Free Microcontroller and Interface Programming

Single Chip Temperature Data Logger

2011-03-30T17:25:00.000+07:00

A data logger is a device that records measurements over time. The measurements could be any physical variable like temperature, pressure, voltage, humidity, etc. This project describes how to build a mini logger that records surrounding temperature values. This is the figure of the circuit;
Temperature will be measured with a DS1820 temperature sensor. DS1820 is a one wire digital temperature sensor from Dallas Semiconductor (now MAXIM). The operating temperature range of the device is -55°C to +125°C with an accuracy of ±0.5°C over the range of -10°C to +85°C. The temperature sensor output is 9?bit Celsius temperature measurement, and so the temperature resolution corresponds to the least significant bit, and which is 0.5°C. But in this project we will use only the most significant eight bits. Therefore, the temperature resolution will be 1°C. The measured temperatures will be recorded into the internal EEPROM memory of PIC12F683.

The first location of the internal EEPROM will store the sampling interval of data logger. Sampling interval defines the time gap between two successive measurements. This project will have 3 options for sampling time: 1 sec, 1 min, and 10 min. These are user selectable. The second location of EEPROM will store the number of measurements recorded so far. And the remaining 254 EEPROM locations will store 8?bit temperatures. So, using 10 min sampling interval, 254 bytes of EEPROM will provide data logging for 42 hours. The recorded measurements can be sent to PC at any time through a serial link at 9600 baud.

LCD Module Control Using PC

2011-03-30T17:22:00.000+07:00

Here’s a design circuit for simple circuit controls a popular 2-line x 16-character LCD by a PC via printer port. It doesn't use the Bi-directional feature found on newer printer ports, thus it should work with most, if not all Parallel Ports. These LCD Modules are very common these days, and are quite simple to work with, as all the logic required to run them is on board. This is the figure of the circuit;

The LCD panel's Enable and Register Select is connected to the Control Port. The Control Port is an open collector/open drain output. While most Parallel Ports have internal pull-up resistors, there are a few which don't. Therefore by incorporating the two 10K external pull up resistors, the circuit is more portable for a wider range of computers, some of which may have no internal pull up resistors. The 10k Potentiometer controls the contrast of the LCD panel. The software source code has been written in Borland C++.

Electronic MIDI Drum

2011-03-30T17:16:00.000+07:00

Here’s a design circuit for a MIDI interface between drum pads and computer or hardware sequencer. Using this circuit you can hit pads with drumsticks and store the MIDI data in real time. This is the figure of the circuit;

This circuit is based around the PIC16C84 microcontroller which scans the inputs on RB0 to RB7 and when a high is detected the software transmits the equivalent note-on (and then the MIDI note-off after a short delay) for the required drum sound on the MIDI output on RA0.

Digital Light Sensor to Microcontroller Circuit

2011-03-30T17:06:00.000+07:00

This is a design circuit for digital light sensor circuit using microcontroller. The ISL29001 is an integrated ambient light sensor with ADC and I2C interface. With a spectral sensitivity curve matched to that of the human eye, the ISL29001 provides 15-bit effective resolution while rejecting 50Hz and 60Hz flicker caused by artificial light sources. This is the figure of the circuit;

In normal operation, the ISL29001 consumes less than 300µA of supply current. A software power-down mode controlled via the I2C interface disables all but the I2C interface. A power-down pin is also provided, which reduces power consumption to less than 1µA. The ISL29001 includes an internal oscillator, which provides 100ms automatic integration periods, or can be externally timed by I2C commands. Both the internal timing and the illuminance resolution can be adjusted with an external resistor.

