be converted into low-level (hex code) which can be understood by the micro-controller.

2) This hex code must be ported or burnt into the micro-controller.

WINAVR is the software required to convert the code written in our high-level language (C Language) into hex code and burn it into the micro-controller.

Let us see how to install WINAVR. If you are not using the support CD, then you will first need to download the setup file. Double click on the installation file of WINAVR and install it in a preferred location.

Once WINAVR is installed, we will proceed to install the driver of the USBdude programmer. In order to do this, first open Device Manager on your computer.

Plug in the programmer into the USB port of your computer. You will find the Programmer added to the list of devices attached to the computer. However, it will tell you that the driver for USBtiny was not installed correctly.

(Download and) Right click on the USBdude in the device manager and select ‘update device driver’. You will have to manually browse the folder location to identify the folder containing the device driver. Browse through to the folder named USBdude Driver. The folder contains drivers for all the configurations of windows computers. You need not select the driver specifically. Your computer will choose the right driver from the folder. Once you have directed to the folder, click ‘Update’.

Device Manager before installation of driver

Device manager after installation of driver

You have now installed the driver of the USBasp programmer.

Once WINAVR and USBdude are both installed on your computer, you will not require the setup and driver files again.

Now, whenever you want to write a new code, you may follow the steps given below. The aforementioned steps are not required to be repeated.

Now, let us see how to connect the programmer to the AtMega16 micro-controller.

Connecting the programmer to the micro-controller:

Fig :- AVR DUDE Programmer

When we program a micro-controller, we must always make sure that each specific programming pin of the programmer is connected to each programming pin of the micro-controller we want to program.

This USBdude programmer is designed in such a way that it’s six programming pins and the six programming pins of the AtMega16 mirco-controller are in order. Hence, we can directly program an AtMega16 micro-controller on a breadboard using this programmer without using any wires.

If you have to program a micro-controller with different configuration of programming pins, you will have to connect the programming pins of the programmer to those of the micro-controller using wires.

The six programming pins of any micro-controller (MOSI, MISO, SCK, RESET, Vcc and GND) can be found in its datasheet. The datasheet of the AtMega16 micro-controller has been provided in this support CD.

Ensure that the Ground (GND) pin of the programmer is connected to the GND pin of the microcontroller, the Vcc pin of the programmer is connected to the Vcc pin of the micro-controller and so on.

Note: If can be seen that the micro-controller is being powered by the programmer while it is being programmed (as the power pins of the programmer and the micro-controller are connected). Similarly, after the micro-controller is programmed, we can use the programmer itself to power the micro-controller. The programmer in turn is being powered by your computer. However, the amount of current that the programmer can provide is limited. It is, therefore, not recommended to power the circuit using the programmer.

The GND pin of the AtMega16 micro-controller is its 11th pin and the MOSI pin is the 6th pin. This is how the micro-controller and the programmer sit on the breadboard when you want to program the micro-controller.

_________________________________________________________________________________

Programming the Micro-controller:

Now, we may proceed to write the C code. We will write our code in a software called Programmers Notepad (pn.exe) which automatically installs when you install WINAVR. Create a separate folder with an appropriate name. Go to the folder where WINAVR was installed. In the WINAVR folder, select the pn folder. In this folder, open the pn.exe file. You can also find this file in the WINAVR folder in the All Programs menu when you open START.

This opens the ‘Programmer’s Notepad’, a commonly used editing software for programming.

Write your C code in the programmer’s notepad and save the file in the new folder with a “.c”

extension. For example, if your program is called main, you will have to save it as main.c

In order to program the micro-controller successfully, we have to pass on certain information about the hardware we are using to the compiler. We do this with the help of a MakeFile. You will find this MakeFile in the Support CD or in the ‘Resources’ tab.

Open this MakeFile with Programmer’s notepad. It will open as a separate tab in addition to the tab containing your C code.

Save this MakeFile in the same folder as your C code. This step is very important and is often

forgotten by beginners. Next, we need to modify certain parameters of the MakeFile.

Generally, we will modify only three parameters of the Makefile;

1) The microcontroller used: Change it to atmege16 (all small and no gaps)

#MCU name

MCU = atmega16

2) The TARGET (referring to the code to be burnt): Change it to the <name of your C code> without the .c extension

#Target File name (without extension)

TARGET=my program

3) The programmer used: Change it to usbtiny (all small and no gaps).

