Can unplugged electronics be dangerous?

[Olic2]

I don't remember the video specifically but in one episode of Scrapyard Wars, Linus was was looking for parts and came across a bunch of PSU units just kind of jumbled together in a box. He pointed out that it was hella dangerous, and that it could kill someone if something happened. Can someone smarter than me explain what's dangerous about that? Thanks in advance.

[Bombastinator]

3 minutes ago, Olic2 said:

I don't remember the video specifically but in one episode of Scrapyard Wars, Linus was was looking for parts and came across a bunch of PSU units just kind of jumbled together in a box. He pointed out that it was hella dangerous, and that it could kill someone if something happened. Can someone smarter than me explain what's dangerous about that? Thanks in advance.

Lacking a smartness gauge I’ll try it anyway ‘cause I got hubris like that:

 

PSUs have capacitors.  They’re not unlike batteries.  The result is a pile of random PSUs could still be holding charge and it could be a lot of charge.

 

When I read the headline I imagined someone swinging a toaster around their head like a flail though so still yes.

[Srijan Verma]

All except ones with capacitors even those can be discharged

[Samfisher]

Exposed electronics can be, electronics as a whole no.

[GenericFanboy]

12 minutes ago, Olic2 said:

I don't remember the video specifically but in one episode of Scrapyard Wars, Linus was was looking for parts and came across a bunch of PSU units just kind of jumbled together in a box. He pointed out that it was hella dangerous, and that it could kill someone if something happened. Can someone smarter than me explain what's dangerous about that? Thanks in advance.

Capacitors are always dangerous, 

 Dont think you'd ever wanna touch a capacitor like that.

 

Also! everything could be dangerous. If you throw a potato hard enough at someone its dangerous too.

[Srijan Verma]

3 minutes ago, Samfisher said:

Exposed electronics can be, electronics as a whole no.

well you know psus are closed

(yes i know what you gonna say, just  a joke)

[Samfisher]

4 minutes ago, Srijan Verma said:

well you know psus are closed

(yes i know what you gonna say, just  a joke)

Not the ones Linus was rummaging around in a box in a random shop for that video

[GenericFanboy]

5 minutes ago, Srijan Verma said:

well you know psus are closed

(yes i know what you gonna say, just  a joke)

Have you ever seen mac's psu's? those are a joke in how dangerous they are

[YellowJersey]

CRT monitors/TVs are also something you need to be careful with.

[Olic2]

24 minutes ago, Bombastinator said:

Lacking a smartness gauge I’ll try it anyway ‘cause I got hubris like that:

 

PSUs have capacitors.  They’re not unlike batteries.  The result is a pile of random PSUs could still be holding charge and it could be a lot of charge.

 

When I read the headline I imagined someone swinging a toaster around their head like a flail though so still yes.

Thank you for your answer. These capacitors; do they still hold enough charge to hurt someone? Even after being turned off for an indefinite amount of time? 

[Gegger]

4 minutes ago, Olic2 said:

Thank you for your answer. These capacitors; do they still hold enough charge to hurt someone? Even after being turned off for an indefinite amount of time? 

caps can hold charge for a long time, sometimes years. it depends on the quality of the caps and other factors. can they hurt someone? definitely, don't be a @Schnoz and shock yourself painfully with a camera flash cap, but they can kill at higher capacities/charges. properly discharged caps won't do anything even if you short it(not like you should)

[Bombastinator]

13 minutes ago, Olic2 said:

Thank you for your answer. These capacitors; do they still hold enough charge to hurt someone? Even after being turned off for an indefinite amount of time? 

Can they? Oh yeah.  Will they? Far less likely.  Capacitors lose charge spontaneously.  It’s kind of random though, so it can vary a lot.  “ livery dangerous” in this case means statistically significant (but low) chance of a customer zapping themselves when they stick their arm in given hundreds of customers a week, the bin being regularly topped off, and the whole thing going on for a long time.  Even tiny chances can add up.

[Bombastinator]

35 minutes ago, Samfisher said:

Exposed electronics can be, electronics as a whole no.

*imagines the situation*
1st person: ”NO! Don’t make me look at your dirty dirty electronics!”

 

2nd person: ”but it’s natural”

[Kisai]

56 minutes ago, Olic2 said:

I don't remember the video specifically but in one episode of Scrapyard Wars, Linus was was looking for parts and came across a bunch of PSU units just kind of jumbled together in a box. He pointed out that it was hella dangerous, and that it could kill someone if something happened. Can someone smarter than me explain what's dangerous about that? Thanks in advance.

 

PSU's, CRT Monitors and disposable cameras can all be charged to lethal levels, and you need to discharge them to dispose of them properly. In the case of PSU's, mostly you just need to turn the power switch on while there is a load and leave it unplugged. 

 

I've been shocked a few times from CRT's, even after they've been unplugged for some time, not a huge shock, but enough it was felt and would have certainly resulted in dropping the CRT if not expecting it. Back in the days of 17" monitors.

 

[Bombastinator]

5 hours ago, Kisai said:

 

PSU's, CRT Monitors and disposable cameras can all be charged to lethal levels, and you need to discharge them to dispose of them properly. In the case of PSU's, mostly you just need to turn the power switch on while there is a load and leave it unplugged. 