Led Matrix Circuit With AT90S2313 Microcontroller

2011-03-19T02:29:00.000+07:00

LED ball physically assembled in a matrix of dimension 20 Rays and 7 LEDs. LEDs are governed microcontroller and two decoder K155ID10. Operating current 80mA decoders, this is enough to connect the LED matrix in the dynamics of directly between the microcontroller and decoders, excluding transistors, the brightness of LEDs is sufficient. The control circuit assembled on two boards, located in the center of the ball, moving away from them rays – soldered in one line cathodes, LEDs, and the anodes are connected by layers of thin wire as a cobweb. This is the figure of the circuit;

Before installing the need to bend legs of chips at 90 degrees, solder all the details of one party to the first charge, then at the opposite conclusions to put a second charge and finish soldering. Podpayat supply wires and programming, flash microcontroller and check the output signals. Only then can continue mounting LEDs. To facilitate the work necessary to prepare a template – a hole in the cardboard (plywood, plastic) 7 holes for the LEDs on the same line two centimeters. Then bend cathodes of LEDs 90 degrees right next to their body, insert the LEDs into the template and unsolder beam deflected conclusions. Each of the 20 rays soldered into the board and turn down under the picture. To give the rigidity of the whole structure, anodes maximum distance from the center LED solder together a 10-centimeter segments of tinned copper wire, giving the correct type of construction of the dodecahedron (face-pentagon at each vertex, three edges). Then solder each layer remaining anodes of LEDs and connect each layer to the relevant conclusions resistance. With proper installation will start building a microcontroller embedded in his light effects. For a change, it automatically changes the number of repetitions, speed, brute force effects. This is enough to exclude the interference of the operator. The program is written in a medium BASCOMAVR, if desired in the source code can add or change inherent effects.

Infrared and Ultrasonic Scanner Using ATMega

2011-03-19T02:23:00.000+07:00

This is a project that is a short range, infrared and ultrasonic scanner that uses a standard hobby servo to move the sensors and a color LCD screen to display the information from the distance sensors. The information displayed on the LCD is an overhead view of the scanning area, with increments of distance from the distance sensors. This is the figure of the project;

The core of the project is the ATMEGA32 microcontroller from Atmel. It controls the servo, gathers information from the sensors and places the information on the LCD screen. There is 32K of flash in the microcontroller and the software uses about 13K of that. Since the LCD uses a maximum of 3.3V, the microcontroller is run at 3.3V.

Counter Wall 7 Segment Circuit

2011-03-19T02:18:00.000+07:00

This is a design circuit that is simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily. This is the figure of the circuit;

All pulses to be counted are to be TTL compatible. They should not exeed 5V and not fall below ground. You can add more digits by building a second (or third, or fourth, etc…) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.

Compass Sensor Circuit Using Microcontroller Project

2011-03-19T02:11:00.000+07:00

This circuit is design circuit to build a digital compass that displays both the direction and cardinal points on a television. Other functionalities were added to complement the sensor interface, such as, temperature display, magnetic declination input and disability option. This is the figure of the circuit;

The HMC1052 two-axis magnetic sensor contains two Anisotropic Magneto-Resistive (AMR) sensor elements in a singleMSOP-10 package. Each element is a full wheat stone bridge sensor that varies the resistance of the bridge magneto resistors in proportion to the vector magnetic field component on its sensitive axis. The two bridges on the HMC1052 are orientated orthogonal to each other so that a two-dimensional representation of an magnetic field can be measured. The bridges have a common positive bridge power supply connection (Vb); and with all the bridge ground connections tied together, form the complete two-axis magnetic sensor. Each bridge has about an 1100-ohm load resistance, so each bridge will draw several milli-amperes of current from typical digital power supplies. The bridge output pins will present a differential output voltage in proportion to the exposed magnetic field strength and the amount of voltage supply across the bridge. Because the total earth’s magnetic field strength this very small (~0.6 gauss), each bridge’s vector component of the earth’s field will even be smaller and yield only a couple milli-volts with nominal bridge supply values. An instrumentation amplifier circuit; to interface with the differential bridge outputs, and to amplify the sensor signal by hundreds of times, will then follow each bridge voltage output.

Uninterruptible Power Supply Using PIC17C43 Microcontroller

2011-01-30T18:59:00.000+07:00

That is a design circuit for Microchip Uninterruptible Power Supply (UPS) reference design with PIC17C43 microcontroller. Here’s the figure of the power supply;

At times, power from a wall socket is neither clean nor uninterruptible. Many abnormalities such as blackouts, brownouts, spikes, surges, and noise can occur. Under the best conditions, power interruptions can be an inconvenience. At their worst, they can cause loss of data in computer systems or damage to electronic equipment.