AVRDUDE_PROGRAMMER=usbasp

Save the Makefile and the code. Remember, the MakeFile and the C code should be in the same folder.

Now we are ready to compile and burn the code. Go to Tools in the menu and select ‘Make All’.

This command converts the C code into the hex code. On completion of this process, the output

window says ‘Process Exit Code 0’. This indicates that the hex file has been generated without any errors. You will now find the generated hex file in the folder which had your C code and the MakeFile.

Next, go to Tools in the menu and select ‘Program’. This command burns the hex code from your computer into the micro-controller. You can see the progress of this process in the output window. The code is first written onto the micro-controller and is then read, by the programmer. This is done to check for any errors that might have occurred during writing the code.

On completion of this write process, the output window says ‘Process Exit Code 0’. This indicates that the write operation has been completed without any errors.

Components that are use in Programming of a Micro Controller

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Main components that are use in Programming of a Micro Controller

>>Micro controller(here At-mega 16)

>>Micro controller Programmer kit

>>Cable for connecting PC USB(usb2.0/usb3.0) to micro controller kit

fig: different components reqd for programming

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Making Sense of Actuators

What is an actuator?

An “actuator” can be defined as a device that converts energy (in robotics, that energy tends to be electrical) into physical motion. The vast majority of actuators produce either rotational or linear motion. For instance, a “DC motor” is therefore a type of actuator.

Choosing the right actuators for your robot requires an understanding of what actuators are available, some imagination, and a bit of math and physics.

Rotational Actuators

As the name indicates, this type of actuators transform electrical energy into a rotating motion. There are two main mechanical parameters distinguishing them from one another: (1) torque, the force they can produce at a given distance (usually expressed in N•m or Oz•in), and (2) the rotational speed (usually measured in revolutions per minutes, or rpm).

AC Motor

AC (alternating current) is rarely used in mobile robots since most of them are powered with direct current (DC) coming from batteries. Also, since electronic components use DC, it is more convenient to have the same type of power supply for the actuators as well. AC motors are mainly used in industrial environments where very high torque is required, or where the motors are connected to the mains / wall outlet.

DC Motors

DC motors come in a variety of shapes and sized although most are cylindrical. They feature an output shaft which rotates at high speeds usually in the 5 000 to 10 000 rpm range. Although DC motors rotate very quickly in general, most are notstrong (low torque). In order to reduce the speed and increase the torque, a gear can be added.

To incorporate a motor into a robot, you need to fix the body of the motor to the frame of the robot. For this reason motors often feature mounting holes which are generally located on the face of the motor so they can be mounted perpendicularly to a surface. DC motors can operate in clockwise (CW) and counter clockwise (CCW) rotation. The angular motion of the turning shaft can be measured using encoders or potentiometers.

Geared DC Motors

A DC gear motor is a DC motor combined with a gearbox that works to decrease the motor’s speed and increase the torque. For example, if a DC motor rotates at 10 000 rpm and produces 0.001 N•m of torque, adding a 256:1 (“two hundred and fifty six to one”) gear down would reduce the speed by a factor of 256 (resulting in 10 000rpm / 256 = 39 rpm), and increase the torque by a factor of 256 (0.001 x 256 = 0.256 N•m). The most common types of gearing are “spur” (the most common), “planetary” (more complex but allows for higher gear-downs in a more confined space, as well as higher efficiency) and “worm” (which allows for very high gear ratio with just a single stage, and also prevents the output shaft from moving if the motor s not powered). Just like a DC motor, a DC gear motor can also rotate CW and CCW. If you need to know the number of rotations of the motor, an “encoder” can be added to the shaft.

R/C Servo Motors

R/C (or hobby) servo motors are types of actuators that rotate to a specific angular position, and were classically used in more expensive remote controlled vehicles for steering or controlling flight surfaces. Now that they are used in a variety of applications, the price of hobby servos has gone down significantly, and the variety (different sizes, technologies, and strength) has increased.

