This circuit was obtained in an old Elektor and can be adapted to use white power LEDs. The transistor must be equipped with a heat sink. The circuit has a battery charger.
This control circuit was obtained in a 1971 technical documentation. The operational amplifier can be the...
This simple timer, which activates an LED indicator, but which can be modified to activate a...
This temperature compensated circuit was found in a 1980s American documentation. The power supply...