Hi all,
I'm sending a frequency signal with an arduino on a output, I want to be able to read this frequency from another arduino with a single pin.
I can't have a common ground between them.
In the following scheme you can see my idea:
the arduino 1 should be able to send a signal trough the connection with the arduino 2 and this should be able to read the frequency.
Is it possible to read the frequency in this scenario or the lack of common ground would invalidate the measure?
Hi,
Why?
What is the application?
How far between the two Arduinos?
What model Arduino are you using?
Thanks.. Tom... 
The most straightforward solution would be to use an optocoupler between both Arduinos.
There's no safe way in which you can link data pins of both Arduino's without them having a common ground. It would likely end up in spurious readings, or worse, blown up Arduinos.
The application is a wireless system for scoring in fencing.
The idea is to apply the signal on the guard of the opponent and to be able to distinguish between a hit on the guard or a hit on the body (on the first there is the signal on the second there is not).
The distance between the Arduinos it's more or less of 2 meters.
I'm not constrained by the type of the Arduino. I currently have a Uno and a Nano home, but I can think about buying another type if it will be necessary.
Yeah, sounds like something a Uno/Nano with an optocoupler for each player/device should handle with ease. Shouldn't be too complicated.
Thanks for the answer. This is definitely useful.
I have a really bad background in electronics so I didn't even know about the existence of such components.
If I use an optocoupler would I be able to read a valid signal or it would end up with a bad unreliable reading?
An optocoupler if used correctly would give a usable signal and fast enough for this application as well. Since it will offer galvanic isolation between both arduinos your situation of not having a common ground would no longer be an issue.
Thank you! I will buy it and study how to use it!
Thanks again.
HI,
This subject has been posted before, this may help.
Tom..
Then you need capacitive sensing perhaps? With no circuit you only have capacitance to the surroundings to work with.
Having an RF signal present can also work - here you have active electronics on
both objects, so that when they touch RF current flows. But this is really just a
clever way to do capacitive sensing.
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