The common factor to most servos is that the majority only rotate about 180 degrees. A hobby servo motor actually includes a DC motor, gearing, electronics and a rotary potentiometer (which, in essence, measures the angle). The electronics and potentiometer work in unison to activate the motor and stop the output shaft at a specified angle. These servos are generally have three wires: ground, voltage in, and a control pulse. The control pulse is usually generated with a servo motor controller. A “robot servo“ is a new type of servo that offers both continuous rotation and position feedback. All servos can rotate CW and CCW.

Industrial Servo Motors

An industrial servo motor is controlled differently than a hobby servo motor and is more commonly found on very large machines. An industrial servo motor is usually made up of a large AC (sometimes three-phase) motor, a gear down and an encoder which provides feedback about angular position and speed. These motors are rarely used in mobile robots because of their weight, size, cost and complexity. You might find an industrial servo in a more powerful industrial robotic arm or very large robotic vehicles.

Stepper Motors

A stepper motor does exactly as its name implies; it rotates in specified “steps” (actually, specific degrees). The number of degrees the shaft rotates with each step (step size) varies based on several factors. Most stepper motors do not include gearing, so just like a DC motor, the torque is often low. Configured properly, a stepper can rotate CW and CCW and can be moved to a desired angular position. There are unipolar and bipolar stepper motor types. One notable downside to stepper motors is that if the motor is not powered, it’s difficult to be certain of the motor’s starting angle.

Adding gears to a stepper motor has the same effect as a adding gears to a DC motors: it increases the torque and decreases the output angular speed. Since the speed is reduced by the gear ratio, the step size is also reduced by that same factor. If the non geared down stepper motor had a step size of 1.2 degrees, and you add a gear down of 55:1, the new step size would be 1.2 / 55 = 0.0218 degrees.

Linear Actuators

A linear actuator produces linear motion (motion along one straight line) and have three main distinguishing mechanical characteristics: the minimum and maximum distance the rod can move “a.k.a. the “stroke”, in mm or inches), their force (in Kg or lbs), and their speed (in m/s or inch/s).

DC Linear Actuator

A DC linear actuator is often made up of a DC motor connected to a lead screw. As the motor turns, so does the lead screw. A traveller on the lead screw is forced either towards or away from the motor, essentially converting the rotating motion to a linear motion. Some DC linear actuators incorporate a linear potentiometer which provides linear position feedback. In order to stop the actuator from destroying itself, many manufacturers include limit switches at either end which cuts power to the actuator when pressed. DC linear actuators come in a wide variety of sizes, strokes and forces.

Solenoids

Solenoids are composed of a coil wound around a mobile core. When the coil is energized, the core is pushed away from the magnetic field and produces a motion in a single direction. Multiple coils or some mechanical arrangements would be required in order to provide a motion in two directions. A solenoid’s stroke is usually very small but their speed is very fast. The strength depends mainly on the coil size and the current going trough it. This type of actuator is commonly used in valves or latching systems and there is usually no position feedback (it’s either fully retracted or fully extended).

Muscle wire

Muscle wire is a special type of wire that will contract when an electric current traverses it. Once the current is gone (and the wire cools down) it returns to its original length. This type of actuator is not very strong, fast or provides a long stroke. Nevertheless, it is very convenient when working with very small parts or in a very confined space.

Pneumatic and Hydraulic

Pneumatic and hydraulic actuators use air or a liquid (e.g. water or oil) respectively in order to produce a linear motion. These types of actuators can have very long strokes, high force and high speed. In order to be operated they require the use of a fluid compressor which makes them more difficult to operate than regular electrical actuators. Because of they high force speed and generally large size, they are mainly used in industrial environments.

Choosing an Actuator

To help you with the selection of an actuator for a specific task, we have developed the following questions to guide you in the right direction.

It is important to note that there are always new and innovative technologies being brought to market and nothing is set in stone. Also note that an single actuator may perform very different task in different contexts. For instance, with additional mechanics, an actuator that produces linear motion may be used to rotate an object and vice versa (like on a car’s windshield wiper).

(1) Is the actuator being used to move a wheeled robot?

