Is it OK to power the Duem. with a 5 volt supply connected to the 5V pin on the board? I ask because I'm using a boost converter that's supplying 5volts of power from a Li-Poly battery and it only puts out 4 volts when I connect to Vin. My concern is damaging the voltage regulator by putting 5volts on the output. Any thoughts?
as long as the output is regulated you should be fine. though i don't know what would happen if you also plugged in another source to the vin at the same time. probably nothing, but if you don't do it it wont matter.
I'm using a boost converter that's supplying 5volts of power from a Li-Poly battery and it only puts out 4 volts when I connect to Vin
That implies that it can't supply the required current which means it might misbehave as you start to use it.
i don't know what would happen if you also plugged in another source to the vin at the same time.
The 5V rail would then back feed current to the boost converter. What that would do to the boost converter is hard to say, it would probably shut down.
To prevent back-feed possiblity, one method I use is to take a spare USB cable and cut off the PC end, find the plus and negative power wires and connect that to the external regulated +5vdc supply. Allows the on-board 500ma thermofuse to be utilized also.
if he connects it to vin, wouldnt that mean that his regulated 5 volts is being dropped by the linear voltage regulator? if it was connected to the 5v line and then dropped, then i'd be more suspicious about not enough current.
Thanks for all help guys...not sure what the discussion around not enough current is in reference too though (probably my poorly worded question). I should really look at the schematics more closely before I ask questions. If I'm reading the schematic correctly it's OK to supply an external supply (boost convedrter) to the 5V pin without damaging the onboard regulator because that's basically what we're doing when we connect the USB cable anyway. From what I can see the USB is switched onto the rail through the MOSFET which would drop 5volts across the regulator anyway so that basically answers my question right there. I do like the idea of using the cut USB cable because that way if I accidentally connect a wall wart at the same time (sometimes beer and electronics don't mix) it should safely(assuming the voltage is over 6-7 volts) switch the boost converter voltage off the 5v rail. Thanks again for all the help this forum is awesome.