It is the function of an Uninterruptible Power Supply (UPS) to act as a buffer and provide clean, reliable power to vulnerable electronic equipment. The basic concept of a UPS is to store energy during normal operation (through battery charging) and release energy (through DC to AC conversion) during a power failure. UPS systems are traditionally designed using analog components. Today these systems can integrate a microcontroller with AC sine wave generation, offering the many benefits. The PIC17C43 microcontroller handles all the control of the UPS system. The PIC17C43 is unique because it provides a high performance and low cost solution not found in other microcontrollers.

Centigrade and Fahrenheit Scale Digital Thermometer Using LCD Display

2011-01-30T18:54:00.000+07:00

This is a design circuit for Digital thermometers are cool devices as they show temperatures in human readable formats. This digital thermometer project is based on a PIC16F688 microcontroller and a DS1820 temperature sensor, and it displays temperature on a character LCD screen in both Celsius and Fahrenheit scales. I selected PIC16F688 for this project because it is cheap (I bought one for $1.50). DS1820 is a 3-pin digital temperature sensor from Dallas semiconductors (now Maxim) which is designed to measure temperatures ranging from -55 to +125 °C in 0.5 °C increments. Here’s the figure of the circuit;

The firmware I have written is able to read and display the entire temperature range of DS1820. In order to test for temperature measurements below 0°C, I put the sensor inside my freezer. While trying this, don’t put the whole unit inside the freezer as LCD display unit may stop working at the freezer temperature. Similarly, bringing a soldering iron tip close to the sensor can do testing for the higher range temperature values.

Using Reset IC in Microcontroller

2011-01-25T20:28:00.000+07:00

This is a the design of microcontroller based electronics project, the use of Reset IC is critical for highly critical applications that need to ensure that the MCU will only operate at its optimum voltage. Without the use of reset circuitry, the MCU may go into a tristate of which it may go into abnormal operation. This is the figure if the circuit;

During power up, once Vcc exceeds the reset threshold, the reset line will be kept low for a period after which the line will be pulled high. This resets the MCU afterwhich it will go into normal operation.

If the Vcc drops below the reset threshold, the reset pin will go low. It will stay low for at least the reset time out period and go back to high again. This operation will ensure that the MCU power supply is monitored and will only go into operation when the Vcc is within the range of its operation. The threshold voltage of the IC is chosen based on the minimum Vcc of the MCU. MCU supply can range from 1.8V to 5.0V and a suitable IC can be chosen to monitor the supply voltage to the MCU.

The Voltage Regulator

2011-01-25T20:20:00.000+07:00

The DC voltage produce by this circuit is depend on the load; the heavier the load (more current to the load) means the capacitor discharge time will be more faster and as a result the DC voltage output level will be drop. The circuit above is called unregulated AC to DC converter; because it could not maintain its voltage output level, this kind of power source could not be use in electronic circuit that required constant voltage level in order to operate properly such as in digital and microcontroller circuit. Therefore we need what is called Voltage Regulator Circuit and at the same time works as the DC to DC voltage step down.

The first one is the analog voltage regulator, this type of regulator operate the transistor in its linear region (current gainer). The current supplied to the transistor base lead is depend on the voltage different between the reference voltage and output voltage apply to the error amplifier input; for example when the output voltage is greater than the reference voltage, than the error amplifier will make the transistor to conduct less, this mean the voltage drop across the collector and emitter (Vce) will be increase this will make the output voltage to decrease and vice verse. With output voltage being continuously compared to the reference voltage (close loop feedback) by the error amplifier, this kind of circuit could maintain its voltage output level constantly. The disadvantage of using this type of voltage regulator is the power dissipation (power lost as a heat) on the transistor is high especially when we want to use 5 Volt output from 11.33 volt from the unregulated DC source or drain lot of current from it.

