[rcheshire (Rowland)]

Hi Jo. If you want hands off regulated cooling I can show you how to setup a microprocessor - code is complete and working. If you want to build a 555 timer PWM circuit there are a number of tutorials online and all the parts are available at jaycar. Just add my circuit by connecting your pwm output to the MOSFET gate. Importantly, make sure you earth any metal such as cold finger, casing and camera framework first.

I will draw up a schematic to show my complete set up.

EDIT: SPICE based circuit. I've changed the snubber design to the gate adding a small capacitor. OSC output Red channel, A Blue channel B

EDIT: With PNP transistor switching higher gate voltage as per Chris's spice circuit - not tested.