ATtiny85 Flasher for Mother’s Day

Images

In action

The code on Github

Link to my blog

See this project also on my blog.

About this project

To help my kids celebrate Mother’s Day this year, I wanted to do something a little different. Instead of just a present, I wanted the kids to be able to give her something a bit more one-of-a-kind.

I’d bought an ATtiny85 to play with some of the ATtiny Arduino support (or failing that, work out how to use avr-gcc directly). I also had a bunch of very bright LEDs and some cheapy cell batteries sitting around doing nothing.

First, I took one of the spiffy cases from when we bought some kids’ earrings recently, and drilled holes to shape out a heart. (Image 1)

Poking the LEDs through, I kept the cathodes all in the centre, so I could bend them all inwards and haphazardly solder them all together. I also used wire to bridge each LED with its opposite, so I’m driving a ring of ten LEDs with five pins. (Image 2)

Finally, I soldered the pre-programmed ATtiny85 to the LED anodes, using a small piece of electrical tape to ensure it isn’t going to inadvertently touch any of the mess below it. The cells (wrapped in electrical tape) go directly to the power & ground pins on the chip, and a resistor feeds the ground to the LED cathodes. (Image 3)

Brilliant.

Except I made an off-by-one error in my sketch that I didn’t notice during testing (c % 6, instead of c % 5). Thankfully, I was able to fairly easily solder on wires to a 6-pin ISP header and flash a new program.

See the final result in the video!

ATtiny85 Arduino Support