Closed loop 1/2" water cooling system water level sensor.

Discussion in 'The Projects Forum' started by Propaganda, Jun 13, 2009.

  1. Propaganda

    Thread Starter Member

    Jun 3, 2009
    22
    1
    Hello everybody!

    My application calls for a simple water level switch for a closed loop 1/2" water cooling system. The fill tube also acts as a low volume reservoir which is two feet in direct vertical height. The water temperature reaches only 35F above room temperature. Space is tight, I would like it not much more than 3" high and 2" wide. The tubing is translucent silicon type tubing (clearflex). The fluid is mostly distilled water with only trace amounts of antibacteria solutions, hence not very corrosive and rather clear. Copper fittings are fine, absolutely no aluminum, plastic fittings are acceptable and perfered.

    When the water level reaches near the bottom I would like the switch/circuit to close.

    The issue is the actual sensor. There are no comercial products which I found, even so if I found no doubtedly it would be $100+.

    So far my only thougths are adding a white ball in the reservoir tube with a stop at the top and a stop near the bottem. There will be a IR LED and a IR sensor near the bottom stop so when the water level lowers the ball lowers eventually reaching the IR LED and reflecting the beam back to the sensor. Or I can use a black ball and block the beam, what ever.

    A concern is running the system for several years the water becomes brackish and depending on growth it may become too dark. Perhaps a higher power LED.

    I seeking some feedback before I construct a prototype.

    Any thoughts on this? Thinking along the lines of actual hobbiest inplementation using at hand materials creating a end unit fairly reproducable with a low price.


    Thanks 'all


    "When the boogie man goes to sleep at night he checks his closet for Chuck Norris."


    -Prop
     
  2. Propaganda

    Thread Starter Member

    Jun 3, 2009
    22
    1
    While looking for IR LEDs in a MOUSER catalog I ran across these...

    http://www.optekinc.com/datasheets/OPB350.PDF

    The above is exactly the concept I was going after. They are set up for 1/4 and lower sizes but I could scale up and adapt it for the 1/2" thicker tube.
     
    Last edited: Jun 14, 2009
  3. leftyretro

    Active Member

    Nov 25, 2008
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  4. bertus

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  5. franzschluter

    Active Member

    Jun 1, 2009
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    Hall effect magnet sensor will work more precise and last longer. Even if the water becomes more unclear... You only need to put a magnet on a floater and when it reaches at the top or bottom it'll trigger. I use this same setup but for my water tank at home. You can use Hall effect Transistors that react only on south poles or north poles. Professional level meters also use magnets. Distance sensitivity can go up to 30cm. Plus its cheap. Allegro builds em

    When using IR maybe it'll work. You'll need a light beam that's constantly emitting. It is a new approach I guess. But like remote controls.. Over time when the sender gets dirty from dust and mold etc etc.. It might not be able to send signal properly.. Tell me how it works if you use the IR method.

    Hope this helps

    Cheers
    Franz
     
  6. Propaganda

    Thread Starter Member

    Jun 3, 2009
    22
    1
    Thanks for replies and links.

    The reservoir is the tubing so the diameter is 1/2" (the tubing's inner diameter).

    Having the IR LED always on is not a problem, and I could pot/seal it to block out contaminants. But, the problem lies in the tubing and the clearness of the water... the main loop the tubing becomes cloudy over time. hmmm

    The http://search.digikey.com/scripts/Dk...me=365-1262-ND is what I will go for with my own parts.

    So, it should be pretty simple to calibrate, basically I will make a ADC read (using PICs) while the tube is empty then another when full... hopefully there is enough of a difference to make definite water/nowater triggers.


    The floating magnet would be the best trigger in the sense of reliability. A 1/8" cube magnet could be epoxied to a 3/8 hollow ball then inserted between two stops with the sensor at the bottom stop.


    Ok, IR leds and sensors along with a few HALL sensors are now going to find their way to the my current Mouser.com cart. Which leaves me to pick up a few Neodymium magnets from where ever. But, the tiny ball might prove more challenging to find.


    Thanks 'all. I will post my findings in a few weeks.

    "symbols are for the symbol minded" - George Carlin
     
  7. Wendy

    Moderator

    Mar 24, 2008
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  8. Propaganda

    Thread Starter Member

    Jun 3, 2009
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  9. franzschluter

    Active Member

    Jun 1, 2009
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    Well the neodymium magnets are hardcore stuff hehe and very powerful. I used regular refrigerator magnets on my setup and had no difficulties. It sometimes amazes me the range of these hall effect sensors.. They are still sensitive up to 20cm with a strong magnet. You should also choose which you prefer: a unipolar hall effect or those that react only to certain poles.

    When you like to go into more complicated stuff you can let it run along a nylon line (Your floater) so it will run a linear up and down motion. And use a linear hall effect sensor and perhaps with luck you can then indicate the amount of fluid in percent or bar display :cool:

    But for less complications like mines.. A regular hall effect should do the trick. For floaters you can check out your old mans fishing gear or a local fishing shop. They usually got different kinds of small sized floaters that should work fine. I know some floaters had light bulbs inside. Perhaps you can interchange it with a magnet.

    Cheers
    Franz
     
  10. bertus

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  11. Wendy

    Moderator

    Mar 24, 2008
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    Just curious, did you notice the small float switches the other project was using?

    If you're using magnets reed switches will also work. There is nothing wrong with hall effect, but you'll need a bit more support circuitry.
     
  12. leftyretro

    Active Member

    Nov 25, 2008
    394
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    Keep in mind that the volume of water in a 12" X 1/2" column is pretty small and because of that the level can change very rapidly and erratically depending on system flow rate, with high and turbulent flow being the worst case. Not sure what purpose your level switch is to perform, alarm? shutdown, control? but you may find that working with such a limited volume challenging.

    Lefty
     
  13. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Neodymium magnets would be maximum overkill for your application.

    Check out some datasheets for Hall-effect sensors before you start ordering magnets.

    I think you'll find that you just need a float with iron or steel attached, and you use the magnet on the back side of the Hall-effect sensor. The strength of the magnet and orientation would need to be determined from the datasheet of the Hall-effect sensor.
     
  14. Propaganda

    Thread Starter Member

    Jun 3, 2009
    22
    1
    Thanks again guys. =)

    3/8", 1/4", 5/16", and 1/2" plastic balls are ordered. The are not hollow but have a gravity of .91 so they will float. If the magnet weighs too much to allow positive buoyancy a hole can be drilled the magnet placed inside then filled with styrofoam and sealed.

    The neodymium mags are quite small; cubes in the followings sizes 1/16", 1/8", 3/16", etc.
     
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