S@Robotics

Electronics projects #1: Making a emergency mini usb mobile charger using 7805 IC

2019-05-05T09:46:00.000+05:30

Making a mini usb mobile charger using 7805 voltage regulator ic:

Introduction:

Mobile phones,are essential commodity in nowadays life.There are often when we find ourselves in those situations when our phone's battery level is about to go off,leaving us in emergency.people generally keep powerbanks or car chargers with themselves but they are also useful upto an extent.
In this post i've decided to make a useful project on 7805 voltage regulator IC that can be used to charge a device with a 9v battery or any 12v car battery.so next time you find yourself in tough situation,just buy a 9v battery at the corner shop and you will have enough power to handle the emergency situations.
*it's recommended to use a high current 9v battery like Duracell or energiser.A normal cheap Chinese battery will not provide enough backup.

Step 1:

Gather these parts:

At first you have to gather or buy those underwritten parts from anywhere.

7805 IC along with heatsink and nut bolt
100 uf capacitor (1 pcs)
10 uf capacitor (1 pcs)
LED and a 100 ohms resistor(if required)
USB female connector
Breadboard,perfboard,solder and soldering iron
Multimeter(optional)
Wires
9v battery connector

Step 2:

schematics:

Schematics for 9v mini usb mobile charger

Connecting and testing on breadboard:

Connecting and testing the circuit on breadboard

At first build the circuit on breadboard as shown in the schematics and test with a Multimeter.If 5v output not coming,rebuild it again according to the schematics.

Step 3:

Soldering:

Soldering all the components

After 1st step is successful,solder the components on perfboard as shown in the schematics or follow the below written instructions-

Take a 7805 voltage regulator IC.Solder the Vcc wire from the usb port to the output terminal(pin 3) of the 7805 IC.
Similarly solder the gnd wire to the gnd terminal(pin 2) of 7805 IC.
If you want to add a indicator LED,connect the ‘-ve’ LED leg to the gnd terminal of 7805 IC
Connect the 100 ohms resistor in series with the other leg of LED,and the other terminal of resistor is to be connected with the input terminal (pin 1) of 7805 IC
Take a 9v battery connector clip and connect the ‘+ve’ battery terminal to the input terminal (pin 1) of 7805 IC
Connect the ‘-ve’ battery terminal to the gnd terminal (pin 2) of 7805 IC

Step-4

Finally testing after soldering:

Finally testing after soldering

Now after the soldering is complete,test the circuit again with a multimeter.also connect your phone to see whether it's charging or not.Now add the heatsink to the 7805 IC.

Step-5

Let's start application:

Let's start applications

Our mini portable usb charger is now ready.connect a 9v battery to the charger.Plug a usb cable in the usb port and connect it to the mobile phone.

The mobile device begins to charge and the backup will depend on the quality of 9v battery used.A good quality battery can charge a 3000 mah cell phone battery upto 15-20%.

*This device can also be used to charge a cell phone using any wall adapter upto 12v incase of emergency situations.Because of 7805 voltage regulator IC will provide regulated 5v to cell phone.

Digital electronics:some integrated circuits and their implementation

2019-04-27T11:26:00.000+05:30

Some integrated circuits and their implementation:

some ics and their implementation

In previous post i talked about the basics of digital electronics,if you don't see this you can read this post here.Now we discuss about some integrated circuits and their implementation according to the schedule sequentially.So let's learn-

555 timer IC:

The 555 is a single chip version of a commonly used circuit called a multivibrator.

The IC used in a variety of timer,pulse generation, and oscillator applications.
The 555 timer has three modes- monostable,astable and bistable.

555 timer ic pinout

Monostable mode:

Monostable or 'one shot' mode,produces a single pulse of a set length in response to a trigger input.Here's the formulas written below to find out the time (T),capacitance (c) and resistance (R)-

T=1.1RC

C= T/1.1R

R= T/1.1c

Monostable mode of 555 timer IC

Astable mode:

Astable or free running mode, has no stable state and output switches between high and low.Producing a square wave output.We can set the clock frequency and duty cycle D by the formulae:

t1=0.693(R1+R2)C

t2=0.693R2C

f=1.44/(R1+2R2)C

Duty cycle= (R1+R2)/(R1+2R2)×100

T=t1+t2

=0.693(R1+2R2)C

Astable mode of 555 timer IC

Bistable mode:

Bistable or schmitt trigger mode, has two stable states-high and low,taking the trigger input low makes the output of the circuit go into the high state taking the reset input low makes the output of the circuit go into the low state.

Bistable mode 555 timer

4029 counter IC:

4017 counter IC pinout

One of the most common requirements in digital equipment is counting. And the most common counting requirement has to do with time. From a basic digital clock (which is incorporated into most digitally-controlled appliances) to interval timers and event counters, the need for counting circuits is very great.

