I'm working on a Christmas light project and i would like to keep my arduino duo inside and trigger relays outside the house.
What I would like to do is use some bulk cat 5 cable I have to run from the arduino to the relays. I would run three 75 foot lines (each has 8 stranded wires) for a total of 16 channels and a ground line.
Has anyone done something like this? What I want to know is:
Is there a way to splice the individual network strands to jumper wires? The jumper wires are for plugging directly into the duo or a breadboard on one end and then for plugging into the relay board.
Will there be any crosstalk between the wires?
I understand the output is 5volts. Is the cat5 wires sufficient enough to transmit a signal 75 feet?
Cat5 wires are alas a little too thin for most breadboards and headers, and standard RJ45
connectors aren't breadboard friendly. Soldering the wires onto 0.1" header pins is one
approach.
At that length the cable may have problems carry power if the end device is power hungry,
and high speed logic signals should be sent as signal+ground on a pair of wires each
with reasonable termination.
Lower speed signals are less demanding and termination may not be needed.
Sending signals from an Arduino into twisted pair over long distance can be done by
terminating with two resistors, one to ground and one to 5V, each about 220 to 270 ohms.
The other wire in the pair should be GND or Vcc. This will give good high speed
transmission as you are basically matching the natural impedance of the twisted pair
(approx 120 ohms) with the termination resistors (which for AC are effectively in
parallel). However about 20mA is needed to drive the line this way, and not all
logic outputs can do this (ATmega can).
For lower speed signals just put a resistor in series with the line to suppress
reflections (1k will do), but the signal will be effectively low-pass filtered by this.
Is there a way to splice the individual network strands to jumper wires? The jumper wires are for plugging directly into the duo or a breadboard on one end and then for plugging into the relay board.
You can solder & heatshrink to the jumpers or solder & heatshrink to a piece of solid wire, or solder some solid wires to an RJ45 socket, then you can plug-in network cables. Of course, you'd need RJ45 sockets on the other end too.
Will there be any crosstalk between the wires?
No. Not with DC powering relays. If you are sending signals/data, then you have to make sure the cable is driven & terminated with the right impedance. IIRC, for Ethernet can go 100 meters.
I understand the output is 5volts. Is the cat5 wires sufficient enough to transmit a signal 75 feet?
That should be fine. If you run lots of current through small wires you'll get a voltage drop, but with a few milliamps to a relay coil you won't get much voltage drop over the distance.