Breaking up an automatic room deodoriser – part one

In this article we attempt to break down an automatic room deodoriser and have some fun.

Updated 18/03/2013

[Update – we won round two]

Today we are going to tear down an automatic room deodoriser. Why? Why not! After walking around the supermarket as one does, pontificating over the need for doughnuts – I noticed this package on sale for eight dollars:


What grabbed my attention was the words “movement sensor” and the price tag. A sensor by itself can cost more. Where’s the catch? I am sure the company makes their money back from selling the refills, in a similar method to ink cartridges and razor blades. Good for them. However, perhaps this can be good for us! So into the basket and home it came. My flatmates thought it was a lovely gesture to have one in the hallway. Hah! As Dave Jones would say, “don’t turn it on – take it apart!” So let’s go…

The can of spray went straight into the WC, nothing of interest there. Three alkaline AA cells were included:


Well that’s a good start, you can always use these in a camera or something else. Armed with a philips-head screwdriver and a pair of needle-nosed pliers, the entire assembly came apart very easily and without force. I must congratulate the designers, you almost get the feeling that this is designed to be repaired if broken, and not replaced. The process of disassembly was quite easy:


The front cover came off quite easily. The switch on the right enables/disables the movement sensor; the LED indicates the repeat mode for the spray; and the black switch controls the duration between sprays – off, 9, 18 or 36 minutes.


After removing the rear panel with four screws, we can see the motor and one of the two PCBs. Two more screws, and we can remove the electronics and mechanical sections:


This is the front-facing part of the motor board. The motor turns one direction then another to have the plastic ‘finger’ push down and release on the aerosol can nozzle. The gear ratios are quite large, allowing the motor to exert quite an amount of torque. The metal base board has some convenient mounting holes as well, so this could be reused easily. If you had a pair of these you could drive something that is quite heavy at a sedate speed.


Here is the main controller board, with nicely colour-coded JST connectors for leads to the motor, power source (those 3 x AA cells, 4.5V) and to the switch that turns the sensor on and off. The underside is very professional, all SMD:


The motion detector’s board plugs nicely into the main board, thanks to the 2×9 pin header and socket arrangement:


Now it is time to see how things work. The first step will be the motor – how much voltage and current does it use? I ran the motor without a load for thirty minutes at 4.5 volts DC – the  motor body did not warm up at all, a good sign that this voltage was suitable. With regards to current, there are two measurements to take – current while free-running, and under maximum load (i.e. feeding the motor 4.5 volts while holding the gears still). While free running, the current drawn was 34 milliamps:


… and when I held down the gears so the motor could not turn, the current drawn was 305 milliamps:


So now we have a nice strong motor that can run at 4.5 DC, and draws between 34 and 305 milliamps. That’s a good start. Furthermore, being able to stick the meter display to the desk lamp really makes life easy. Now it is time to investigate the detector. It had a few codes on the PCBs, such as KT-7964, Smart Motion A-06 and RB-S04 which I searched for on the Internet without any luck.

So the next thought was to feed it 4.5 volts DC, and use the Scanalogic2 to analyse any signals or voltages around the PIR sensor module to see what happens. However, the entire system was dead, it would not do a thing. The same problem occurred at four volts DC. No luck either. After the initial power up, the unit should light the LED for one second, then activate the motor for a “first spray” – but nothing. Hmmm.

So at this point we are at a brick wall, however this is not the end. Research will continue to look for details of the PIR unit, and once it is working independently a new post will be published.

This article also shows to me and others that not everything is a success first time. It can be disappointing, however it’s not the end of the world. With every failure comes knowledge which can be used the next time around. So subscribe to the web page updates, and keep an eye out in the future. High resolution images are available from flickr.

In the meanwhile have fun and keep checking into 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

Person. Founder and original author for VK3FJBX


  1. Nice find for $8!

    Is the reason for not finding any info on the detector because a company like AirWick would use parts that are custom made only for them?

    • Hi Tom
      Possibly. But you never know. Normally if something is custom-made or OEM’d, it wouldn’t be covered with part numbers and so on. Have emailed the ANZ distributor asking for more information… which I suspect they will not want to reply with. Wait and see I guess.

  2. $8 is a steal! Could the problem with not getting a reading on the detector be due to the timer switch? If it only accepts a signal from the sensor every 9/18/36 minutes, could that be the cause for not seeing anything?

    • Hi Stu
      Unfortunately no… but a good question 🙂 On the first “boot up” (!) the LED is supposed to light for one second, then activate the motor after 15 seconds. This one was just dead.
      Will have another look at it on the weekend

  3. Take it back to the shop. It’s clearly defective. Use your consumer rights!


    This is great. I’m all for harvesting parts. I’ve just been building a motion sensing night-light using a PIR. As it happens, I picked up some surplus PIRs from B&Q (big hardware store in the UK) for just 25p each!

    I’ve been running an Arduino based sensor-light for about 3 years in our bedroom and now wanted one to cover the route from our little boy’s bedroom to ours. I’ve now cut out the Arduino and am just running an LED from a couple of 4700uF caps in parallel. It’s less sophisticated but it works sufficiently well and cost a fraction of the cost of the Arduino version.

    More PIRs from things like smell-makers would be welcome!


    • Oh Marcel thanks for that, I needed a laugh. 🙂
      It certainly is interesting to see what you can get out of something isn’t it?
      With your night-light system, that is a good idea. As great as Arduino is, sometimes we forget that the simplest way is often the best.

  4. G’day Alan
    Yes, it took me by surprise as well. I think I’ll get another one and be a little more careful with it next week. You’re right, if we can get these things working just as PIRs the manufacturers might have to have a rethink!
    cheers 🙂

  5. John, just a thought. I have been in similar situations where I have eagerly pulled something apart without first trying it out assuming the unit was in a working state.

    Perhaps you were just unlucky with this particular unit. Hopefully the next one will shed more light.



    • Hi Dale
      No, the bloody thing worked before I stripped it apart. To be honest I forgot about it! Will go and get another one when they’re on sale and see what happens.

  6. Bought one of these today at Target in Phoenix, AZ for $4.59 but without batteries. It has a pine scent so plan to use it during Xmas which will make my wife very happy to have our artificial tree smelling like pine. Afterwards it’s parts will be harvested for my next project.

    Great idea to whoever thought of it first.


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