Whether it actually accomplishes the function intended (or at least asserted), the low price tag and enduring controversy sufficed to motivate a look inside.
Electronic pest control devices have a longstanding reputation (largely-to-completely justified, my own research of others’ studies has concluded) for being ineffective at encouraging mice and other rodents, along with a variety of insects and arachnids, to flee in their actively broadcasting presence. Sometimes it’s because they don’t work at all; the speaker inside might be a flat-out “dummy”, or at minimum nonfunctional over the claimed operating frequency range, for example (all conveniently obscured by the fact that you’re not supposed to be able to hear them anyway). And even when working as designed, there’s little to no evidence that ultrasonic pummeling does anything meaningful to deter pests, particularly after long-term use.
That all said, a teardown video from fellow teardown-er “Big Clive” that I recently came across still piqued my interest.
Clive, like me, made no definitive judgement as to the functional viability of the device, while still noting the overall skepticism derived by studies from others. That said, observations such as the following would, I felt, be unexpected in a product solely intended as a scam:
The PCB in this unit looks very competently designed, with good clearances and logical design. The bulk of the unit’s magic is in the software, and they’ve been quite clever in creating a swept ultrasonic output, while also pulse width modulating the indicator LED. It could even be said that the programmer may have been showboating.
So, when I subsequently came across a set of six ultrasonic pest repellers selling for $14.99 total, I couldn’t resist (nor could others, apparently, as inventory eventually sold out). They’re AC-powered, and each unit is claimed to cover up to 1,600 square feet. I’ll start with some “stock” shots, several of which include “creative” grammar and spelling terms. Can you spot them?
Dual smart chip? Inquiring minds want to know.
I’m not going to proactively point out all of the “creative” English language examples in these, to avoid ruining your investigatory fun, but “Desinsectisation” is just…awesome.
A half dozen for a bit more than a dozen (dollars)
Now for some real-life shots, as usual beginning with the outer box, also as usual accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:
I couldn’t resist:
Now let’s peer inside:
Remove one of the still-wrapped devices:
and the sliver of literature below them comes into view:
which, of course, I promptly tore while getting it out:
English on one side I’d expected. German on the other? Unexpected.
Here’s our now-“unclothed” patient:
When I first glanced at the screw heads on the back side, their seeming deviation had me wondering whether this was some sort of crude intrusion-prevention security scheme.
Turns out the bottom one had just come into my possession already partially stripped:
And have you yet noticed a curious omission both from the outer packaging and the device itself? Ponder for a bit…I’m not going anywhere…
…time’s up! Although there’s a FCC logo on the back of the box, there’s no actual FCC certification ID to be found anywhere. Even though…y’know…it’s a broadcast device. Anyhoo, onward:
Let’s plug ‘er in before taking ‘er apart. Thar she glows, just like in the stock photos:
For what it’s worth, my Collie seemingly wasn’t phased in the slightest by the supposed ultrasonic broadcast!
Getting to the guts
And now let’s dive inside:
Here’s the supposed ultrasonic-frequency transducer:
and the diminutive PCB:
See that screw, identical to the other two you’ve already seen, at the bottom? Interestingly, at least to me, there’s another screw hole, this one unpopulated, above the PCB. Apparently, the chassis was designed for multiple PCB variants, including one larger than this one. Regardless, removing the screw led to subsequent easy removal of the PCB itself.
Leaving nothing particularly exciting behind.
Let’s start with the PCB front side, which you’ve already seen in several past photos:
There are indeed two main ICs here, to the earlier “dual chip” reference, although still stretching the association. The upper four-lead one, toward the left side of the photo, is faintly marked “MB6F” and appears to be a bridge rectifier, with the “BD1” PCB mark presumably standing for “bridge diode” (not, in this case at least, ferrite bead). Its presumed-by-me function, as we’ve seen before, is to act as a crude AC/DC converter in conjunction with a yet-to-be-seen low pass filter (capacitor).
The other IC, labeled U1, eight-lead and below and to the right of its companion, is absent any topside mark and therefore something of a mystery, although if I was a betting man, I’d lay odds it’s an inexpensive MCU, akin to the one in Big Clive’s teardown victim. What about those glowing LEDs you saw in the earlier plugged-in device photo? They’re at the far upper right and left, with their PCB markings on the other side, which you’ll see next.
They operate somewhat oddly. When I preview them through my smartphone’s camera and display in “still” image capture mode, they generally blink at what I’m guessing is a 60-Hz rate. That said, they also occasionally dim and then return to their prior illumination intensity, and sometimes the blinking also temporarily ceases. When previewed in “video” mode on the smartphone (which I know because I tried to capture a clip of the aforementioned behavior), they exhibit constant illumination. Mysterious!
You might have also noticed PCB sites for two other LEDs, LED3 and LED4, although they seem to be unpopulated, along with multiple other unpopulated locations on this side of the PCB. Chassis placeholders for multiple PCBs…placeholders for additional components on this PCB variant…once again, all very mysterious!
In closing, let’s flip the PCB over.
At top is capacitor C2 which, given its proximity both to the AC inputs to the PCB and to the bridge rectifier, I’m guessing is our aforementioned low-pass filter. The resistor below is specifically labeled “FR1”, presumably referencing its augmented fuse function.
Aside from one other electrolytic capacitor, along with pass-through holes to solder sites on the other side of the PCB for the dual two-wire harnesses (one going to the “ultrasonic speaker”, the other to the AC plug), that’s it of note.
And with that, I’ll conclude for today. At some point after this teardown is published, as usual allowing time for reader questions, I’ll put the device back together, presumably still functional afterward (to whatever degree that term is relevant in this particular case).
But what do I do then? Donate the lot to some pest-plagued recipient hoping against hope for a miracle? Or donate all of ’em to the dump? Let me know your thoughts on this ethical quagmire, or anything else I’ve discussed here, in the comments!
—Brian Dipert is the associate editor, as well as a contributing editor, at EDN.
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