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I recently tried inserting a 5M USB extension cable in between my WIFI dongle and my PI, which didn't work, so I removed immediately; but the PI still wouldn't connect following a reboot for ages.

Can adding a 5 meter USB extension cable to the WIFI dongle cause problems even after it's removed?

  • I2R losses can lower the effective voltage reaching the wifi dongle at the end of a long cable, but it shouldn't affect the Pi at all after it's removed. In general, the Pi is limited in the current/voltage it can spare to power usb peripherals. You might try adding a powered usb hub to the Pi, from which you can extend the wifi dongle. Or even a long cable from Pi to hub, then long cable to dongle, you just need the power supplying boost of the powered hub to make it work. – lornix Jun 27 '14 at 19:47
  • The camera draws 200mA, The WIFI with a weak signal will draw approx 200-300mA, the PI model B will draw 375mA. Therefore total current drawn by the PI could be 775-875mA (figures not measured, approximates found online). There is a PTC thermal fuse F3 that starts to act at 750mA, so at boot up, in a weak signal area, the PI is close to F3 threshold. The WIFI power saving mode probably is suspended at boot, coupled with any extra IIR losses, could very easily tip it; but with unknown cable resistance, I cannot conclude. The quick succession of reboots probably loaded F3 to lock out anyway. – reggie Jun 29 '14 at 7:32
  • I'm not about to measure the cable resistance, or hack it up to find the AWG, to work out its resistance; as disabling the power saving mode in the network interfaces file, and removing the 5m cable seems to work for me. – reggie Jun 29 '14 at 7:40

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