This is a list of various electronics projects I've been involved with. They vary in complexity, but most are pretty simple. I've been having fun with Atmel AVR microprocessors recently and pondering all sorts of random projects.
This simply little reminder sets off a buzzer and flashes a light after 24 hours. The idea is to remind my grandmother to take her daily medication. All she has to do is press the button when she takes her pills, and if she forgets it will start chirping.
The design is simple, based on an Atmel AVR ATTiny22 8-pin micro I got from DonTronics. For reasonably accurate timing, it uses a simple RC oscilator (using three IO pins on the processor being driven as a pair of inverters - now thats programable logic!). The other two I/O pins drive the LED and the buzzer (in this case, a little 1.5Volt chirper I got for christmas which comes from the Australian Geographic shop).
The circuit is built on strip board and housed in a little box, driven via a 9V DC power pack from Oatley Electronics.
The CPU can be in-circuit programmed via the SPI interface, so the design is very flexible. The code is here.