16-01-2012, 03:19 PM
SIMPLE AUTOMATIC WATER-LEVEL CONTROLLER
[attachment=16109]
Water-level controllers are
common nowadays. The
one described here is
built around timer NE555 and
inverter buffer CMOS IC CD4049.
It uses readily-available, low-cost
components, and is easy to build
and install on the over-head
tank (OHT) to prevent wastage of
water.
The circuit works off a 12V battery
or 230V AC mains using a 12V
adaptor. The three sensors built
from non-corrosive metal are fitted
to the OHT as shown in Fig. 2 and
connected to the circuit (Fig. 1) at appropriate
terminals. Power supply tersors
in the OHT and connected the
power supply, the circuit is ready to
use.
Since Vcc terminal is at the bottom
of the tank, when the water level falls
below sensor L,
timer IC2 is
triggered at pin
2 via inverters
N1 and N2 and
its output goes
high. As a result,
the output
of timer IC2
goes high. Relay
energises and
the motor starts
filling water in
the tank. The
motor remains
‘on’ even when
the water level
crosses sensor
As water in
the tank rises to
touch sensor H, timer IC2 is retriggered
at pin 6 via inverters N3
and N4 and as a result, its output
goes low. The relay de-energises and
the motor stops filling water in the
tank. The motor remains ‘off’ even
when the water level falls below sensor
As water is consumed and its level
falls below sensor L, the motor restarts.
Thereafter, the cycle repeats.
You can also manually start and
stop the motor using switch S1.
minal Vcc is at the bottom of the tank,
sensor terminal L is just above the
bottom of the tank and sensor terminal
H is at the top of the tank. After
you have properly installed the sen
