Picture of Re-purposing an Air Wick Freshmatic Compact i-Motion

The Air Wick Freshmatic Compact i-Motion air freshener is an intriguing target for re-purposing. It uses a passive infrared (PIR) sensor to detect motion in a room and then increases the rate that it dispenses air freshener. This air freshener sells for $8, but you can sometimes get it cheaper with coupons.

Radio Shack carries the Parallax PIR module for $10. So the question is why bother re-purposing the Air Wick air freshener?

If you just want to replicate the Parallax PIR module, you can modify the air freshener by drilling 2 holes, adding a wire, and cutting a trace. Stopping here, you end up with a can of air freshener, 3 batteries, 2 slide and 1 push button switches, a cool aerosol valve, a medium power PNP transistor, a two wire connector with leads, and a LED.  I will show you two ways to do this; the simplest way, and a way to make the module the smallest.

However, If you want to go a bit farther, you can access the amplified analog sensor output as well as the digital signal, and have an externally accessible relay driver, and LED. I describe how all of these features are brought out to an easy to interface connector. You still end up with the air freshener, batteries, switches, and cool aerosol valve.

This last approach is a little more complicated.


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khammond42 years ago
Any chance theres a part number on the solenoid valve? I need a way to control the flow of butane electronically and the part needs to be as small as possible, and I also need several of them, but I don't want to have to purchase several air fresheners for the part... Thanks for this though! I'll probably buy one to prototype. :)
Smitho2 years ago
HI, this hack is great. Thanks. I want to add upstaris-light to sd, how can i do this? i haven't idea. Thanks
Doug Paradis (author)  Smitho2 years ago
You have to be real careful when building a circuit that will be interfacing with a home's mains power.

You could use this module with a triac (with opto-isolation) or a relay to power a lamp. However, I believe that hacking an outside security lamp with a motion detector would be easier and safer.

These types of lights use the same type of PIR sensor.

You might be interested in
Johnh3682 years ago
I would like to attach a simple 4.5v load this project. I don't have any training in electronics but am capable of performing the approaches above. Which is the appropriate approach and how do I connect the load in the end? Thanks in advance for any advice.
Doug Paradis (author)  Johnh3682 years ago
If you have kept the full circuit board and modified it as shown in step 9, you should be able to connect your load as described in test 2 on step 10 (testing the white socket).

You should keep your load's current requirements at 200 mA or less. If you need more current than that you might try a small relay.

Please note that this module doesn't latch, so your load will switch as people come and go.
3gen3 years ago
Can i use this to light up some leds i want it to turn on when i drive up to driveway where there is no 120volt power available
Doug Paradis (author)  3gen3 years ago
This hack could be used as the sensor for the system that you describe. However, I would suggest that you look at Harbor Freight's 36 LED solar security light (item: 98085). This item is ~$20 when you use a 20% coupon and seems to be a good fit for your purpose.

It uses a similar PIR sensor to detect movement.
Thanks for your help that is just what i needed
cmacdonald33 years ago
Great instructable!
I want to add a motion sensor to an artwork to simply switch on a large LED powered at 5v, when there's motion this seems like a easy access and low cost solution.
legoman444 years ago

Not exactly sure why you drilled holes through the PCB for the jumpers. Could you not jumper the points from the other side of the board and not drill?
ya i dont see the point to drill other than neat ness
DIY-Guy R.A.T.M3 years ago
I like neatness, but my worktable is a pile of projects without visible order to the untrained eye.
Doug Paradis (author)  legoman444 years ago
     There is no requirement to drill the holes, however I believe there are a few benefits.

      Usually when first trying to understand the circuit, I drill locations that appear to be manufacturing test points or where blocks of circuitry seem to end. I then solder a small piece of wire into each hole and use them as test points while determining what the circuit is doing. The wires make it easy to make measurements with either meters or oscilloscope. I also found that when I drill the holes, I reduce my chance of disturbing surrounding surface mounted devices or lifting a solder lead. I'm not the most skilled person with a solder gun. As R.A.T.M mentioned I also find it a little neater and stronger.
Robot Lover3 years ago
Great hack! I personally would have just soldered the coil in a relay to the leads that would go to the motor. That way whenever someone walks by, it energizes the coil in the relay instead of the motor.
skylen4 years ago
I have to ask, Air Wick: What is the point of the "security screw" in this instance? I understand the use in public places to help impede theft/vandalism, but for an air freshner... really? Anyone who actually would be interested in re-purposing (hacking) the internals would laugh in the face of this silly fastener as an impedance to entry.
iectyx3c skylen4 years ago
Good question. I thought about why they would put these TP3 tamper-proof screws throughout the gadget.

