Simple Water operated relay

Advertise in delabs

This was done in my early days, i have upgraded it, it ought to work, reduce the number of transistors to make it less sensitive, also a lower value in place of 10M will reduce its sensitivity, use clamping diodes to protect.

More such ideas at – Hobby Hound – Hobby, DIY, Do it Yourself Projects.

BD139 is used to drive the relay as it has good Ic. So you can even use a low ohm relay. If a Relay resistance is high its quality is higher, its power consumption is less and it needs thinner wire SWG-AWG. T2 and T3 form a darlington pair which drives T1. LED1 shows that the water level has reached the top of tank and also that the Relay is energised. D1 a freewheeling diode. R3 10M ensures that the high gain input does not float, yet the low leakage current thru the water is not drawn away by the 10M. R2 limits base current in case water is saline.

Simple Water operated relay

The Source file in EAGLE format is here del00006.zip

More delabs Schematic Diagrams

  • Thermocouple Amplifier StandardThermocouple Amplifier Standard
    Thermocouple is the most common sensor in Industrial Temperature Measurement. The Signal Conditioning involves Cold Junction Compensation and High Gain DC Amplification. The output of [...]
  • 2N2646 based Voltage controlled SCR Pulser2N2646 based Voltage controlled SCR Pulser
    A Center tap 50Hz Step Down Transformer with two diodes is used to get a train of Positive Sine Pulses at 100Hz which is applied [...]
  • Telephone status indicator with LEDTelephone status indicator with LED
    This will monitor telephone status without loading the telephone line, this way if you have two phones in parallel you will know if one of [...]
  • Dual Polarity Analog Output Op-AmpsDual Polarity Analog Output Op-Amps
    When you have to buffer and invert the polarity of mV input levels. This is the circuit you can use, as OP07 has uV offset. [...]
  • Resistance Measurement Analog LED MeterResistance Measurement Analog LED Meter
    This is a LED Analog Meter, This can be used as a Resistance Meter and Low Impedance Voltmeter for Battery Levels. To measure battery voltage, [...]
  • Ammeter and Precision RectifierAmmeter and Precision Rectifier
    Studying current measurement is a prerequisite for many of the measuring techniques. The current parameter mainly specifies the power consumption in a circuit, given the [...]
  • Digital gain control of Opamp.Digital gain control of Opamp.
    The gain of U1 can be controlled by a digital binary 1248 nibble at ABC. The gain at digital 000 is unity or 1 and [...]
  • Display On Timer with 555Display On Timer with 555
    This is related to the earlier post. This was done to save battery power. The output of some equipment may be in the form of [...]
About delabs 152 Articles
Product Design - Industrial Automation and Instrumentation. -

Be the first to comment

Leave a Reply