We found this circuit in a Radio Electronics issue from July 1969. The lamp remains on until C1 opens. The time is given by capacitor C1.
This circuit was found in Electronics Now magazine and can be applied to any JFET. The circuit has high...
When this alarm is off current drained is very low, only about 60 µA. The circuit can be powered...
This circuit was published in an English magazine from 1977, but it can be easily assembled since...