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Dettol no touch soap dispenser ~ ques ~

herzeleid008

Jan 9, 2013
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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 !
 

davenn

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Sep 5, 2009
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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
 

herzeleid008

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

below are the images

fmkpz7.jpg

sazlmx.jpg
 

davenn

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

Dave
 

davenn

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good try :)

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

Dave
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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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:

herzeleid008

Jan 9, 2013
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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
 

davenn

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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
 

davenn

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Steve shorter response beat my waffle lol

D
 

herzeleid008

Jan 9, 2013
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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
 

davenn

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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
 

herzeleid008

Jan 9, 2013
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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

54x07t.jpg
 

davenn

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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
 

herzeleid008

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

how does this thing detect movement ?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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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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