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Pump Controller with Liquid Level Detection Schematic Circuit Diagram

Automated Cellar Drainage Pump Control

In this circuit, precise control over a cellar drainage pump is achieved, enabling it to activate when a specific liquid level is reached and deactivate when a different predetermined level is attained. Various approaches were explored to address this challenge. Commercial pumps with float switches were deemed unsuitable due to their potential to cause ground movement beneath buildings, making them unreliable. The solution presented here offers a more dependable method. A straightforward circuit assesses the water level through a pair of appropriately spaced electrodes, ensuring accurate monitoring. When the water level reaches a preconfigured threshold, a preset quantity of water is pumped out. The author has successfully employed this circuit for a decade in a sump (a pit excavated in the cellar) to detect any groundwater presence below a designated level beneath the cellar floor.

Pump Controller with Liquid Level Detection Schematic Circuit Diagram

The circuit can be used in two situations.

  1. It can be installed in a sump to keep the groundwater level more than a set distance below the cellar floor. In this case a pumping cycle can be designed to reduce the level by say an inch (perhaps a gallon). Because of the small change in level there is no risk of causing movement of the ground below the building.
  2. When the heating or the boiler in the cellar must be emptied, for example to replace the sacrificial anode, the water can be drained into a tank and pumped from there to the garden: using this pump control circuit means that the process does not have to be closely monitored.

Simple and Reliable Pump Control Circuit

The circuit design prioritizes simplicity to ensure high reliability. Utilizing gates IC2.A and IC2.B, a bistable flip-flop is created. Its state altered by the two electrodes. Remarkably, this operation is achieved using a single, cost-effective CMOS IC. Power switching is facilitated through a relay, compatible with both 12 V and conventional 230 V / 115 V pumps. The author employs both types: a 12 V marine pump as the primary unit and, as a backup in case of failure, a conventional pump. The latter activates only when the water level surpasses a higher threshold, indicating primary pump malfunction. The 12 V system is powered by a car battery (12 V, 70 Ah), maintained through trickle-charging. The circuit diagram features two relays, each corresponding to different positions on the printed circuit board with distinct pin configurations.

However, only one of the two possibilities is utilized. The three electrodes, made from solid copper wire (1.5 mm to 2 mm cross-section) with stripped PVC insulation at the ends, serve distinct roles. EL1 functions as the ground, EL2 establishes the switch-off level, and EL3 triggers pumping at a specific level. State changes occur when a current flows between these electrodes, facilitated by water contact. Despite the minimal currents involved, electrolysis of the electrode material occurs, necessitating replacement every year or so. Notably, the exposed copper length on EL1 (the ground electrode) should be twice that of the other two electrodes.

Cautionary Measures for AC Powered Pumps

When employing an AC-powered pump (115 V or 230 V), meticulous attention must be given to galvanic isolation of the power supply, selection of an appropriate relay, and insulation of all wires carrying live voltages. Installation of circuits operating at live potential should strictly be handled by qualified professionals.


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