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Topic: Voltage divider: Separate GND (Read 1 time) previous topic - next topic

Stian

Hi all!

Im using an arduino to control some of the features of my DIY Amplifier, i would also like to be able to read out the current voltage of my amplifier. For this feature i where thinking of using a voltage divider to get voltage down to a readable level. But, i don`t wanna connect my noisy digital ground to my quiet analog ground, is there anyways to separate this and still be able to use a voltage divider?
What would happend if i used a 1k resistor to separate it?

Thanks,
Stian

baum

Common practice is to attach all the grounds together as long as you don't have a short. I have attached the GND from two 9V batteries directly to by arduino's ground. The 18V went to an arduino-controlled mosfet, which operated no problem. If you are worried, just put a diode on each ground like this:

Digital Ground----->|------
                                  |--- GND
Analog Ground----->|-----


And you won't have a problem.

Grumpy_Mike

Quote
But, i don`t wanna connect my noisy digital ground to my quiet analog ground,


You could use an opto isolator but you don't get a very linear response unless you use a proper dual opto with a feedback loop.

Otherwise you could use a small 1:1 audio transformer to isolate the output signal.

Without this form of isolation you need to connect the grounds together, make sure it is only at one point to minimise currents flowing between them.

I would disagree with the diode suggestion.

Stian

Thank you all.

hall-effect current sensor sounds very interesting, maybe ill try one like that.
Yes, it is for a power amplifier

igor86

#4
Feb 03, 2011, 10:00 am Last Edit: Feb 03, 2011, 10:02 am by igor86 Reason: 1
Hi,

I have used a hall effect transducer for a similar application with great success. I used the following component:
http://au.element14.com/allegro-microsystems/acs756sca-050b-pff-t/ic-current-sensor-50a-3ca/dp/1791390&PRED=True&trackKey=VNC_HMP_MID

Very easy to setup, so I highly reccomend it. (The link is for a 50A sensor, if you need to measure smaller currents, it would be better to find a sensor with a lower current rating)

HTH
-Igor

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