Water level controller using 8051

A water level controller based using 8051 is shown in this article. A lot of water level controller projects have been published in this website but the is the first one based on a microcontroller. This water level controller monitors the level of the over head tank and automatically switches on the water pump when ever the level goes below a pres
Water level controller using 8051 - schematic

et limit. The level of the over head tank is indicated using 5 leds and the pump is switched of when the over head tank is filled. The pump is not allowed to start if the water level in the sump tank is low and also the pump is switched off when the level inside the sump tank goes low during a pumping cycle. The circuit diagram of the water level controller is shown below. The level sensor probes for the overhead tank are interfaced to the port 2 of the microcontroller through transistors. Have a look at the sensor probe arrangement for the overhead tank in Fig1. A positive voltage supply probe goes to the down bottom of the tank. The probes for sensing 1/4, 1/2, 3/4 and FULL levels are placed with equal spacing one by one above the bottom positive probe. Consider the topmost (full level) probe, its other end is connected to the base of transistor Q4 through resistor R16. Whenever water rises to the full level current flows into the base of transistor Q4 which makes it ON and so its collector voltage goes low. The collector of Q4 is connected to P2. 4 and a low voltage at P2. 4 means the over head tank is not FULL. When water level goes below the full level probe, the base of Q2 becomes open making it OFF. Now its collector voltage goes high and high at P2. 4 means the tank is not full. The same applies to other sensor probes (3/4, 1/2, 1/4) and the microprocessor understands the current level by scanning the port pins P2....

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