Water Tank Full Indicator

Today, the first prototype of one of the possible solutions to the Overhead Tank overflowing problem was built. More importantly, we were happy about the material used:

1. Old Bisleri (or any such 1 litre capacity) plastic water bottle
2. A cheap hard plastic ball a little less in diameter than the water bottle
3. Aluminum Foil to wrap the ball
4. Some electrical wire
5. Bucket
6. LED/ Alarm
7. Any type of Batteries
8. Cardboard or plastic disc 
9. Thread 

Water Tank Full Indicator

How to do it?

1. Cut off the bottle’s base (under adult supervision)
2. Wrap the aluminum foil on the plastic ball.
3. Strip off both ends of 2 pieces (about a foot long) of an electric wire
4. Tie one end of one wire to the ball with thread tightly while ensuring that the stripped end is touching the aluminum foil.
5. Cut the cardboard/ plastic in a small circular shape and punch a small hole close to its centre.
6. Through a small hole in the bottle (closer to its base), insert the other wire into the hole in the cardboard disc.
7. Wrap aluminum foil on the disc ensuring that the stripped off end is kept closely in contact with the foil.
8. Fix up the simple electric circuit as (a) Battery (+) --> disk (b) Battery (-) --> Resistor --> LED(#1), and (c) LED(#2) --> Ball
9. Test the circuit by touching the ball and the disc together to glow the LED.
10. Now dip the inverted bottle (without the cap) in the bucket and hold it close to the top.
11. Fill the bucket and the ball will move up when the water level rises. Once the ball touches the disc, the LED will glow indicating the bucket is full.
12. The narrow mouth of the bottle prevents the ball from dropping out when the bucket is empty.