7 ms·

If you scroll down a bit, you'll see that sure enough this involved a switched-mode power supply, /probably some very cheap no-name/ [nope, missed that they inc

by xoa 10y ago

If you scroll down a bit, you'll see that sure enough this involved a switched-mode power supply, /probably some very cheap no-name/ [nope, missed that they included pictures of it]. Even though they're supposed to be at least minimally regulated under Title 47 part 15(B), in practice they're often a plague upon RF and as the article states sometimes the FCC has trouble mustering the energy for small spot trouble. While I feel more generous towards the FCC then some of the commentary I've seen on this, in that I don't think they've been remotely allocated the resources they should have to deal with this kind of small hotspot popping up since historically it was less an emergency matter, it's an issue (and a bit more surprising when it's a request from law enforcement, even if local). I think it's a good reminder though that while modern wireless links represent a lot of fantastic engineering and are very valuable they can also be pretty fragile, and it's important to have a physical (be it digital or mechanical) fallback for critical tasks like authentication (in this case to access or startup a vehicle). There are situations where being surprisingly unable to operate ones vehicle (or access a building or whatever) could be quite serious, and the IoT ecosystem needs to give surprise interference some consideration as well. These sorts of incidents should also make society think about failure modes when it comes to interference, be it accidental or intentional. Law enforcement in particular should consider it from two sides, both in terms of emergency planning for if there was a major case (during an emergency or not), and as a strong note of caution vs some of the noises that have been made about LEOs themselves purposefully doing jamming during "periods of unrest" or the like. In an age of ever proliferating wireless devices, beware unintended consequences. [Edit]: Thanks to Animats below for pointing out that it's UL approved Ventex, it's not in the article text but a photo is included at the bottom. So I guess that underlines SMPS quality control issues can be tough even with more attention paid, and shouldn't be taken for granted in planning even with part control. Though this also seems like it should make it something the FCC should give more attention in terms of confirming that this was a lemon and not an indicator of some more widespread problem. It should be easier for them to do that with a US-based operation.