The second one is the most efficient voltage regulator as this type of voltage regulator operates the transistor in its saturate region or known as a switching voltage regulator. The working principal is the same as the analog one, but instead of using the constant current to the transistor base lead; this voltage regulator type use pulse current or known as PWM (Pulse Width Modulation) to the transistor base lead and this make the transistor to turn on and off according to the PWM duty cycle supplied by the error amplifier. Therefore by changing the PWM duty cycle we could change the average voltage drop across the collector and emitter (Vce). The inductor (L) is used to release its energy to the load through the diode (D) when the transistor is turn off; and when the transistor is turn on then the transistor will supply the current to the load and the inductor will store the energy in the electromagnetic form; in other word the inductor and diode will ensure that the load will always get a constant current when the transistor is turn off.

Making a Binary Clock Using a PIC Microcontroller

2011-01-25T20:17:00.000+07:00

This is a design circuit for binary clock circuit. This circuit is the same hardware as the led matrix project using a 16F88 PIC microcontroller and an LED matrix. Its worth taking a look there as the same hardware description applies on how to multiplex the display. This is the figure of the circuit;

To display hours, minutes and seconds (2 digits each) you need 6 binary digits in total (depending on whether you use a 24 hour clock the top digit needs only 1 or 2 LEDs).

DC to DC Step-Up Regulator

2011-01-25T20:12:00.000+07:00

This is a design circuit for the Maxim MAX756 is the sample of easy to use DC to DC step-up switching regulator; this chip is used to increase the typically low input DC voltage 1.1 volt - 1.8 volt to the output DC voltage of 3.3 Volt or 5 Volt at maximum 200mA load (300mA on 3.3 Volt output). This is the figure of the circuit;

This means you could easily power your microcontroller project using just a single AA/AAA battery. This kind of step-up power is widely use on digital and microcontroller circuit that powered by low input voltage battery such as micro alkaline 1.5 volt battery. The basic schematic for 5 volt output from 1.5 volt battery. The output voltage of Maxim MAX756 could be selected from 5 volt or 3.3 volt by putting logical low or high on pin 2 (3/5), it also supply the low output indicator detector to the circuit if needed through the pin 4 (LBO). The following picture shows the Maxim MAX756 IC circuit powering the microcontroller’s board using just 1 AA alkaline battery (1.5 Volt).

PIC Frequency Counter Operating Up To 50 MHz

2011-01-17T22:41:00.000+07:00

This is a design circuit for general theory of operation of this circuit and notes on frequency counting. This circuit is based on PIC microcontrollers for the main control unit of the circuit. This is the figure of the circuit;

The LCD is used in 4 bit mode interface so you only need 4 data lines and three control lines and it then fits into a single 8 bit port.

The crystal oscillator is simply a crystal and two capacitors connected to the PIC oscillator port at OSC1 and OSC2. The capacitors can both be fixed at the same value unless you want to tune it using a frequency reference. If you don't have an accurate reference then use fixed capacitors. The PIC micro can be any type that has a Timer 1 hardware and and has enough memory to hold the program. The LED is toggled at the end of every gate time to indicate that the processor is alive - so if there is no input signal you can tell that the software is working.

Multiple PIC16F84 Proteus Simulated Projects

2011-01-17T22:39:00.000+07:00

Proteus is a software tool that allows simulation of various circuits including microcontroller based ones. You can complete entire project with simulator including hardware and software parts. And only then you can move towards manufacturing real device. This page is dedicated only to PIC16F84 microcontroller projects where you can download ready to simulate about 31 complete project.

Projects include implementation of popular interfaces like LCD, Timers, EEPROM writing, Interrupts, I2C and 1-wire communication, motor control and so on. Each project include Proteus project file and microcontroller hex file that has to be attached to model to start simulate.

