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2 × Dual = 1 × Quad Schematic Circuit Diagram


This is a sort of sequel to the article ‘2 × single = 1 × dual’. In this case, two dual opamps are combined to make one new quad opamp. This allows many possible variations, and again it allows two completely different types of dual-opamps to be used. It is very easy to replace a[…]

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Pump Protector Schematic Circuit Diagram

This circuit has been developed to limit the running time of a sump pump since the pump can be damaged if it runs too long when the sump is dry. The circuit detects how long the pump has been switched on, and if this time exceeds a previously set limit (30 minutes in this case),[…]

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Fuse Failure Indicator Schematic Circuit Diagram

This circuit indicates when a device is functioning or when its fuse has blown. It is a development of the Mains/Fuse Failure Indicator published in Elektor Electronics July/August 1995. It is smaller and cheaper than the previous design, even though it works on any mains supply voltage. A single bi-color LED (D2) with separate anode[…]

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Alternating Blinker Schematic Circuit Diagram

The circuit represents a general-purpose astable multivibrator that alternatively energizes two heavy loads via a relay (in this case, the loads are 12-V incandescent lamps). In contrast to an ‘analogue’ flip-flop, here it is not necessary to use power transistors with heatsinks. This alternating blinker can thus be built at a lower cost, more easily[…]

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