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Circuit Review

s1buell over 7 years ago

I`m currently making some proto circuits and I would love some feed back/Ideas etc.

All these circuits will connect to Arduino or Arduino compatible devices.

Anyone have time to help out with some reviews?

First circuit is a 4-20ma board

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genebren over 7 years ago in reply to s1buell +4

You might need to modify your 4-20ma loop front end somewhat. First, the circuit as shown does not have a return path for the current loops. Also, the current loop may not necessarily be directly referenced…
genebren over 7 years ago in reply to s1buell +4

Tom, Again, I am not sure that you can count on the second leg of the 4-20ma loop to be at ground potential. You might end up shorting out a driver or introducing ground noise into the circuit. Here is…
genebren over 7 years ago in reply to s1buell +4

Tom, Here is an even better link. This shows how to differential sense the loop current. https://www.sensorsmag.com/components/implementing-a-4-ma-to-20-ma-sensor-interface Good luck! Gene

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s1buell over 7 years ago

Question, I`ve also been questioning the optical part. You think its needed? Should I leave it? Or save the circuit cost and remove.

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genebren over 7 years ago in reply to s1buell

Tom,

I would drop the optoisolators, as they are not really buying you much protection. Typically, I would only use optoisolator to cross the boundary of a separate power supply (isolating the transceiver which is also on isolated power rails), or to protect against high voltage bleed through to the microcontroller.

Gene
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genebren over 7 years ago in reply to s1buell

Tom,

I would drop the optoisolators, as they are not really buying you much protection. Typically, I would only use optoisolator to cross the boundary of a separate power supply (isolating the transceiver which is also on isolated power rails), or to protect against high voltage bleed through to the microcontroller.

Gene
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