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Ceramic capacitors don't have polarity. Electrolytic ones do. Thing is, electrolytic capacitors have far higher capacitance for their size -- though also higher

Ceramic capacitors don't have polarity. Electrolytic ones do. Thing is, electrolytic capacitors have far higher capacitance for their size -- though also higher resistance. It's something to check, but the polar ones should be clearly marked as such.

magic_smoke_ee 2y ago
Electrolytic capacitors are kinda like lead-acid batteries in that they are polarized through manufacturing processes. A voltage is applied in the factory to anodize the anode with a thin oxide layer. For fun, I think it would be possible to buy a quality low voltage cap and reverse the polarity of it in-situ which would remove the anodization from the new cathode and deposit a new layer on the new anode (former cathode) hopefully without over-pressurizing it to bursting, albeit with much less anticipated lifespan. PSA: Electrolytic capacitors have a rough lifespan of 10 years. Any much older than that need to be checked out-of-circuit for ESR and then capacitance. Also, tantalums (historically) suck(ed). [0] Quality audio equipment from the 80's like a/d/s/ car amps used only ceramic caps and other over-engineered passives, and have the potential (pun intended) to basically last forever. 0. https://www.eevblog.com/forum/projects/whenwhy-(not)-to-use-tantalum-capacitors-pros-cons-alternatives/msg359601/#msg359601 https://www.eevblog.com/forum/projects/whenwhy-(not)-to-use-...
- kevindamm 2y ago
  Or much shorter, around two years, if it was part of the Capacitor Plague. https://en.wikipedia.org/wiki/Capacitor_plague#Premature_failure https://en.wikipedia.org/wiki/Capacitor_plague#Premature_fai... The normal lifespan of a non-solid electrolytic capacitor of consumer quality, typically rated at 2000 h/85 °C and operating at 40 °C, is roughly 6 years. It can be more than 10 years for a 1000 h/105 °C capacitor operating at 40 °C. Electrolytic capacitors that operate at a lower temperature can have a considerably longer lifespan. ... The life of an electrolytic capacitor with defective electrolyte can be as little as two years.
  - Workaccount2 2y ago
    This is also why so many LED bulbs are shit, lots of heat in a small space full of electrolytic caps.
    - magic_smoke_ee 2y ago
      Intentional planned consumption/obsolescence by design. This class of problem is where under-regulation and lack of standards benefits only sellers and cheats buyers. PS: Also, Amazon should be required to test all of the electronic, safety, and food products on its site such that they can prove safety and standards conformance.
      - Filligree 2y ago
        That, and customers insisting on preexisting form factors. Fitting the electronics and LEDs into the space of a traditional lightbulb comes with compromises, such as not having proper heat dissipation on either.
        BlueTemplar 2y ago
        Yeah, you would think they would be two separate devices by now...
      - Workaccount2 2y ago
        I am assuming you are an ee (like myself)...I have never designed a product with a built in expiration, nor have I ever seen any app notes or write ups on the engineering of it - something engineers love to do. What I have seen done is cheaping out on parts in order to get the price as low as possible, because customers shop primarily on price. Not to lash out, but it kind of hits a nerve for me, because people think we design products to purposely fail. Hell no, we try really hard to do the opposite, but everyone just loves to buy the cheapest shit. The $25 LED bulb that will last for eternity will rot on the shelf next to the $3 bulb that will probably be dead in 6 months. And one more "they build these things to fail" complaint will be posted online.
- outworlder 2y ago
  > Any much older than that need to be checked out-of-circuit for ESR and then capacitance And that's a very time consuming and somewhat risky operation on an old machine you want to keep running. Some old PCBs are quite fragile. I wish there was a way to test capacitors without removing them.
  - mgsouth 2y ago
    You can test ESR in-circuit, with caveats. Here's a good thread from EEVblog [1]. [1] https://www.eevblog.com/forum/beginners/is-there-any-way-to-test-capacitors-while-on-the-circuit-board/ https://www.eevblog.com/forum/beginners/is-there-any-way-to-...
- anon_cow1111 2y ago
  Here's a question for EE nerds that happen to be reading this (maybe in the future). What if I have a stash of big electrolytics that have been out of service for 10+ years? I know that I need to reform them over a few days, but can they even run at spec after so long out of operation? We're talking BIG stuff, 400v, 200+J each
  - buescher 2y ago
    For hobby or laboratory purposes, it’s worth a try. Some probably will come back completely. But if you wanted to use them in production, and be able to blame me when it didn’t work, I’d say no.
canadianfella 2y ago
[dead]
83 2y ago
Bipolar electrolytic capacitors are a thing, I recently had to solder up a handful of them in some audio circuits.