@ First idea was to prevent kids (ages 8-108) from tampering with it.

@ Then it might be to keep smarty-pants from repairing it so ya have to buy a new one.

@ But finally the true (!) reason hit me: it's a failed preemptive strike against I'ble makers from buying the unit for parts!
#3 is TOTALLY TRUE. They often sell these kinds of things for a loss so that you will by the refills and they can make the real money. It's the same thing they do with razors and printers.

#2 is definitely not it. They don't want you to buy replacements units that they make no money on. They want you buying the refills that are very profitable.
Often the security type screws are used in robotic assembly type constuction, because the heads tend not to strip out, and the bits tend to last longer because of the larger surface area in contact with the fastener.
Doug Paradis (author)  thines24 years ago

Good point.


I noticed after using square drive screws (for decking) that the star or "Torx" tip pattern almost never strips out. How do the triangle head screws compare to others? Can someone comment on the quality of the triangle head screws please?
lferrier3 years ago
This is a very useful hack as PIRs can be used for lots of things. I found it incredibly easy to do and use. Thanks so much.
I took the simple approach; just connected the led of a cheap optocoupler (CNY 17-3) in parallel with the Wick unit's green LED. Ten minutes and done ...


Ross McKenzie
Melbourne Australia
asorton4 years ago
I want to hack the unit so it works with the PIR but does not spray eery half hour when nobody is about, can this be done?
Doug Paradis (author)  asorton4 years ago
If you cut the trace near node "R" in the picture on step 6 and step 7, you disconnect the controller under the epoxy from the preamp of the power transistor that drives the spray solenoid.

If you jumper between nodes "Sd" and "R", the air freshener should spray every time the PIR is tripped. This could be a lot of spraying in a short time. You most likely would prefer to have a delay after spraying before spraying again.

One thought would be to rig up a 555 timer circuit on a small piece of perfboard, with node "Sd" as the input and node "R" as the output.

Please note that I haven't actually tried this particular modification. You should also read the comments below discussing adding a small reed relay.
R.A.T.M4 years ago
could you hook the black one to a mortor and whit to power sours and can you chang the timming so it go off evrtime that it senses moten
PatYoungers4 years ago
I put this small circuit to use as an IR activated nightlight.

Regarding your circuit, can you be more specific on the mosfets you used (depletion zone/enhancment zone). Why are you using a pfet and nfet? could you not use two nfets?
The P-channel is a Vishay Si4413ADY power FET enhancement mode device.
The N-channel is a Supertex TD9944 dual FET enhancement mode device.
This circuit does not require special FETs to work, just some that are good enough since this is not a power amp or a radio. I had "easy access" to these so I used them.
Both are surface mount packages and require good eyes or a microscope to handle. At 50+ yrs old, I had to use a microscope. I'll use vacuum tubes next time.
Have a look at the schematic at the link in my original post above to go with this explanation.
An N-Channel FET would not work for the first stage when driven by the SD signal because the logic is inverted. That is, the SD signal is at 4.5v when not activated. So you need a transistor that will be off when the gate and source are at 4.5v. So I used a P-channel FET. When iMotion circuit is activated, the SD signal drops to about zero volts, turning on the P-Channel FET. That charges the capacitor up to 4.5v, which in then turns on the N-channel FET, lighting up the LEDs. When the iMotion stops sensing the IR disturbances, the SD signal returns to 4.5v and the N-Channel FET turns off. This allows the 100K resistor to slowly discharge the capacitor which slowly turns off the N-channel FET reducing the current through the LEDs and making them slowly fade out. When the voltage on the capacitor reaches something less than 0.5 volts, the N-channel FET and the LEDs are basically off.
That's a bit more than what you asked, but I was on a roll so I kept typing. I really need to turn this into an instructable.
hoonflap4 years ago
just to verify, the digital signal available after completing step 3 is a solid 5v, correct? or 4.5ish, i see 3 AA's? i want to trigger a 5v reed relay. would i need any additional steps?
Doug Paradis (author)  hoonflap4 years ago
       I believe that your question has 4 parts:

O1:  Can the Vcc for the module be 5V?
 A1:  Yes, I have used the module in circuits from 3V to 6V. I do not know
         the BVCDO of the transistors or the BV rating of the capacitors
         in the module, but they are greater than 6V.

