I've seen these oil diffusers from more and more vendors recently, evolving from a novelty item to a mass-produced commodity. Cheap enough that someone may buy one, try it for a while, and decided against it sometime after the store return period. Which was the case for this unit, which was given to me not because I wanted a diffuser (I didn't) but for me to take apart.

This particular unit has the Target logo and "Made by Design" stamped on the bottom. I recently read an entertaining article about Costco's "Kirkland Signature" brand, and motivated by that knowledge I went and researched Target's (much longer) list of brands. Indeed, "Made By Design" was one of them. Not that it matters too much right now (unless I want to buy another) the fact it is available from a house brand just confirms the commodity status of such products.

I put a bit of water in the device, plugged it in, and turned it on without the lid. The water started bubbling (making a mess of my workbench) and some of it dispersed into fine fog.

It's much neater with the lid on, where only the mist exited a dedicated vent in a soft breeze.

We can see all major airflow elements in this picture.

  1. The circular fan intakes air from the bottom....
  2. That air exits a rectangular chimney in the side of the base. This air circulates around the space between the base and the lid until...
  3. Air enters the fogging area, picking up some aerosolized liquids, then...
  4. Exits out to the room.

Each of the three foam feet hid a Philips-head screw.

Once removed, the base came apart easily exposing its main circuit board. Eight LED modules are visible, as is an IC that appears to run this particular show.

The power socket slid from its position easily, far easier than a recent power socket recovery.

The button board was also easily removed, sliding out from its slot without any fasteners or glue in the way.

Only two buttons are present on this device, with provision for a third. And we can see how the control board can read up to three buttons with just two wires. When pressed, each of these buttons bridge a resistor, so the control board can read the resistance and decipher which button (or combination of buttons) are pressed.

Two more screws allowed me to remove the control board, and I was pleasantly surprised by what I saw: every peripheral is connected to the control board by a JST-XH (or compatible) polarized connector. But even more than that, each peripheral has a color-coded connector. Wow! I did not expect to see that. Color coding makes sense to ease assembly and visual inspection, but stocking separate color connectors usually add cost that manufacturers skimp on.

IR1 appears to be an unused provision for infrared remote control. The heat sink is screwed onto what appears to be a power MOSFET, but the screw is inaccessible while the MOSFET is soldered in place on the board. Unsoldering the MOSFET would be a challenge, because it would be dissipating heat out of that heat sink we could not remove while MOSFET is soldered in place. A curious circular puzzle making it difficult to disassemble, I wonder how it was assembled.

In the bottom corner we see a name "asiamist" and a URL "www.fogger.cn" leading to a company that manufacturers such devices for many different house brands.

The single generic fan serves double duty: a cooling fan for that big heat sink and moving air to disperse the fog. It isn't driven very quickly, which helps keep the noise down and probably also helps extends its service lifespan.

Finally, the star of the attraction. I know nothing of how ultrasonic devices work and I look forward to taking this apart. I might see interesting and fascinating mechanisms of mystery, or I might find something that physically looks unremarkable and give no sign to how it works.

And it is... option B. The heart of the machine is a little metal disc with the following markings

AM1911
2.45M

and otherwise completely unremarkable. If I didn't already know it was an ultrasonic transducer I would not have guessed its purpose. I was a little disappointed, but its simplicity also implies I didn't break anything taking it apart. Would it work if I plug everything back in again?

Yes it does! I stopped this experiment very quickly because splattering water and electronics do not make for a happy mix.

Now I have a problem: I can't think of a reason why I'd want a fogger, but it is still working and I'd hate to just destroy it. But I also didn't want to store the device intact as it is bulky and consumes a lot of space. As a tradeoff, I'll cut out and keep just the "business end" of the diffuser with my new toy the Wondercutter S. It was pretty slow going through the plastic, but much neater than if I had used a Dremel and much safer than manual cutting with an X-Acto knife.

Now the heart of the machine can be stored away in a fraction of the space consumed by the full device, leaving the option to reuse this in a future project.