 

I've been shocked a few times from CRT's, even after they've been unplugged for some time, not a huge shock, but enough it was felt and would have certainly resulted in dropping the CRT if not expecting it. Back in the days of 17" monitors.

 

Im recalling a video where some fools set up a nerf gun filled with capacitors that had their leads filed into spikes and then shot them at people as a kind of taser.  
 

Im also liking the bludgeoning weapon angle myself.  I kinda want to post a video of some half clothed over weight man screaming incoherently while waving some heavy kitchen appliance.  There probably is one but I don’t think I can handle going through the videos looking for something appropriate.

[Lady Fitzgerald]

6 hours ago, YellowJersey said:

CRT monitors/TVs are also something you need to be careful with.

 

5 hours ago, Kisai said:

 

PSU's, CRT Monitors and disposable cameras can all be charged to lethal levels, and you need to discharge them to dispose of them properly. In the case of PSU's, mostly you just need to turn the power switch on while there is a load and leave it unplugged. 

 

I've been shocked a few times from CRT's, even after they've been unplugged for some time, not a huge shock, but enough it was felt and would have certainly resulted in dropping the CRT if not expecting it. Back in the days of 17" monitors.

 

That reminds me when back when I was a kid and used to strip down old TV chassis I would find in the junk pile behind a TV repair shop. I occasionally would get knocked on my backside when I would get careless removing the flyback lead from the picture tube. (Did they call it the flyback lead because that's what I did when it zapped me? )

[RejZoR]

Capacitors have a charge retention span of few seconds to maximum of few minutes depending on type and capacitance and charge is dropping as time goes by. If PSU's are in a pile, they pose no danger what so ever. They lost their charge before someone managed to take them out of the case they were in...

[greenhorn]

In theory, an unplugged charged capacitor will hold its charge forever, but real capacitors do lose it slowly over time and also many circuits using capacitors have a high-value resistor in parallel that causes the capacitor to discharge slowly (high value resistor in order not to cause any meaningful waste of power during normal operation).

In order for a charged capacitor to be dangerous, it both has to have a high voltage and enough charge. If you are unsure whether an unplugged capacitor is charged or not, you can measure its voltage and/or discharge it by putting a suitable resistor in parallel. In any case, you shouldn't attempt these things unless you are qualified and ready to do it at your own risk.

Capacitors can also become hazardous in another way: Because of their low internal resistance, they can deliver quite high currents when accidentally shorted, which can produce a lot of heat and potentially cause burns/fires.

[WereCatf]

3 minutes ago, greenhorn said:

Capacitors can also become hazardous in another way: Because of their low internal resistance, they can deliver quite high currents when accidentally shorted, which can produce a lot of heat and potentially cause burns/fires.

I've got some supercaps, they're a boatload of fun for creating massive sparks and burning stuff!

[mariushm]

Modern power supplies are designed with discharge resistors or chips which drain the capacitors as soon as the power supply is shut down.

So, technically, a power supply should be safe let's say 5-10s or so after you pulled the power cable from the back.

 

Still, it makes good sense to not expect that those protections are functional and to make sure those capacitors are discharged. You can do that by connecting a resistor between the terminals of the capacitors for a few seconds... for example a 470...1000 ohm 1w resistor across the big capacitors.

 

 

[Srijan Verma]

6 hours ago, GenericFanboy said:

mac's

i shit away from shit like that

[Lady Fitzgerald]

33 minutes ago, RejZoR said:

Capacitors have a charge retention span of few seconds to maximum of few minutes depending on type and capacitance and charge is dropping as time goes by. If PSU's are in a pile, they pose no danger what so ever. They lost their charge before someone managed to take them out of the case they were in...

Again, back when I was a kid, my Daddy brought home a couple of 2000µf 12v capacitors (yes, they were huge) he rescued from a trash can at work. Those puppies could hold a charge for weeks that was still strong enough create a pretty impressive zap.

 

Obviously, smaller caps won't hold a charge as long but they will hold one longer than you seem to think.

[mariushm]

On 1/22/2020 at 4:33 PM, Lady Fitzgerald said:

Again, back when I was a kid, my Daddy brought home a couple of 2000µf 12v capacitors (yes, they were huge) he rescued from a trash can at work. Those puppies could hold a charge for weeks that was still strong enough create a pretty impressive zap.

 

Obviously, smaller caps won't hold a charge as long but they will hold one longer than you seem to think.

2000uF 12v is nothing. You probably missed a few zeroes.

Computer power supplies used to have multiple 3300uF 16v capacitors inside.

 

The total charge is not enough to shock you

[Bombastinator]

Original premise:

 

Q: can a PSU be potentially dangerous enough

to make a giant pile of random PSUs potentially unsafe?

A: Sometimes yes, usually no.  so still more or less yes.

[Bombastinator]

So many levels.  So Not ever ever ever no because new stuff. But caveats.  Other pints are   Not ever ever ever no because power levels.  But caveats.  Also Not ever ever ever no because discharge.  But caveats.

 

deadly vs merely unpleasant

New vs unknown age

Undamaged vs unknown damage level.

 

So it’s not zero but it’s not very high either because multiplying fractions even adding more random instances.

 

Still don’t wanna stick my hand in it.