1. We will be in Read Only mode (no new threads, replies, registration) starting at 9:00 EDT for a number of hours as we migrate the forums to upgraded software.

Need help with Latching Relay using float sensors to power pump.

Discussion in 'The Projects Forum' started by matthewholloway10, Mar 15, 2019.

  1. matthewholloway10

    Thread Starter New Member

    Mar 14, 2019
    I am a long term troll, first time poster. I love all the useful information on this forum, but have ran into a snag with a latching relay I recently purchased.

    My goal is to use a latching relay and two float sensors or switches, one at the top, and one at the bottom to power a pump that fills a reservoir.
    The bottom sensor will turn the pump on, and when the top sensor, when engaged will will turn the pump off.

    I have the Bistable/Latching DPDT 8 Amp Power Relay Module, DC12V Coil, RT424F12 from Electronics-Salon, and have wired it according to my understanding of the circuit, but get absolutely nothing. Cant even get the relay to switch at all.
    The specs are available on the website, and seemed to be pretty straight forward.
    There's also a schematic on the website and on Amazon
    I tried to post a link but the forum wouldn't let me.

    I am using horizontally mounted float sensors or switches I purchased from Amazon
    again, I tried posting links, but it wouldn't let me.

    I had 12vDC 3A going to the VCC on the left terminal block,
    Then one wire from the the bottom sensor to S
    One wire from the top sensor to R
    Both of the other wires from the sensors to the other GRND

    I then had the GRND in of the pump into C1
    and the GRND out of S1

    I tried touching wires to the terminal blocks in various ways to see if I could get anything to do... well, anything.
    I've tried using different sensors, I ordered two relays, so tried both, Ive tried a momentary push button etc..

    Any help would be very much appreciated
  2. eetech00

    Senior Member

    Jun 8, 2013
    Here's the schematic:

    matthewholloway10 likes this.
  3. eetech00

    Senior Member

    Jun 8, 2013

    +12 connects to VCC (pin 2)
    -12 (or GND) connects to GND (pin 3 or 4)
    You should be able to momentarily touch +12 to either S or R (But not at the same time) to "set" or "reset" the relay.

  4. matthewholloway10

    Thread Starter New Member

    Mar 14, 2019
    Thank you for posting the schematic for me, and thank you for the comment.
    I tried touching a wire from 12v to s, and it worked, then to R and it reset! Thank you for clearing that up.

    Now my question is, does it have to be +12v to "set" and "reset" the relay? and if so that means my float switches will not work?
    Sorry for the ignorance but this is all new to me.
  5. crutschow


    Mar 14, 2008
    The relay requires 12V power but the control input to the transistors could be less if needed.
    But you just connect the 12V power to the common of the float switches and have the appropriate switch output go to the transistor set and reset inputs (likely the NC contact for the bottom float and the NO contact for the top float).
    matthewholloway10 likes this.