Drive motors must move the weight of the entire robot and will most likely require a gear down. Most robots use “skid steering” while cars or trucks tend to use rack-and-pinion steering. If you choose skid steering, DC gear motors are the ideal choice for robots with wheels or tracks as they provide continuous rotation, and can have optional position feedback using optical encoders and are very easy to program and use. If you want to use rack-and-pinion, you will need one drive motor (DC gear is also suggested) and one motor to steer the front wheels). For stirring, since the rotation required is restricted to a specific angle, an R/C servo would be the logical choice.

(2) Is the motor being used to lift or turn a heavy weight?

Lifting a weight requires significantly more power than moving a weight on a flat surface. Speed must be sacrificed in order to gain torque and it is best to use a gearbox with a high gear ratio and powerful DC motor or a DC linear actuator. Consider using system (either with worm gears, or clamps) that prevents the mass from falling in case of a power loss.

(3) Is the range of motion limited to 180 degrees?

If the range is limited to 180 degrees and the torque required is not significant, an R/C servo motor is ideal. Servo motors are offered in a variety of different torques and sizes and provide angular position feedback (most use a potentiometer, and some specialized ones use optical encoders). R/C servos are used more and more to create small walking robots.

(4) Does the angle need to be very precise?

Stepper motors and geared stepper motors (coupled with a stepper motor controller) can offer very precise angular motion. They are sometimes preferred to servo motors because they offer continuous rotation. However, some high-end digital servo motors use optical encoders and can offer very high precision.

(5) Is the motion in a straight line?

Linear actuators are best for moving objects and positioning them along a straight line. They come in a variety of sizes and configurations. Muscle wire should be considered only if your motion requires very little force. For very fast motion, consider pneumatics or solenoids, and for very high forces, consider DC linear actuators (up to about 500 pounds) and then

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Choosing a Robotic Platform

Now, it is time to decide on the type if robot you are going to build. A custom robot design often starts with a “vision” of what the robot will look like and what it will do. The types of robots possible are unlimited, though the more popular are:

Land wheeled, tracked, and legged robots
Aerial planes, helicopters, and blimp
Aquatic boats, submarines, and swimming robots
Misc. and mixed robots
Stationary robot arms, and manipulators

This lesson is intended to help you decide what type of robot to build to best suite your mission.

Land

Land-based robots, especially the wheeled ones, are the most popular mobile robots among beginners as they usually require the least investment while providing significant exposure to robotics. On the other hand, the most complex type of robots is the humanoid (akin to a human), as it requires many degrees of freedom and synchronizing the motion of many motors, and uses many sensors.

Wheeled Robots

Wheels are by far the most popular method of providing mobility to a robot and are used to propel many different sized robots and robotic platforms.Wheels can be just about any size, from a few centimetres up to 30 cm and more . Tabletop robots tend to have the smallest wheels, usually less than 5 cm in diameter. Robots can have just about any number of wheels, although 3 and 4 are the most common. Normally a three-wheeled robotuses two wheels and a caster at one end. More complex two wheeled robots may use gyroscopic stabilization. It is rare that a wheeled robot use anything but skid steering (like that of a tank). Rack and pinion steering such as that found on a car requires too many parts and its complexity and cost outweigh most of its advantages.

Four and six wheeled robots have the advantage of using multiple drive motors (one connected to each wheel) which reduces slip. Also, omni-directional wheels or mecanum wheels, used properly, can give the robot significant mobility advantages. A common misconception about building a wheeled robot is that large, low-cost DC motors can propel a medium sized robot.

Advantages

Usually low-cost compared to other methods
Simple design and construction
Abundance of choice
Six wheels or more rival a track system
Excellent choice for beginners

Disadvantages

May lose traction (slip)
Small contact area (only a small rectangle or line underneath each wheel is in contact with the ground)

Tracked Robots

Tracks (or treads) are what tanks use. Although tracks do not provide added “force” (torque), they do reduce slip and more evenly distribute the weight of the robot, making them useful for loose surfaces such as sand and gravel. Also, a track system with some flexibility can better conform to a bumpy surface. Finally, most people tend to agree that tank tracks add an “aggressive” look to the robot as well.

