Design assistance with Temp. controller

[J_M]

Hello everyone! I am attempting to build a thermal controller with the following criteria:

1) Able to match target temp to ambient temp.
2) High power - ~100 watts or greater 12 or 24vDC (12v preferred).
3) Solid state (non-mechanical relay).

The application is cooling electronic components with T.E.C.

note: suggestions to modify existing 'off the self' kits to meet the above might simplify this for me.

My expertise in design is practically nil but I have experience with semiconductors. Any assistance would be greatly appreciated.

Thanks for reading.


Edit:

Would it be possible/practical to replace the trimmer with a thermistor in the following Vellman kit to cause the thermostat to maintain ambient at the sensor?

 

[chuckey]

Why not just use the "sensor NTC 10K0" terminals for your thermistor. The trimmer is used to set the operating range. As its set up, at your wanted temperature your thermistor must be in the range of (120/176) X 10K ohms and (220/56) X 10 K ohms. (6K-> 40K). If your thermistor's resistance at your operating temperature falls outside of this range let us know , we will give your compensating values of R5, R6, R4.
As for driving a large DC current at 12/24V, the relay can be left in but used as a resistor. A Darlington type power transistor can then be wired to The circuit board to actual switch your 5A supply.
I would have a go at the first step, first to make sure that your thermistor can be set in range and its "polarity", i.e. if the temperature of it is too low, is the relay on or off?.
Frank
Frank

 

[J_M]

Chuckey,

Thank you for replying. Just to be clear, what I am hoping to achieve is a circuit that will be closed when the sensor is above ambient temperature and open at or below ambient temperature ( I would expect ambient to range from ~65 - 80 degrees F) - I need the controller to compensate for changes in ambient to avoid any chance of condensation. Will it be practical to use the kit in my first post or would I be better served going in another direction?.

 

[J_M]

Update:

I have located a controller that is virtually ideal for my application.

Output range: 4 - 12vDC
10 watts max:sad: - I need to control the voltage to a 226 watt T.E.C.

Would someone please instruct me on choosing a transistor and how to build a 'daughter board' to increase the available current?