This simple charger was found in a 1980s documentation. The transistor may be the TIP42 with a heat sink. R1 adjusts the load current. The transformer has 1 A of secondary current.
This circuit locks when the sensors are opened. The relay can be 6 or 12 V depending on the power...
Found on an 80's Elektor, this circuit uses common components, being the diode a general purpose...
This circuit can either directly supply a piezoelectric transducer (BZ) or a stage with a...