This project is an attempt to approve upon a previous board I designed to control the radiator fan in a car a friend is restoring (see section in Other, eventually). In additon to providing a more accurate control of the fan, the ability to control a gauge that will replace the broken gauge in the exisiting dash cluster is also added.

The gauge used is a cheap 0-5v gauge from spark fun. The gauge its self is small enough to fit in the cars gauge cluster with little modification, and the face plate can be easily changed to show a temperature scale that the circuit is programmed for.

The heart of the system is the PIC 12F675. This is a neat little microcontroller which has a 10bit A/D on board, with enough pins to interface to a serial DAC that is used to control the gauge and to control a relay for the fan. While this chip lacks a lot of power, its is perfect for this role.

While it might seem odd using a microcontroller for such a simple odd, this is actually a much simpler board then what I had previously designed which as all automatic and only controlled the fan.

Currently I'm working on the board layout for this. Before I can finish that, I need to double check the current draw on the fan to make sure that relay used has a high enough current rating.