Can someone tell how to build a working model of water level indicator with alarm or without alarm?

Answer 1

Yes I can tell how to make one without an alarm. Let us assume that you want it to be very simple and easy to understand, and safe to work on. First, you need a "float", a ball with a rod attached. You could use an old ball from a toilet tank. Attach the rod to a fixed point of the tank, or if in a pond, attach to a post or pier in the pond. Tie a cord to the float rod, near the ball. Run the cord over a pivot point (a pully or nail). Put a small weight (metal object or lead fishing sinker) on the end of the string. Paint a scale (level indication of the body of water) on a piece of plywood. Mount the scale near the weight on the end of the cord. Now as the water level rises and falls, the weight will move up and down. The higher the water level, the lower the scale, so this will be an "inverse scale" with the highest level at the bottom and the lowest level at the top. If you want an alarm, you could place a bell below the weight. As the level rises, the weight will strike the bell, ringing the alarm.