Handy temperature controller

Jesper have built this thermostat to control electric heating element. For this he used Dallas thermal sensor DS1621 which can be read via I2C interface. He used AVR 2313 series MCU for reading sensor data and displaying it on 2 seven segment LED indicators.   Controlling relay toggle point is made easy – Just two buttons UP and DOWN. Pressing both buttons at same time allows to set hysteresis and LED refresh duty cycle. Nice thing that device has power supply converter built int that is ready to be plugged anywhere in you need to control temperature. Circuit and source code is available for download. Continue reading

Control up to 8 devices by sending SMS

Seradiris Vasilis designed SMS control circuit some time ago. It allows to control up to 8 devices through relays. He uses an old Ericsson mobile phone model which is connected to AT90S2313(now Attiny2313).   Circuit is very easy to build as it requires very few components. To activate on of 8 relays you have to send specific SMS message with device number and ON/OFF command. Source code and firmware is available for download. This handy device may be useful in many areas. As author says it may restart Servers, ADSL modems, lock the doors, switch lights or block car engine enywhere without reaching them. Continue reading

HDD mp3 player

This is stand alone mp3 player built from scratch. The Idea was to build MP3 player by using components available world wide.   MP3 player reads FAT32 file system from IDE drive up to 128Gigabytes. It can have from 4 to 32 Megabytes SIMM ram, Information is displayed on large LCD, music reaches the ear through 24-bit DAC. Firmware is open-source and is ready to be flashed. You can build it by yourself as all information is available or you can order fully assembled and tested board just for 150$. Continue reading

Flexible DDS function generator

Andreas Schwarz have built an AVR DDS generator which can generate Sine, Rectangle, saw signals from 0.5Hz to 25kHz. Frequency can be changed in 0.5Hz steps.   Signal generator also has amplitude(0-10V) regulation feature with offset(-6V to +6V) adjustments. Whole control program is written in asm language, what makes it compact and optimal. Continue reading

Electronic door unlocker

Dheera Venkatraman have decided that using keys is boring and obsolete. So he managed to build electronic door unlocker.   He used PIC16F630 microcontroller attached to PS/2 keyboard and stepper motor to slide the head. Keyboard is placed outside the door. When 5 correct numbers are pressed – the door unlocks itself. Circuit and C program is available if you want to modernize your college dorm room. Continue reading

10MHz function generator based on AD9835

Signal generator is must have tool on your working table. Buying one may be too expensive especially if you are hobbyist. So why not to build one. There are many generator chips available. One of them is Analog Devices AD9835 Direct Digital Synthesis (DDS) generator chip which is capable to generate sine wave up to 50MHz.   This signal generator is programmed to output frequencies from 1Hz up to 10Mhz with 1 Hz step resolution. Generator is controlled with three pushbuttons while information is displayed on one sliding window LED display. DDS generator is controlled via PIC16F628 microcontroller. Continue reading