About 20 years ago, a friend of mine came to me saying that he had to repair a customer’s water level control made out of electromechanical relays which was falling apart. He understood that the original control relied on conductivity of water. The customer didn’t want any type of float switch so he had to stick to the way it was meant to work.
He could start the pump whenever water fell below the “low” level electrode and pump would stop once it reached the “high” level electrode but, as water was consumed and its level barely dropped just below “high”, his circuit would re-start the pump just to stop it as soon as “high” electrode was touched by water again. This process kept going on and on until he switched power off. His circuit was oscillating which was not good for a 5 HP water pump or any pump at all.
He needed help. At this point I asked him that instead of working with relays, wouldn’t it be nice if the control were electronic which would probably be less expensive, more reliable and have a longer life?
I intended to build a kit for Club Jameco out of how I remembered this control worked and this is what this instructable is all about.
*** Disclaimer: This 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. ***
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Signing UpStep 1: Proposed Control Slide show
The slide show included in this instructable shows the basic operating theory behind this control. It assumes that the pump is a small plug-in pump. This control has a small 12V coil relay whose contacts are rated at 10A 120V. You can select any relay to suit your water pump's power source.
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i am a noob and very interested in doing these stuff.
I would like to install on a half HP motor .. can u please help me the components?.
The easiest thing to do is to use this kit the way it is with an external relay. This means, the on-board relay can switch on an external relay/contactor which in turn could switch on your 1/2HP motor.
Keep in mind that rating for on-board relay contacts is 10A @ 120V so this will determine your external relay's coil voltage. If your motor's voltage is 240V, you can use Jameco P/N: 282247 and a socket to mount this relay Jameco P/N: 282191. If your motor voltage is 120V, you need something bigger like Jameco P/N: 552462.
so kind of you
Now I am curious, what are your needs? I may be able to help.
We have three cement 5000 gallon tanks, the top up pumping is not required, we get around 2000mm of rain per year, so only need to keep an eye on the levels to switch them in/out of service if the level of one drops too low.
I dont particularly want to have anything hanging in them, so that reduces the best options to a sonar pickup, or a pressure sensor in the outlet valve at the base of the tanks.
Don't want to cut through the tanks, or introduce weak points that may cause leakage, and would like to run wireless transmitters to the house with solar chargers. One tank is around 30 metres away, the other two around 5 metres. Can you feel a migraine coming on?
I've seen a few sensors on:
http://www.gemssensors.com/Products/Level
And both shown there, ultrasonic and pressure sensors have parts hanging inside the tanks. Washing machines use some sort of pressure sensors to detect water level in them so I guess you'll have to continue searching for something similar.
Sorry for not being able to give you more info than the one you already got.
Beyond the water supply for our house/garden I have a greenhouse project I am about to start (when i get home again), and want that to be practically self sufficient/sustaining with hydroponic setup and its own mini water tank.
Your water level control 'ible may be useful there for keeping the nutrient tank at the correct level.
I may be wrong but i think the C1 capacitor is to "smooth" out the electrodes detection? ( so it doesn't trigger until there is a real contact with the water )
Why use C2 and C3 in parallel and why C3 is 1uF ?
Cheers
C1 is the non-regulated DC supply's main filter. After reading your comments, I checked ripple voltage at this capacitor and saw it's about 1 Vp-p when relay and green LED both come on which is when the most power is drawn by the board.
C2 is the regulator's output main filter. This one is to keep +12V as constant as possible every time relay and green LED come on and off, both draw about 50 something mA.
C3 is the IC's decoupling capacitor to help improve transient response as close as possible to CD4001. Eagle's model for CD4001 does not include supply and ground leads for this IC, so I drew them the way they appeared on the schematic to compensate for this and yet have them included on the PCB layout.
Thanks for your comments !
I have yet to learn many things about Eagle software. I really appreciate your taking your time to let me know about power rails to ICs. However, before I learn how to do what you just mentioned, I modified the schematic by hand to show pin numbers and make sure parts and wiring look clearer
I do appreciate it. Thanks so much!
In one of the libraries (supply1.lbr and supply2.lbr) are the symbols for creating a VDD/VSS attachment point that should link up all the VDD/VSS pins automatically without you having to hand draw them and label them yourself.
Hope those hints point you in the right direction. Been using Eagle on and off for years and it always trips me somewhere :)
Sorry i miss-read the schematic, i now understand with your explanations, very clever :)
Cheers
Thank you!
Thanks for your comments ! I have read some of your instructables and I can tell that you are awesome !
Thanks for your comment.
I measured the voltage drop when the electrodes are not in contact with water. All are at about 9.75V except Pump Protect which is at 9.1V due to Q1 input circuit. As per National Semiconductors CD4001 datasheet at 25°C:
Min Typ Max
Vdd=3V 3.5 3 -
High Level Input voltage: Vdd=10V 7 6 -
Vdd=15V: 11 9 -
By interpolation we may determine that for Vdd=12V, Min voltage might be 8.7V and, typical 8V? Well, I am guessing as I am not a professional digital designer.
On the other hand, when any electrode is in the water, the voltage is 0.56V - 0.6V. For a Logic "0" input should be between 0V and 3.5V when Vdd=12V.
I believe that our voltages are still within limits. So, to answer your question, the logic "1" voltage I got is not 12V as shown on the slide show, logic "0" was below 0.8V. The goal was to illustrate the principle.
By the way, thanks for your comments and I hope to have answered your question.