Counters are required for various counting ranges and in all sorts of circumstances. A simple digital clock, for example, requires a decimal counter for the units positions of seconds and minutes, but must count only from 0 to 5 (modulo-6) for the tens positions of minutes and seconds. Hours digits require special handling, since the two-digit output must count either from 1 to 12 or 0 to 23, depending on how we want the display to appear. Some clocks skip the 0 to 23 military display and run from 1 to 24 in that mode. And some simple clocks make no effort at that, or to distinguish between AM and PM.

No matter how the hours are handled, the basic element required to make any digital clock work is the counter circuit. Indeed, counters are so important in so many applications that many different kinds of counter ICs have been designed for both TTL and CMOS logic families. Some count up for clocks and time intervals; others count down to show time remaining until some event. Some are specifically designed to count in decimal mode, while others count in binary, and still others have selectable counting ranges. The list of capabilities and options is quite large, leaving the circuit designer with only the task of selecting the particular IC that best suits the need.

Hence 4029 can also be used as a memory element that remembers its immediate previous state.

Pin description:4017 counter IC-

Pin description:4017 counter

7447 IC: BCD to 7 segment display decoder:

For displaying the number in the counter output on a seven segment display (i.e. 7 LEDs making up a figure of ‘8’ as in a general calculator. See fig.) we need to decode the 4 bits and match them to the 7 pins for lighting the LEDs corresponding to the number. This work is done by 7447.

7447 ic and seven segment display pinout

Pin Description of 7447 IC:

Here's the pin description of 7447 IC scheduled below-

7447 pin description

LDR (Light Dependent Resistor):

Light Dependent Resistor (LDR) or photo resistor is a device that acts like a resistance and its resistance varies with the intensity of light incident on it. In this device, if photons of sufficient energy fall on it, the resistance drops drastically as the electrons in the semiconductor are able to jump from the valence band to the conduction band and are available for conduction.The LDRs used are mostly responsive to visible light. The resistance might drop from as high as 1MΩ in the dark to 1 k Ω in bright light.

LDR pinout:The coiled portion of LDR is responsive to light

Operational Amplifier (Opamp):

op-amp is a very important device used in everyday electronics .It is essentially a differential amplifier with a very high gain of the order of 10^5! By differential amplifier I mean that it amplifies the difference of 2 signals and gives the output.

Opamp equation:

Vout= A (V+ - V- ), where A is the gain of the order 10^5

Op-amp pinout

Ironically, this high gain in open loop makes it impossible to use it as a general purpose differential amplifier directly

Op-amp as a comparator:

The Op-amp comparator compares one analogue voltage level with another analogue voltage level, or some preset reference voltage, VREF and produces an output signal based on this voltage comparison. In other words, the op-amp voltage comparator compares the magnitudes of two voltage inputs and determines which is the largest of the two.

7805 Voltage Regulator:

7805 IC pinout

7805 voltage regulator is used to get +5 V output out of a higher voltage supply (7.5V-20V).We use adapter’s supply to generate +5V here. Connect the gnd and +12V of adapter to the pins as shown and get +5V directly as an output out of the 3rd pin. Current up to 0.5 A can be obtained from this regulator without any significant fall in voltage level.

7805 circuit diagram

*Use 2 capacitors of value say 0.1µF to filter the noise in the input and output of regulator’s supply as shown. Also put a capacitor of 10 – 100 uF at output to take care of the low frequency dip in the voltages.

Circuit symbols

2019-04-21T19:34:00.001+05:30

Circuit symbols

Circuit symbols:

The list above covers almost every symbol you will find on an electronic circuit diagram.It allows you to identify a symbol and also draw circuits. It is a handy reference and has some symbols that have never had a symbol before, such as a Flashing LED and electroluminescence panel.
Once you have identified a symbol on a diagram you will need to refer to specification sheets to identify each lead on the actual component.
The symbol does not identify the actual pins on the device. It only shows the component in the circuit and how it is wired to the other components, such as input line, output, drive lines etc.You cannot relate the shape or size of the symbol with the component you have in your hand or on the circuit-board.
Sometimes a component is drawn with each pin in the same place as on the chip etc. But this is rarely the case.
Most often there is no relationship between the position of the lines on the circuit and the pins on the component.
That’s what makes reading a circuit so complex.
This is very important to remember with transistors, voltage regulators, chips and so many other components as the position of the pins on the symbol are not in the same places as the pins on the component and sometimes the pins have different functions according to the manufacturer. Sometimes the pin numbering is different according to the component, such as positive and negative regulators.
You must to refer to the manufacturer’s specification sheet to identify each pin, to be sure you have identified them correctly.These symbols also helps you to understand schematics of any circuit.

Digital electronics: Basics of digital electronics

2019-04-18T19:44:00.000+05:30

Basics of digital electronics:

Basics of digital electronics

Digital systems
A system which deals with quantities and variables having two discrete values or states are called is called digital system. In these circuits, the input and output can have any one of the two values “1” or “0”. Following are the examples of such quantities:

A switch can either open or closed.
The answer of a question can be either yes or no.
A certain statement can be either true or false.
A bulb can be either on or off.

