9 ms·

Consumer-grade routers on puny power supplies (2024)

84 points by fanf2 2y ago

Animats 2y ago
Huh. Is that line on the scope a one-time glitch at power up, or does it happen on every cycle? "Rummaging through my old parts box unearthed a power supply that was a bit more powerful than the one that came with the router, and even fit the connector." Is he describing a "wall wart" type power supply? A picture would help. A teardown would help more. There are large numbers of really crappy wall-powered DC supplies available, mostly from China.[1] Look for a UL approval marking and a UL approval number. That indicates at least some attention to quality. UL is mostly concerned about fire safety, but their basic test for power supplies includes connecting it to a load box at the power supply's maximum rating, then running it for a while to see if it overheats. This catches power supplies with exaggerated ratings. Avoid no-name power supplies. This is a well-known headache. [1] https://hackaday.com/tag/wall-wart/ https://hackaday.com/tag/wall-wart/
- giantrobot 2y ago
  I've found that a lot of devices anymore just pack in those no-name power supplies. Many things don't even ship with branded PSUs now. It makes sorting my box-o-wallwarts a giant pain in the ass. Edit: don't repeat myself
  - deleted 2y ago
    [deleted]
  - themaninthedark 2y ago
    Label maker, apply to power supply!
    - giantrobot 2y ago
      This has been my exact strategy. I've finally got about half my box-o-wallwarts labeled for their associated device.
      - LeifCarrotson 2y ago
        This is the opposite of my strategy: each wall wart in my box gets a legible label with voltage and ampacity. Eg 9V 200mA, 12V 500mA, etc. Each device gets a corresponding legible label with its required voltage and maximum current. Then it's just a matter of picking out one that's adequate for the selected device, it's a many-to-many mapping with lots of valid solutions, not one-to-one.
        pests 2y ago
        Connector size doesn’t matter to you?
- devwastaken 2y ago
  Listing labs are a known scam. you pay them significant amounts to curb what result you want. then you change the components to cheaper quality and sell those. The correct and effective means to have safe and correct products is to monetarily and criminally punish corps that produce faulty goods.
  - immibis 2y ago
    None of us have the power to do that. The ones with the power do that aren't among us.
- ssl-3 2y ago
  UL tests electrical products for safety. It isn't a mark of quality, or of fitness for purpose. It does mean that the device(s) submitted for testing are unlikely to burn your house down, though.
  - immibis 2y ago
    And it wouldn't be expected to imply anything about how the device works on a non-standard power source, anyway.
    - ssl-3 2y ago
      No, of course not. UL doesn't test the brainbox part at all. The AC -> DC power supply is tested for safety by UL, but the thing powered by that power supply is not tested at all. Normal UL testing and listing deals with mains-powered devices, not low-voltage DC-powered devices.
gruez 2y ago
>Clearly, the router is pulling more current during the dip than the power supply on my solar circuit can supply. >[...] >Ideally, we’d want manufacturers to put capacitance to that effect into their router power supplies or at least routers. But we realise that capacitors cost a few cents each and aren’t really required on stable grid supplies. And manufacturing costs matter. Weird this was being seemingly blamed on "puny power supplies", and that "ideally" manufacturers should be overspecing their power supplies to accommodate his use case. Does he also think manufacturers should "ideally" add a battery to routers on the off chance that there's a transient blackout? More to the point, he supposedly has a "4500W peak solar sinewave inverter", and his router probably consumes no more than 50W. That 50W is unlikely to cause issues with such a system, and even if it was the straw that broke the camel's back, it's weird to blame it on the router, rather than the inverter or the entire system. If you had a take-home salary of $10k, blew it all on gambling, then your card got declined on a starbucks purchase, you wouldn't characterize this as "my coffee habit was using more money than my income can supply".
- krunck 2y ago
  There are server power supplies that won't work on non-sinusoidal power sources. (read: cheap UPSs) I learned that the hard way.
  - namibj 2y ago
    Use one that has the "240VDC (China only)" rating, and feed them proper DC. Or get the modern western ~300V DC input ones, there's no good (technical) reason to feed AC from a non-grid-tie inverter to a SMPS-only circuit. The DC can be quite passive, just switched in via a relay and anti-reverse-current-diode together with bridge-rectified mains, she otherwise just bare battery bank voltage There's a reason modern data centers use that style of setup (except with a central power factor correcting rectifier, not a plain bridge rectifier, and often hanging the batteries on it directly using controlled rectifier output voltage to control battery charging).
- digitalPhonix 2y ago
  The 50W load (if that) isn’t the problem - a lot of cheap power supplies assume a perfect sinusoid which you get from a spinning mechanical source of electricity. The inverter probably only does a few step approximation of a sin wave which is fine for most things, but clearly not for this power supply which browns out (I’m guessing during an extended period of 0v on the stair step sin approximation). Whether your average power supply should be tolerant is unclear, but if it’s the only device playing up it’s clearly less tolerant of imperfect power than everything else.
ajuc 2y ago
Some things never change. I remember waking up early on Saturdays in 90s to load some game from tape on my C64 before the neighbor starts his sawmill. Couldn't load anything when it was running :)
- mmcgaha 2y ago
  I used to run my mother's vacuum cleaner plugged into the same outlet as my C64 to keep it from crashing.
