CO2, temperature and humidity logger on Atmega328

There are many indoor temperature and humidity meters and loggers already built. But there is always a space to do something new and useful in this area. Davide decided that measuring temperature and humidity isn’t enough for complete climate meter, so he added CO2 meter.

His project consist of NDIR infrared MZ-Z14 CO2 meter, DHT22 temperature and humidity sensor. Atmega328 reads sensor data, displays it on LCD screen and also logs to feed. Connection to internet is established with network board based on EC28J60. Where most of project code he brought from his previous projects.

Automatic flashing of AVRs with CNC

Imagine that you need to flash hundreds of microcontrolelr chips. One way is to do this one by one, but this can be exhausting task and plus inefficient. If you use standard ISP adapter your boards has to be with ISP headers soldered on- this also rises overall cost. So how to do this faster and efficient. If you have a CNC platform lying around, it may be fairly easy.

Pleasantsoftware shared his rig where he managed to set up an automated solution of AVR flashing. He needed to flash several hundred of AVRs so building this rig seemed quite reasonable. On his boards he used special programming connector which sits on SMD chip directly to ISP and power pins. Assembled PCBs come in panels of 40. All he had to do is to build a programming connector holder which was 3D printed. He used his G-Code sender app to send position commands to CNC. Hex code and fuses are hard coded in to source since it is same for all batch. Single panel of 40 AVRs are flashed in 10-12 minutes. I doubt that this can be done manually and still be enthusiastic about this.

Color shifting LED lamps to change your mood

Mood lamps may be a great design element in various places. Building one is fairly easy especially electronics part. Batkin build one lamp from scratch where he uses 3W RGB LED with star heat-sink. It gives more than enough light to be visible. Lamp is driven by Attiny85 microcontroller which drives LEDs with ULN2003AN Darlington transistor array.


He also built a custom enclosure and acrylic tube to diffuse light. Build several of those and you have a party.

Attiny45 based reflow oven controller

If you want to solder SMT components professionally, you should use reflow oven. OF course, no one suggests using specialized oven which is really pricy and used in PCB houses where tons of boards are soldered. With a little bit of effort you can build pretty good oven that can solder small PCB batches. Zaggo simply purchased a toaster oven for about 40€. He also wanted to keep warranty, so he started building external controller that doesn’t mess with internals.


Oven controller is based on Attiny45 microcontroller that comes with 4K of flash. He was able to squeeze in full PID algorithm along with minimal user interface. Temperature is measured by using 100k thermistor and oven is controlled with simple mechanical relay via transistor. Single push button is used to start program. Its performance is indicated with single LED. The circuit turned out to be very compact and easy to build with through hole components. Practically any simple oven can be turned in to reflow station without loosing warranty. Source code and other files can be downloaded from GitHub.