Simple Water Level Detector Using a LM555 in Astable Mode:

Introduction: Simple Water Level Detector Using a LM555 in Astable Mode:

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  1. One LM555
  2. Two 330 Ohms resistors
  3. One red LED
  4. One green LED
  5. One 10 nF capacitor
  6. One 100 uF capacitor
  7. One 1 KOhms resistor
  8. One 100 Ohms resistor
  9. Wires for connections
  10. Protoboard
  11. 9 volts battery
  12. 9 volts battery connector
  13. Cutting pliers
  14. Transparent glass
  15. Water
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Step 1: Diagram Circuit

1. Connect in the protoboard the following circuit:

Step 2: Connect LM555

2. Connect LM555 terminal 1 to GND.

Step 3: Connect LM555 Terminals

3. Connect LM555 terminals 4 and 8 to the 9 volts battery positive terminal.

Step 4: Connect LM555 Terminals

4. Connect LM555 terminals 2 and 6.

Step 5: Connect

5. Connect one terminal of R1 to LM555 terminal 7.
6. The other terminal of R1 should be left free for one of the open terminals connection.

Step 6: Connect

7. Connect R2 between LM555 terminals 6 and 7.

Step 7: Connect

8. Connect the other terminal of R2 to the possitive terminal of C1.

Step 8: Connect

9. Connect the negative  terminal of C1 to GND.

Step 9: Connect LM555 Terminal

10. Connect LM555 terminal 5 to a 10 nF capacitor.

Step 10: Free Terminal

11. Then connect the free terminal of the 10 nF to GND.

Step 11: Connect LM555

12. Connect LM555 terminal 3 to R4.

Step 12: Connect

13. Connect the negative terminal of D2 to R4.

Step 13: Connect

14. Connect the positive terminal of D2 to the 9 volts battery positive terminal.

Step 14: Connect

15. Connect R3 to GND.

Step 15: Connect the Free Terminal

16. Connect the free terminal of R3 to the negative terminal of D1.

Step 16: Connect D1 Positive Terminal

17. Connect D1 positive terminal to the 9 volts battery positive terminal.

Step 17: Connect

18. Connect the free R1 terminal to one of the open terminals.

Step 18: Place

19. Place the other end of the terminal with tape at a specified level of the glass.

Step 19: Place the Other

20. Place the other open terminal with tape at the bottom of the glass.

Step 20: Connect the Other End

21. Connect the other end of the open terminal to the positive terminal of the 9 volts battery.

Step 21: Turn the Circuit On

22. Turn the circuit on by connecting the 9 volts battery.

Step 22: The Green LED

23. The green LED will turn on indicating the circuit/device is on.

Step 23: The Red LED Will Start to Flash

24. Pour water into the glass and, once the water level reaches the higher open terminal, the red LED will start to flash.

When the open terminals aren’t closed the red LED D2 will be off. It is intended for the open terminals to be closed with a determined water level. Once the water lever reaches the desired quantity, the water will close the open terminals (or this part of the circuit) and, as the LM555 is configured in Astable mode, the LM555 output (terminal 3) will send a continuous squared wave form into D2 which will make the red LED to flash at a determined frequency. The frecuency of the squared wave is determined by the values of R1, R2, C1 and the impedance of the water.

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    It doesn't work......
    Followed each and every instruction and even what the picture said but it doesn't work.

    Waste of Time


    Reply 7 years ago on Introduction

    I don't have much time. So please reply asap if you can help me.


    Reply 7 years ago

    Please understand about Breadboard connection. It is wrong.

    Molvi Bhai
    Molvi Bhai

    7 years ago

    Dude your instructions are awesome and I have copied and try 3 times but still it is not working...I have checked leds,battery ...What should I do?

    Molvi Bhai
    Molvi Bhai

    Reply 7 years ago

    Also in step 6 u have written connect R2 with LM555 terminal 6 and 7 but you also joined the other end of resistor to terminal 2 as shown figure and if you look circuit diagram there is no connection between R 2 and terminal 2 please explain


    9 years ago on Introduction

    Nice! And perfect instructions for someone like me, who really doesn't understand schematics! I am going to use this to make a water level alert for filling my pool. Thanks for posting.