Sometimes, it seems the posts around here have no rhyme or reason, and that’s exactly the way I like it. As a part of a sampling “club”, a while back, I received a Glade Sense and Spray Automatic Air Freshener. This rather interesting device claims to have “motion sensor technology”, featuring a small refill that lasts about a month.
Having tried mine, and emptied the refill, I figured it wasn’t really my thing. But it does seem rather amazing that such a product is in the consumer market. What’s inside? How does it work? These are merely some of the questions I had. Let the teardown begin!
What is it made of?
Well, the unit feels plastic-ey. The exterior of the unit is brown, with speckles, a sort of poor wood imitation that reminds me of tupperware. It is adorned by curves, with a tapered top.
A look at the tapered top shows a hole where the inner mechanism shows through. The top of it contains a very small tapered hole, no doubt a nozzle that helps to further atomize the spray from the refill.
The bottom of the unit shows the identification marks – S.C. Johnson and Son is probably the parent company, with this unit designated model number SCJ-158. There are numerous variations of this unit, some of the same size with different plastic exterior. It is likely the internals are very similar. As you can see from the design of the base, the unit hinges open by pushing on the sides.
Inside, we see the main unit, which is the white plastic section. This is hinged at the top where the nozzle is, and clips into the rear brown segment. This suggests the different exterior coverings share a common internal unit.
The unit itself has the front panel push button for an immediate spray (termed boost), with a translucent white plastic for the LED to shine through, and a hole for the sensor. The unit is supplied with two Hi-Watt ER6X Super Heavy Duty carbon-zinc cells.
The canister itself deserves special mention. Aside from the fact it is marketed as Forbidden Berry in Australia and New Zealand, and Winter Romance Berry in Japan, the unit is a special dosed canister arrangement. The plastic nib at the top is depressed to release a specific dose of the liquid inside, in a similar way to asthma inhalers. This simplifies the timing of the mechanism quite a bit, but might increase the cost of the canisters themselves. The canister isn’t particularly big either.
The canister is installed into the unit simply by pushing it into place, and is removed with the skin-coloured plastic pull-tab. Some users have complained of leaks at the base of the sprayer, which seems rather unlikely as it is a pressurized spray canister. It, instead, seems likely that the canister was not fully pushed in or aligned with the nozzle shown above, instead resulting in the ejected liquid collecting in the plastic nozzle piece and eventually dripping to the bottom of the mechanism.
This is how the unit looks like after being de-populated of batteries and refill canister. It’s also been removed from the rear plastic shell.
It seems the internal section of the unit is marked much the same as the outside, with FCC and CE approval markings. The internal unit is held together with four screws. Inside, we can see …
… quite a few gears. The motor is on the left, coated in lubricant. This drives two reduction gears in sequence (i.e. the big white geared wheels) which then drive a sector-shaped gear which helps to convert the rotational motion into linear motion, pulling down on the plastic nozzle piece and then returning it to its original position.
Removing the middle reduction gear “breaks” the chain of processes, and allows you to see how the sector-shaped gear works. There are two limit stop posts, which limits the travel of the sector shaped gear, and by extension, the amount of pull-down the nozzle piece has.
This makes the system remarkably simple – it’s actually free of any feedback on this end. It literally runs the motor forward for a given time, letting the gearing hit the limit stop, then runs it in reverse for a given time, until it hits the other limit stop. Simplicity! Here, I actually ran it without any gear in the middle, but it still happily spun away.
A closer examination of the motor shows it’s a Techni Micro Motor, likely an RT-310P (2.5v nominal, 2200rpm/0.06A/0.072W), which strangely enough is stated on their product information page as being targeted to products including air fresheners. I never knew there was a whole motor market for air fresheners!
The main PCB isn’t adorned with much components, and is a simple single-sided board. It looks to be marked PB775B01M20-R Revision 0, dated 3rd August 2010 (a while back) but made Week 38 of 2013. There is an electrolytic capacitor, a ceramic capacitor, a micro-switch, an LED, what appears to be a phototransistor and a black plastic shroud (to limit the interference from the LED and limit the viewing angle).
It seems that their motion sensing is nothing more sophisticated than monitoring when the light level on the phototransistor falls – this is why they claim a maximum 5-feet range, and the need for adequate light. So, it’s more of a shadow detection system.
The bulk of the work seems to be done by a daughter PCB that stands vertically on the main PCB. This one seems to probably have some sort of ASIC which is glob topped onto the PCB. There are three resistance jumper settings on the left – these are fixed on this model, but is likely to set the lock-out time, as the other model they have on their web page can be configured for 15-minute, 20-minute and 30-minute lock-outs.
The rear of the PCB shows the way the other PCB is slotted in and utilizes its edge connector to be “solder bridged” to the main PCB. A rather sophisticated system, and it seems some of the connections are not even necessary. I wonder if this is indicative that the daughter PCB is actually a programmable microcontroller, that’s factory programmed/tested through the unused pins, or whether this controller can be utilized for more sophisticated air fresheners.
Well, there you go. A tour of the guts of a Glade Sense and Spray. Unfortunately, there’s not much in there that will give hobbyists something to salvage, but it was interesting to see how simple it is given the fact it uses a dosed canister (thus, the timing of the nozzle up/down is not as important) and the use of limit stops to limit the travel (thus, no positional feedback is required).
In terms of its operation, all it does is:
- Look for a significant dip in the phototransistor signal.
- Blink LED quickly for a few seconds to indicate an impending spray.
- Run the motor in one direction for a given time, which releases the spray.
- Run the motor in the other direction for a given time, which resets the spray.
- Go into lock-out mode for a given amount of time and blink LED slowly to indicate this while looking for a push-button signal – if there is, then go to 3.
- Turn LED off and go to 1.
I call this the air freshener algorithm (tongue in cheek).