Bug zapper "tennis racket"

[NiHaoMike]

You want longer wavelength near-UV LEDs, not the sterilising kind, which are no good as insect attractants. Incidentally LEDs are low efficiency  emitters of short wavelengh UV, thus are only used in niche applications, where glass and mercury are a hazard. Mercury lamps  are much better for most applications. On the other hand, near-UV LEDs are now more efficient than fluorescent tubes, so are ideal for blacklight and insect killers.

I read that some are looking at using UVA and UVB LEDs for sterilizing occupied spaces, since UVC can only be used for unoccupied spaces.

[james_s]

I'm skeptical of the efficacy. Does UVA and UVB affect bacteria and viruses? I thought the thing that makes UV effective for sterilization is that it breaks apart molecular bonds, it damages skin the same way it damages microorganisms.

[MarkMLl]

But should still be adequate once the internal resistance of the crappy "5800mAh" cells I've got lying around is taken into account

Fake capacity rating means nothing about internal resistance.

Although I think that it's legitimate to infer that it's going to be higher than from cells which are fully traceable and test consistently.

I've got one of those little EBD-M05 battery testers, but haven't really got the hang of it yet. What is supposedly a less-capable tester appeared to show that these cheap batteries lose about 10% of their capacity every time they are cycled, at which point I think I'm entitled to be very dubious about their performance.

However, my intended point was that the resistance is probably lower than that of the 2x AA cells being replaced, and probably higher than the 2x D cells I mentioned as having used the last time I did this.

plus the drop on the gnat's whiskers the manufacturer has used to wire up the LV end. If the device had been rated for say 3.5V I'd not have bothered.

IR drop for even the thinnest wires for a few centimeters is mostly ignorable. Plus it is a voltage multiplied self resonant, self regulated flyback design, and the steady state current is rather low once the output cap is charged.

The weakest link is going to be the pushbutton, which looks like it would be underspecced for a TTL signal.

Millions if not billions of these things have been built, and most work fine for their intended design lifetime (1~2 years, which is what most jurisdictions require for warranty).
Self resonating flyback has a maximum duty cycle limit, and that limits maximum inrush current regardless output impedance.

Meaning the power on inrush will not be more than a few amps. For power off, the source is a battery and the sink has a capacitor, so no arcing is possible with a few cm of wire.
Finally, when lifetime of a TTL switch is rated, they are rated to have a maximum bounce time, which the standard can be greatly lowered in power switching applications.

So, a TTL switch rated for millions of cycles can easily operate for ten thousand cycles at 4V 2A. If you use it 10 times a day, it lasts for 3 years. If you intend to use it as a steady HV power supply, then you are at fault, not the device.

Indisputable, but the LV wiring and switch really are /spectacularly/ weedy. It would obviously be possible to replace the wire with something better, but there'd be little point doing that without finding a slightly better switch... which would be unlikely to fit without a bit of hacking. So this really is a "rabbit hole".

Curiously, the HV connections are in nicely braided and impregnated sleeving...

Better quality doesn't mean more expensive. If you can buy high quality leftovers at the same price of low quality brand news, which one would you buy?

Except that it doesn't even need insulated wire: it's a link from the PCB to the exposed electrodes held in place by the moulding of the case, so doesn't need insulation.

somebody really ought to teach these Chinese a bit about industrial design.

We can take over your own market on your own land. That says something.
Western engineers are so much indoctrinated with quality and have no sense to the art of cost reduction.
The goal is not to make utter shit with every cent stripped. The goal is to build products lasting one day more than warranty period (or psychologically accepted lifetime for most people) that is the cheapest to build.

More over, I've seen quite some bad designs with top parts lasting as short if not shorter than good designs with cheap parts. As long as the parts are not utter shit, they should last for at least two or three years in a good design.
That's why you see most cheap consumer devices last for two or three years on average. It is basically the point where costly reliability designs are not needed (DFR is expensive), and cheap parts can be used, while still be legit to sell and keep  a reasonable customer satisfaction.

Well, I did obviously write that with my tongue firmly in my cheek and I can assure you that I have the utmost respect for what the Far East has achieved: I'm old enough to have seen Japan, Hong Kong and Taiwan mature from purveyors of tat although not with the stunning trajectory of Central-Kingdom China, and sufficiently well-read to be aware of at least some of the history.

If called upon to make a point, I would criticise not the ingenuity and focussed aggression of the mainland Chinese, but the utter stupidity of Western consumers who let their greed for "stuff" outweigh the money that they were prepared to plough back into their own manufacturing economy, and in particular I would criticise young people whose culture based on "teh shiny" places no value on study so that they can work out how to design and manufacture it themselves.

MarkMLl

[Zero999]

You want longer wavelength near-UV LEDs, not the sterilising kind, which are no good as insect attractants. Incidentally LEDs are low efficiency  emitters of short wavelengh UV, thus are only used in niche applications, where glass and mercury are a hazard. Mercury lamps  are much better for most applications. On the other hand, near-UV LEDs are now more efficient than fluorescent tubes, so are ideal for blacklight and insect killers.

I read that some are looking at using UVA and UVB LEDs for sterilizing occupied spaces, since UVC can only be used for unoccupied spaces.

I'm skeptical of the efficacy. Does UVA and UVB affect bacteria and viruses? I thought the thing that makes UV effective for sterilization is that it breaks apart molecular bonds, it damages skin the same way it damages microorganisms.

UVA has little impact on viruses. UVB does have some germicidal effect, which is one of the reasons why viruses spread less readily in the summer, but it also causes sunburn, so it can't be used when people are around.