Alex over at InsideGadgets has posted an article describing how he built an ATtiny25 voltage controlled oscillator (VCO):
I recently bought a Rigol DS1052E and have been playing around with the different functionality it has. Eventually I came to the point that I’d like to see what frequency does to various components and wanted to build a voltage controller oscillator (VCO).
ATtiny25 Basic VCO, RC oscillator overclocking and testing frequency pickup - [Link]
Zak Kemble build an AVR based PWM fan controller. He writes:
So this is a bit of a continuation on my 555 timer based PWM controllers, but now using microcontrollers and MOSFETs instead of 555 ICs and transistors. I made 2 versions, one with switches for speeding up and down and the other with a potentiometer like the previous controllers. I used ATtiny25 controllers running at 31.25KHz (8MHz internal RC / 256 prescaler) with a 3.3V supply, the MOSFETs I used are STP36NF06L with 0.045Rds and 2.5Vgs max, perfect for 3.3V, the MOSFETs only generate ~180mW of heat at 2A ((0.045Rds * (2A * 2)) = 0.18W) so no heatsink needed, you can barely feel them getting warm.
AVR microcontroller based PWM fan controller - [Link]
This is a simple project to add an intelligent rapid fire button to a mouse using a microcontroller (ATTiny25). Because the project is simple both in schematics and code (both posted), it’s a great example of how to attack a real life project with a microcontroller-based solution. Although other rapidfire button mods are out there (many involving 555 chips), this one is special because one press triggers it (no need to hold it down), and it fires (left-clicks) 25 times a second for exactly 5 seconds (the time it takes to fully unload a magazine in Counter-Strike Source! The video shows all steps of the project, including programming the microcontroller, and even demonstrates practical usage of an oscilloscope! This is a fun project which may serve as inspiration for anyone just getting into microcontrollers.
Full-Auto Rapidfire Mouse Modification – [Link]
VUSBTiny AVR SPI Programmer - [Link]
These are two new prototyping boards based on ATtiny25 and ATtiny2313 Atmel microcontrollers. They include most of the standard components like a reset button, an ISP header and also they have a prototyping area to build your own circuit. Even a 3 AA cell battery holder with on/off switch is included in the kit. Check details on the link below.
Tiny Proto Boards – [Link]