Snow in nativity scene Komenda 2017

We had a white Christmas in Komenda this year, even though the weather outside was sunny. Some (over 1000) leds, some AVR control with TLC5925 led controllers and we had a nice snow animation that could be changed to show stars arranged in real constellations. The clouds are made from 5mm white plexiglass and illuminated with leds from begind. I have been etching my own PCBs for almost 10 years now, but now has come a time, when China is so fast and cheap that making your own PCB just does not make sense. Read more →

LED Traffic Light

Traffic lights are all around us, and they seem simple enough but are they really? Real traffic lights can be a very complicated system because it requires sophisticated control and coordination for smooth and safe traffic. The traffic light I made is much simpler. My sister works in a kindergarten where kids needed a simple traffic light for when they are riding their bikes on the playground. The traffic light uses some cheap LEDs from China, a step-up converter and an Atmel attiny841 microcontroller to change the light from red to green at a programmed interval. Read more →

Temperature alarm for boiling milk

Anyone who has ever boiled milk on the stove knows, that it has a nasty habit of overflowing. That is why I created the temperature alarm for boiling milk to be used my mother. It continuously measures the temperature of the milk and sounds an alarm when the temperature is over the preset alarm value. Temperature alarm uses an Atmel attiny841 microcontroller, DS18B20 high temperature waterproof temperature sensor from adafruit, 2x16 HD44780 LCD and a buzzer to do its job. Read more →

Project nativity scene 2014

The nativity scene is a several years project, that I upgrade every year. This year I decided they are complex enough to describe on my website. First a few pictures of the scene, followed by the description of electronics that run the thing. Control The system is controlled by Raspberry Pi. It provides a web interface for the system. The RPi communicates with all parts of the system via an I2C bus. Read more →

Game cubes

Game cubes consist of 4 wooden blocks. Primery box with LED display, slave box connected by RF link and two secondary boxes connected only with IR signals. Pairs of boxes are connected with 5 IR lines, with which we can detect passage. The two pairs are connected with CC1101 wireless module. Each box has a 2S LiPo battery and a soft power button. On primary box is an LED display. Read more →

Lego robot

Lego robot is a cheaper alternative to a (too) expensive LEGO NXT. Two HUB-ee wheels are used for driving. It is controlled by two AVR microcontrollers - ATTiny 2313A takes care of PID control, soft-power button and USB communication over ft232, ATMega 32A is user programmable (over USB and ATTiny) and it controls everything else. On main PCB are also a 1117 5v regulator, standard hd44780 2x16 character LCD, a few buttons, a speaker and connectors for external sensors and LEDs. Read more →

USB AVR programmer

I’ve already had a programmer for Atmel’s AVR microcontrollers, but I couldn’t use it in my lab, because my laptop doesn’t have a LPT port. So I decided to make a new programmer with USB connection. I’ve found an open source programmer AVR doper, and for the basis I took a modified version from the web page. I designed a new singled sided PCB board, that I was able to make at home. Read more →

Avr lpt programmer

This programmer is a simple version of STK-200 ISP AVR programmer. I designed it using several schematics from the internet as a basis. It is not my design, I simply combined several designs and designed the pcb. The programmer can be connected to computer with a lpt cable. It’s a very simple design and uses only one IC - the 74hc244 buffer. It’s used to convert different voltage levels between computer and the programmed AVR microcontroller. Read more →