MIC 702 Mictronics Circuit

2011-01-17T22:35:00.000+07:00

This is a design circuit that can be used to convert a standard LCD interface parallel to serial interface model, use a microcontroller or a dedicated circuit such as the MIC 702 Mictronics you can download the complete data sheet and French by clicking this link. This is a circuit specially designed to transform the parallel interface and LCD display logic integrated asynchronous serial interface standard. This is the figure of the circuit;

The MIC 702 is connected directly to the display with which it is perfectly compatible. Notice the connection with only 4 data bits of high weight since the MIC 702 operates in the display mode twice 4 bits. PC side, the connection with the serial output of the PC does not involve any level converter for RS 232 TTL, this role being played by the only resistor R1 22 ohm whose presence is essential. BAUD The tab allows you to choose the operating speed of the circuit between two speeds: 9600 bps up with S1 or S2 with 2400 baud up. The leg POL allows the circuit to interpret the serial data as direct or inverted. As it is in direct RS232 link should be link this foot to ground to indicate the MIC 702 that receives data reversed. Linkage to +5 volts it would receive direct evidence as would be the case if we wanted to use this circuit with a Basic Stamp example.

Subject to use a display not backlit, the total consumption of the circuit is low enough that it can take its power directly from the output control signals to the RS 232. It is the role of diodes D2 and D3 associated with IC1, which is a regulator with low dropout voltage and low consumption. If you insist on using a backlit display, it is possible that consumption of its single backlight exceeds the possibilities of the PC's serial port. You can use an external power supply via the diode D1. A voltage of 9 volts at a flow rate of a hundred mA appropriate.

Driver an RGB LED Using Three Microcontroller Pins

2011-01-17T22:31:00.000+07:00

The RGB LED contains three LEDs encased in one shell: Red, Green and Blue (some contain an extra blue led - as blue LEDs generate less output intensity (candela) per mA). It looks like a single white led except that it has four leads - one for the common ground connection and one for each led. This is the figure of the circuit;

This project uses puls width modulation to drive each of the leds in the RGB led. By changing the duty cycle of each PWM signal you can control the average current flowing through each led creating any color you want. The limit is set by the resoelution of the PWM (set at 256 steps per channel). The project relies on persistence of vision to make it appear that the led is continuously driven (the PWM signals must be repeated quickly enough so that you do not see any flicker) at a rate greater than 50Hz (approx). Too slow and you begin to see the led flickering.

By varying the current through each led you can create almost any other color but at close range you only see the individual colors of each LED. To see the 'merged' color view it from a distance or put a diffuser over it. I used a small piece of baking paper - which is transparent enough to let the light through and opaque enough to diffuse the light from the three LEDs. In a proper design you would use a semi-transparent plastic.

PIC Serial Port

2011-01-06T19:37:00.000+07:00

This is a tutorial for microcontroller tutorial circuit (you can use it on any other PIC device even a 16F84 as it uses a software implementation of the transmit part of a USART). The circuit uses the standard MAX232 level translator chip but you could use an SP202ECP which has identical pin out (and is cheaper!) and lets you use 100nF capacitors instead of electrolytic ones. Connect the ground and transmit output to a serial port connector as shown and to a serial cable from it to the PC and it's ready to go. This is the figure of the circuit;

The code for the TX part of the USART is simplified in that it generates 10 bits of serial data with no parity bit. Since each bit takes 1/2400 seconds the total time to transmit a digit is 4.16ms. Adding a pic serial port connection to the circuit gives you scope for much more interesting projects as you can collect data from the ADC (inputs) or comparator or external infrared receiver module etc. and transmit it to a PC.

TEA6320 Multichannel Audio Selector and Volume Control Circuit

2010-12-07T06:29:00.000+07:00

This is a design circuit for high-end audio equipments are normally digitally controlled by a microprocessor (microcontroller) system. It’s necessary to have digital interface that provide control for audio signal switching, as well as programming the gain to control the signal volume. This is the figure of the circuit;

TEA6320 comes with the solution for digital control of audio source channel selector and volume control, very useful integrated circuit for modern audio or stereo application with embedded digital control. For more information on how to use this audio signal control IC chip, see the datasheet.

