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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SCR Delay Circuit (CB14713E)
With the capacitor used, this circuit provides delays of 40 to 60 seconds. Larger capacitors can...
Stepper Motor Control (CB21247E)
Found in an Electronic Design from the 90's, this circuit generates signals for stepper motor...
Tunnel Diode Oscillaor (CB4602E)
The circuit shown in the figure can generate signals up to 1.6 GHz. Coil L1 and capacitor C2 are...