This circuit indicates when the voltage of a 12 V battery is low. With changes, for example, the zener, the circuit can be used to monitor other voltages.
This circuit is from a Linear Technology integrated circuit manual from the 1990s. The circuit...
The IC used in this project is not common these days, but if you have one you can build a high...
With this circuit, it is possible to excite a white LED or another type of high brightness with...