simple water level sensor

Discussion in 'The Projects Forum' started by livehho, Dec 23, 2009.

  1. livehho

    Thread Starter New Member

    Nov 20, 2009
    I've checked the other threads regarding this topic and none works for my application. VERY SIMPLE, 2" ID acrylic tube. 10" high. When the water level reaches near the bottom (3" from bottom) I would like the switch/circuit to close and activate a LED. that's it.

    I was looking at some right-angle float switches but they are too big to fit inside a 2" ID tube. anyway, I prefer something simpler than that.. like using two metal rods instead.

    some weeks ago I saw a thread on some electronics forum about a level sensor using two metal rods, when there was water between them whey would conduct and the circuit would close. bad thing is I lost the link to the website. they claimed it worked on tap water (didn't work on distilled water because of very poor conductivity.. that's fine coz I use tap water). I remember it involved some electronics but not too fancy. i've been looking for the link it now but can't seem to find it again.

    anybody with an idea or a link?
  2. Wendy


    Mar 24, 2008
    It is a long read, but we discussed several sensors in this thread.

    Basically the one I liked was an optical sensor. If the head is wet it reflects a built in LED differently than if it is dry. You might be able to use aspects of it.
  3. Duane P Wetick

    AAC Fanatic!

    Apr 23, 2009
    See my thread in the subject of liquid level sensing. The 2 probe conductivity design that I saw used an op-amp in a bridge circuit design. I don't have the exact circuit unfortunately, so some design work on your side will be needed. There is a liquid level sensing IC offered ST semiconductor, L4620, I believe that will work in your design.

    Cheers, DPW [ Everyone's knowledge is in-complete...Albert Einstein]
  4. whatsthatsmell

    Active Member

    Oct 9, 2009
    Would a float that rides in the tube be too simple?

    Run a rod through it and attach a trip lever to activate a switch attached to the top of the tube.
  5. Wendy


    Mar 24, 2008
    Yes, it would be too simple. :D Come to think of it, I've seen ping pong balls used to break a light beam. With modern LEDs (high intensity) and photosensors this might work, assuming ambient light isn't an issue.
  6. someonesdad

    Senior Member

    Jul 7, 2009
    One possibility would be to use a mercury float switch, assuming you can find one. Simple and reliable; just make sure it doesn't break, as then you're faced with a toxic mess. I used one on a home-made float switch I made for a ditch pump I put in 20 years ago and it continues to work fine. At that time, you could easily buy them at Radio Shack. Now, you'd probably have to scrounge one from an old thermostat.
  7. KMoffett

    AAC Fanatic!

    Dec 19, 2007

    I've used variations of this successfully. The advantage of using an AC signal to the probes is that it minimizes corrosion of ones that are in the water most of the time. DC (most of the alarm circuits out there) is OK if the probes only touch the water in an alarm condition. I would also recommend stainless steel wire/rod for the probes.

    The attached is a combination of Tony van Roon's (mostly his) and variations from a two-level one I made with a PICAXE for an automatic Christmas tree stand waterer. ;) I think this will work for your situation.

    Last edited: Dec 24, 2009
    absf likes this.
  8. BillB3857

    AAC Fanatic!

    Feb 28, 2009
    A reed switch on the outside of the tube and a magnet on a float works, too.
    Patryk Korbut likes this.
  9. kebssi

    New Member

    Jan 8, 2010
    If you are looking for any information on a water level switch or anything of the sort, you should look at Madison Company's website. not only will they provide you with information on the topic, they will also help you decide which specific item is right for your needs.
    I hope that this helps!
  10. JLodge

    New Member

    Jun 13, 2014
    In regards to your question, an easy alternative is just purchasing something that already works, rather than trying to create your own, which can lead to several faulty "bugs" in the system. I know it sounds lazy, but it really is easier. I am currently using this water level sensor in my aquarium, and it works great:

    Hope you found this helpful! (Sorry it came a little late...)
  11. wayneh


    Sep 9, 2010
    Wow, back to life after 4-1/2 years. That might be a record around here.
  12. stargazzn

    New Member

    May 26, 2016
  13. stargazzn

    New Member

    May 26, 2016
    You can take some simple 5k ohm resistors and solder them in together. Two rows 5 to a row. Place them side by side in the level to measure. As the level gets lower the resistance will be increase by 5k ohm every time it goes below the next level of resistors. So long as the liquid is not distilled water.