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### Topic: Noise in Due DAC (Read 967 times)previous topic - next topic

#### fishbulb

##### Apr 01, 2014, 03:22 am
Hello all,

I can't seem to find much information online about this. I would like to use an Arduino Due to deliver analog signals for a series of experiments we have coming up. We need to deliver a signal that is ~5 mV. How much peak to peak noise should we expect in the Due's DAC? Thank you tremendously for any information you can provide.

Thanks,
FB

#### mcleung

#1
##### Apr 01, 2014, 05:06 am
You won't be able to output 5mV directly. You will probably need to use voltage divider (resistors) to achieve it.
I can't find the source anymore, but the Due's DAC only output from 1/6 to 5/6 of the full (0 to 3.3V) voltage range.

Hence analogWrite(DAC1, 0); would correspond to 0.55V, and it goes up to 2.75V (ish)

Noise will depend on how much current is drawn, as well as EMF and capacitors you use. From my experience this should be a few  millivolts, but it also depends on what you are making your Due compute (timer interupts, etc)

#### fishbulb

#2
##### Apr 01, 2014, 02:43 pm
Thanks for the reply. I appreciate. A voltage divider should be easy to build to adjust the voltage range down. This seems like something we should just build and see if it works, given how cheap these are in the grand scheme of things.

Thank you again,
FB

#### MarkT

#3
##### Apr 01, 2014, 05:42 pmLast Edit: Apr 01, 2014, 05:45 pm by MarkT Reason: 1
The DAC seems to have sparkle codes so I'd avoid it - its also hard to use with its output
range restrictions (its designed for audio, not precision, as far as I can tell)
A separate DAC on a low-noise analog supply rail would be a wiser choice (the 3.3V rail
on the Due is very noisy).

[ see http://forum.arduino.cc/index.php?topic=194694.0 ]
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### fishbulb

#4
##### Apr 01, 2014, 05:47 pm
Thank you for the tip Mark. I'll check out the link.

FB

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