causality0 2y ago
So he repeatedly feeds dirty power into consumer routers and is surprised when they don't function correctly. Then he writes an article complaining about it while being careful to exclude any relevant facts like the models of router and power supply or any actual measurements from his oscilloscope. Gold star writing this is.
ianhowson 2y ago
Irrelevant. 1. Downstream of the mains power supply are DC-DC converters that run the router hardware. Those contain the filters and capacitance you think you're fixing. Nothing in that router actually cares about mains power quality. They absolutely do not care about perfect sinusoids. 2. If you were seeing insufficient power to the router, you would observe crashes and faults -- not slowdowns. 3. Two different routers showed the same behavior, which suggests that the fault lies outside the router+power supply and more to do with something common (e.g. network, laptop). The dip shows a reduction in voltage, and a larger one than I would like, but without a scale on either time or voltage, it's difficult to guess if it actually matters. I would suspect not, since the device does boot successfully. Again, the voltage doesn't matter, since the router runs off its internal DC-DC supplies, not the external power supply. I'm happy that the capacitor and new supply has fixed the issue, but I'm unconvinced by the explanation. Check grounding between inverter and laptop.
- Panzer04 2y ago
  Generic issues like brownouts and crashes I can believe as a power fault. Slowdowns? Not likely. Possibly he's not describing the problems right. I can certainly believe a shitty enough power supply would cause problems.
  - PaulDavisThe1st 2y ago
    Yeah, I've lost two modem/routers to power outage incidents, despite them being on a reasonable quality surge protector. But that was an all-or-nothing failure mode in which they would power up but never do anything else. Performance changes is a claim that requires much stronger evidence.
  - mindslight 2y ago
    When I hooked a Raspberry Pi (model B maybe?) up to an analog input on my Marantz NR1605, the UI of the receiver got noticeably laggier until it was barely responsive. Disconnecting made the UI perk back up. I noticed the Pi had a 2.5V DC bias on its audio out. I didn't investigate further. As for the article, I'm left with more questions. Surely the solar inverter wasn't running all the time in series, like a double conversion UPS, right? So how how would the mains waveform have been significantly affected in normal operation? Also those scope traces, what's the scale? Are we talking 100mV dip, or a 1V dip? And is that a storage scope, or is that one cycle of the supply's ongoing ripple? And the complete lack of any dip on the "fixed" trace with extra capacitance makes me wonder if they even got the triggering right.
deleted 2y ago
[deleted]
timewizard 2y ago
> But we realise that capacitors cost a few cents each and aren’t really required on stable grid supplies. The type that can do this also fail at a rate that depends on temperature. Which is why they shouldn't use them internally. If you truly need to condition your power than you need to do it separately as almost no one shares in this problem and would not be benefited by adding these degradable parts.
baobun 2y ago
Similarly: I thought I had some bad workstation hardware (brand-name mobo and PSU), seeing severe memory corruption issues. After putting it behind a UPS (only after losing a zpool from it), it's all clean.
deleted 2y ago
[deleted]
friend_Fernando 2y ago
An even better fix for this category of problems is DC distribution at the homelab scale. I've replaced most of my 5V and 12V wall warts with a PC PSU. A number of transient issues that used to affect some of the gear disappeared.
- immibis 2y ago
  At Chaos Communication Camp (2023) I brought a hard drive to attach to a Raspberry Pi with a USB adapter, and a little solar power system because I could. I realized the inverter was using about 5 watts idle and that was about half of my average power budget for the camp (counting night time), so I cut the adapter's cable and re-wired it directly to the battery. Worked fine. Most components in a computer that nominally run at 12V are passing it through some sort of adaptive converter (either a buck converter or directly to a speed-controlled motor) so they have a fairly wide voltage tolerance. I obviously didn't find out if it reduced the lifespan at all.
patrakov 2y ago
I think I know what has happened. The PSU manufacturer has cheaped out on the capacitor in the input, in hope that the circuit which switches the primary coil would still be able to extract enough power even if the instantaneous mains voltage drops to something as low as 30V (which it does twice every period). So, on a pure sine wave input, they only need to cover this (relatively short, below 3%) below-30V gap twice every period. But with the UPS feeding the circuit, the situation is different: most of the time, the rectified voltage is 340V, however, there is a significant period of exactly 0V that still needs to be covered by the capacitor.
klaff 2y ago
My guess is something about the waveform of the inverter is tripping up something in the power supply. Many moons ago I worked on laser printers and we had a customer who was melting fusers. Turned out their UPS had small but fast spikes around the zero-crossing that would exceed the allowable dV/dt and trigger the triac to turn on even though there was no gate signal present. That's not the mechanism here but I would scope the AC line from the inverter. I bet it's not clean and something about the weird waveform is confusing the power supply. I don't think the 4500 W inverter is even noticing the loads from the router power supply. The power supply is misbehaving browning out briefly. Nothing in the router will run straight from that supply though, there are DC-DC converters to make the lower voltage used on the board. It would be kinda fascinating to figure out what is really happening to lead to the described behaviors.

