01-08-2012, 03:58 PM
VERSATILE WATER-LEVEL CONTROLLER
555 water level controller.pdf (Size: 116.43 KB / Downloads: 33)
T his simple, economical and versatile
circuit switches on the
motor pump when water in the
overhead tank falls below the lowest
level and turns it ‘off’ when the tank
is full. Moreover, if the pump is running
dry due to low voltage, it sounds
an alarm to alert you to switch off the
controller circuit (and hence the motrodes
are suspended into the tank
such that they don’t touch each other.
Points B, L and U of the water-level
controller circuit are connected to the
respective points of the sensor electrodes
assembly.
When water in the tank is below
the lowest level L1, all the electrodes
are electrically separated and hence
points L and U (pins 6 and 2 of IC2,
respectively) are pulled up to the sup-
When water rises to the overflow
level L2 and touches electrode E3,
point U (pin 2 of IC2) is connected to
already sunken ground electrode E2,
thereby triggering it. IC2 resets to give
a high output at pin 3. This is inverted
by transistor T1 to cut off transistor
T2 and de-energise relay RL1. The motor
pump now stops to prevent water
overflow.
CIRCUIT IDEAS
filter out unwanted noise. Switches S2
and S3 can be used to manually switch
on and off the motor pump, respectively,
when water is in between the
upper and lower levels. Switch S1 is
used to disable the unit during dry
pump run or while flushing the tank.
For the sensor electrodes, use a
moulded-type AC chord (used for tape
recorders) with its pair of wires sleeved
at the end and connected together to
form the electrode. Other electrodes can
be made similarly. These three AC
chords are suspended inside the tank.