This control for 12 V drills was found in a 90s Elektor. The components are current, and Q1 can be replaced by a TIP42 mounted on a heat radiator.
When the sensor of this circuit is cut for a moment, the second 555 produces a tone for a time...
This two-stage circuit has a voltage gain of 100 times, with a high input impedance. The circuit is...
A quartz crystal-controlled oscillator, capable of operating up to approximately 1 MHz, can be...