View Full Version : DAC and long cable run.

T Chap
05-02-2008, 02:09 PM
Using the 10k and .1 cap for the internal DAC and a long noisey cable run, if I use a .01 on the far end as well to knock some noise down, does that affect the voltage?

I can't test this at the moment but need to figure it out.

I'd rather use a .1 at the far end if having both .1's doesn't affect the output.


Post Edited (Originator) : 5/2/2008 7:16:20 AM GMT

Peter Jakacki
05-02-2008, 03:15 PM
Your time constants are way too long for audio, maybe speech will work, but normally it's 10K + 0.01uF total. Can't you use some kind of transistor or opamp buffer to drive the line because unless the cable is well shielded even 1uF won't help you. Anyway, it's not much info to go on, not much at all. How long is a piece of string? What can I say.


T Chap
05-03-2008, 08:20 AM
The DAC is to set a reference voltage between 0 - .5 volts to a motor driver for current regulation, the leel will change depending on the load. It is not audio.

The motor and motor driver will have some noise and I want to keep the Ref level as clean as possible. The line is only 6 feet.

05-05-2008, 04:00 AM

how about placing the DAC as close as possible to the motorcontroller shielded with an aluminiumhousing ? And send the noise-insensitive frequency-signal along the 6feet-line?

What is the maximum changespeed of the Ref-Voltage ? If this changespeed is low you could use an OP-Amp as a voltagefollower with smoothing-capacitors on input- and outputside
Depending on your maximum changespeed the capacity could go up to 1000 uF

best regards