Dettol no touch soap dispenser

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 !

many dispensors works with IR diodes and detectors. if the IR radiation is reflected back, the motor can work and then pump the liquid. its very simple indeed.

To save on battery life, there maybe some basic form of intelligenc ein there, such as a microcontroller. They can't leave the IR LED permenantly on, as this would drain the battery, but at the same time, it needs to be turned on regularly so it doesn't 'miss' someone placing their hand there. I suspect it turns on the IR LED for a very short period, every half a second or so, and once detected with a photodiode, double checks, then starts the pump.

There could also be a timer, so the pump doesn't constantly 'pump out' soap if someone leaves their hand there (waste of soap, and battery power).

I have noticed that these don't trigger in high ambient lighting conditions, so perhaps the IR LED is 'modulated' with a high frequency - the photodiode circuit only triggers when it detects this frequency (and so, ignoring 'DC' such as permenant light, and tv remote control signals).

Whilst all of this could well be in a simple analogue circuit, these days it is likely to be a very small microcontroller inside. This would reduce parts count, enable fine control over parameters, and increase battery life by going to sleep inbetween detections.

Just my two cents/pennies

Recently one of the paper towel dispensers at work failed. One of our technicians decided it would be fun to take it apart and I told him to have at it as it was destined for the trash. Small board with a large plate on it, a few components and a LED. Nice little geared 12 volt motor.

Anyway, it uses a proximity detector circuit much like the one seen here. My guess is the plate acts as the antenna. It likely uses a one shot that when triggered runs the motor for a given period of time. Last I saw the thing it was laying on a bench in my lab area and I won't likely see it again till Monday morning. Anyway, my guess is paper towel, soap or whatever they use a small proximity detector similar to the link. Current drain is low other than when the motor dispenses a towel or soap.

That's my guess...

Ron

<EDIT> Here is an example of a reflective IR circuit. I have no clue how well it would work with a human hand being the reflective surface? </EDIT>

probably works the same way as those automatic flush toilets, some one, some where is watching via the little cameras and pushes a button when you walk away or walk up to them.

I fitted some ant bacterial dispensors here at work when the last flu epidemic scare was in force, they use infra red leds and photodiodes, theres probably a microcontroller that checks to see if the beam is broken every couple of seconds, as there is a delay before you get your hands squirted.

The sensor you refer to could be both infra red led and photodiode, allthough that would probably have 3 wires, even a pyro infred red motion sensor would usually have 3 or 4 wires.

Some info on how it works here as part of a fault investigation
https://elecrepair.blogspot.co.uk/