Agreed with Michael; the values are consistent and only move around by
a few millivolts even based on load, that is good.  A simple LED that
is on, as opposed to off, can affect the voltage read by the
microcontroller.

-Joe

On 3/24/07, Michael Schippling <[EMAIL PROTECTED]> wrote:
I think tmotes have a 12 bit converter so each bit ~= 70 micro-volts.
There's probably more noise in the ground line than that.
Also the battery voltage will fluctuate a bit due to load.
I'm surprised the values are so consistent...

MS


Madhu Mudigonda wrote:
> Hello Everybody,
>
> I'm trying to read Tmote battery voltage values through ADC. What I have
> observed is, the values are very inconsistent. For example, If I  run
> the Voltage sampling experiment, the values I'm getting are like this:
>
> Details of Experiment:
> I have wired to VoltageC component available inTinyOS.
> Sampling rate of ADC is : 1 sample/min
> Sample Results:2989,2988,2987,2986,2989,2985,2989,2986,2984.............
>
> If you observe the results, after reading a battery voltage of 2986,
> it's shooting upto 2989. It is not  consistent. Is there any correct
> procedure to read the Voltage(ADC) values consistently. Am I doing correct?
>
> Any kind of suggestions or help is appreciated.
>
> Thanks--
> Madhu Mudigonda
> Research Assistant,
> SE-Lab,Fenn College, CSU.
> Ph.# 216-856-0127
> Fax.#: 360-233-0127
>
>
> ------------------------------------------------------------------------
>
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