DIY Optical Water Level Sensor wiring

Bonvivant

Bonvivant

New member
Hello all,

I'm new here and was wondering if you could share some of your knowledge with me? I'm attempting (more like utterly failing) to wire up an optical water level sensor. However, I really do not understand the wiring diagrams. I have a 12v dc power source. I have a relay socket and dpdi relay but I just cant get it right. I'm using a OLS-11 Optical sensor from Dwyer. Any ideas or better yet photos? Please no wiring diagrams! Explain it to me like a five year old.
 
Here is the datasheet:
http://www.dwyer-inst.com/PDF_files/ols_iom.pdf

Your "LOAD" is your relay coil. Observe the polairty. Use the "LOAD WITH 1 SUPPLY" circuit shown in the datasheet. Don't forget the DIODE connected between the relay coil terminals! Again observe the polarity. It is there to protect the transistor in the sensor. Any 1N400x type diode from radioshack will do.

Connect the AC MAINS HOT (black) wire to the COMMON terminal on the relay and the HOT wire from the pump to the NO or NC (depending on what mode you want the pump to run, presense of liquid or not) terminal of the relay. Connect the AC MAINS NEUTRAL (white) to the pump.
 
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Out of curiosity, where did you pick this up? We used them in my last jab, and was looking for something like this to play with again.
 
Did you mean DPDT relay? I've never heard of a DPDI one :)

Your simple drawing would be the 'External load with 1 supply' like Bean mentioned. Take note that your sensor can only put out 100ma of current. It might not be enough to power your relay coil. You didn't specify what relay you are using, but check it's spec sheet to make sure its coil draws less than 100ma or it won't work.

Follow these steps and you should be OK (no suing if I am wrong!):
1) Connect the +12V from your power supply to the red wire of your sensor.
2) Connect the 0V from your power supply to the black wire of your sensor.
3) Connect the +12V from your power supply to the coil + terminal on your relay.
4) Connect the white wire from your sensor to the coil - terminal on your relay.
5) Eat some icecream
6) Test it out
 
Sorry, I meant DPDT-12v relay. I bought it at aquahub. here are the specs: Specifications:

* Coil voltage: 12VDC
* Coil resistance: 160 Ohms
* Contact rating: 10A at 250VAC or 30VDC
 
Using Ohm's law (I=V/R) you can figure out the amount of current your relay requires. Your V is 12, your R is 160. Punch the numbers in the calculator and you get I=0.075 amps or 75 milliamps. Looks like you will be ok.
 
Don't skipe the DIODE! It is a MUST!

The 75mA is kind of pushing it if the sensor is only capable of sinking 100mA. Using a transistor to drive the relay (or using a lower power relay) would not be a bad idea.
 
Great! So, the diode would go between the connections to the sensor correct? So, I need two? If I understand what your saying this is how it should be wired:

Positive from the AC Adapter is combined with diode and red wire from sensor. This is then attached to the positive terminal on the relay.

Negative from the AC adapter is connected to the black wire from the sensor (do I need a diode here?).

White wire from the sensor is connected to negative terminal on the relay (do I need a diode here?)

Pump positive is wired to either NO or NC on relay (do you know which is for opening the valve when no water is present?)

Pump negative is wired to the negative terminal of the relay.

Is this correct? I can't tell you how helpful your info has been!
 
In the kindest way... It may be a good idea to solicit hands on help from somebody who understands electricity :) You are dealing with mains voltage, something not to be taken lightly.

Just a single diode. It goes in reverse polarity across the relay coil, exactly like shown in the datasheet. Place it AT the terminals.

Be careful in your terminology. AC does not have a "postive and negative". The AC has "HOT" and "NEUTRAL". Hot is commonly colored BLACK and NEUTRAL colored WHITE. These have NOTHING to do with the sensor wire colors, as those are DC.

We ALWAYS want to break the HOT wire when switching power on and off. In your case you COULD break both the HOT and NEUTRAL as you have a double pole relay. It has (2) sets of NO-C-NC contacts.

Get the sensor up and running before you connect an AC mains power or pumps to it. You should hear the relay click as water covers the sensor.
 
You are correct! I used the wrong terminology. What I meant is the positive and negative from my 12v source. I didn't mean AC current. I'm fairly new to this but I want to learn it. So it is actually:

Positive from the 12v adapter is connected to red wire from sensor. This is then attached to the positive terminal on the relay.

Negative from the 12v Adapter is connected to the black wire from the sensor.

White wire from the sensor is connected to negative terminal on the relay.

Pump positive is wired to either NO or NC on relay (do you know which is for opening the valve when no water is present?)

Pump negative is wired to the negative terminal of the relay.

Can you explain the installation of the diode a bit? I don't understand the wiring chart.

Thanks again! I really would like to learn this.
 
Great! So, the diode would go between the connections to the sensor correct? So, I need two? If I understand what your saying this is how it should be wired:

Positive from the AC Adapter is combined with diode and red wire from sensor. This is then attached to the positive terminal on the relay.

Negative from the AC adapter is connected to the black wire from the sensor (do I need a diode here?).

White wire from the sensor is connected to negative terminal on the relay (do I need a diode here?)

Pump positive is wired to either NO or NC on relay (do you know which is for opening the valve when no water is present?)

Pump negative is wired to the negative terminal of the relay.

Is this correct? I can't tell you how helpful your info has been!
 
I made a mistake in my previous post. I meant the positive and negative from the 12v Adapter. Can you explain the connection of the diode? I don't understand the wiring diagram. I know I am new but I want to learn. Your assistance has been great.
 
Diodes are like check valves, they only allow current to flow in one direction. The direction is in the same direction as the arrow on the schematic symbol. The arrow points from the postive lead to the negative lead. Current flows from positive to negative. The real diode will have a stripe on the negative end.

In this case we want the NEGATIVE end of the diode hooked to the POSTIVE terminal of the relay coil and the POSTIVE end of the diode hooked to the negative end of the relay coil.

Why?
When you power the relay OFF the plunger gets sucked back through the coil of wire by the spring. When it does this, current is generated and the diode in the opposite direction that it was flowing before. The diode short circuits this current and prevents the surge from reaching the sensor.

Hope that helps a bit...
 
Ok, after a few delays, I finally got it to work. No fires, no deaths! lol. The problem I have is that it works in reverse of what I need. It turns the valve on when covered with water and off when dry. So I just purchased a normally open valve. It should work fine. I hope. There are three other float switches with NC valves so everything is nice and redundant.
 
"So I just purchased a normally open valve."

Ahhhhhh!!! If you are using this as an ATO or a RO/DI tank filler that is BAD!

If the power goes out, the valve will open letting water flow.

Also, this is less dependable because the coil needs to be energized for MOST of the time.
This will cause the valve to fail sooner than a NC valve.

Stu
 
I agree. That is why I have three other float valves that are attached to NC valves. I can't figure out how to reverse the sensor. If I could I would use a NC valve.
 
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