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Topic: sensor data via Cat6 / RJ45 / breakout board (Read 2 times) previous topic - next topic

inoukdemers

Hello all,

I'm trying to feed sensor data from multiple sources into an Arduino via network cables (Cat6). These are currently plugged into an RJ45 connector + breakout board at both ends. Here are the parts:

http://www.sparkfun.com/products/8915
http://www.sparkfun.com/products/643
http://www.sparkfun.com/products/716

The trouble is I'm unsure how to get a clean signal. When I feed one (photoreflective) sensor output into the Arduino (A0 input), the signal is clean. When I feed it into one of the Ethernet lines (say orange), and take the output at the other end to feed it into the Arduino, the signal is all over the place.

Is this noise caused by the cable picking up my PC's electromagnetic interference? Or is the signal being encoded somehow? What is the proper way to hook up the sensor output to the network cable? For example, do I have to have one line for signal and another (matching color) for ground? Is the cable powered through the sensor output, or should I be powering it at the Arduino end?

A friend suggested I stick with regular shielded coaxial cable, one per sensor output. But I was hoping to get 4 sensor inputs (1 per cable pair) running through a single network cable to simplify.

Anyway, any clarification would be a huge help at this point. I'm quite new to this. Thank you for your patience!

SnJDK

HI,
how long is a cable, what exactly is your sensors (name, type, results signal). How look your schematic ?

I normally use 1-wire sensors over UTP cable without any problem.

inoukdemers

Here are the sensors I'm using (8 in all):
http://www.sparkfun.com/products/246

The cables will extend around 10 feet.

UTP looks to be pretty much the same as Ethernet/Cat6; I'm not sure, but the Cat6 cable I have may be unshielded too, which might be the reason I'm getting interference (being next to a PC).

I don't have a schematic; the QRD1114 circuits work though, and I'm temporarily testing by sending the sensor outputs to the Arduino via audio cable, which also works.

Still, is it a simple matter of connecting a sensor output to one of the Cat6 inputs, then taking that at the other end of the Cat6 and feeding it into the Arduino analog in? Because right now that's not working.





Graynomad

Do you have a common ground between the sensor and the Arduino?

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

inoukdemers

Rob,

At the moment yes: since I'm working off the breadboard, all sensors are going to the GND pin on the Arduino. But the installation will ultimately be designed so that each sensor operates off its own battery power (each one will be in a separate location in the hall), so each one will have its own ground.

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