84 points by fanf2 2y ago

Huh. Is that line on the scope a one-time glitch at power up, or does it happen on every cycle? "Rummaging through my old parts box unearthed a power supply that was a bit more powerful than the one that came with the router, and even fit the connector." Is he describing a "wall wart" type power supply? A picture would help. A teardown would help more. There are large numbers of really crappy wall-powered DC supplies available, mostly from China.[1] Look for a UL approval marking and a UL approval number. That indicates at least some attention to quality. UL is mostly concerned about fire safety, but their basic test for power supplies includes connecting it to a load box at the power supply's maximum rating, then running it for a while to see if it overheats. This catches power supplies with exaggerated ratings. Avoid no-name power supplies. This is a well-known headache. [1] https://hackaday.com/tag/wall-wart/ https://hackaday.com/tag/wall-wart/

giantrobot 2y ago
I've found that a lot of devices anymore just pack in those no-name power supplies. Many things don't even ship with branded PSUs now. It makes sorting my box-o-wallwarts a giant pain in the ass. Edit: don't repeat myself
- deleted 2y ago
  [deleted]
- themaninthedark 2y ago
  Label maker, apply to power supply!
  - giantrobot 2y ago
    This has been my exact strategy. I've finally got about half my box-o-wallwarts labeled for their associated device.
    - LeifCarrotson 2y ago
      This is the opposite of my strategy: each wall wart in my box gets a legible label with voltage and ampacity. Eg 9V 200mA, 12V 500mA, etc. Each device gets a corresponding legible label with its required voltage and maximum current. Then it's just a matter of picking out one that's adequate for the selected device, it's a many-to-many mapping with lots of valid solutions, not one-to-one.
      - pests 2y ago
        Connector size doesn’t matter to you?
devwastaken 2y ago
Listing labs are a known scam. you pay them significant amounts to curb what result you want. then you change the components to cheaper quality and sell those. The correct and effective means to have safe and correct products is to monetarily and criminally punish corps that produce faulty goods.
- immibis 2y ago
  None of us have the power to do that. The ones with the power do that aren't among us.
ssl-3 2y ago
UL tests electrical products for safety. It isn't a mark of quality, or of fitness for purpose. It does mean that the device(s) submitted for testing are unlikely to burn your house down, though.
- immibis 2y ago
  And it wouldn't be expected to imply anything about how the device works on a non-standard power source, anyway.
  - ssl-3 2y ago
    No, of course not. UL doesn't test the brainbox part at all. The AC -> DC power supply is tested for safety by UL, but the thing powered by that power supply is not tested at all. Normal UL testing and listing deals with mains-powered devices, not low-voltage DC-powered devices.