AT89C2051 A Serial to Parallel Converter

2010-08-14T23:11:00.000+07:00

The converter runs at 9600 baud, 89C2051 and outputs each byte received on a centronics style parallel port, together with a nominal 50 microsecond strobe. The converter buffers up the bytes received if busy is active, and is bidirectional – when the sample switch is pushed, the converter samples the parallel port and transmits the value back out the serial port. All the parameters are adjustable in the code. This is the figure for the connection circuit;

The example program should be assembled with the shareware assembler TASM. This assember is actually a very good assembler for 8051, (and other 8 bit micros) with 32 bit arithmetic, and a linux version available. TASM is produced by Squak valley software. The serial-to-parallel example program was intended to run on an AT89C2051 using the prototype board that was originally supplied as part of the evaluation kit in our programmer. But the circuit is pretty darn simple, and a competent electronics person could build one up themselves, by hand, if they need to. The code should run on any 8051 target with modification to the port locations – the equates for the pin & port locations are near the start of the code.

Note the pin functions are not shown on the circuit, as the circuit was intended to be a general purpose evaluation board, not just a serial to parallel converter.

Dual Channel 70V Voltmeter Using PIC

2010-08-02T15:36:00.000+07:00

This is a circuit for dual channel voltmeter. This circuit is based on PIC microcontroller. This is the figure of the circuit;

PIC voltmeter can measure 0-70 Volts which should be more than enough for most of electronic projects providing excellent reading accuracy and resolution. It has two input channels for measuring two voltage sources at the same time. This PIC voltmeter project uses PIC16F876 microcontroller with built-in ADC (Analog to Digital Converter) and 2x16 back lighted LCD display.

Dual Digital Voltmeter Circuit Using PICXXX

2010-07-30T12:45:00.002+07:00

This is a circuit for digital voltmeter that can use for two channel. This thermometer is a simple thermometer using DS1820 thermal probes that have a tolerance within 0.5Â°C. This is the figure of the circuit;

The three holes seen to the left of the 14pin SIP are for a potentiometer if the display you use requires a contrast control. My display did not have this function so I did not have to put a potentiometer on it. However all the connections are there, so if you need a pot for your display one just needs to be soldered in. This circuit is the display running with probe 1 sitting next to it monitoring ambient house temperature, and the second probe left in the fridge for a couple minutes.

Digital Clock Timer Circuit

2010-07-30T12:40:00.002+07:00

This is circuit for clock timer uses a PIC16F628 microcontroller to display digital time and control an external load. Timer output duration can be programmed from 1 to 59 minutes and can be manually switched on and off. This is the figure of complete circuit;

The clock has a correction feature that allows an additional second to be added every so many hours to compensate for a slightly slow running oscillator. The oscillator uses a common 32.768 KHz watch crystal and the frequency can be adjusted slightly with the 24pF capacitor on the right side of the crystal. The clock will also adjust itself for daylight savings time and add or subtract an hour on the first Sunday in April and last Sunday in October. The daylight savings feature is disabled at boot up and needs to be enabled after turn on.

Setting the time of day and other features is done with 3 momentary single pole, double throw switches and one non-momentary single pole, double throw. The switch functions are shown in the chart below with the letters A-H indicating the switch combination for each function. Some entries can be made with one momentary switch closure while others require toggling 2 switches at the same time.

Color BAR Generator Circuit Using AT90SXX

2010-07-30T12:39:00.000+07:00

This is a design circuit for color BAR generator circuit. The circuit (see Color bar Schematic.jpg)it is constituted by AT90s2313 running at 17.734475 MHz (over clocked) and one, 5 bits DA converter (R2R-ladder) with 10 resistors. This is the figure of the circuit;

Program the MCU with colour_bar_gen.hex that its included in colour_bar_gen.zip file, connect it on composite video connector (or scart adapter) of your TV, power-on the circuit and you will see on TV, 6 vertical bars, 4 in color, 1 white and 1 black.

Partlist
1 x AT90s2313
1 x 17.734475Mhz crystal
2 x 22 pF condensator
6 x 1 kOhm resistor
4 x 500 Ohm resistor