Raspberry Pi Forums

Can the Pi get damaged by plugging in a device with too high of a current.. i.e. amps..?

Or will it simply just not run, and then you unplug it without causing damage?

Thanks

kingneil wrote:Can the Pi get damaged by plugging in a device with too high of a current.. i.e. amps..?

Or will it simply just not run, and then you unplug it without causing damage?

Thanks

If USB >1.2A then the device will stop working but the RPi should not be affected.
If too much current drawn from GPIO then the RPi may crash and possibly corrupt the SD card and/or blow the polyfuse. The fuse will self reset after several hours.
The total input current allowed on the RPi 3B is 2.6A limited by the polyfuse.

It likely will not run. I believe there is a poly-fuse protecting the USB ports as well.

Which Pi model, and what are the power requirements of the device you are wanting to power?

The original Raspberry Pi A/B had limited power available on USB, so you really need to use a powered USB hub with the old ones. The Pi B+ and Pi2 can deliver up to 1.2A (combined) on USB if you include "max_usb_current=1" in config.txt. The Pi3 has this setting on by default.

Note that the USB 2.0 standard is 500mA per port, which would be 2A for all four ports, so even with the newer Pi B+, Pi2 and Pi3 computers, the power output from USB is less than spec (1.2A/4=300mA per port with all 4 ports in use).

Using a 5.3V, 2.4A power supply I have successfully gotten two portable hard drives to spin up and mount when powered directly from my Pi3's USB ports. However, I could only use one at a time (trying to use both at once, like when copying from one to the other, would result in drive disconnects).

HawaiianPi wrote:It likely will not run. I believe there is a poly-fuse protecting the USB ports as well.

Only the first few thousand Pi 1Bs had polyfuses specifically to protect the USB ports. They were 140mA per port.

The later 1Bs and 1As only had the main polyfuse for protection. All other models (except the Zero, which has no protection), have a USB current limiting circuit.

No USB 2.0 device should be looking for more than 500mA. If USB 2.0 device wants more than that (or a USB 3.0 device wants more than 900mA) there is something seriously wrong with the device.

W. H. Heydt wrote:No USB 2.0 device should be looking for more than 500mA. If USB 2.0 device wants more than that (or a USB 3.0 device wants more than 900mA) there is something seriously wrong with the device.

However some HDD disk caddies "cheat" by using the (infamous) 'Y' lead which presumes that when the "upper arms" of the 'Y' are plugged into two USB ports it will be able to draw up to 500mA "per arm". In my experience that's only (just about) true for laptop/netbook ports and, for virtually all of the powered USB hubs I've investigated, albeit low-to-medium cost ones, all of the ports were connected in parallel and there appeared to be no per port or overall current limit other than that provided(?) by the hub PSU (ie. such hubs failed to meet the full USB specs., which, AFAICT, are not an ISO or equivalent "standard" and so not "enforceable"**)
Trev.
** in the country of manufacture and/or import?

FTrevorGowen wrote:

W. H. Heydt wrote:No USB 2.0 device should be looking for more than 500mA. If USB 2.0 device wants more than that (or a USB 3.0 device wants more than 900mA) there is something seriously wrong with the device.

However some HDD disk caddies "cheat" by using the (infamous) 'Y' lead which presumes that when the "upper arms" of the 'Y' are plugged into two USB ports it will be able to draw up to 500mA "per arm". In my experience that's only (just about) true for laptop/netbook ports and, for virtually all of the powered USB hubs I've investigated, albeit low-to-medium cost ones, all of the ports were connected in parallel and there appeared to be no per port or overall current limit other than that provided(?) by the hub PSU (ie. such hubs failed to meet the full USB specs., which, AFAICT, are not an ISO or equivalent "standard" and so not "enforceable"**)
Trev.
** in the country of manufacture and/or import?

I have an external DVD burner that uses a "Y" cable. At least in theory, that would still conform to the 500mA per port.

W. H. Heydt wrote:No USB 2.0 device should be looking for more than 500mA. If USB 2.0 device wants more than that (or a USB 3.0 device wants more than 900mA) there is something seriously wrong with the device.

A Galaxy Note 7 might draw over 1amp from USB when plugged in. I think it's charging the battery or something. Right now I've got a Pi 2B plugged into the USB port of a 3B. While I'm not sure how that's going to work out under load, I'm not expecting any sort of explosion.

W. H. Heydt wrote:

FTrevorGowen wrote: ...
However some HDD disk caddies "cheat" by using the (infamous) 'Y' lead which presumes that when the "upper arms" of the 'Y' are plugged into two USB ports it will be able to draw up to 500mA "per arm". In my experience that's only (just about) true for laptop/netbook ports and, for virtually all of the powered USB hubs I've investigated, albeit low-to-medium cost ones, all of the ports were connected in parallel and there appeared to be no per port or overall current limit other than that provided(?) by the hub PSU (ie. such hubs failed to meet the full USB specs., which, AFAICT, are not an ISO or equivalent "standard" and so not "enforceable"**)
Trev.
** in the country of manufacture and/or import?

I have an external DVD burner that uses a "Y" cable. At least in theory, that would still conform to the 500mA per port.

Similar to this one perhaps (supplied with a "Woolworths" sold laptop, something like a decade ago):
http://www.cpmspectrepi.uk/raspberry_pi ... vices.html
IIRC, I did get it to work, via a powered hub with a good PSU, with one of my older Pi's (pre-B+), but I think I only used it in read mode.
Trev.

FTrevorGowen wrote:

W. H. Heydt wrote: I have an external DVD burner that uses a "Y" cable. At least in theory, that would still conform to the 500mA per port.

Similar to this one perhaps (supplied with a "Woolworths" sold laptop, something like a decade ago):
http://www.cpmspectrepi.uk/raspberry_pi ... vices.html
IIRC, I did get it to work, via a powered hub with a good PSU, with one of my older Pi's (pre-B+), but I think I only used it in read mode.
Trev.

Similar, and, yes, I use with a good quality powered hub (when I started, SBCs weren't handling 1+A on the USB ports). It's one of these: https://www.bhphotovideo.com/bnh/contro ... details&Q= and you can still get 'em. (The link is just the first convenient one. I haven't ordered from that vendor since before ordering on line was a thing.)

My experience of plugging in a device with a high power draw is a device that does not work until you plug it into a powered hub. Nothing happens in the Pi 3. When you plug in several high current drawing devices, the Pi hiccups and you have to reboot Raspbian. No damage to the Pi. Never had a Pi fail or a card fail or a fuse blow.

I have not tested four high current drawing devices because one of the four USB ports has a tiny keyboard/mouse wireless dongle.