When I connect it directly to my voltmeter, am I measuring it with no load? How would I use my voltmeter to measure it under load? I assume by load, I would do some Ohms law math and pick a resistor that would give me some amps, no? I'm trying to think how to measure that with the multimeter. (It does do current. Or did I just answer my own question: A Resistor tied to the charger and using ohms law somehow...?) I can check it with the scope and I look then for smoothness, no? Also with a resistor between? By good sized electrolytic, do you mean like this? + -----|+------- + Charger Cap( - -----|-------- - -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Richard Prosser Sent: Wednesday, May 11, 2005 22:32 To: Microcontroller discussion list - Public. Subject: Re: [EE] Will phone charger work as a 5v DC power supply? Lindy, Yes - but you will probably still need a regulator to get a smooth 5V out of it. Some plugpacks include a regulator, most do not. Those that don't will provide something like 5V at the rated current but the output voltage is likely to be significantly higher under lower load conditions. Protection against overload is likely to be minimal - possibly a thermal fuse - so an inadvertant short could break it. If it does not include a regulator, then it is likely to have significant ripple under loaded conditions. I'd measure the output voltage under no load, likely maximum load (100mA ?) and full load conditions & work out what sort of regulator is needed - e.g. at 100mA if the volts exceed ~7V then you can probably just fit a 7805, rather than a LDO type. If you can view the output on a scope then use the minimum trough voltage for the determination. Otherwise add a good sized electrolytic to the input of the regulator. Richard P On 5/12/05, Lindy Mayfield wrote: > I found today lying around (and scavenged) a phone charger that reads on it: Output 5.0v DC 1.7A. > > Can I use this as a power supply to my breadboards for simple projects, Pics and other testing, etc? > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist