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L67, Water Level Indicator Type-6

A very simple water level indicator electronic circuit project can be designed using the ULN2004 high voltage, high current Darlington arrays that contain seven open collector Darlington pairs with common emitters Each channel rated at 500mA and can withstand peak currents of 600mA.


  • IC1 = ULN2004

  • R1-R7 = 47K

  • R8-R14 = 1K

  • C1 = 100uf 25v

  • LED1 – LED6 = Green LED

  • LED8 = Red LED

  • Battery 9v – 12v

  • S1 = on/off switch

This ULN2004 water level indicator is very simple and require few external electronic parts. As the water level rise in the tank. It comes in contact with probes P1 through P7 and thereby makes pins 7 trough1 high sequentially. The corresponding output pins 10 trough16 go low one after other and LED1 through LED7 will light up.

When water comes in contact with the last probe P7, the buzzer connected to the last pin 16 will sound. The circuit is very simple and does not require any settings. This electronic circuit project must be powered from a fixed output DC voltage that will provide an output voltage between 9 and 12 volts.

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