This circuit is better than the previous one in that the control is isolated by a transformer. The transformer has 110 or 220 V primary and 6.3 to 12 V secondary with 200 to 500 mA current.
The simple low voltage source that can be used as a battery eliminator, shown in the figure was...
Placed inside the refrigerator, this circuit triggers an oscillator when the part is opened...
This circuit was obtained in a 1972 Corriente Alterna magazine (Uruguay), using the traditional pair of...