[time-nuts] Net4501's cheap...

David J Taylor david-taylor at blueyonder.co.uk
Fri May 24 01:42:43 EDT 2013

Perhaps you have the older boards.

google "Raspberry Pi Reboots on inserting a USB device"

"by mahjongg » Mon Nov 19, 2012 12:09 am
Don't hot plug USB devices directly into the PI, if you must hot plug
plug into a hub instead!

Its called "the rush in current problem", and it makes that the
current PI itself is non "hot pluggable", note that the revision 1 PI
was hot pluggable, as the two polyfuses prevented any rush in current
because the fuses had a non zero resistance. But in the current board
there is literally zero resistance between the PI's 5V supply, and any
USB device you plug in, that means that if you plug in any USB device
with empty power decouplers, (which act as a complete short for a very
small time) then you are actually simply shorting the 5V when you plug
de USB device in.

The polyfuses in the revision 1 board however caused much greater
problems than this problem, and for that reason have been removed."

My Raspberry Pis are all model B with the 512 MB RAM, purchased in Oct 2012, 
Nov 2012 and April 2013.  I have been using devices which conform to the USB 
spec, not hard disks which may take a higher transient initial current than 
500 mA (note that some of these devices are supplied with two USB leads, one 
of which is power only).  Devices such as a Wi-Fi adapter and a DVB 
receiver.  I am also using a good power supply, not a minimally spec'ed 
unit - it's a 5.25V 2A model as supplied by ModMyPi.

Photo of successfully hot-plugged devices:


Performance of three Raspberry Pis as timekeepers with indoor GPS antennas:


SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk 

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