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HELP: Solenoid valve Relay circuit with IR sensor

Discussion in 'Sensors and Actuators' started by Dominicmark, Jun 4, 2015.

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  1. Dominicmark


    Jun 4, 2015
    Please help me troubleshoot the relay in this circuit.

    I'm not an electronics engineer, just a distributor of sensor systems for flushes..

    In this particular setup, my IR sensor is connected to my circuit board housing the relay unit and that to the solenoid valve. The sensor by means of relay is supposed to trigger the solenoid to open for a few seconds for flushing.

    However in 75% of my units, the relay gets problematic and my engineer charges me a bomb to fix it.. I just need to understand how this particular circuit works and what's the relay chip here..

    My electronics knowledge is minimal but am ready to read up and understand with any suggestions..

    I look fwd to ur replies

    Attached Files:

  2. ADRT


    Nov 25, 2014
    In the red box is a micro controller. These are programmable controllers that can be used for any number of things. The program that is in the controller dictates how it is used. The brown box is a transformer used to take line voltage down to something the controller can handle probably anywhere from 5vdc to 9vdc. The white box is dip switches used to configure the auto flush most likely the delay possibly a couple of other things. These would be linked the the controller inputs. Blue box is a trim POT probably used to adjust the sensitivity of the IR sensor. Green box is an Optocoupler used to isolate the output of the controller from the line voltage to the little yellow box, a TRIAC likely, that actually fires the solenoid.
  3. ADRT


    Nov 25, 2014
  4. ADRT


    Nov 25, 2014
    Most of the components are easily replaceable, but if you damage the micro controller you would not be able to replace it without getting one from the manufacturer with the program loaded or be able to get a hold of the program and program them yourself.
  5. Minder


    Apr 24, 2015
    If the solenoid is DC then a reverse diode should be used across the coil as close as possible to the coil, for AC a R/C snubber should be used, they save damage to the board components.
    ADRT likes this.
  6. PAFMElb


    Mar 20, 2017
    Diode needed only if solenoid is a DC type. If ADRT's analysis is right - and his surmises about the optocoupler look right, then the optocoupler kind of implies a triac as the driver stage) and if the driver is indeed a triac then the solenoid does not/should not have a DC coil, and adding a diode will cause smoke and tears.

    I don't agree that the pot is for sensitivity adjustment. The PE beam has 5 wires - likely to be Pos and Neg supply, and the other three being a relay contact output of Common, Normally Open and Normally Closed. Most PE beams have a relay output - it's a de-facto standard for maximum compatibility with interfacing devices. I think the pot is for timing adjustment, and the dip switch for configuration and possibly some bits used as a multiplier for the time scale.

    What is the nature of the failure? Driver board fails? Or solenoid fails? Device won't turn off? Valve chatters?

    Not sure which component you mean by "relay". No relays to be seen. The valvey thing is a solenoid operated valve, and while the board might function as a relay it isn't one.

    Would it be close to guess this thing is a urinal flush device? Step up to the plate - break the photoelectric beam - nothing happens - but then when you step down the beam re-seals and water flows?

    Personally I think it absurd that such a simple function uses a microprocessor when a few seconds timing could be done with a handful of analogue components, and leave you with a more serviceable unit that any tech could fix.
    Last edited: Apr 26, 2018
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