Freezing sensor (CB21288E)

This circuit was found in a Popular Electronics from the 90's. The components are common. The potentiometer adjusts the circuit's trigger point.

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Digital Thermometer (CB24564E)
This circuit was found in the July 1978 issue of Radio Electronics magazine. The circuit uses a...
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The very high-input impedance of the CMOS gate allows this kind of device to be used as a...
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This circuit was found in an American publication called Ham Radio. The circuit uses still current...