I decided to make a cool gift for my wife anniversary so I designed a PCB jewel. She loves butterflies so I tried to make her one.
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It uses a standard 3V CR1220 battery in order to blink 12 LEDs. The micro-controller is an ATTiny85-20MU that drives directly the LED’s. The first iteration used 3 AG1 batteries but I switched to the more covenant CR1220.
I need a voltage over 2.2V in order to light the LED’s but I don’t power on all LED’s at once, so I don’t need a driver for them. I can easily get 20mA from the digital pins of the ATTiny85.
Check the working video:
After looking through the projects of Gerben I learned that I can use the tristate input of the uC to mask the unwanted LEDs. Basically it divides the 3.3V voltage in two sub 2.2V that I need to light a LED. It was too much code to use the pinMode function of the Arduino so I put the needed DDRB register values in an array. Now I can do some nice rotating and bouncing effects - wrote some helper functions for them.
So I've updated the Github project files accordingly.
Thanks Gerben!
Very pretty.
Interesting way of placing the resistors in your schematic. I always have both the anodes and cathodes go through a resistor (and use halve the calculated resistor value).
Is it running stable without any capacitors?
strofo
Chris Hamilton
DIY GUY Chris
Rebelj12a
youkito1991
Thanks! Yes it's been running for several days now. I don't think I need the caps because I don't have any communication going on. It's just internal processing and I don't care about timing too much.