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Topic: 5V pin actual power output. (Read 580 times) previous topic - next topic

a-marshal

I have a project that was just about complete, it uses/d 3 analog temperature sensors and displays some values. Anyway I was playing with the type of display to use when i somehow bricked my original 3+ y/o UNO.

When I replaced the board my project wouldn't work anymore, the values from the sensors would bounce up and down pretty randomly, even under test conditions where the values are known. I've ripped everything apart a couple times now and I've tried 3 different arduino UNOs (from different sources) plus one knock-off.  The problem appears to be power fluctuations on the 5V reference pin.

Using a constant current power supply at 9V as a regulated power...
My old board puts out 5.01V solid and stable begining seconds after it has been plugged in.
The knock-off board puts out 3.47V on both the 3.3V and 5V pins so clearly there are bigger problems there..

Of the three new Arduino boards

one will after a few (say 5?) minutes stabilize to produce a solid 4.99V
one varies between 4.97 and 4.99 even after quite some time
the last holds at 4.97 but will very occasionally drop or add 0.01V

What I am wondering is this...
1) Is there a different board I could/should use to get better power regulation?

2) Is there some sort of backup circut I can build in to ensure a more stable power level?

3) Other than smoothing, which I fear will round down my values bellow my margin of error, is there any way I can detect and discard anomalous values in code? (I guess I mean efficient way)

And I suppose at the end of the day how do others deal with the fact that the reference Voltage for analog sensors does not seem to be reliable?

a-marshal

Ok feel free to ignore the above post.. or delete it if you're a mod...
The voltage issue looks to be a red herring, I worked the math backwards and would need a voltage change of over 1/5th of a volt to account for the changes in reading I'm seeing. The changes that would be caused by the fluctuations in voltage would be handled by the standard smoothing techniques.

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