Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

Very simple low power fireflies based on Attiny micros

attiny led based fireflies

Fireflies are interesting creatures that glow in dark due to biochemical reactions. They come in special season time and stay for a really short time period (probably while mating). Anyway if you enjoy the show of fireflies and would like to make them stay longer then you should consider making artificial swarm. Karl decided to experiment with simple low power solution. The circuit is based on Attiny13a microcontroller which has 8 legs. It is powered from CR2032 coin-cell battery. Chip carries single green LED and 1MOhm resistor. This resistor is connected parallel to LED. This resistor is necessary because LED also is used as light sensor. Fireflies most of the times are in sleep mode and occasionally checks ambient light. If it is dark enough, they stat flashing. I would expect some sort of swarm behavior when fireflies detect near by pattern and so adjust flashing that would create multiple flashing patterns. Anyway this is great weekend project to do with kids. Continue reading

Adding MIDI output to the vintage analog organ

Michael likes his vintage organ KORG CX-3. It sounds good and keyboard feels right to play. But in early 70s there were no MIDI. But today almost any electronic music instrument comes with MIDI or other output interface. He decided to add a MIDI to CX-3 organ. For getting data you normally need to detect each key pressed. Luckily Michael found a great source on Internet with schematics where couple ICs are connected to keys that generate serial data stream. This gave him an access to keys by using couple of wires. Next step is a midi interface. Attiny2313 seemed to be enough for generating MIDI. A home made PCB looks really great next to vintage organ schematic and it does job well. To see how to generate MIDI on AVR check out this resource on AVRfreaks. Continue reading

Brewer controller with Android access

Brewer controller with Android access

In order to make great beer most important part is brewing at right temperate. Why not to leave this task to controller which takes care of timing and temperature regulation. Kalle decided not only to make the process automatic, but also added wireless access to it. The controller itself is based on Atmega88 microcontroller which takes care of controlling valve using H-bridge. LM35 temperature sensor is used for feedback reading. Wireless access is done by using nRF24L01 2.4GHz module. Receiver is connected to PC serial port. Process can be viewed and controlled from PC using terminal or COM logger, but in these days many things tend to be moved to smart devices with Android. A special Android app allows seeing and setting temperature values in nice graphical interface. Continue reading

Automatic shutdown of any circuit

Any modern battery powered device has a automatic power off function. It is easy to forget switch device off. And so it slowly drains the batteries leaving you with blank screen next time you decide to use it. If you are designing a battery driven project, think about adding auto power off. If this is a microcontroller based circuit it is easy to do by adding a transistor switch. But if you are looking for more universal approach, then check out following small circuit. It is based on Attiny85 which takes control of power lines through couple of transistors (NPN and PNP). Once device is powered timer starts counting which after countdown cuts the power. Prototype is based on pin through components, but with SMT parts it could be squeezes in to really small piece. Transistors could also be replaced with MOSFETS for better efficiency. Continue reading

Crazy ohmmeter displays resistance color code

When we take unknown resistor we usually take a multimeter to get numerical value. Many not even bother to decode color bands using tables – it takes time and in some cases it may be hard to detect colors right. Anyway each one of you have your own methods of detecting part values. If you like playing with color codes then check out this dun ohmmeter which displays a color code instead of numerical value. If not practical, it may be a great addition to your workbench. The ohmmeter uses Atmega168 to perform measurement. The method lies behind measuring capacitor discharge time. Once value is determined, RGB LEDs are lit behind acrylic bands. Luckily there is a small 7 segment display module on one band which displays so wanted numerical value. So in the end this can be useful tool. Continue reading

Stopwatch with 8 digits LED display

Making watch or stopwatch isn’t a rocket science. All you need is to set up microcontroller timer and capture interrupts to update time. rwb has made pretty simple stopwatch which uses 8 digit seven segment LED display. Display is driven using MAX719 chip that connects to microcontroller via SPI interface. He made great work on documenting project. He takes through all steps of process starting with hardware. He speaks on how to connect display and even how to expand to 16 digits and more using cascading of driver chips. Then he goes in to details on how to set up Atmega328P timer, generate interrupt and update time. Here you will find good info on running external interrupts that are used to detect button click. So even if you don’t intend building stopwatch it is worth looking for good tutorial material with great illustrations. Continue reading