Most of the time we wish to have a water low level alarm (liquid level alarm) circuit to know if the amount of water inside the tank has decreased in order to switch ON the water pump set. Don’t worry about that, we can implement a simple water low level indicator sensor alarm circuit for your home or office with the help of liquid level probes. Our water level sensor alarm detects the fluid level using a transistor switching circuit. We have already discussed about different types of fluid level alarms and water tank level indicators, they are mainly to detect overflow from the water tank. But this one indicates that the tank is near to be emptied.(This circuit is posted as per the request from one of our reader MR. Ramz)
Circuit diagram of water tank low level alarm
- Power supply
- BC 547 transistor
- Resistors ¼ Watt (100Ω; 1kΩ)
- Buzzer 6V
Working of fluid level sensor
- Working of this schematic is almost similar to the water tank overflow alarm circuit based on transistor switch for digital logic.
- When the probe that is connected to the BC547 transistor via 100Ω resistor is covered by water, the potential at the point ‘A’ is 0V (ground potential).
- Thus the transistor remains in OFF state. So buzzer won’t produce any sound.
- If the water level goes below the ‘Low’ liquid level probe, the potential at the point ‘A’ becomes almost equal to Vcc.
- This turns ON the BC547 transistor, then a current will start to flow from Vcc to ground through the transistor.
- Thus the buzzer produces a beep sound, indicating that the water level inside the tank has reached to bottom and you need to switch ON the water pump set.
- Our previous project automatic water tank controller will help you to switch ON the water pump set automatically.