AT89C51RE2 based development board

AT89C51RE2 based development board

Jesus Echavarriahave built pretty handy development board based on Atmel AT89C51RE2 microcontroller. This is a small board that packs few features that enable fast prototyping. First of all it is powered at 3.3V using low dropout regulator. So it can be powered from 5V USB port. Microcontroller is 8051 architecture with 128KB of Flash and 8KB of RAM. Development board carries TUSB3410 chip from Texas Instruments, which converts MCU serial interface to USB. It can be used on PC as virtual COM. There are also couple switches, buttons, LEDs and buzzer. They can speed up prototyping significantly. The list continues with External I2C bus which his isolated using ADUM1250. It also works as voltage level convertor from 3 to 5V. The nthere is a standard 1-wire temperature sensor DS18B20. To internal I2C interface there are RTC, EEPROM and ADC connected. As you can see it is quite powerful collection to do some serious projects. Continue reading

Temperature sensor with LCD

This is an 8051 based project with AT89C51AC2 microcontroller that reads temperature sensor LM35 value and displays it on standard LCD screen. As LM35 scale factor is 10mV per 1ºC there is a fixed gain amplifier used that pulls the voltage to 2.5V (VREF=2.5V) limit for 100ºC instead of 1V. This gives better accuracy of readings. Code is written in C and ASM languages – this gives quite some clue of working internals. Project is nicely documented and put in to Google doc. Continue reading

Digital Thermometer powered by AT89S52 microcontroller

8051 microcontrollers are mature microcontrollers that have been used for quite long time and they still are popular in many applications. So here it is a standard temperature sensor project which has some educational aspects. As you know AT89S52 microcontroller has no ADC interface so there is an external ADC used which is built from scratch. In few words it is a counting type ADC which is based on DAC where digital to analog conversion is continued until match is found with comparator. So building such device is more fun. In this project a NTC type thermal resistor is used which value is red by custom ADC and value is displayed on 3 digit 7 segment LED indicator which is also driven dynamically. So again this is simple interesting and well explained project to move on. Continue reading

Contact-less tachometer counts up to 99kRPM

There may be some situations when it is hard to use a tachometer only because it is impossible to read revolutions per minute mechanically. The only way is to read RPM without touching rotating shaft.   This great design was constructed by Ibrahim Kamal who used an IR signal to transmit and receive it reflected from reflective stripe fixed to rotating shaft. Device is controlled by AT89S52 microcontroller which counts reflected pulses and displays value on LCD. RPM counting algorithm uses last three times between pulses and this way constantly gives instant RPM value. RPM meter consists of two parts: microcontroller board and IR proximity sensor connected to microcontroller board via simple 4 wire cable. Project files are available for download in a single zip. Continue reading