Breaking up an automatic room deodoriser – round two

Again we attempt to break down an automatic room deodoriser.

Updated 18/03/2013

Today we are going to tear down another automatic room deodoriser. Why? Well the first attempt beat me, so it was time to even the score and try again with another type. The supermarket had the following units for $7.99, which seemed a little too cheap:

brandnewss1

The “satisfaction guarantee” gave me a chuckle, the thought of writing to SC Johnson complaining that their products were not that hackable would be interesting. But would it be hackable at all? Let’s find out. The packaging promises a squirt of scent when the unit detects motion, then holds out for 30 minutes until the next release. The word motion hints that there would be a PIR inside the unit. However the instructions mention that the unit does not work that well in dark or bright rooms – which is odd, as PIRs usually work in the dark. Hmm. This unit is somewhat smaller than the previous attempt, yet still offers us a pair of alkaline AA cells:

insidess

Moving on, time to start the disassembly process. The rear shows four screws, easily removed:

backss

revealing the fun things:

gearsss

The motor drive is reduced twice, which then has a geared arm which causes the vertical motion to pressure the cylinder to release the scent. The whole mess of gears was lubricated generously, the whole lot literally came out with the touch of a finger. Removing the gears and goop reveals the motor and control boards, which clipped out easily:

motorpcbss

Interesting – a labelled motor. Very good, what looks like to be a 3V DC motor. The control board is made up of two PCBs, a smaller module that holds a control IC of some sort, and the larger, lesser-densely populated board with the button, status LED and “motion detector”. Let’s have a close-up of that PCB:

pcbaloness

So we have the button, which causes the motor to run; a yellow LED which blinks once every five seconds; and out motion detector in the black casing. The motion detector seemed rather familiar, so I removed the black housing around it with some pliers, which revealed this:

lightsensorss

Huh – that looks just like an LED. The metal object inside the clear casing was even identical to what you would see inside an LED. However, foolishly I broke it off the PCB when removing the housing, so could not get any voltage to it. From reading the instructions earlier on – that mention the light/dark issue, causes me to ponder if this is some sort of light-dependent sensor?

No – it is a photodiode! However the motor looked quite worthwhile. Curious to see what is driving it, I hooked up Mr Fluke to see what happens:

No surprises there, almost three volts DC forward voltage. After applying forward current the circuit applies a quick reverse current to release, thereby causing the gears and arm to ‘squeeze’ down on the scent cylinder. So now we have a circuit board that runs on 3V, which can output 3V for a few seconds every 30 minutes – or at the press of a button.

With regards to current, another measurement was taken:


When free-running, the motor draws around 45 milliamps – and the stall current (that is, the current drawn when I force the spindle to stop) is around 675 milliamps. That is quite a strong little motor, and worth the effort. In general, this has been a good tear down, we scored some AA cells, a good motor and gears, some stink spray, and a timing circuit that could have uses elsewhere. So overall a win – the score has evened with the deodoriser world! High resolution photos available on flickr.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitterGoogle+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

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John Boxall

Founder, owner and managing editor of tronixstuff.com.

4 Responses to “Breaking up an automatic room deodoriser – round two”

  1. Marcel says:

    Yay! One all. ;)

    Could be a handy little circuit. Do you think those caps might be responsible for the timing? because it would be nice to able to reduce the hold-out time to say a few minutes.

  2. penbex says:

    I liked the previous one better :)
    I will start looking for one around here. Do you have any closeups of the PIR in that one?

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