Lindy,

 Plug the phone charger into an outlet (AC) and using a voltmeter measure
 the open circuit voltage at the phone connector end.   If it is 5 volts,
 or thereabout, you're okay as far as voltage goes.  If you have a scope,
 connect the scope to the phone connector end and look at the ripple
 voltage.  If it is higher than say a few millivolts, you'll need to filter
 it out.   A high value electrolytic capacitor across the output in 
 parallel with a low value should do it.  There is a formula for
 calculating the needed capacitance to achieve a give ripple voltage, but I
 don't recall what it is off hand.  But in the past as a starting point, I
 have used 2500 uF / amp and it has worked well.  In your case with the 
 output current rated at 1.7 amp, I'd use a mininum of 5000 uF on the 
 output.  And I'd put a .047 uF to .1 uF in parallel with this to improve
 the high speed transient performance.   This will remove most of the 
 ripple.  If there is still too much ripple voltage, go to a higher 
 capacitance on the output.

 If the open circuit voltage is higher than 5 volts or so, you'll need an
 external regulator to take care of it.   I'd probably just install a 7805
 regulator to the output, along with a good heat sink to be able to handle
 the current at full load, if you ever get there. 

 Of course, by adding all these things to the output, if needed, sort of 
 ruins the portability of the unit.  But you could build all of these
 external things into the breadboard, along with a bridge rectifier, then
 you could use virtually any wall wart as a power supply regardless of
 voltage rating, current rating, polarity, or whether it is AC or DC.

 Hope this helps you out.   Have fun.


                                             Regards,

                                               Jim



> Do you mean it might not be exactly 5 volts, or that it might
> fluctuate?  Can I check it with my multimeter?  
> 
> Would it be ok if I used a 5v voltage regulator?
> 
> Is this along the same lines as to why those small 220v to 110v
> converters say that you cannot use them with electronics?  
> 
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
> Behalf Of Paul James E. Sent: Wednesday, May 11, 2005 12:15
> To: piclist@mit.edu
> Subject: Re: [EE] Will phone charger work as a 5v DC power supply?
> 
> 
>  Yes you can, but the filtering on the output may not be very good, 
>  and it may not be regulated to 5 volts.   It probably is, but no 
>  guarantee.   I would build up a dummy load out of some resistors  and
>  check it out that way.  Or you could try powering something 
>  that takes 5 volts, but that would be risky.
> 
>                                             Regards,
> 
>                                               Jim
> 
> 
> 
>> 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? 
>> 
>> 
>> 
>> 
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