Tea Gallows

https://www.youtube.com/watch?v=_GosO-r_sI8

Update: If you like to build the Tea Gallows with a professional PCB instead of a breadboard look here:

https://www.thingiverse.com/thing:2749364

The „Tea-Gallows“ is a nice little gadget working with an Atmel Atmega328 on an application board. Pushing the button increases the brewing time indicated from LEDs for one minute until a maximum of eight minutes. A long push starts the countdown. The alarm starts ten seconds before the end with short peeps until finally the tea bag will be pulled out through a weight falling down along a little pole made of stainless steel. The release process is caused by a tiny servo pulling back a bolt holding the weight in place. I decided to power it with 4,5V, supplied by three AAA-batteries. Therefore there’s no external crystal; besides the µC goes into power-down-mode when the µC is not active for 10 seconds, consuming only about 25µA.

Programming the µCs needs a ISP-programmer, because you have to set some fuses of the µC, which you can’t do with serial programming (I’m no expert, but I think that’s right). I recommend the following little application board:

http://shop.anvilex.de/index.php?route=product/product&path=115_222&product_id=2641

You can use a Arduino NanoProMini too, but regarding battery life you have to desolder a power LED and a voltage regulator. ISP-programming means a little bit more effort, because the Arduinos are in first line made for FTDI-programming.

Please be sure to use LEDs with integrated protective resistor, never connect a normal LED directly to a µC. Don't forget the protective resistor for the photomos relay too, it will be damaged without.