Advantages

Constant contact with the ground prevents slipping that might occur with wheels
Evenly distributed weight helps your robot tackle a variety of surfaces
Can be used to significantly increase a robot’s ground clearance without incorporating a larger drive wheel

Disadvantages

When turning, there is a sideways force that acts on the ground; this can cause damage to the surface the robot is being used on, and cause the tracks to wear
Not many different tracks are available (robot is usually constructed around the tracks)
Drive sprocket might significantly limit the number of motors that can be used.
Increased mechanical complexity (idler placement and number, # of links) and connections

Legs

An increasing number of robots use legs for mobility. Legs are often preferred for robots that must navigate on very uneven terrain. Most amateur robots are designed with six legs, which allow the robot to be statically balanced (balanced at all times on 3 legs); robots with fewer legs are harder to balance. The latter require “dynamic stability”, meaning that if the robot stops moving mid-stride, it might fall over. Researchers have experimented with monopod (one legged “hopping”) designs, though bipeds (two legs), quadrupeds (four legs), andhexapods (six legs) are the most popular.

Advantages

Closer to organic or natural motion
Can potentially overcome large obstacles and navigate very rough terrain

Disadvantages

Increased mechanical, electronic and coding complexity (not the easiest way to get into robotics).
Lower battery size despite increased power demands
Higher cost to build

Air

A AUAV (Autonomous Unmanned Aerial Vehicle) is very appealing and is entirely within the capability of many robot enthusiasts. However, the advantages of building an autonomous unmanned aerial vehicles, especially if you are a beginner, have yet to outweigh the risks. When considering an aerial vehicle, most hobbyists still use existing commercial remote controlled aircraft. On the professional side, aircraft such as the US military Predator were initially semi-autonomous though in recent years Predator aircraft have flown missions autonomously.

Advantages

Remote controlled aircraft have been in existence for decades (so there is a large community, at least for the mechanics)
Excellent for surveillance

Disadvantages

The entire investment can be lost in one crash.
Limited robotic community to provide help for autonomous control

Water

An increasing number of hobbyists, institutions and companies are developing unmanned underwater vehicles. There are many obstacles yet to overcome to make underwater robots attractive to the wider robotic community though in recent years, several companies have commercialized pool cleaning “robots”. Underwater vehicles can use ballast (compressed air and flooded compartments), thrusters, tail and fins or even wings to submerge. Other aquatic robots such as pool cleaners are useful commercial products.

Advantages

Most of our planet is water, so there is a lot to explore and discover
Design is almost guaranteed to be unique
Can be used and/or tested in a pool

Disadvantages

Robot can be lost many ways (sinking, leaking, entangled…)
Most electronic parts do not like water (also consider water falling on electronics when accessing the robot after a dive)
Surpassing depths of 10m or more can require significant research and investment
Very limited robotic community to provide help
Limited wireless communication options

Miscellaneous and hybrid combinations

Your idea for a robot may not fall nicely into any of the above categories or may be comprised of several different functional sections. Note again that this guide is intended for mobile robots as opposed to stationary or permanently fixed designs (other than robotic arms and grippers). It is wise to consider when building a hybrid design, to use a modular design (each functional part can be taken off and tested separately). Miscellaneous designs can include hovercraft, snake-like designs, turrets and more.

Advantages

Designed and built to meet specific needs
Multi-tasking and can be comprised of modules
Can lead to increased functionality and versatility

Disadvantages

Possible Increased complexity and cost
Often times, parts must be custom designed and built

Arms & Grippers

Although these do not fall under the category of mobile robotics, the field of robotics essentially started with arms and end-effectors (devices that attach to the end of an arm such as grippers, electromagnets etc). Arms and grippers are the best way for a robot to interact with the environment it is exploring. Simple robot arms can have just one motion, while more complex arms can have a dozen or more unique degrees of freedom.

Advantages

Very simple to very complex design possibilities
Easy to make a 3 or 4 degree of freedom robot arm (two joints and turning base)

Disadvantages

Stationary unless mounted on a mobile platform
Cost to build is proportional to lifting capability

Practical Example

In our case, we have opted for building a robot that will provide the maximum exposure to robotics. A programmable tracked platform that can accommodate a variety of sensors and gripper sees ideal in this case, specially since we consider tank tracks are far cooler than wheels.

In order to keep the costs down, we opted to build a small desktop robot that will be able to roam indoors and on tabletops. We also have taken into consideration the fact that there are not many tracks available, and to keep things simple, we’ll only consider a single drive sprocket and single idler sprocket system, this should not be a problem since the robot will be very light weight.

