I was expecting this unit to be based on a single motor driving a separate fluid pump and aeration system. But they've got a very clever pump system that combines the two into one.
The infrared sensor seems to put out four pulses a second. I didn't reverse engineer the op-amp section because I have a feeling that it may just be a pre-filter and amplifier, with the microcontroller processing the resultant voltage level via an analogue input.
On eBay this type of unit has the description:-
350ml Automatic Foam Soap Dispenser Infrared Motion Sensor Touchless Hand Washer
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16 thoughts on “Inside an automatic foam soap dispenser with clever pump.”
  1. Avataaar/Circle Created with python_avatars Caleb Epley says:

    Splooge

  2. Avataaar/Circle Created with python_avatars Hadi says:

    very clever pump system !

  3. Avataaar/Circle Created with python_avatars SpotOn Cam says:

    Thanks for the tear down.

  4. Avataaar/Circle Created with python_avatars Practical by [ waleed ] says:

    Hy can you provide it's circuit board gerber file or a clear picture please 🥺

  5. Avataaar/Circle Created with python_avatars aabsc says:

    "When this signals back to the processor that mousse is required" lol

  6. Avataaar/Circle Created with python_avatars Andy Fraser says:

    I just bought one of these very cheap on eBay, but it wasn't triggering reliably, so I dismantled it. It has a much reduced circuit board, no LM358, but 3 transistors on the IR sub-board. It's working reliably while apart; squirting foam all over my workbench. The foam isn't as moussy as yours, so I'm wondering if they've also cheaped out with the gauze foamer (although it looks the same.

  7. Avataaar/Circle Created with python_avatars Peppermint says:

    The problem with these is the soap sediments at the bottom after 1 day and the foam starts being runny. You need to stir the reservoir every day to keep the soap mixed well with the water.

  8. Avataaar/Circle Created with python_avatars mariana lopes says:

    My soap dispenser suddenly stopped working. It's was working fine but now the engine is not working. What can I do?

  9. Avataaar/Circle Created with python_avatars daves465 says:

    I have several foam dispensers, and most of them stopped pulling the diluted liquid soap after a few uses.

  10. Avataaar/Circle Created with python_avatars Creative star says:

    Please make detail video of lm358 section. I want to repeat it. Thanks

  11. Avataaar/Circle Created with python_avatars Araz Mammadguliyev says:

    i got one from aliexpress. different type. but it doesn't work. i opened it its another system inside. could you help me somehow to fix that?

  12. Avataaar/Circle Created with python_avatars Tony W says:

    Thanks for vid Clive. I just bought two of these. Ad didnt sa you needed special foaming liquid. I gonna try your dilution method… Tnx again. Edit…..yep it works fine…..

  13. Avataaar/Circle Created with python_avatars Paul Allen says:

    SOAP. ALREADY. FOAMS.
    Whomever invented the "foam dispensers" should be shot…
    One of the most frustrating things on the planet, because a double handful of foam ends up being like .003 of a drop of soap, so you have to stand there waiting to get 100x more of it… 😡😡

    What the hell was wrong with a drop of soap?!?
    /rant

    😂🤣

  14. Avataaar/Circle Created with python_avatars Jacob Vad says:

    Can the "foam adapterr" be bough seperately from somewhere? will need it for a similair project 😀

  15. Avataaar/Circle Created with python_avatars Jacob Vad says:

    why is there so many tiny holes in the board?

  16. Avataaar/Circle Created with python_avatars John Woo says:

    Just bought that dispenser. Love it. Thanks for the breakdown. Takeaway is don't get any particulates in the soap as they may clog the tiny holes.

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