Q2:  Can I drive a 5V reed relay directly from the Sd node on the
   I am going to make 2 assumptions here;
                1. You are using a reed relay similar to Radio Shack part
                     275-232 (i.e., 5V, 250 ohm coil). So you are asking
                     can the Sd node source 20 mA.
                2.  Since the Sd node goes low when the PIR is upset,
                     the coil would be energized most of the time.
        The Sd node is the collector of transistor Q4, which is connected
        to Vcc through resistor R14. R14 is ~100 ohms. At 20 mA, the
       voltage at Sd would be 3V (i.e., Vsd = 5V - (100 ohms * 20 mA)).
       I do not know if this is enough to energize the relay's coil. I would 
       have to try it to find out. If you use the diode protection I mention
       below,  I do not think that you will damage the module.

Q3:  Would I need to do anything else to the circuit?
A3:   You need to put a reverse diode across the relay coil to
         handle the inductive kick when the relay switches.

Q4:  What if that doesn't work?
  I would go through the Instructible a little farther and make the 
        power transistor and its pre-amp accessible (node R). It was
        designed for this type of purpose and has the necessary diode
        in place.  It would also have the additional advantage of inverting 
        the signal so that the relay coil would not be energized except
        when the PIR sensor was upset. 

Doug Paradis (author)  Doug Paradis4 years ago
BVCEO not BVCDO..... dang typos
Doug Paradis (author)  Doug Paradis4 years ago
    I just rethought my answer a bit. If you...

1. Connect one end of the relay coil to Vcc and the other end to the SD 

2. Put in the reverse biased diode to handle the inductive kick across
     the coil.

3.  Disconnect or remove R14.

Q4 should be able to handle a small reed relay directly. It would also
only be activated when a disturbance occurred.

Hope this helps.
Doug Paradis (author)  Doug Paradis4 years ago
One last thing, just to make sure you are aware...

     The PIR will give multiple trips as someone moves or walks across its path. It will detect movement or sudden changes in IR radiation (i.e., an object in shade suddenly becomes an object in direct sun light or a warm object, say leaves on a  tree in sunlight, start to wave with the wind).

    The Sd node doesn't latch or lock itself out for a delay. It wil report the continous status of the PIR sensor. When the sensor is unbalanced, the node will go from Vcc to ~gnd. See the last photo
on step 3.

You might be interested in http://www.instructables.com/id/Cheap-Motion-Detection-Wildlife-Camera/ for some ideas how to handle these issues. 
Annoymous4 years ago
They Suck i know people that have them. Not this type but they have the Freshmatic and Straight Freshmatic Mini and they get sprayed in the face all day.
What is the point of this? I mean it looks really neat but i'm not sure if i understand the point.
Sorry someone didn't respond to your question sooner kelceysyoung! You can use this modified/repurposed PIR to trigger several projects but the best one is one member KipKay did with another PIR and a miniture DVR camera to take pictures when warm body moves into view i.e. as a game camera, snoop on a unknown nanny, (or any other person who deserves it), use it to catch that bad neighbor in the act, or perhaps to find out info on who has been breaking in?
You can just use a small flat-headed screwdriver (the ones that look like this "--" on the end") and just wedge it in between the two points of the triangle on the screw :)
I've found that the tip of one side of a pair of needle nose pliers sometimes works as well
I suppose it would work quite well if the head is quite large
Hmm mine looked complete different inside, but it did have the pir. Mine was wall powered and had two boards. The board with the pir had 3 wires coming off of it. the power supply was in the other board. There was no motor inside also. Maybe I can get a schematic from the fcc if I can numbers off the board. I am amateur at this.
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