Water Level Control Kit

Sense high and low water levels

Assembly Time: 1-2 Hours
Difficulty: Intermediate
Designer: rlarios

Water Level Controller Design a simple water controller in which electrodes are required to sense high and low water levels in a tank. Whenever the water level falls below the low level electrode, the water pump starts and it stops once the water level touches the high level electrode.

There is a third electrode which is used to detect the water level from the pump suction port tank. If this electrode does not sense water, then the pump is not allowed to run, protecting it from burning out. You must supply your own water pump for this electronics project.

This electronics kit is meant to operate with equipment such as line operated water pumps or motor starter relays and/or contactors at lower control voltages. Line voltage is dangerous and if mishandled can cause injury or death. If you are not familiar or have not worked with line operated equipment, have a licensed electrician do the power wiring for you. This kit is meant to be educational in nature and can be used with line operated equipment if National Electric Code Guidelines are followed.

Build your own water level controller

Required tools and components:

Description Mfr. P/N
IC, CD4001 CD4001
PNP Transistor 2N3906
NPN Transistor 2N3904
+12V Voltage Regulator 7812T
Rectifier 1N4004
Red LED HLMP-3301
Green LED HLMP-1503
2.2MΩ Resistor CF1/4W225JRC
120KΩ Resistor CF1/4W124JRC
470Ω Resistor CF1/2W471JRC
4.7KΩ Resistor CF1/4W472JRC
330µF 35V Capacitor EC33035H1017-R
220µF 25V Capacitor R220/25
1µF 25V Capacitor RA1/25-R
Connector Terminal block 2 Pos 10A OSTTE020161
Relay,[email protected],Single Pole Double Throw (SPDT) VR15M121C
15KΩ Resistor CF1/4W153JRC
IC Socket 6000-14DW-R

Soldering iron
Wire stripper and cutter
Needle nose pliers
100' roll of 24AWG wire
AC-to-AC wall adapter
Small flat screwdriver

Step 1 - Schemetic with Circuit Component Reference Numbers

Water Level Controller Schematic

Step 2 - Check parts

Before soldering anything in place, make sure you have all parts required.

Check PartsCheck Parts
Solder the Passive ComponentsSolder the Passive Components

Step 3 - Solder the Passive Components

Solder in R1, R2 and R3 which form part of signal input circuits. These resistors are 2.2MΩ. Then solder the R4 (4.7KΩ resistor) which is a base resistor for transistor Q3 whose task is to switch on-off relay RLY1.

Next solder in the R5 (120KΩ emitter resistor) for Q1. R8 (15KΩ resistor) that connects Q1 collector to Q2 base. The purpose of these two transistors is to turn on a red LED to give a visual indication when the water level is low at the pump suction port. Solder in R6 and R7 (470Ω 1/2W resistors) that are LED1 and LED2 current limiters.

Now insert electrolytic capacitors C1 (330µF) and C2 (200µF) in their corresponding holes paying attention to the marked up negative lead of capacitors for polarity before soldering in place. Insert C3 (1µF) decoupling capacitor following the same guidelines as C1 and C2.

Step 4 - Install power supply components and IC socket.

Before installing the diodes, make sure they are properly oriented for polarity. The black band mark on the body of the diode tells you that lead is the cathode. The printed circuit board should also have a mark indicating the cathode.

Insert D1 rectifier diode in its intended space and solder one lead at a time. Clip on a heat sink between the solder joint and the body of rectifier. This heat sink will absorb excess heat and keep the semiconductor cool to avoid prematurely shortening its lifespan.

Before soldering the other lead of same semiconductor, wait about 15 to 30 seconds to let the rectifier to cool off before continuing with the other rectifier leads. Always use a clip-on heat sink before soldering any semiconductor lead. Do the same with D2, D3 and D4 rectifiers.

Diode D5's function is not meant to operate as a power supply rectifier but is the same device as the previously soldered rectifiers. Solder diode into D5 location paying attention to where the cathode goes. The function of D5 is to protect transistor Q3 from the relay's coil kick back voltage when it is de-energized.

Put 7812T in place and before soldering its first lead, use the same clip-on heat sink between the soldering joint and the body of the regulator. After soldering first lead, wait a few seconds to let the device cool off. Touch the 7812T regulator to make sure it's not too hot before proceeding with next terminal and so on until you're finished with the third and last terminal of the regulator.

Install the 14-pin IC socket and solder it in place. Use just enough solder for each pin to keep adjacent pins from shorting together with excess solder. Note the position of the notch on one side.

