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Topic: Standalone Arduino power supply trouble (Read 857 times) previous topic - next topic

Nick Gammon


Only difference between them is that the router one runs effectively at 5,17V and can provide 2,5 amps and the mobile charger runs at 4,95V and can provide 550 milliamps. So why would the phone charger work and not the router one?


Also is it "can provide" or "does provide"? Did you measure it under load?

siggivara

#6
Jun 05, 2011, 01:29 pm Last Edit: Jun 05, 2011, 01:30 pm by siggivara Reason: 1

Interesting. Read this:

http://www.alternatezone.com/electronics/ucurrent/

Effectively measuring the current changes the voltage.


Really? I had no idea. Thanks. It's a good thing to keep in mind.




Only difference between them is that the router one runs effectively at 5,17V and can provide 2,5 amps and the mobile charger runs at 4,95V and can provide 550 milliamps. So why would the phone charger work and not the router one?


Also is it "can provide" or "does provide"? Did you measure it under load?


I measured the voltage, but the 2,5 amps and 550 milliamps was written on the power supplies. I measured my circuit to draw around 125 milliamps at max load.

Nick Gammon

Yes but did you measure the voltage when the circuit was operating? Especially when reset occurred. An unregulated supply might drop the voltage under load. If you can't see the word "regulated" on the supply it might be supplying a nominal 5V, which could drop under load (probably would).

kalum


Yes but did you measure the voltage when the circuit was operating? Especially when reset occurred. An unregulated supply might drop the voltage under load. If you can't see the word "regulated" on the supply it might be supplying a nominal 5V, which could drop under load (probably would).


I concur with your analysis  NIck. This sounds like either the power supply has a lot of ripple (in which case i would recommend a 100uf capacitor in parallel with the 0.1uf power decopling caps) or cant supply enough current.  I would strongly recommend the authour of this thread to get a higher voltage supply like a 9v one, and use a linear voltage regulator like the 7805 to get a perfectly regualted supply. Microcontrollers are fickle beasts, they need a precision voltage supply.

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