Skip to main content

Reservoir Pump Controller


This circuit operates an automotive windscreen washer pump to fill a 20-litre drum from a 205-litre water reservoir. The drum is suspended above a drip line, which irrigates a vegetable garden. Two stainless steel probes mounted in the drum act as sensors for the system. One probe is positioned at the high water mark, the other at about half-full. The pump power is switched by a 12V automotive relay (RLY1). Two op amps (IC1a & IC1b) connected as voltage comparators form the basis of the circuit. Initially, assume a falling water level with the pump switched off. When the water level exposes the lower probe, the non-inverting input (pin 5) of IC1b rises to about 7.4V. With trimpot VR2 correctly adjusted, this will be higher than the voltage on pin 6.

The output (pin 7) therefore swings high, biasing Q1 into conduction. This in turn causes Q4 to conduct, switching on the relay and starting the pump. In addition, when Q4 switches on it supplies base current to Q3 via a 6.8kO resistor. Initially, this current flows through the 47µF capacitor, but once its base-emitter voltage reaches about 0.6V, Q3 conducts. This action latches Q4 in the "on" state, as its base current can flow to ground via Q3 when Q1 stops conducting – which will occur when the rising water level reaches the low probe. When the water level reaches the high probe, the voltage on the non-inverting input (pin 2) of IC1a decreases markedly due to the conductivity of the water.
Reservoir Pump Controller Circuit Diagram

If trimpot VR1 is correctly adjusted, the output (pin 1) swings high, switching on Q2. This discharges the 47µF capacitor and robs Q3 of its base current, switching this transistor off. This in turn switches off Q4 and the relay. The zener diodes and 1kO series resistors at the probe inputs protect the op amp’s high impedance inputs from the effects of static discharge. The 47µF capacitor in parallel with the base-emitter junction of Q1 prevents the latching function from being activated when power is applied to the circuit. The author’s setup is powered from an old car battery charged from a 12V solar panel.
Author: Peter Howarth
Copyright: Silicon Chip Electronics

Labels:

Comments

Post a Comment

Popular posts from this blog

Electronic Extended Play Circuit Diagram

This is a Electronic Extended Play Circuit Diagram. A single op amp-one of four contained in the popular LM324-is operating in a variable pulse width, free-running square wave oscillator circuit, with its timed output driving two transistors that control the on/ off cycle of the tape-drive motor. The Oscillator` s positive feedback path holds the secret to the successful operation of the variable on/ off timing signal.   Electronic Extended Play Circuit Diagram The two diodes and pulse width potentiometer R8 allows the setting of the on and off time, without affecting the oscillator`s operating frequency. One diode allows only the discharge current to flow through it and the section of R8 that it`s connected to. The other diode, and its portion of R8, sets the charge time for the timing capacitor, C3. Since the recorder`s speed is controlled by the precise off/on timing of the oscillator, a simple voltage-regulator circuit (Ql, R3, and D4) is included.  Connecting the spe...
Post a Comment
Read more

Power Amplifier with voltage regulator 4 × 50 Watt TDA8588

Power Amplifier with voltage regulator 4 × 50 Watt TDA8588    The TDA8588 is a multiple voltage regulator combined with four independent audio power amplifiers configured in bridge tied load with diagnostic capability. The output voltages of all regulators except regulators 2 and 3 can be controlled via the I2C-bus. However, regulator 3 can be set to 0 V via the I2C-bus. The output voltage of regulator 2 (microcontroller supply) and the maximum output voltage of regulator 3 (mechanical digital and microcontroller supplies) can both be either 5 V or 3.3 V depending on the type number. The maximum output voltages of both regulators are fixed to avoid any risk of damaging the microcontroller that may occur during a disturbance of the I 2C-bus. The amplifier diagnostic functions give information about output offset, load, or short-circuit. Diagnostic functions are controlled via the I2C-bus. The TDA8588 is protected against short-circuit, over-temperature, open ground and open VP ...
Post a Comment
Read more

Digital Voltmeter Circuit with ICL7107

Description. The circuit given here is of a very useful and accurate digital voltmeter with LED display using the ICL7107 from Intersil. The ICL7107 is a high performance, low power, 3.5 digit analog to digital converter. The IC includes internal circuitry for seven segment decoders, display drivers, reference voltage source and a clock. The power dissipation is less than 10mW and the display stability is very high. The working of this electronic circuit is very simple. The voltage to be measured is converted into a digital equivalent by the ADC inside the IC and then this digital equivalent is decoded to the seven segment format and then displayed. The ADC used in ICL7107 is dual slope type ADC. The process taking place inside our ADC can be stated as follows. For a fixed period of time the voltage to be measured is integrated to obtain a ramp at the output of the integrator. Then a known reference voltage of opposite polarity is applied to the input of the integrator and allowed to r...
Post a Comment
Read more