Power-on delay

The power supply for this analogue circuit, which affords delays of up to 330 seconds, is taken directly from the mains. The direct voltage at the output of the bridge rectifier is held at 22 V by zenzer diode D5. Resistor R6, which enables C1 to discharge rapidly as soon as the mains is switched off, must[…]

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Overload Indicator

The overload indicator consists of a window comparator that measures the magnitude of an a.f signal. Two of the opamps contained in a TL072 is supplied with a reference voltage by potential divider R1-R2-R3-P1. The outputs of the opamps drive T1 via diodes D1 and D2 (that function as the half-waved rectifier), which in turn actuates D3.[…]

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