On 25/01/13 17:41, Mark Rogers wrote:
I have several 5V USB supplies, which if the labels on them are to be believed will supply anything from 1 to 2.5A, although I have serious doubts that I can believe the labels. Based on how sowly they charge my phone I think some that are labelled 2.5A are more like 200mA... They're from various sources, which include the likes of eBay. Some will power my RPi, but only if I don't try to plug in a USB device as well.
Assuming very little in the way of electrical knowledge (which I guess is obvious as I don't know the answer to my question), what's the "best" way to see what current a power supply can deliver?
Read the spec.
It's the voltage which determines the speed of charging, not the rated amps - but if the amperage at the required voltage isn't sufficient to cope, either the delivered voltage will drop, or the supply will lose all its magic smoke.
I have a multimeter, and could doubtless obtain some resisters (or other components) if I need to. I also have a shiny new temperature controlled soldering iron that's never been used if that helps :-)
Not really. Just choose the supply which delivers enough and then a bit. You *could* look for a circuit diagram online, visit somewhere like Maplin or go online again to (say) Farnellto get some Veraboard and components, and build yourself a better PSU - that's if you want to use your soldering iron...
Really - it's not that difficult.