Tank filling system test
1,340 views · Published 7 September 2012 · 2:01 · Indexed 11 October 2026
Channel: Paul Nathan · 2012 · Science & Technology
Testing a system that maintains a constant water level in a tank. The bottom cup represents the reservoir tank, the top cup the working tank. The leak at the bottom of the top cup simulates water usage / loss from the working tank. The electrical circuit is based on a Darlington pair (two sequential NPN transistors) that has inputs at the desired water level. The output from this pair goes into a 'not' gate. So if there is no water between the level sensors the power relay is activated and the water pump starts running. LEDs are used to indicate the state of the system, with green meaning the tank is at or beyond the desired level, and yellow meaning that filling is in progress. All powered by a 24V AC supply, rectified and filtered on the breadboard (all the 24V DC supplies were being used, otherwise I would have used one of those to keep it simple).
