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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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The Air Wick air freshener uses a PIR sensor. The fragrance canister nozzle is depressed when it is inserted into the air freshener. The fragrance is dispensed by a valve in the air freshener that is activated by a relay driver type circuit. The PIR will detect large movements to about 15 feet with the Fresnel lens attached.
The Glade air freshener uses a light level (shadow) detector and a motor and gear train to depress the canister nozzle and dispense the fragrance. The motion detection on this product has much shorter range than the Air Wick air freshener. It generally sells for $5. It has a nice Sanyo motor that runs on 3 volts.
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@ 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!
#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.
Good point.
.
Cheers,
Ross McKenzie
Melbourne Australia
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.
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?
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.
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.
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
module?
A2: 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?
A4; 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.
.
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
node.
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.
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.
I would be interested in what you found inside of the oil warmer. Would you post some pictures of the insides? Does the power supply look like it might be something that could be used on other projects?
I have inserted a picture of the packaging into step 1 of the instructable. I hope that helps.
From your picture it looks like the oil heater version has a nice power supply. I will have to take a look the next time they go on sale.
Them crazy couponing folk are real; and they ain't all that crazy. I'm married to one. Like the l337 to the n00bz, she scoffs when people mention their 25, 30, 50 percent savings. She's to the point where she spends very little time doing the prep-work. She has fun doing it, anyway-- 'cept when Walgreens gives her a hard time. She loathes Walgreens. Well, I'm sure there're more than one coupon -ibles out there.
Oh, thanks for the -ible, Doug.
And of course, depending on an 'INDIVIDUAL' store policy [yeah, right], you may or may not have MMA matches with store managers, fist-a-cuffs with crotchitty old bats, or be incarcerated for putting your fist down an obnoxious teenie boppers throat. Prepare to be treated like a criminal when you leave some of these stores; but then you'll know you're doing it properly [and legally]. Here's a hint though, my wife always says she'll choose a teen boy cashier when in doubt. To quote her, "...they just don't give a crap..."