In all these situations, one of the states is represented by “1” and the other state by “0”.
"1" represents:
i. ON circuit
ii. High voltage
iii. True statement
"0" represents:
i. OFF circuit
ii. Low voltage
iii. False statement

Number systems in digital electronics:

Types of digital circuits:

There are mainly two types of digital circuits-

Combinatorial Circuits: In these circuits, the past states are immaterial

and the output depends only upon the present state. Example: logic gates

Sequential circuits: In these circuits, the next state is completely determined by the past states. Hence these follow a predictable structure and essentially require a timing device. Example: counters, flip flops.

Clock: Building block of a sequential circuit:

A clock is simply alternate high and low states of voltage with time i.e. essentially a square wave.Important terms related to clock are its duty cycle and its frequency:

Duty cycle: It is the ratio of Th and Th+Tl, D=Th/𝑇𝑙+𝑇ℎ

table of logic gates

Logic Gates: Building block of a combinatorial circuit:
These are essentially combinational circuits are used to implement logical Boolean operations like AND, NAND, OR, XOR and NOT. NOT and NAND are called universal gates as any other gate can be formed

using either of them!

Identification of some Practical Circuiting Elements:

Resistance:

A color scheme is followed to give the specifications of a resistor. The table for color code is shown below:

Resistor values are calculated one band at a time,from left to right.Match each band color with the corresponding value on the color chart.The 1st two bands specify the 2 digits of the resistor value whereas the 3 rd band specifies the multiplier in terms of the power to which 10 is raised and multiplied to the 2 digits.

The tolerance tells the possible % variation of the resistor value about the value indicated by bands.

Inductors:

A color scheme is followed to give the specifications of a inductor. The table for color code is shown below:

Inductors values are calculated one band at a time, from left to right.Match each band color with the corresponding value on the color chart.The 1st two bands specify the 2 digits of the inductors value whereas the 3 rd band specifies the multiplier in terms of the power to which 10 is raised and multiplied to the 2 digits.

The tolerance tells the possible % variation of the inductor value about the value indicated by bands.

Capacitors:

The 2 types of capacitors we frequently use in circuits are ceramic and electrolytic capacitors. While ceramic capacitors do not have a fixed polarity; electrolytic capacitors should be connected in their specified polarities only else they might blow off! This polarity is usually provided on the side of the capacitors ‘corresponding leg.There's a very useful chart for calculation the right value of Ceramic / Non – Polarized Capacitors given below.

Diodes:

A Diode is a two terminal semiconductor device with a single pn junction,which has the ability to pass current in only one direction.which made of two electrodes called the anode and the cathode.generally cathode is identified by a silver or colored band.

Diode can be used as rectifiers,signal limiters,voltage regulators,switches,signal modulators,signal mixers,signal demodulators or oscillators.

Some of the different types of diodes are:

Rectifier diode:

These diodes are used to rectify alternating current inputs in power supplies.

Zener diode:

This type of diode provides a stable reference voltage.It's designed to conduct in the reverse direction when the breakdown voltage is reached.

Light Emitting Diode[L.E.D]:

One of the most popular types of diodes.The LED emmits light when diode is in forward bias.The longer lead is the anode(+) and the flat side is the cathode (-).

Photodiodes:

Conduct only when they are exposed to light.

Breadboard:

This is the base used for setting up the circuit. This has embedded metal strips in it that form a grid of connections inside its body. This allows us to take multiple connections from a single point without any need of soldering/disordering as in PCBs. It is always a good habit to test the circuit on breadboard before making it on a PCB.

Top view showing the connecting holes. Bottom view shows the contact metal strips

Integrated circuits [I.C]:

ICs or Integrated Circuits are packaged circuits designed for some fixed purpose. An IC has its fixed IC name/number that can be used to get catalog of its functions and pin configuration. ICs come in various sizes and packages depending upon the purpose.Different ICs may have different number of pins.

Integrated circuit (I.C)

Introduction to the embeded systems and robotics

2019-04-15T10:48:00.000+05:30

Introduction to embedded systems and robotics:

Introduction to embedded systems and robotics

Hey friends, you are mostly welcome to my blog "s@robotics".I'm souvik,a physics lover and from this platform you may learn robotics easily for free.I promise you to upload two posts on Thursday and Sunday of each week.I will cover those following contents throughout my posts sequentially.

There are mainly three parts i.e- Digital electronics,embedded system and Robotics.And these parts will be devided into some subtopics written below.

Contents covered:

A. Digital Electronics:

Basics of digital electronics
Some integrated circuits and their implementation

B. Embedded systems:

Introduction to microcontrollers
Code vision AVR (CVAVR)
Introduction to Atmega 16 microcontroller
I/O ports
LCD interfacing
UART communication
Timers
SPI [serial peripheral interface]
ADC [analog to digital converter]
Interrupts

C. Robotics:

Introduction to autonomous robots
Motor driver
Sensors

And i will post a project based on robotics every month.So friends let's enjoy the world of robotics.Thank you.