how to setup water level sensor on battery



  • Hello,

    I've bought a water level sensor one year ago, and would now like to set it up on a battery powered sensor in order to detect a flood in my basement.

    I'm not sure about the infos I've found about this sensor, but if I'm correct, it can work at 3.3v (not below) and it takes 20mA, which could be ok if I power it on only when needed, which would be about once or twice a day.

    Would you have a suggestion / example about which way to handle power on/off for this thing (which would have to be wired to a 3.3v step up to cope with discharge) ?

    Regards
    Mikael


  • Hardware Contributor

    Hi!

    You should check out http://forum.mysensors.org/topic/486/my-2aa-battery-sensor/ and how to create a normal battery operated node. This is how i prefer to make my battery nodes.

    You can sleep the node and use a interupt to wake it up if there is water.



  • Hello,

    Do you mean I should use water as a conductor between 2 unjoined wires or some other technique ?

    I'm affraid relying on water as a conductor would lead to many false positives as my basement is always quite wet (old house on granit with unsufficient drainage), and I've choosen this sensor because it should give a better understanding of how much water there is.

    Actually, I've read some posts where people use mosfets and feel it could be an option but that's a unknown field to me, so I'm looking for alternatives or examples.

    Regards
    Mikael


  • Hardware Contributor

    Sorry, didnt se it was only analog pin and not a digital...
    There are some threads with other sensors used to achieve this (digital pin to interrupt).

    Im not sure how to proceed with this sensor - a transistor of some kind maybe?


  • Hero Member

    If you want to actually measure 1 or few water levels (as it is always wet ;-)) you better use a "floating" sensor. Just search for "arduino float sensor". These are electrically isolated and can be "polled" on a time base or attached to interrupt pins.



  • Thanks. That seems indeed a good and simple alternative. And potentially cheap as I've found this one.

    Besides, I've read a (very little) bit about mosfets and concluded that a N-Channel where one digital pin feeding 0 or 3.3v to the gate, and the load (3.3v step-up + sensor) could be a nice solution. I read about the IRL540N which could be a relevant mosfet. Well, I would not be surprised my conclusions are wrong. Any thought about that ?

    Regards,
    Mikael


  • Hero Member

    @Mikael-Kermorgant If the level sensor you are referring to suits your needs...this on acts as a switch so no need for a regulated power supply. Just a pull up.

    The Mosfet can be used to switch the power on/off but if it is not needed why bother. Same for a step-up..



  • @AWI it was not clear, but I was thinking of using a mosfet in combination with the water level sensor shown in my first post, which is in fact drawing about 1.4mA when dry, and around 15mA when put in water.

    Add those 1.4mA to the those taken by the step up, and it feels like the mosfet would lower that a lot when the node is sleeping (if I read the datasheet correctly, it draws between 25 and 250µA, depending on its operating temperature).


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