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Dettol no touch soap dispenser ~ ques ~

Discussion in 'General Electronics Discussion' started by herzeleid008, Jan 9, 2013.

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  1. herzeleid008

    herzeleid008

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    Jan 9, 2013
    hi all,

    im new in circuit - trying to understand how does the circuit in this dettol no touch soap dispenser works.

    i've currently dismantled the parts looking at the circuit but still new

    anyone can help to explain how does the circuit works

    from what i see there are:-

    1) 1 yellow + 1 green wires connecting to the sensor
    2) 1 brown + 1 white wire connecting to left side of the pump
    3) 2 yellow to the top side of the pump
    4) 2 green to the right side of the pump
    5) 1 red + 1 black to the battery

    All this wires are soldered on a circuit block

    Would greatly appreciate if someone can help me out in the basic understanding how this pump works in terms of electronics

    Thanks all !
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    hi there
    welcome to the forums:)

    how about a photo or 2 of the circuitry, I like most people probably have never seen inside one

    Dave
     
  3. herzeleid008

    herzeleid008

    11
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    Jan 9, 2013
    hi there, thank you much for ur fast response.

    below are the images

    [​IMG]
    [​IMG]
     
  4. herzeleid008

    herzeleid008

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    Jan 9, 2013
    [​IMG]
     
  5. davenn

    davenn Moderator

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    what's on the circuit board
    do a clear well lit pic of both sides of the PCB :)

    Dave
     
  6. herzeleid008

    herzeleid008

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    Jan 9, 2013
    hi dave ~ below are more pictures :)

    [​IMG]
    [​IMG]
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    good try :)

    but unfortunately not close enough up to determine component types or circuit traces

    Dave
     
  8. herzeleid008

    herzeleid008

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    Jan 9, 2013
    hi dave, i hope this will sufficient.
    thanks again for looking at this

    [​IMG]
    [​IMG]
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,449
    2,809
    Jan 21, 2010
    They're pretty simple. You break the beam and they turn on the pump for a while.

    Once you take them apart they can be a real bugger to put back together.

    edit: that black blob on the underside hides a silicon chip that has been bonded directly to the board. The epoxy over the top protects it. It is unlikely you'll ever know exactly it is.
     
    Last edited: Jan 9, 2013
  10. herzeleid008

    herzeleid008

    11
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    Jan 9, 2013
    hi steve - thanks for the reply


    i would think its pretty clear cut that red & black is for the battery and orange/green is for the infra red sensor. pls correct me if im wrong

    i have a few questions:-
    what are the purpose of the wires below :-
    2) 1 brown + 1 white wire connecting to left side of the pump
    3) 2 yellow to the top side of the pump
    4) 2 green to the right side of the pump

    what does the diff wires on the pump play a role for? thanks

    btw. i don't plan to put them back together anymore. It's more like a guinea pig to be tear apart
     
  11. davenn

    davenn Moderator

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    Sep 5, 2009
    ahhhh
    thats better more curious myself, one of those things very few people
    would have seen inside
    in that second pic can see a LED and a RX, the RX is probably a photo-diode
    that will be set up to detect the hands moving close to the unit to trigger it

    cant tell what that thing is between them tho ... the small black bit directly to the right of that EC1 marking on the PCB

    on the other side, I suspect there's a small microcontroller hidden under that black blob of goo. What happens in there ... well only the manufacturer would know

    Dave
     
  12. davenn

    davenn Moderator

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    Sep 5, 2009
    Steve shorter response beat my waffle lol

    D
     
  13. herzeleid008

    herzeleid008

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    Jan 9, 2013
    hi dave, another question - doest this system uses a infra red proximity sensor
    why is there a need for a photo-diode ?

    photo diode converts light to current/voltage right ? what role does it play in this circuit
     
  14. davenn

    davenn Moderator

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    Sep 5, 2009
    well maybe it doesnt,
    else I dont see the need to a LED and a RX close to it ??

    can you describe better what I asked about... cant tell what that thing is between them tho ... the small black bit directly to the right of that EC1 marking on the PCB
    between the LED and the RX
     
  15. herzeleid008

    herzeleid008

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    Jan 9, 2013
    hi dave. tbh i have no idea whats that thing

    this is another clearer pic. hope this helps

    btw dave, do u know what does all the diff wires attach to the pump does

    [​IMG]
     
  16. davenn

    davenn Moderator

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    Sep 5, 2009
    OK the terminals of the connector down the side of the board are labelled

    so make a list of terminal label - wire colour - and where it goes
     
  17. herzeleid008

    herzeleid008

    11
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    Jan 9, 2013
    im still confused

    so this thing here uses a photo diode or infra red sensor ?
     
  18. herzeleid008

    herzeleid008

    11
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    Jan 9, 2013
    [​IMG]
    [​IMG]
     
  19. herzeleid008

    herzeleid008

    11
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    Jan 9, 2013
    can someone tell me whats that in the previous 2 pic?

    how does this thing detect movement ?
     
  20. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,449
    2,809
    Jan 21, 2010
    It doesn't detect movement.

    I assume the thing at the top is a photodiode.

    At the bottom you have 2 LEDs, a red one that you can see, and another IR one pointing at the photodiode near the outlet.

    When your hand breaks the beam, you get a squirt.
     
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