AVR Fuse Reset with HVSP

If you have been working with AVR, you know about the concept of fuses. They are mainly responsible for deciding the clock source and also the JTAG feature. However, if you program them wrong, your chip would no longer be programmed using an ISP. As a solution to this, there exist a circuit which can rest your fuses just by a push of a button using high voltage serial programming. This method normally applies to the chip which lacks pins to use high voltage parallel programming.

A 12V power supply, along with a transistor, a regulator and a ATtiny2313 is needed to control the circuit. 4 seven segment displays are also required for feedback and a normal push-button for control. Upon attaching power firmware reads target MCU device signature via AVR’s HVSP (High-Voltage Serial Programming) interface. It then look up the device name by matching the device signature and on a press of a button it simply write the factory default settings for the chip. This is a must have thing for all the AVR users particularly the beginners. You can hook up to the project website to learn about the schematics, working and also the code required for the project.

Sound Impulse Tracker

The project is a 2-dimentional Acoustic Impulse Marker system which is capable of detecting a sharp sound anywhere in its range and precisely marking its source vector with a servo based pointer. It has been developed by students of Cornell University. It uses an array of three microphone to detect the sharp sound and can detect the sound with a 5 degree of accuracy. Apart from the microphones a ATmega1284p microcontroller is also used which detects the acoustic delays between the microphones and calculates the sound’s source vector.

The microphone signals are passed an analog system comprising of eight stages in order to convert them to a binary signal, indicating when each of them is triggered by a sound. The analog system filters, amplifies, and processes the sounds obtained from the microphones. A good advantage of the system is that use of slow ADC of microcontroller is eliminated, since the signal is processed in the system and converted to pulses. The core use of interrupts runs the system in real time for timing data acquisition, and also gives higher precision. For those interested in the project, source code is available on the website of the university along with the algorithm and schematics.

LM35 thermometer based on Attiny26

There will be never enough of thermometers as we know. There are tons of projects with different sensors and displays. You can choose the one which suits your needs best. SO here is another simple to built thermometer by using LM35 temperature sensor. Temperature sensor gives 10mV per ºC. This means that at 25ºC the output will be 250mV. If you connect this sensor directly to 5V referenced MCU with 10-bit ADC accuracy, you get 4.9mV step or 0.49ºC resolution. In order to increase resolution there is an operation amplifier used which adds gain of 11 to sensor signal. Gain increases resolution by order of magnitude – to 0.0445ºC.


Attiny26 reads temperature value and displays it on 4-digit 7-segment LED display. LED display is common anode where each anode is driven with transistor key. Microcontroller simply scans through digits at 60fps rate to make impression that all digits are light at once. Power supply is provided by using 7805 voltage regulator which drops voltage from 9V to 5v. For longer battery life there could be switched DC/DC converter used.

AVR based thermostat for home heater

Candrian wanted to optimize home fireplace which heats water for radiators. The idea is first to heat up water inside fireplace and then open valve to let hot water to radiators. Original thermostat suppose to work that way, but in reality thermostat shuts the valve once cool return water cycles around. In order to prevent opening and closing valve frequently he designed his own thermostat which would allow to set time span when valve stays open even if water temperature drops. Some may not agree that this idea is good, because first priority would be to keep fireplace water temperature at working level to get optimal burn and prolong life-cycle due to condensation and corrosion. Anyway, everyone have their own needs and lets focus more on electronic part of thermostat,


Schematic of thermostat is pretty simple. It is built around Atmega198 microcontroller which controls couple mechanical relays. They drive electrical valves. Temperature is captured by using LM35 sensor which is attached to microcontrollers analog input. Standard LCD and rotary encoder gives simple and intuitive user interface where time delays and temperature thresholds may be selected. Some care is dedicated to enclosure. PCB is hidden inside plastic box but front panel is really nicely done by using color laser printed transparent with all user information. Project files are open and can be found on GitHub.