This model shows how a water level indicator works. When the water reaches the level of the two safety pins, it completes the electric circuit, turning on the red LED light and the buzzer.
This indicates that the tank is full and water should be stopped. It helps in preventing water overflow and wastage, and can be used in overhead tanks, water coolers, or water purifiers.”
Materials Needed
- Half plastic bottle (cut from the top or bottom)
- 2 safety pins (as water level contacts)
- 9V battery and battery clip
- Buzzer
- Red LED light
- Wires
- Tape or glue
- Small container of water (to simulate the rising level)
How to Make Water Level Indicator
Step 1: Prepare the Bottle
- Take a half plastic bottle (vertically cut) so you can see inside.
- Fix it upright on a cardboard base using tape/glue.
Step 2: Insert Safety Pins
- Insert 2 safety pins horizontally opposite each other near the top of the bottle.
- Ensure the metal part of the pins is exposed inside the bottle and connected to wires outside the bottle.
Step 3: Wiring
- Connect one safety pin to the positive terminal of the 9V battery.
- Connect the other safety pin to the long leg (anode) of the LED and one wire to the buzzer’s red terminal (both can be connected together using a jumper).
- Connect the short leg (cathode) of the LED and black terminal of the buzzer to the negative terminal of the battery.
Step 4: Test It
- Slowly pour water into the bottle.
- When water touches both safety pins, the circuit completes → LED glows and buzzer sounds