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Momentary Switch Bypass

Discussion in 'General Electronics Discussion' started by Gbannard, Apr 2, 2020.

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  1. Gbannard

    Gbannard

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    Apr 2, 2020
    Hello people-whom-are-better-at-the-electronics,

    I’m working on making an aroma diffuser that can be used as an alarm clock. This requires that the diffuser turn on with power rather than by switch. I found the Stadler Form Mia diffuser which is nice and simple as it has only one diffusing mode. Taking it apart, it is composed of two pcbs, one the main board and the second the board for the switch.

    Sadly, it’s a momentary switch, which would be very complicated (to me) to bypass. Happily, it only functions to turn the unit ON never off. The switch is a three-wire connection from the main board, presumably ground and the in and out. I figure if I remove the switch entirely and short the in and out to each other, the thing will start up with power.

    But I need a sanity check because I am the lowliest of hobbyists and don’t want to be making an obvious blunder. Please advice give.
     
  2. Bluejets

    Bluejets

    3,993
    824
    Oct 5, 2014
    So to get this in perspective, you want to connect some form of alarm clock contacts to this aroma thingo, correct?

    I would be inclined to think the 3 wires are negative, 1 switch wire from the momentary switch and one back from the main board as an LED indicator.

    As this is really just academic at present, perhaps some photos of the switch pcb (both sides and in focus) would be of assistance.
     
  3. Gbannard

    Gbannard

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    Apr 2, 2020
    Not quite. I have quite the family of smart plugs in my house which automate a whole bunch of things. So I could actually just plug it into a smart plug and then have it turn on at the time I want to wake up. So the project is simply to make the switch non-functioning and have the unit start up on power.

    Image (2)-1.jpg Image (3)-1.jpg Image (4)-1.jpg
    As of right now, I haven't pulled the boards off their supports. The LED light dims after about 3 seconds after being pressed.
     
  4. Bluejets

    Bluejets

    3,993
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    Oct 5, 2014
    As I said in #2.

    As far as the "smart plug" is concerned, details of how it works would also be necessary.
    What is the smart plug output, relay or semiconductor...??

    If it has a programmable momentary output and is a set of dead contacts, all being safe etc. it can simply be wired across the existing switch (last photo circled component) in the aroma unit.
    If not, then possible to mod to suit but without any detail, then it remains a mystery and any mods could be any of a dozen or more ways.
     
  5. Gbannard

    Gbannard

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    Apr 2, 2020
    You are thinking much too complicated. Consider me a 2 year old right now. The power goes into the unit from a dc wall plug. I plug that into a smart plug something like this which plugs into the wall. I only need to modify the switch component of the diffuser, everything else can stay as it is. The smart plug is connected by wifi and can turn power on and off at the wall rather than an internal unit inside the diffuser.

    If you think that a smart plug wired directly to the switch is a better idea then I’m game to try but it is currently above my skill level.
     
  6. Bluejets

    Bluejets

    3,993
    824
    Oct 5, 2014
    I'd say off hand,any mods are beyond your understanding.
    Perhaps a local friend with some degree of electronics knowledge would be a big help.
     
  7. Gbannard

    Gbannard

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    Apr 2, 2020
    I mean, I guess I asked for it, but being patronising is a bit rude. Just say “I don’t think there’s something you could do” or even just ghosting me might be better. It’s just a switch.
     
  8. Bluejets

    Bluejets

    3,993
    824
    Oct 5, 2014
    Information given should therefore be no problem to follow then at that rate.
    Still waiting for you to provide useful details on the "smart plug".
    What you have to recognise is, we have no idea what you have in front of you until you provide the details we require.
    Jump up and down as much as you like but that is the situation we face here.
     
  9. Gbannard

    Gbannard

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    Apr 2, 2020
    I literally linked to a page showing the exact smart plug I’m going to use in the reply before last. Click the blue link.
     
  10. iimagine

    iimagine

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    Oct 23, 2013
    Easiest solution: Duct tape the button!
    Or take a pic of the back of the switch board
     
  11. AnalogKid

    AnalogKid

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    Jun 10, 2015
    It looks like all of the brains are on the small vertical pc board you show edge-on. A full view of its front side would help.

    The switch is SPST. You forgot to mention the LED on the switch board. As a guess, the three wires are GND, LED power, and Switch out. When you press the button, the switch out wire is connected to GND. When the unit is running, limited current goes through the LED wire, through the LED, to GND. On the main board, the switch wire goes to a pull-up resistor and a uC input. The LED wire goes to a resistor to Vcc. Or something like that.

    Modifying the board so the unit turns itself on when power is applies probably is not possible, but you might get lucky. Unplug the unit, hold down the power switch, and plug in the unit. If the unit powers up, then keep holding the switch for at least 1 minute to see if the microcontroller detects this as some kind of error condition and shuts down the unit.

    ak
     
  12. Gbannard

    Gbannard

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    Apr 2, 2020
    AK, thanks for the explanation. & imagine, it seems plugging the power in whilst holding the switch does not start the machine. I had attempted the “mechanical” solution but it is not to be.

    I did forget the LED. It turns on when switch is pressed then turns off after 2 seconds.

    As for a picture of the small vertical pcb, see below. The brains, as you put it, are helpfully covered by a protective coating.

    C10E6CF6-541A-422B-87F0-46C7E83F37A0.jpeg 84F615D3-02E8-4C2C-8750-DD04696357ED.jpeg

    As this seems to be going in one direction ... is there such a thing a button pusher?

    ETA: I forgot to put a pic of the back of the switch board.
    89820597-3D72-4780-A99A-A095F3A091F9.jpeg
     
  13. Gbannard

    Gbannard

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    Apr 2, 2020
    I’ve been thinking, and I wonder if I could replace the switch with a resistor and capacitor to act as a long enough delay to trick the controller into thinking the switch has been pressed? I have no idea how long enough of a delay would be needed though.

    There doesn’t appear to be any negative effects from holding the switch down for a long period of time.
     
  14. iimagine

    iimagine

    55
    8
    Oct 23, 2013
    You can try this:
    You'll need to identify the 2 pins that turns on the unit by contact. Do you have a multi-meter?
     

    Attached Files:

  15. Gbannard

    Gbannard

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    0
    Apr 2, 2020
    I do have a multimeter and I was able to determine the wire configuration (below).

    As for your circuit diagram, I’m not sure the purpose of the part branching off between the resistor and capacitor. Could you tell me what that is? I can research it I just don’t know what it is called.

    I was thinking something more like the alternate diagram I have below, where a time delay circuit is created by placing a resistor between the two wires controlled by the switch and a capacitor branching off to ground. Forgive the liberties I’ve taken with the colour scheme.

    I also included last a circuit diagram is ripped the design from.

    C8D6290E-5251-4FAD-92AE-EE16BEE99130.jpeg 0F1B7078-02E6-4E76-8785-EDA2FFD026D4.png
     
  16. iimagine

    iimagine

    55
    8
    Oct 23, 2013
    If you are lucky that the MCU isnt picky, that RC circuit could work, try it.
    That part in the circuit i posted is called a mosfet. That circuit is commonly known as 'delay on'
     
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