magic_smoke_ee 2y ago

Electrolytic capacitors are kinda like lead-acid batteries in that they are polarized through manufacturing processes. A voltage is applied in the factory to anodize the anode with a thin oxide layer. For fun, I think it would be possible to buy a quality low voltage cap and reverse the polarity of it in-situ which would remove the anodization from the new cathode and deposit a new layer on the new anode (former cathode) hopefully without over-pressurizing it to bursting, albeit with much less anticipated lifespan. PSA: Electrolytic capacitors have a rough lifespan of 10 years. Any much older than that need to be checked out-of-circuit for ESR and then capacitance. Also, tantalums (historically) suck(ed). [0] Quality audio equipment from the 80's like a/d/s/ car amps used only ceramic caps and other over-engineered passives, and have the potential (pun intended) to basically last forever. 0. https://www.eevblog.com/forum/projects/whenwhy-(not)-to-use-tantalum-capacitors-pros-cons-alternatives/msg359601/#msg359601 https://www.eevblog.com/forum/projects/whenwhy-(not)-to-use-...

kevindamm 2y ago
Or much shorter, around two years, if it was part of the Capacitor Plague. https://en.wikipedia.org/wiki/Capacitor_plague#Premature_failure https://en.wikipedia.org/wiki/Capacitor_plague#Premature_fai... The normal lifespan of a non-solid electrolytic capacitor of consumer quality, typically rated at 2000 h/85 °C and operating at 40 °C, is roughly 6 years. It can be more than 10 years for a 1000 h/105 °C capacitor operating at 40 °C. Electrolytic capacitors that operate at a lower temperature can have a considerably longer lifespan. ... The life of an electrolytic capacitor with defective electrolyte can be as little as two years.
- Workaccount2 2y ago
  This is also why so many LED bulbs are shit, lots of heat in a small space full of electrolytic caps.
  - magic_smoke_ee 2y ago
    Intentional planned consumption/obsolescence by design. This class of problem is where under-regulation and lack of standards benefits only sellers and cheats buyers. PS: Also, Amazon should be required to test all of the electronic, safety, and food products on its site such that they can prove safety and standards conformance.
    - Filligree 2y ago
      That, and customers insisting on preexisting form factors. Fitting the electronics and LEDs into the space of a traditional lightbulb comes with compromises, such as not having proper heat dissipation on either.
      - BlueTemplar 2y ago
        Yeah, you would think they would be two separate devices by now...
    - Workaccount2 2y ago
      I am assuming you are an ee (like myself)...I have never designed a product with a built in expiration, nor have I ever seen any app notes or write ups on the engineering of it - something engineers love to do. What I have seen done is cheaping out on parts in order to get the price as low as possible, because customers shop primarily on price. Not to lash out, but it kind of hits a nerve for me, because people think we design products to purposely fail. Hell no, we try really hard to do the opposite, but everyone just loves to buy the cheapest shit. The $25 LED bulb that will last for eternity will rot on the shelf next to the $3 bulb that will probably be dead in 6 months. And one more "they build these things to fail" complaint will be posted online.
outworlder 2y ago
> Any much older than that need to be checked out-of-circuit for ESR and then capacitance And that's a very time consuming and somewhat risky operation on an old machine you want to keep running. Some old PCBs are quite fragile. I wish there was a way to test capacitors without removing them.
- mgsouth 2y ago
  You can test ESR in-circuit, with caveats. Here's a good thread from EEVblog [1]. [1] https://www.eevblog.com/forum/beginners/is-there-any-way-to-test-capacitors-while-on-the-circuit-board/ https://www.eevblog.com/forum/beginners/is-there-any-way-to-...
anon_cow1111 2y ago
Here's a question for EE nerds that happen to be reading this (maybe in the future). What if I have a stash of big electrolytics that have been out of service for 10+ years? I know that I need to reform them over a few days, but can they even run at spec after so long out of operation? We're talking BIG stuff, 400v, 200+J each
- buescher 2y ago
  For hobby or laboratory purposes, it’s worth a try. Some probably will come back completely. But if you wanted to use them in production, and be able to blame me when it didn’t work, I’d say no.

canadianfella 2y ago

[dead]

83 2y ago

Bipolar electrolytic capacitors are a thing, I recently had to solder up a handful of them in some audio circuits.