Power Supplies

# 12-volt Cellar Drain Pump Schematic Circuit Diagram

This circuit lets you control a pump, to keep the level of water in a cellar below a certain threshold, for example. Power is supplied to the pump by a battery that is recharged automatically when the AC power line voltage is present.

If the water level rises, the electrodes touch the liquid and a current begins to flow. The transistor then conducts and the pump runs. The pump stops when the water level has dropped sufficiently for the electrodes to no longer be in contact with it — but not straight away, as the voltage on the transistor gate is maintained for a few seconds more by the 470 µF capacitors. This makes it possible to ensure the electrodes are completely clear of the water.

The battery is constantly tested by the comparator circuit around the TL071 IC. Its output drives the gate of the Triac in the transformer primary circuit via the optoisolator.

The transformer secondary charges the battery via the rectifier, using as little power as possible, and in this way keeps the battery at 13.2 V.

Note. Some component values may need modifying to suit operation on 115 VAC power.

Line voltage is the voltage measured between any two lines in a three-phase circuit. Phase voltage is the voltage measured across a single component in a three-phase source or load. Line current is the current through any one line between a three-phase source and load.
What is line voltage lighting? Most lighting systems run off of line voltage. It is standard in lighting, while “low voltage (12v or 24v) lighting” is used less commonly. Line voltage lighting systems typically use 120v or 277v to supply power to lighting fixtures. As long as these two assumptions hold true, then the magnitude of the line-to-line voltage is 1.732 * Vp, where Vp is the line-to-neutral voltage. If the line-to-neutral voltage is 240Vrms, then the line-to-line voltage will be 416 Vrms.
The US transmission line voltages vary and include lines with transmission voltages of 115, 138, 161, 230, 345, 500, and 765 kV (Silverstein, 2011). It also includes high-voltage direct-current transmission lines.

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