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I have about a dozen Raspberry Pis running in an industrial environment with a lot of motors and variable frequency drives. I detect when a machine is running via a heart beat to one of my inputs.

On a couple of the machines I experience false inputs due to what I believe is electrical noise. I have adjusted the debounce settings on the input, but still experience the issue intermittently. The input is pulled up with such a low voltage (3.3V D.C.) it's easy for noise to interfere.

I am looking for recommended solutions to this issue.

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    Difficult to diagnose based on your description. Can you provide any kind of schematic or photograph of your setup? – goobering Mar 1 '16 at 13:29
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No details have been given, but help can be provided in general terms.

The two main entry points of noise (interference) into your Pi would be through the I/O and the power supply.

I have adjusted the debounce settings on the input, but still experience the issue intermittently.

Since you have reduced your problem, you may be able to do just a little bit of filtering to get to your final goal of noise immunity.

Shielded Cable : The wire pair from an input (sensor or switch) to the Rpi could use a shielded cable. It is Important to only ground the shield at one end. Grounding a shielded cable at both ends creates a “ground loop”, which can aggravate the problem.

Resistor Filter can be used to reduce noise on an input signal. I have shown R1 as 100 ohms, to minimize voltage drop in a 3.3 volt system. Placing the filter very near the Rpi is important.

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Power Supply Filter can be used to reduce noise also. The inductor L1 is not critical and could be a range of values from 10 uHy to much larger (such as 100 uHy). The inductor needs to be rated to carry your power supply current. Placing the filter very near the Rpi is important.
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Opto-Couplers can be used to isolate your inputs. There is plenty of information on Stack Exchange on how to use Opto-Couplers. However, this would make major changes to your system and should probably be used only as a last resort.

Using the Raspberry Pi for your industrial environment may have peen “penny wise but pound foolish”. Industrial controllers (PLC) can be had for about $US 100. They are designed to be immune (mostly) from industrial noise. However, not knowing your needs for processing power leaves this option unknown.

  • +1 The low pass filter is the cheapest, fastest and mostly better option when noise attack. Also if you can, use a metalic box for the Raspberrys. Aislate the box to make a Faraday('s) Cage. – Elber CM Mar 1 '16 at 20:40

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