Florin_Andrei 10y ago
As someone who has designed and built switching power supplies, the article brought back funny memories. It's so easy to make an SPS that is essentially a disaster for all RF spectrum around it. In fact, some of my early SPSs, I could "detect" they were on because the noise coming out of a radio receiver nearby would change when I turned the supply on. OTOH, it's pretty easy to take measures that ensure the RF is kept under control. Shielding is important, but first make sure your circuit doesn't make excessive amounts of RF to begin with.
- lutusp 10y ago
  > As someone who has designed and built switching power supplies, the article brought back funny memories. Myself also. I designed switching power supplies for the Space Shuttle, some of which were meant to power fluorescent lights. NASA wanted dimmable fluorescent lights in the crew quarters, but they also wanted no EMI. Well, they got both -- I figured out a way to dim the fluorescents using a magnetic amplifier instead of the semiconductor switching methods that were common at the time, and (as I intended) the magnetic amplifier created no interference at all. The details: http://arachnoid.com/PDF_archive/IES_october_1976.pdf http://arachnoid.com/PDF_archive/IES_october_1976.pdf
  - Gibbon1 10y ago
    That's amusing. I have a bombarder for a neon shop, it uses a magnetic amplifiers to control the current. Thing weighs about 75lbs.
    - deleted 10y ago
      [deleted]
- Gibbon1 10y ago
  I have this feeling that in this case the neon tube or wiring on the sign is 'bad' and also unfortunately working unusually well as an antenna. Considering that unit might put out 30 Watts, if a fraction of that ends up at RF it'll cause problems for radio's around it. It'd be interesting to probe that sign with a high voltage oscilloscope probe.
  - Florin_Andrei 10y ago
    > the neon tube or wiring on the sign [...] unfortunately working unusually well as an antenna Sounds about right.
- lathiat 10y ago
  Fun EEVBlog episode: EEVblog #767 - Super Regenerative Receiver Problems (https://www.youtube.com/watch?v=XzwEymOslFo https://www.youtube.com/watch?v=XzwEymOslFo) TL;DR: Wireless power switch, if you put two of the wireless switches next to each other - they both stop working because they interfere with each other. Sold every day at Bunnings (australian home hardware/etc store) by a major brand (Arlec)
paulgerhardt 10y ago
>the IoT ecosystem needs to give surprise interference some consideration as well. In the early days of Lockitron we were using the 433MHz bandwidth. We would occasionally experience state wide non-response to our locks despite having full backend network connectivity. Eventually we tracked the problem down to sunspots. Coming from software it was one of the more bizarre things to debug.
- robterrell 10y ago
  Seriously, sunspots? Would love to see more about this. Did you write it up anywhere?
  - paulgerhardt 10y ago
    I mean...there's not much more to the story than that. 2011 was a bit crazy for the Sun [1]. There were two or three x-class flares that jammed transmission for a short period. Multiple customer reports coincided with the February and August events that year. The February flare was caused by sunspot 1158 [2] and the August flare was caused by sunspot 1263 [3]. Deploying those locks across hundreds of locations we saw quite a bit of unusual stuff. Locks would work fine on one side of a building but not the other - the bad side faced the San Francisco bay - deduced it was from all the SF/Oakland Radio traffic. Another location would experience problems during baseball games. (Stadium was next door). Cell tower guys have even crazier stories. One involves my colleague who had a bitcoin mine in his garage. Few dozen graphics cards humming along at ~900MHz knocked out the whole voice uplink for 4 square miles. (He happened to be pretty close to the cell tower and raised the noise floor just enough to make cell phones all but useless.) Working in ISM bands can be brutal, but it will teach you a lot and quickly. [1] http://www.space.com/14060-2011-restless-sun-solar-activity-review.html http://www.space.com/14060-2011-restless-sun-solar-activity-... [2] http://www.space.com/10862-sun-erupts-powerful-solar-flare.html http://www.space.com/10862-sun-erupts-powerful-solar-flare.h... [3] https://www.youtube.com/watch?v=heVeq_anewU https://www.youtube.com/watch?v=heVeq_anewU
  - CamperBob2 10y ago
    The "sunspots" explanation doesn't pass the smell test for several reasons. It's the sort of thing you tell a customer to get them to go away and give the problem a chance to resolve itself. More likely, in that part of the spectrum, they were seeing adverse effects from (probably undisclosed) military R&D activities. Might as well have been sunspots, for all they could've done about it.
superuser2 10y ago
And still people will point and laugh at the fools who wasted money on brand-name phone chargers when the generic ones on eBay work just as well.
- andai 10y ago
  My problem with generic chargers is a bit less subtle: my phone battery melted.
  - kevin_thibedeau 10y ago
    > My problem with generic chargers is a bit less subtle: my phone battery melted. Which is a problem with the electronics in your phone not the charger. All Lithium-Ion batteries need to have an on board charge management IC to guard against overcharging. The power supply is just a dumb DC supply possibly with a way to request higher currents. In the end it is the responsibility of the phone electronics to limit current into the battery. Either they failed, were poorly designed, or the battery itself failed.
    - Sanddancer 10y ago
      Unless the cheap transformer in the supply failed, and the charger started pumping wall current into the charger. Here's one disassembly of a crappy charger https://www.youtube.com/watch?v=afePhiXpsoA https://www.youtube.com/watch?v=afePhiXpsoA
Animats 10y ago
you'll see that sure enough this involved a switched-mode power supply, probably some very cheap no-name. No, made in USA and UL approved.[1][2][3] [1] http://www.arrl.org/news/view/amateur-radio-sleuthing-pins-down-source-of-strange-rf-interference http://www.arrl.org/news/view/amateur-radio-sleuthing-pins-d... [2] http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=PWIK.E187585&ccnshorttitle=Neon+Transformers+and+Power+Supplies&objid=1074113979&cfgid=1073741824&version=versionless&parent_id=1073991515&sequence=1 http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/sh... [3] http://ventextech.com/ http://ventextech.com/
- cperciva 10y ago
  ... or possibly a cheap imitation of an approved power supply.
  - Cthulhu_ 10y ago
    Or a manufacturing error that wasn't detected in QA.
deleted 10y ago
[deleted]

by xoa 10y ago

Florin_Andrei 10y ago

As someone who has designed and built switching power supplies, the article brought back funny memories. It's so easy to make an SPS that is essentially a disaster for all RF spectrum around it. In fact, some of my early SPSs, I could "detect" they were on because the noise coming out of a radio receiver nearby would change when I turned the supply on. OTOH, it's pretty easy to take measures that ensure the RF is kept under control. Shielding is important, but first make sure your circuit doesn't make excessive amounts of RF to begin with.

lutusp 10y ago
> As someone who has designed and built switching power supplies, the article brought back funny memories. Myself also. I designed switching power supplies for the Space Shuttle, some of which were meant to power fluorescent lights. NASA wanted dimmable fluorescent lights in the crew quarters, but they also wanted no EMI. Well, they got both -- I figured out a way to dim the fluorescents using a magnetic amplifier instead of the semiconductor switching methods that were common at the time, and (as I intended) the magnetic amplifier created no interference at all. The details: http://arachnoid.com/PDF_archive/IES_october_1976.pdf http://arachnoid.com/PDF_archive/IES_october_1976.pdf
- Gibbon1 10y ago
  That's amusing. I have a bombarder for a neon shop, it uses a magnetic amplifiers to control the current. Thing weighs about 75lbs.
  - deleted 10y ago
    [deleted]
Gibbon1 10y ago
I have this feeling that in this case the neon tube or wiring on the sign is 'bad' and also unfortunately working unusually well as an antenna. Considering that unit might put out 30 Watts, if a fraction of that ends up at RF it'll cause problems for radio's around it. It'd be interesting to probe that sign with a high voltage oscilloscope probe.
- Florin_Andrei 10y ago
  > the neon tube or wiring on the sign [...] unfortunately working unusually well as an antenna Sounds about right.
lathiat 10y ago
Fun EEVBlog episode: EEVblog #767 - Super Regenerative Receiver Problems (https://www.youtube.com/watch?v=XzwEymOslFo https://www.youtube.com/watch?v=XzwEymOslFo) TL;DR: Wireless power switch, if you put two of the wireless switches next to each other - they both stop working because they interfere with each other. Sold every day at Bunnings (australian home hardware/etc store) by a major brand (Arlec)