gruez 2y ago

>Clearly, the router is pulling more current during the dip than the power supply on my solar circuit can supply. >[...] >Ideally, we’d want manufacturers to put capacitance to that effect into their router power supplies or at least routers. But we realise that capacitors cost a few cents each and aren’t really required on stable grid supplies. And manufacturing costs matter. Weird this was being seemingly blamed on "puny power supplies", and that "ideally" manufacturers should be overspecing their power supplies to accommodate his use case. Does he also think manufacturers should "ideally" add a battery to routers on the off chance that there's a transient blackout? More to the point, he supposedly has a "4500W peak solar sinewave inverter", and his router probably consumes no more than 50W. That 50W is unlikely to cause issues with such a system, and even if it was the straw that broke the camel's back, it's weird to blame it on the router, rather than the inverter or the entire system. If you had a take-home salary of $10k, blew it all on gambling, then your card got declined on a starbucks purchase, you wouldn't characterize this as "my coffee habit was using more money than my income can supply".

krunck 2y ago
There are server power supplies that won't work on non-sinusoidal power sources. (read: cheap UPSs) I learned that the hard way.
- namibj 2y ago
  Use one that has the "240VDC (China only)" rating, and feed them proper DC. Or get the modern western ~300V DC input ones, there's no good (technical) reason to feed AC from a non-grid-tie inverter to a SMPS-only circuit. The DC can be quite passive, just switched in via a relay and anti-reverse-current-diode together with bridge-rectified mains, she otherwise just bare battery bank voltage There's a reason modern data centers use that style of setup (except with a central power factor correcting rectifier, not a plain bridge rectifier, and often hanging the batteries on it directly using controlled rectifier output voltage to control battery charging).
digitalPhonix 2y ago
The 50W load (if that) isn’t the problem - a lot of cheap power supplies assume a perfect sinusoid which you get from a spinning mechanical source of electricity. The inverter probably only does a few step approximation of a sin wave which is fine for most things, but clearly not for this power supply which browns out (I’m guessing during an extended period of 0v on the stair step sin approximation). Whether your average power supply should be tolerant is unclear, but if it’s the only device playing up it’s clearly less tolerant of imperfect power than everything else.

ajuc 2y ago

Some things never change. I remember waking up early on Saturdays in 90s to load some game from tape on my C64 before the neighbor starts his sawmill. Couldn't load anything when it was running :)

mmcgaha 2y ago
I used to run my mother's vacuum cleaner plugged into the same outlet as my C64 to keep it from crashing.

causality0 2y ago

So he repeatedly feeds dirty power into consumer routers and is surprised when they don't function correctly. Then he writes an article complaining about it while being careful to exclude any relevant facts like the models of router and power supply or any actual measurements from his oscilloscope. Gold star writing this is.

ianhowson 2y ago

Irrelevant. 1. Downstream of the mains power supply are DC-DC converters that run the router hardware. Those contain the filters and capacitance you think you're fixing. Nothing in that router actually cares about mains power quality. They absolutely do not care about perfect sinusoids. 2. If you were seeing insufficient power to the router, you would observe crashes and faults -- not slowdowns. 3. Two different routers showed the same behavior, which suggests that the fault lies outside the router+power supply and more to do with something common (e.g. network, laptop). The dip shows a reduction in voltage, and a larger one than I would like, but without a scale on either time or voltage, it's difficult to guess if it actually matters. I would suspect not, since the device does boot successfully. Again, the voltage doesn't matter, since the router runs off its internal DC-DC supplies, not the external power supply. I'm happy that the capacitor and new supply has fixed the issue, but I'm unconvinced by the explanation. Check grounding between inverter and laptop.

