This “people detector” with pyroelectric sensor was found in the April 1991 issue of Radio Electronics magazine. The circuit is based on an LM324 and a sensor from that time.
This simulation shows how to use an operational amplifier as a voltage comparator. The sample uses the...
This circuit automatically activates the relay when the phone is answered, closing the record...
This car alarm was found in an American '80s documentation. The circuit automatically activates...