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Best practice for long cable run?


#1

I want to place buttons and analog sensors away from a FEZ Reptor mainboard.
The distance is 8-10 meters, my plan is to use Cat-5 cable.

Can I use one Cat-5 with 4 buttons and 2 gadgeteer sensors (temp and light sensor).
The buttons are not gadgeteer, so need some free pins for them.
Will the Hub AP5 Module work over such great length? Or is there a better way :slight_smile: ?

My first plan was to use a Cobra II wifi and send data to the Reptor, but the network/wifi is to unstable.


#2

Light sensor is analog, so you will likely catch all kinds of noise with such cables.

Temperature sensor will work, but you’ll probably need need some sort of RC filter to dampen signal reflections. Not a big thing to add it, though.


#3

The buttons will be fine. But you may want to add some capacitors to filter off any high frequency glitches.

I don’t know the details of your temp and light sensor outputs so take this with a pinch of salt. For simple analogue output stuff these are normally fairly slow changing things you can get away with a fairly hefty amount of low pass filtering. Just make sure your caps still work at the higher frequencies. Good practice is to use several caps in parallel. Something like 20pF for the really high frequency interference through say 100pF to 1uF.

CAT5 cable is a good bet.

At the end of the day you will probably find most noise comes from the Raptor or Cobra boards.

If all else fails you can oversample your ADCs to digitally filter any remaining noise. I do this with a 1024 times oversample running in RLP to get the speed, but it works in managed code just as well if slowly.