Panzer04 2y ago
Generic issues like brownouts and crashes I can believe as a power fault. Slowdowns? Not likely. Possibly he's not describing the problems right. I can certainly believe a shitty enough power supply would cause problems.
- PaulDavisThe1st 2y ago
  Yeah, I've lost two modem/routers to power outage incidents, despite them being on a reasonable quality surge protector. But that was an all-or-nothing failure mode in which they would power up but never do anything else. Performance changes is a claim that requires much stronger evidence.
- mindslight 2y ago
  When I hooked a Raspberry Pi (model B maybe?) up to an analog input on my Marantz NR1605, the UI of the receiver got noticeably laggier until it was barely responsive. Disconnecting made the UI perk back up. I noticed the Pi had a 2.5V DC bias on its audio out. I didn't investigate further. As for the article, I'm left with more questions. Surely the solar inverter wasn't running all the time in series, like a double conversion UPS, right? So how how would the mains waveform have been significantly affected in normal operation? Also those scope traces, what's the scale? Are we talking 100mV dip, or a 1V dip? And is that a storage scope, or is that one cycle of the supply's ongoing ripple? And the complete lack of any dip on the "fixed" trace with extra capacitance makes me wonder if they even got the triggering right.

deleted 2y ago

[deleted]

timewizard 2y ago

> But we realise that capacitors cost a few cents each and aren’t really required on stable grid supplies. The type that can do this also fail at a rate that depends on temperature. Which is why they shouldn't use them internally. If you truly need to condition your power than you need to do it separately as almost no one shares in this problem and would not be benefited by adding these degradable parts.

baobun 2y ago

Similarly: I thought I had some bad workstation hardware (brand-name mobo and PSU), seeing severe memory corruption issues. After putting it behind a UPS (only after losing a zpool from it), it's all clean.

deleted 2y ago

[deleted]

friend_Fernando 2y ago

An even better fix for this category of problems is DC distribution at the homelab scale. I've replaced most of my 5V and 12V wall warts with a PC PSU. A number of transient issues that used to affect some of the gear disappeared.

immibis 2y ago
At Chaos Communication Camp (2023) I brought a hard drive to attach to a Raspberry Pi with a USB adapter, and a little solar power system because I could. I realized the inverter was using about 5 watts idle and that was about half of my average power budget for the camp (counting night time), so I cut the adapter's cable and re-wired it directly to the battery. Worked fine. Most components in a computer that nominally run at 12V are passing it through some sort of adaptive converter (either a buck converter or directly to a speed-controlled motor) so they have a fairly wide voltage tolerance. I obviously didn't find out if it reduced the lifespan at all.

patrakov 2y ago

I think I know what has happened. The PSU manufacturer has cheaped out on the capacitor in the input, in hope that the circuit which switches the primary coil would still be able to extract enough power even if the instantaneous mains voltage drops to something as low as 30V (which it does twice every period). So, on a pure sine wave input, they only need to cover this (relatively short, below 3%) below-30V gap twice every period. But with the UPS feeding the circuit, the situation is different: most of the time, the rectified voltage is 340V, however, there is a significant period of exactly 0V that still needs to be covered by the capacitor.

klaff 2y ago

My guess is something about the waveform of the inverter is tripping up something in the power supply. Many moons ago I worked on laser printers and we had a customer who was melting fusers. Turned out their UPS had small but fast spikes around the zero-crossing that would exceed the allowable dV/dt and trigger the triac to turn on even though there was no gate signal present. That's not the mechanism here but I would scope the AC line from the inverter. I bet it's not clean and something about the weird waveform is confusing the power supply. I don't think the 4500 W inverter is even noticing the loads from the router power supply. The power supply is misbehaving browning out briefly. Nothing in the router will run straight from that supply though, there are DC-DC converters to make the lower voltage used on the board. It would be kinda fascinating to figure out what is really happening to lead to the described behaviors.