paulgerhardt 10y ago

>the IoT ecosystem needs to give surprise interference some consideration as well. In the early days of Lockitron we were using the 433MHz bandwidth. We would occasionally experience state wide non-response to our locks despite having full backend network connectivity. Eventually we tracked the problem down to sunspots. Coming from software it was one of the more bizarre things to debug.

robterrell 10y ago
Seriously, sunspots? Would love to see more about this. Did you write it up anywhere?
- paulgerhardt 10y ago
  I mean...there's not much more to the story than that. 2011 was a bit crazy for the Sun [1]. There were two or three x-class flares that jammed transmission for a short period. Multiple customer reports coincided with the February and August events that year. The February flare was caused by sunspot 1158 [2] and the August flare was caused by sunspot 1263 [3]. Deploying those locks across hundreds of locations we saw quite a bit of unusual stuff. Locks would work fine on one side of a building but not the other - the bad side faced the San Francisco bay - deduced it was from all the SF/Oakland Radio traffic. Another location would experience problems during baseball games. (Stadium was next door). Cell tower guys have even crazier stories. One involves my colleague who had a bitcoin mine in his garage. Few dozen graphics cards humming along at ~900MHz knocked out the whole voice uplink for 4 square miles. (He happened to be pretty close to the cell tower and raised the noise floor just enough to make cell phones all but useless.) Working in ISM bands can be brutal, but it will teach you a lot and quickly. [1] http://www.space.com/14060-2011-restless-sun-solar-activity-review.html http://www.space.com/14060-2011-restless-sun-solar-activity-... [2] http://www.space.com/10862-sun-erupts-powerful-solar-flare.html http://www.space.com/10862-sun-erupts-powerful-solar-flare.h... [3] https://www.youtube.com/watch?v=heVeq_anewU https://www.youtube.com/watch?v=heVeq_anewU
- CamperBob2 10y ago
  The "sunspots" explanation doesn't pass the smell test for several reasons. It's the sort of thing you tell a customer to get them to go away and give the problem a chance to resolve itself. More likely, in that part of the spectrum, they were seeing adverse effects from (probably undisclosed) military R&D activities. Might as well have been sunspots, for all they could've done about it.

superuser2 10y ago

And still people will point and laugh at the fools who wasted money on brand-name phone chargers when the generic ones on eBay work just as well.

andai 10y ago
My problem with generic chargers is a bit less subtle: my phone battery melted.
- kevin_thibedeau 10y ago
  > My problem with generic chargers is a bit less subtle: my phone battery melted. Which is a problem with the electronics in your phone not the charger. All Lithium-Ion batteries need to have an on board charge management IC to guard against overcharging. The power supply is just a dumb DC supply possibly with a way to request higher currents. In the end it is the responsibility of the phone electronics to limit current into the battery. Either they failed, were poorly designed, or the battery itself failed.
  - Sanddancer 10y ago
    Unless the cheap transformer in the supply failed, and the charger started pumping wall current into the charger. Here's one disassembly of a crappy charger https://www.youtube.com/watch?v=afePhiXpsoA https://www.youtube.com/watch?v=afePhiXpsoA

Animats 10y ago

you'll see that sure enough this involved a switched-mode power supply, probably some very cheap no-name. No, made in USA and UL approved.[1][2][3] [1] http://www.arrl.org/news/view/amateur-radio-sleuthing-pins-down-source-of-strange-rf-interference http://www.arrl.org/news/view/amateur-radio-sleuthing-pins-d... [2] http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=PWIK.E187585&ccnshorttitle=Neon+Transformers+and+Power+Supplies&objid=1074113979&cfgid=1073741824&version=versionless&parent_id=1073991515&sequence=1 http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/sh... [3] http://ventextech.com/ http://ventextech.com/

cperciva 10y ago
... or possibly a cheap imitation of an approved power supply.
- Cthulhu_ 10y ago
  Or a manufacturing error that wasn't detected in QA.

deleted 10y ago

[deleted]