Originally when I bought this I thought it was an ioniser variant as it uses the same case, but it turns out to be one of the common ultrasonic insect and rodent repelling devices which normally make at least some effort to create ultrasonic noise that is supposed to deter bugs.

In reality, there's no strong evidence that these things have any effect on bugs/rodents, and the ones that do generate ultrasonic noise may cause distress to some pets who will hear it as a loud electronic siren noise like an alarm going off continuously.

This one is bizarre as it has all the circuitry that COULD produce some ultrasonic sound, but the microcontroller does not actually put a signal out to the transistor that switches the sounder.

Effectively this unit is just a box with an LED that toggles on and off with a button.

Maybe the reason they've specifically described this as a bed/dust mite device is because they are microscopically small and therefore the units operation is hard to disprove.

The meter I used to try and probe the output actually has a frequency range up to 100MHz.

On a plus note, some may find the case quite useful for their own projects.
Here's a non-affiliate link to AliExpress (not a sponsor):-
https://www.aliexpress.com/item/1005009619658768.html
Don't pay more than £3.



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