Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The transistors are from the time and the lamp can be replaced by a high-power LED in a current version.
The power transistor of this circuit can also be the TIP42 mounted on a good heat sink. The...
Using a window comparator, this circuit trips over a certain range of input voltages. Formulas for...
This timer circuit was found in a 1980s documentation. The integrated circuit is the 555, which...