I finally got the circuit in from Thailand yesterday. About three weeks to get stuff from them. A person just needs to have patience which is something I have been saying for three weeks! Anyway, to reiterate what this is all about..
The circuit is very similar to the Ron Francis offering Mike mentioned earlier which uses a thermal resistor to detect temperature as opposed to finding a place in the water jacket to put a sensor. As it comes from Thailand, the thermistor could have a larger lug to bolt it down to the Thermostat Housing, which is my idea for where it could go. It is useable as is, but the lug housing could be larger.
I talked with Alain Stas, an engineer from Brussels, Belgium who works for Vishay Electronics and he spent enough time with me to understand Thermistors. The ones they suggest are here:
http://www.vishay.com/docs/29118/ntcle203.pdfThese radial lead devices can be housed inside of a tin lug housing and then high temp silcon to hold them down to the lug housing. Then, the two leads are connected to a box inside the cab. The Water OverTemp portion of the circuit is basically just this small board that controls a relay that energizes when the lug temperature reaches a certain point. Energizing the relay will control a Piezo Buzzer and an LED to inform the driver of the Overheat condition.
The nice part about this little circuit is, it also can control an electric fan if you so choose. The temperature is adjustable from 120F to 240F via a small pot on the circuit board. The Thermistor is OEM standard equipment on some new vehicles so the technology is widely accepted as well. At this point I have everything I need to make the first prototype for Oil Pressure/Water Temp and Charging. If anyone has any ideas on what else a warning circuit should cover, let me know.
