555 Timer Based Water Level Controller

June 23, 2013 — 7 Comments

Water-DropletWater pump controller senses the level of water in a tank and drives the water pump. The circuit described here is built around timer IC1 (555). When the water level of tank goes below the low level marked by ‘L’ the voltage at pin 2 of IC1 becomes low. As a result, internal SR-flip-flop of IC1 resets and its output goes high. This high output pin 3 of IC1 drives relay driver transistor T1 (BC547) and energies relay RL1. Water pump gets mains power supply through n/o contacts of the relay and is powered on. It starts filling water in the tank.

When the water level goes high and reaches the high level marked by ‘H’, the voltage at pin 6 of IC1 also goes high. As a result, internal SR-flip-flop of IC1 sets and its output goes low. This low output pin 3 of IC1 cuts off relay driver transistor T1 and de-energises relay RL1. Water pump disconnects from the mains power supply through n/c contacts of relay and goes off. This stops the water flow.


Use 12V battery or 12V adaptor to operate the circuit. Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Use three-sensor (thick conductive wire) and fit into the tank ensuring that 12V sensor touches the bottom and low-level sensor remains just above the bottom. High level sensor should be placed at a height till where the water needs to be filled. The circuit is economical, highly reliable and can be easily constructed.

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7 responses to 555 Timer Based Water Level Controller

  1. Hi, I built the circuit just as it is in the diagram.I used a 9 volt battery on a 12 volt relay and it worked perfectly. It is now connected to my toilet cistern and my borehole pump.Thanks for the circuit diagram.

  2. Soumyadip Mishra October 17, 2014 at 4:12 pm

    Dear Jagadesh sir,
    What is the purpose for using the 100k resistor at the pin no. 3?

  3. Dear sir i need this instrument in bulk to control the westage of water at my socity. If u r saleing the same product then lwt me know. So that we can save water and electricity too.
    You can call me on 09462192281

  4. whaaaa … nice schematic, and verry helpfull diagrame thank u..if u have any better diagrame please send me this g-mail

  5. Incredible quest there. What occurred after?

  6. Mohammed shafiquddin December 28, 2013 at 11:54 am


  7. Nice circuit! Do you think those 2 10k input resistors are mandatory?

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