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 was found in an English magazine from August 1982, but it can be easily assembled with...
July 2017 - Microchip's new MCP39F511 demonstration and development boards, which consist of...
This one-transistor alarm can be used with much more sensors than the two shown by the figure....