temp sensor cooling system

[mphotis]

Hi there,

ive been assigned a very interesting project. I need to design a cooling system for a go-cart using CO2 cooling.

Im thinking of using an LM355 temp sensor to sense the temperature on the motor. when the temperature on the motor reaches a certain threshold level, i want a transistor (or something else) to switch on causing a solenoid on the CO2 bottle to open the valve releasing CO2 through nozzles into the engine.

Im quite useless as regards my circuit design. Does anyone have any ideas on how i could maybe connect the transistor to the output of the sensor and calibrate it to switch at a threshold temperature.

thanks alot
Mike ???

[ante]

Mphotis,

Have this sort of cooling been tested before? It sounds like a fast way to kill an engine!

Ante ::)

[mphotis]

The tests have been done in the lab. No harm comes to the motor, as long as the CO2 is sent down the right airgap. Besides, the CO2 is only supposed to be turned on once the motor gets too hot...so it doesnt freeze.....once the temp is back down to a safe temperature the CO2 switches off....so any ideas??

[ante]

Mphotis,

I suppose it must be a controlled burst and at a specific temperature? There are some factors to consider, temperature, pressure, time and volume. Do you have any documentation on the tests?

Ante ::)

[darrins]

Have you considered using the LM34? It's already calibrated in degrees Fahrenheit. I'm from the states, so I prefer the English units. ;)

It seems you could just use a simple comparator circuit.

The following document has a lot of specs and some good application examples. See their example of the "Simple Fan Controller". I think it is similar to your needs.

http://www.national.com/appinfo/tempsensors/files/temphb.pdf

If you have to put the sensor in a hostile environment, you may want to put the IC inside a metal tube. I've noticed that the plastic package fits neatly into a piece of copper tubing (the kind you hook up to your refrigerator's ice maker). Copper is quite malleable, so you can just pinch the end with a pair of pliers to seal it. Copper is also an excellent thermal conductor, so you should get a nice response time.

Good luck.

Darrin

[darrins]

I just remembered that these temperature IC's have an upper range of about 300 deg Fahrenheit (about 150 deg C). This is probably good enough for your project, but just another thing to keep in mind. I think a typical automobile will overheat at about 240 deg F, but that's a water cooled engine. Is it possible that go-cart temperatures (I'm presuming air-cooled) will be much hotter?

Good luck with your project. I'm a mechanical guy myself, so I'll be interested in your results.

Darrin

[steven]

:)

[MP]

darrins,
LM35 for degrees C.

MP

[GPG]

Presuming you are monitoring the cylinder head temp, you will need a thermocouple or RTD for these temperatures.
Sparkplug mtg one here
http://www.performancetrends.com/DatamiteTemperaturePictures.htm

[hotwaterwizard]

Here is a Low-Tech way that I would do it.