Temperature Switch...

Hi I am new to this forum

I have search google for about two days now, and searched this forum also.

I am basically looking for circuit diagram to build a control switch / relay for 12V DC power:

I effectively only want to power the device if the device is between min and max set limit (degrees celcius).

I have seen how they do the incubators regarding temp control ect. but this is not really what I am looking for.

Attached a sample picture of similar device:


I know this device costs $20, but the parts most likely $1.5

My idee is for usage with:

Two approches.

1) Use a temperature sensor, like a LM95071. Read that with a microcontroller. Set the upper and lower switch points in code. Connect to the lload with a relay.

2) Measure the temperature as an analog voltage. That can be from a thermistor or an analog temperature sensor. Use two comparators to compare the voltage with two different set points. Connect the outputs of the comparators with diodes so that either can turn off the output. Again, a relay is needed.

You can also use a temperature sensor and a window comparator (LM393):
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From the page:
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