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I have a micro controller ATxmega128A1U (datasheet) which will have switches and potentiometers attached to the GPIO and ADC input pins. These inputs will have about 2-3 meters of cabling from the panel to the micro-controller.

1) What sort of protection do I need to put on these inputs? Would a TVS diode arrays be necessary? (something like this perhaps)

2) What sort of filters do I need to put on the lines? Would some simple ferrite chips be enough and how do I chose a ferrite based on frequency response if I don't know what sort of noise may be coupled to the system when deployed?

3) Anything else I need to design for when having cabling this long?

Thanks in advance for your help!

EasyOhm
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    What kind of bandwidth are you looking at getting out of your ADC inputs? Ferrites are only so-so protection. You could run common mode chokes if budget provides. Those ESD ICs look very nice. See this related question for some additional ideas: http://electronics.stackexchange.com/questions/28954/esd-protection-of-adc-input?rq=1 – HL-SDK Nov 18 '13 at 00:50
  • The ADCs will only be measuring the potentiometers via a resistor divider and the potentiometers will be toggled by a human so there is no fast signals here. – EasyOhm Nov 18 '13 at 01:23
  • What kind of EMI environment will you unit operate in? For example. Bottom of the ocean - very quiet. Arc welding shop - very strong EMI. – Nick Alexeev Nov 18 '13 at 03:28
  • Living room of a standard home in North America, so except for florescent lamps I am not sure what else would cause issues. – EasyOhm Nov 18 '13 at 04:43
  • In that case, you may use differential inputs to get better ADC readings. Additionally, series resistors [on the gpio] will limit any ESD current while still allowing the GPIO to function correctly. Wintertime is a recipe for static discharge! – HL-SDK Nov 18 '13 at 14:50

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If all you're measuring is a voltage(DC Signal) with the ADC you can probably get away with just putting a small capacitor(~~22nf) to ground to ground along with a voltage follower [a very simple op amp configuration that basically relays a signal while giving the arduino some isolation from noise]. Pretty much any op amp you have laying around will work. An inductor (like one of the ring ones found in computers) in series with the signal wouldn't hurt either. `

pydroponics
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  • The board is not an Arduino. It's an XMEGA not a mega device. I wish to avoid adding active devices and want to provide the shielding/isolation only using passives. – EasyOhm Nov 18 '13 at 07:25