Water Level Indicator
This is the circuit diagram of a simple corrosion free water level indicator
for home and industries. In fact the the level of any conductive non
corrosive liquids can be measured using this circuit. The circuit is
based on 5 transistor switches. Each transistor is switched on to drive
the corresponding LED , when its base is supplied with current through
the water through the electrode probes.
One electrode probe is
(F) with 6V AC is placed at the bottom of tank. Next probes are placed
step by step above the bottom probe. When water is rising the base of
each transistor gets electrical connection to 6V AC through water and
the corresponding probe. Which in turn makes the transistors conduct to
glow LED and indicate the level of water. The ends of probes are
connected to corresponding points in the circuit as shown in circuit
diagram.Insulated Aluminum wires with end insulation removed will do for
the probe. Arrange the probes in order on a PVC pipe according to the
depth and immerse it in the tank.AC voltage is use to prevent
electrolysis at the probes. So this setup will last really long. I
guarantee at least a 2 years of maintenance free operation. That’s what I
got and is still going.
Parts
T1 – T5 BC 548 or 2N2222 Transistors
R1-R5 2.2K 1/4 W Resistors
R6-R10 22K 1/4 W Resistors
D1 – D5 LED’s ( color your choice)
NOTE BEFORE:
Use a transformer with 6V 500 mA output for power
supply. Do not use a rectifier! we need pure AC. Use good quality
insulated Aluminum wire for probes. If Aluminum wires are not available
try Steel or Tin.Copper is the worst. Try the circuit first on a bread
board and if not working properly, make adjustments with the resistance
values. This is often needed because conductivity of water changes
slightly from place to place. The type number of the transistors used
here are not critical and any small signal NPN transistor will do the
job. Few other suitable type numbers are BC546, BC107, PN2222, BC337,
BF494, ZTX300, BEL187 etc. The circuit can be enclosed in a plastic box
with holes for revealing the LEDs .