The preliminary CAD below summarized the features describes so far.

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SENSORS:

A sensor is a device that measures a physical quantity and converts it into a signal which can

be read by micro-controller.

heat,
motion,
gyro,
sonar,
IR,etc…

TSOP 1738:

It is a DIGITAL IR SENSOR, giving outputs of 0V and 5V.

It does not respond to any stray IR, it only responds to IR falling on it at a pulse rate of 38 KHz (given by TIMER of micro-controller)

Can accurately distinguish between 2 colors.

Circuit Diagram:

IR Analog Sensor:

It gives output in the range of 0V to 5V, depending on the amount of IR light falling on the photo diode. (read by ADC of micro-controller)

Hence the name analog…

Circuit Diagram:

QRD1114:

It is an easy-to-use, simple analog sensor (Output range: 0V to 5V)

Has a very small range: 0.5mm to 1cm

Used to distinguish between bright and dark colours

LDR (Light Dependent Resistor)"

•made of calcium sulfate…

•When no light falls on it, the LDR behaves as an open circuit (very high resistance: 10^6 ohms)

•As the intensity of light increases, the resistance drops (to about 10 to 100 ohms)

Circuit Diagram:

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INTRODUCTION ON ROBOTICS
http://youtu.be/DaWMvEY3Qgc

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video lecture about robotics by NPTEL refer link
http://nptel.iitm.ac.in/courses/112101099/1

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Approach required for robotics

Pursuing Robotics is not easy. Even if u r very interested in it,& r fascinated by the possibilities ,always remember few things whenever u think about robotics

NOTHING IS TOO EASY,AND NOTHING IS TOO DIFFICULT

NOTHING IS TOO EASY- U will have a picture in ur mind but to get it working will take a lot of planning,ground work & meticulous execution.
NOTHING IS TOO DIFFICULT-nothing in robotics is too difficult provided u approach the problem with the right plan with the right temperament.First time u look at it, any component,any connections, any logic would look difficult in robotics. u need to rise above the fear of the new,to be able to appreciate the beauty of robotics.

SMALL STEPS LEAD TO BIG SUCCESS

In robotics it is more often that the idea u have in ur mind will become reality only through small steps.

THERE R BAD DAYS & THERE IS A GOOD DAY

Which ever area of robotics u would be working on,this in the most important thing to remember.There will be many days when even if u r investing long hrs of work,the success seems to be little or none for that matter.At the end of the day u may feel.
'IS IT WORTH THE EFFORT ,AND HARDSHIP?'
YES it is.
Key to success in robotics is to preserve though all these days for the good day always comes.Good Day is when things fall in place,everything starts working and then it's magic.Everyone goes through the cycle of bad days and good.Once u learn this,everything else becomes easy.

DREAM.BECAUSE ONLY THOSE WHO DREAM HAVE A CHANCE TO MAKE IT COME TRUE

Be fascinated by ur idea .Imagine its impact.Every time u feel like quitting after a bad day, its ur dream that would keep u going.

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A simple autonomous robot

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The 3 Schools of Robotics:
• Mechanical Design
– Types of motors
– Material selection
– Driving, gripping, clamping, climbing, lifting…
• Electronics
– Micro controllers
– Motor Drivers
– Sensors (Infrared, Ultrasonic, etc)
• Programming
– Microcontroller Programming
– Communicating with a computer.
– Communicating between multiple robots.

2013-03-18T08:27:00.002-07:00

its a long time since posting about starting blogging about basic of robotics,
So here its the things,
1st at starting of basic robotics is a combination of different fields such as
mechanical,electrical,electronics etc.
2nd need to have basic knowledge of different component that are being used.
3rd need a creative mind for problem solving as well as designing part.
So getting started with basic robotics i prefer some knowledge about robotics& what do u mean by the word robotics.
Robotics is the branch of technology that deals with the design, construction, operation, and application of robots, as well as computer systems for their control, sensory feedback, and information processing. These technologies deal with automated machines that can take the place of humans in dangerous environments or manufacturing processes, or resemble humans in appearance, behavior, and/or cognition.

Basics

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Robotics is just the combination of the machine and the logic on it.