3 ms·

PC hardware often (including Macs) often have self-resetting fuses on USB ports that make the port look dead but come back to life after some time. Some fuses t

by zurn 11y ago

PC hardware often (including Macs) often have self-resetting fuses on USB ports that make the port look dead but come back to life after some time. Some fuses take longer than others. So it's sometimes easy to think your USB device killed the port. A friend had this with a Macbook and a USB charged bike torch. Apparently polyfuses can take days to properly un-trip.

bravo22 11y ago
Polyfuses are temperature driven and will reset within a few seconds. USB ports on non-cheap bare-minimum laptops use a chip in monitoring the current draw and can block that port. The OS can re-enable the port right away but I believe OS X requires you to reboot.
- manarth 11y ago
  OS-X (Yosemite + El Capitan) has displayed the message to me: "Your device tried to draw too much current and so the USB port has been disabled". When I took the offending cable out, and tried with a different device, it worked straight away, no reboot required (not sure about earlier versions/alternative scenarios though, it's possible they do require a reboot).
- zurn 11y ago
  I was going by a "polyswitch fundamentals" doc from a manufacturer[1] - and had the weasel-word "properly" :) Apparently the resistance falls quickly at first but can take a long time to fully return to pre-trip level. This has caused trouble in the Raspberry Pi. Users were getting odd effects when voltages didn't quite return to spec after polyfuse trip. [2] [1] http://www.te.com/content/dam/te-com/documents/circuit-protection/global/CPD-Catalog/S11_PolySwitch-Fundamentals.pdf http://www.te.com/content/dam/te-com/documents/circuit-prote... [2] http://elinux.org/Polyfuses_explained http://elinux.org/Polyfuses_explained
thenomad 11y ago
AHA! Interesting. This explains why my computer has a bunch of USB3 ports that work... sometimes. (It also very sporadically has a massive wibble and hard-crashes with an error relating to USB.)

by zurn 11y ago

bravo22 11y ago

Polyfuses are temperature driven and will reset within a few seconds. USB ports on non-cheap bare-minimum laptops use a chip in monitoring the current draw and can block that port. The OS can re-enable the port right away but I believe OS X requires you to reboot.

manarth 11y ago
OS-X (Yosemite + El Capitan) has displayed the message to me: "Your device tried to draw too much current and so the USB port has been disabled". When I took the offending cable out, and tried with a different device, it worked straight away, no reboot required (not sure about earlier versions/alternative scenarios though, it's possible they do require a reboot).
zurn 11y ago
I was going by a "polyswitch fundamentals" doc from a manufacturer[1] - and had the weasel-word "properly" :) Apparently the resistance falls quickly at first but can take a long time to fully return to pre-trip level. This has caused trouble in the Raspberry Pi. Users were getting odd effects when voltages didn't quite return to spec after polyfuse trip. [2] [1] http://www.te.com/content/dam/te-com/documents/circuit-protection/global/CPD-Catalog/S11_PolySwitch-Fundamentals.pdf http://www.te.com/content/dam/te-com/documents/circuit-prote... [2] http://elinux.org/Polyfuses_explained http://elinux.org/Polyfuses_explained

thenomad 11y ago

AHA! Interesting. This explains why my computer has a bunch of USB3 ports that work... sometimes. (It also very sporadically has a massive wibble and hard-crashes with an error relating to USB.)