# 24awg CAT5 or 6 running 24v DC



## hauntedyards (Mar 24, 2005)

I've been looking around at Molex connector and patch wiring trying to find the most efficient way to wire my props to my mainframe. Then it occurred to me that Cat5 and 6 are 24awg. Now I'm thinking a rackmount patch panel and cat5 plugs at the prop I could just run network cables to send the 24v signals to the solenoids.

Any one try running 24v DC over Cat5 or 6? From what I've been reading it should be ok... Its not continuous either...

Actually I've just seen some 23awg and 22awg cat5 as well...


----------



## corey872 (Jan 10, 2010)

Did some searching for another thread I responded to:

http://www.hauntforum.com/showpost.php?p=767874&postcount=6

Seems like 24awg wire is good for about .6A in long runs or up to 3.5A in open air/short runs. The 24V should be fine and if your amps / length are somewhat in those ranges, should be fine, too. That is per strand, so if you use all conductors in the network cable...4 power and 4 ground, you could easily have 2.4 amps+ for long lengths. If not continuous, you could probably increase that current by the duty cycle factor... ie 50% duty cycle, likely 5 amps.

Cat5/Cat6, I don't think will make much difference in the amperage department - it's all 24awg wire, but the Cat6 is a little more immune to noise which isn't really a consideration here. The only other thing would be to make sure to use stranded wire vs solid. The solid is made to be laid one time and not move, where the stranded is more like an extension cord and can withstand bending/flexing multiple times.


----------



## hauntedyards (Mar 24, 2005)

Good call on the strands issue. I did find I can get 22 AWG and 23AWG as well so that might make a bit of a difference... In prop use as far as duty cycle goes for the most part 24v signals to solenoids are short pops here and there and off WAY more than on... they also don't call much in the Amps dept.

I'm just thinking setup would be a breeze and storage etc. Just using standard network cabling made to length. A plug at the prop... a cat5 cable I could run 7 solenoids or relays in one small cable. I like that idea more than investing in molex connectors.

Just found this thread actually... http://www.hauntforum.com/showthread.php?t=13203


----------



## spinman1949 (Jun 29, 2009)

*Re Cat 5 and current flow.*

I can offer this.

I was able to run a 6 servo 3 axis skull with jaw and 2 axis eyes using cat 5. But the traces on the RJ45 connector could not handle the current after awhile and burned out. I ended up using a RC type connector for power and ran a separate speaker wire for the power circuit. Depending on how you intend on doing the circuitry you will need to look at all components as to current capacity. I like being able to use the RJ45 connector, but so far the ones I have found can not handle the amps. I did consider running two cat5 and using one for four wire negative and four wire positive. That would distribute the load.


----------



## corey872 (Jan 10, 2010)

'spin - you bring up a good point. My dealings (and most of our discussion) has centered around using the wires, but not really the connectors.

If a person wished to use the connector, too, those small board traces might be an issue. I'm speculating from your post and 'solder traces' the main issue is coming from the female socket side, not the male connector side? I think the male connectors are a bit more solidly built due to their design. I would have to prowl around digikey, but it strikes me some of the female sockets may lend themselves more to larger traces. ie I have a few surface mount sockets which have all solder tabs in a row and I have some through-hole mounts which have four pins in two separate rows. The wider pitch of the 4 pins naturally allows for a larger circuit board trace than the narrow pitch of the 8 surface mount solder tabs.

Also, if doing your own circuit board, it might be wise to use 2oz copper as opposed to the thinner stuff, tin it with solder to provide extra thickness, and increase the trace width as soon as practical after coming out of the connector.


----------



## hauntedyards (Mar 24, 2005)

I know I won't be plugging into a circuit board but putting a wall type 8pin RJ45 socket and spitting the connections back off from there to the various prop elements.


----------



## HomeyDaClown (Oct 3, 2009)

As far as Cat-5 specs go the cable itself is rated to 60 volts peak at a maximum of 360 mA per wire and a total of 72 watts input.

A lot of the current carrying capability is eaten up by how close the wires are together and the fact that they are covered by an outer sheath as well. Normal copper wire specs are for single wire (stranded or solid) in open air where heat can be dissipated.

The resistance of 24 AWG copper wire is around 2.5Ω per 100 feet so it has a built in voltage drop.

Best thing to do is get a good estimate of the current your solenoid coils will draw and then add some breathing room say 20% or more for safety or reliability. Even a small kink in a copper wire can decrease its ability to carry current. If you double up your wires or join the pairs, you easily double the current capacity. I would think that heavier gauge Cat-5 cable would be expensive compared to #24 given that you could use an older spec cable since you are not looking for a higher data rate. The RJ45s should not be a problem, most are rated at over 1 amp per pin.


----------



## hauntedyards (Mar 24, 2005)

Please correct me if I'm wrong....

Assuming AMPs = watts/volts

My solenoids are all 1.8watts at 24v...

That should be only 75 milliamps or .075 AMPS

Using 24AWG copper wire over even 100' of cable
Voltage drop: 0.39
Voltage drop percentage: 1.63%
Voltage at the end: 23.61

Granted this is shielded and stranded, etc. Should be fine considering solenoid use is brief ON signals and off %95 of the time. I'd be 50" max....


----------



## corey872 (Jan 10, 2010)

Looks correct to me. Intermittent use of 75mA over 50 inches should be no problem.


----------



## hauntedyards (Mar 24, 2005)

I totally meant 50' (feet)... but still it think it won't burn down... lol


----------



## corey872 (Jan 10, 2010)

50 feet is good too. ...and really, 75mA x 7 is only 525mA, so you could run 7 power/control wires and one ground in the bundle if you really needed to. In that case, even all solenoids on all the time and grounding through one wire puts you at about the 1/2 amp or 500mA limit shown in the charts for that one wire. Given the highly intermittent nature and the likelihood all solenoids won't be going on and off at the same time, you would be even further below the limit.

If you go 'off the charts', for comparison, I have some color LEDs driven through 50-75 feet of Cat 5. They have a peak draw 3.8 amps full on. The Cat5 has 3 conductors power, 3 conductors ground, 2 conductors color data, so that amperage is essentially traveling over 3 of the wires - or about 1270mA per wire. Probably not something you'd build into the wall of a house, but for the intended use of an open air wire with the proper fuse in the control box, it has not had any issues in 100s of hours of use.


----------



## hauntedyards (Mar 24, 2005)

Sounds good. I'll add a 1U patch panel to my rack, an RJ45 plug on each prop and just buy network cables to length. easy peasy...

I can even color code the props with matching keystones and cables in 8 different colors.

http://www.diablocable.com/cat5e-cat6-cat6a/cat5e-keystones.html


----------



## spinman1949 (Jun 29, 2009)

Corey,

I did beef up the traces on the power circuit as you described. The weak point was the small piggyback boards to mount the connector. I got them from SparkFun
https://www.sparkfun.com/products/716

There is a member here that also has a very nice board that can control 4 servos. As I recall he uses 2 of the eight for + and two for - Plus his traces are very beefy.

Spin


----------

