 Hi Jay, Cistern Water Level Sensor How this sensor works is low voltage is suppiled from a battery to power one side of the LED's. Voltage then travels thru each coresponding wire to the probe stick located in the cistern to each sensing probe. If the water level covers that probe then it completes the circuit thru the water to the GN wire thus lighting that LED on the light panel inside the house. If the water level is below a probe, then the circuit is broken and can not light the LED inside the house. The GN wire is located near the bottom of the tank. This wire completes the circuit and will always be in water. When the last LED goes out then you don't have but very little water left. Example:
If the R wire probe is covered with water, then all LED's on the light strip would lite up. If the R wire probe is not covered by water, then all LED's on the lite strip would lte up except the "R"-LED. If the Y wire probe is not covered by water, then all LED's on the lite strip would lite up except the "R","Y"-LED. Etc; Until the tank is empty. Battery:
The sensor can be supplied voltage by a battery power. The needed voltage is determined by the number of LED's you install in the circuit. Each LED needs 1.3v to work. So if you use 10 LED's then you would need approx 15v from a battery. Two 9v battery's in series will work just fine. Leave about 2v extra for circuit resistance voltage drop.
Resistors:
R1 thru R7 are 1kohm pull up resistors to keep the LED's from requiring over current demand. Any 1kohm resistor from Radio Shack will work. Add one resistor in series for each LED.
Control Cable:
Any 18awg solid copper multi-wire will work. Thermostat wire is very cheap and will work well for this application upto 250ft in length and is multi colored for keeping the wires straight of where they connect. LEave plenty of extra wire on SS flatbar for each probe. Just strip back the wire insulation 1/2" and use the end of the wire as the probe.
The wire ends inside the water will need cleaned once every two years to make best contact. Be sure to leave extra wire available at the cistern to trim off for new probes when needed.
SS Flatbar:
Use a piece of 1-1/2" wide x 1/16" thick to mount the probe wires on. Just drill two 1/8" holes where you want the probe wire then weave the wire into the two holes. Do not let the wires short to the SS flat bar/rod. You could also use 3/8" round rod for this. Use SS to keep it from
rusting. Bend a "U" to hang the flatbar on the tank lid or?
Radio Shack makes all kinds of nice enclosers to mount the LED's and battery in. You can use all one color of LED or mix different colors of lights. How many LED's to use is how sensitive you want your water level reading. Divide your tank hieght by the number of LED's installed to tell number of gallons left inside the tank. With 10 LED's using a 2000gal tank then each LED would represent 200gal.
Since I don't believe in explaining high voltage wiring via internet I'll let you figure out if you want to add a transformer to replace the battery's. Be sure you know what your doing if your choose this option as you don't EVER want line voltage inside the tank.
T_Bone
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