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Topic: Powering with 5.5V (Read 1 time) previous topic - next topic


Sep 08, 2011, 09:02 pm Last Edit: Sep 08, 2011, 09:15 pm by krzyq Reason: 1
Hi all,

That's my first post, so I want to say "hello" to all of you and "thank you" to Arduino developers whose product gave me long hours of fun!

I'm planning to power my Arduino (duomilanove with 328) with 5.5v USB solar charger (with battery inside), via USB port on Arudino board. The problem is that it's outputting 5.8V without any load and ~5.6V when loaded. I don't know yet how the voltage changes depending on whether there is a sun or not. I know that the maximum recommended voltage is 5.5V, so I will have to add a diode to lower the voltage a bit (if someone gives knows a better and easy to do method, please let me know). The voltage will be in the "safe zone", but as the voltage seems to vary depending on the load, I fear that it won't be stable and probably, afer using a diode, it will oscilate around 5V +/-0.2V.
Now, my question is, what are the implication of such approach? How the voltage variability will affect the clock and the timings within Arduino? My project uses some precise delays (in the range of 50-400 microseconds) and I'm a bit worried about using such an "unregulated" power source, I won't be able to get stable timings. Also, if the voltage will be higher than 5.0V, will that wear the chip (edit: I'm planning to power Arduino 24/7, 365 days a year)?

Any opinions and elaborations are welcome!



Thank you KE7GKP. Yes, I was surprised to (I thought that it only happens on cheap wall wart chargers), and it's cheap chinese indeed, rated to give 5.5 output and giving 5.6-5.8 - I need to take it apart to see what regulates the power. But as I am really experimenting at the moment, I think I can live with a cheap chinese for a while, even if it breaks after a month  :)  I know that a final project will require something better to provide fault-free, stable operation (but first I need to know how the final project will look like and what power requirements will be).
I'm also not quite sure about my meter, as it begun to show weird things recently (I think it's cheap chinese inside too as it is not a "can't-afford-Fluke", but I sort of inherited it, so I can't complain).

Anyway, thank you for all info - my Arduino uses a real crystal, so I feel reasurred by your post. Thanks!

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