This circuit that we found in a 1990 documentation uses an LED as a sensor. The operational amplifier is equivalent to the 741 and the trigger adjustment is made in the potentiometer.
Suggested by Motorola documentation from the 1980s, this circuit makes use of MOSFETs of the time....
In the figure we have a small general-purpose amplifier with the LM386 integrated circuit and...
This circuit allows you to use a digital multimeter as a thermometer. The sensor is mounted in a...