Install power supply components and IC socket
Install power supply components and IC socket
Power Supply Operation Verification
Power Supply Operation Verification

Step 5 - Power Supply Operation Verification

Using an external +15V DC Power Supply (or two +9V batteries in series) and a couple of alligator clips, connect the (+) output of this power supply to the anode of D1 and the GND output of the power supply to the cathode of D4. Measure voltage between pins 7(gnd) and 14(Vdd) of the IC socket which should be +12V ±2%. If this voltage test proves successful, proceed to next step.

Step 6 - Installing the Transistors and LEDs

Install 2N3904 NPN transistors into Q1 and Q3 positions making sure all terminals go into their corresponding holes. Attach the clip-on heat sink before soldering each lead with the right amount of solder and wait at least 20 to 30 seconds before moving to next lead of same device. Do the same with 2N3906 PNP transistor on Q2 position.

Install the green LED into the LED1 position. The shorter lead is the cathode and should go where the cathode lead is marked on the PCB. If LEDs are reversed they won't turn on. Attach clip-on heat sink to the lead you will solder first, wait 20 to 30 seconds before soldering the anode. Do the same with the red LED into the LED2 position.

Installing the Transistors and LEDsInstalling the Transistors and LEDs
Finishing the AssemblyFinishing the Assembly

Step 7 - Finishing the Assembly

These connectors come with two terminals. Install one connector each into X1 and X4 positions and solder in place with the terminals facing to the edge of the PCB. These connectors come with a sliding lip on one side and a groove on the other. Take the remaining two connectors and put them together by sliding one connector's lip into the other connector's groove so they stay attached and insert them into X2 and X3 positions and solder in place with terminals also facing to the edge of the PCB. Install the relay into RLY1 position and solder it in place. This completes the assembly of this kit.

Step 8 - Testing Testing Testing

Place your assembled kit on an insulated surface to avoid shorting the solder joints with conductive material that may be sitting on your work surface. Strip the ends of a couple of one foot 24AWG wire segments. Insert one end into the terminal marked as "Ground", then insert the another wire into the terminal marked as "Pump level protection" leaving the other ends loose without touching one another. This is a test with the same DC power supply used in step 4. Connect it the same way to power up the circuit.

At this point, the CD4001 should already be inserted into its socket. Once power is applied to the board and assuming everything was properly assembled, the red LED should turn on. If you put together the two stripped ends of the wires previously attached, the red LED should go out and the green LED should turn on and one click should be heard coming from the relay. Separating the wires' ends should turn the green LED off and the red LED on while hearing another click from the relay as it de-energizes. This proves the circuit is working.

Fill up a small shallow container with water. With the circuit still energized, the red LED on and the two wires not touching to each other, dip both stripped ends into the container with water. The red LED should turn off and the green LED should turn on with one click heard from the relay. Remove the wires from the water and the green LED should go out, the red LED should turn on with a click heard from the relay. If this goes as outlined, then it is working properly.

AC-to-AC Wall Adapter Test

Now it's time to test that the kit will work with 12VAC coming from an AC-to-AC wall adapter. Our pump controller kit does not include a male connector adapter, so cut off the female plug from the wall adapter cord and strip the ends which should be the 12VAC adapter output. Connect these 12VAC leads into the connector marked as 12VAC IN. Plug the wall transformer into a wall outlet and the board should perform the same as with the DC power supply. If this is the case, then it's time for next test.

Test Simulation: Water Pump

With another pair of wires of about the same length as the wires already connected to your kit, strip their ends and insert one in the "Low level" terminal and the other in the "High level" terminal. With the pump protection and ground wires already dipped into the water container, the green LED should be on. Dip the "low level" wire end into same water and the green LED should still be on, then dip the "High level" wire also into same water container and the green LED should go out with a click heard from the relay. This simulates that the pump filled up the water tank. To simulating water consumption as water level goes down, remove the "High level" wire from the water container and nothing should happen. Then, remove the "low level" wire from the water container and the green LED should turn on and the relay should energize the water pump and the cycle will repeat.

Final InstallationFinal Installation

Step 9 - Final Installation

You will need now an external 12VAC wall transformer to energize the kit. You will also need a proper enclosure which can be found in a Jameco catalog. You will have to run wires between the kit and the water tank and pump water reservoir as shown in the schematic. This schematic shows there are thin metal rods inserted through the walls of the tanks for sake of simplicity. You can somehow accommodate the rods vertically from the top of the tank making sure that these rods don't touch one another.

If you prefer to drill through the tanks' walls, make sure that the rods or bolts used are properly sealed to avoid leaks due to pressure from water on the walls of the tank. Once you do the connections, the controller should work without problems showing when the pump is running or when the pump is protected due to a low level at the pump suction intake.
SchematicFunctional Schematic Diagram (click for larger image)