pritch Posted November 5, 2008 Share Posted November 5, 2008 Woohoo! It seems that after several years of trying to locate funding, our project to replace our lighting gear is finally on the move. Initially, we're going to be replacing the dimmers, and using an analogue-only Sirius that we acquired a while ago. We need to replace our control cabling. As 25-way cable is horrendously expensive (all the stuff I've found so far, anyway), I'm thinking of using four runs of Cat5, and then reusing the same cabling when we finally make the move over to DMX. I can't see any reason why I shouldn't use Cat5 with 0-10v; after all, Power Over Ethernet seems happy enough with it. Can anyone foresee a problem with doing this? Link to comment Share on other sites More sharing options...
Andrew C Posted November 5, 2008 Share Posted November 5, 2008 It'll probably be ok. Check the csa of the recommended stuff, and if CAT5 isn't too much smaller, you'll be fine. Link to comment Share on other sites More sharing options...
JDP Posted November 5, 2008 Share Posted November 5, 2008 I see no reason why not.... Power Over Ethernet....? Whats that? No silly answers please :D Link to comment Share on other sites More sharing options...
Wol Posted November 5, 2008 Share Posted November 5, 2008 Power Over Ethernet....? Whats that? No silly answers please :D Power injected down a spare pair of pairs on the ethernet cable and then taken out at the end which requires the power. different sense resistances can tell proper PoE equipment the power rating of the device for it to change automagically. It runs on 48V (I think, same as phantom power), which will make any voltage drops negligible. I had a look into this a while ago for a project I was doing and I think the voltage drop of the cable wasn't that much to make a big difference and I was only using 0 to 5V. I've had the luxury of never having to work with analogue stuff in my short technical life compared to most on here, so can't comment any further on the matter! Link to comment Share on other sites More sharing options...
Andrew C Posted November 5, 2008 Share Posted November 5, 2008 Power Over Ethernet....? Whats that? No silly answers please :DAs Wol says; often used to power things like wireless access points that are remote from a mains socket (high up on a wall, in a loft etc) Link to comment Share on other sites More sharing options...
pritch Posted November 6, 2008 Author Share Posted November 6, 2008 It'll probably be ok. Check the csa of the recommended stuff, and if CAT5 isn't too much smaller, you'll be fine. Cheers, Andrew. Stupid question time... what actually is the recommended stuff? Link to comment Share on other sites More sharing options...
Andrew C Posted November 6, 2008 Share Posted November 6, 2008 Have a look in the dimmer installation instructions. It all depends on the impedance of the circuit and how much current the racks will draw in the control line and how long they are. Link to comment Share on other sites More sharing options...
daifuse Posted November 6, 2008 Share Posted November 6, 2008 Power Over Ethernet....? Whats that? No silly answers please :D which will make any voltage drops negligible. I had a look into this a while ago for a project I was doing and I think the voltage drop of the cable wasn't that much to make a big difference and I was only using 0 to 5V. Voltage drop depends on current draw - current draw depends on load impedance (or resistance with dc.) :D Link to comment Share on other sites More sharing options...
musht Posted November 6, 2008 Share Posted November 6, 2008 Analogue dimmers are high impedance input, hence the voltage control bit. But Cat 5 typically has a CAS of about 1mm^2 and think POE allows 15W at 48V per device, certainly use Cat5 for current driven devices of a few watts over distance. Link to comment Share on other sites More sharing options...
matt c Posted November 6, 2008 Share Posted November 6, 2008 But Cat 5 typically has a CAS of about 1mm^2 Not sure that's quite right. Not sure about the exact figure, but I have got some cat5 and some 1mmsq light cable side by side, and the light cable is a lot bigger. There is a specification (of sorts) here http://en.wikipedia.org/wiki/Category_5_cable Matt Link to comment Share on other sites More sharing options...
Wol Posted November 6, 2008 Share Posted November 6, 2008 Voltage drop depends on current draw - current draw depends on load impedance (or resistance with dc.) <_<I was running a fair chunk of high brightness LEDs over the line, so the current wasn't negligible in my situation! But because ..... Analogue dimmers are high impedance input ... it should be okay! Link to comment Share on other sites More sharing options...
musht Posted November 7, 2008 Share Posted November 7, 2008 But Cat 5 typically has a CAS of about 1mm^2 Not sure that's quite right. Not sure about the exact figure, but I have got some cat5 and some 1mmsq light cable side by side, and the light cable is a lot bigger. There is a specification (of sorts) here http://en.wikipedia.org/wiki/Category_5_cable Matt er, dosen`t sound quite right does it ,diameter 1mm mebbe, found one reference that put it atCross Sectional AREA,drumming it into own head, of 0.5mm^2 Anyway its cheap as chips,pull loads of it and try to only use crimp on or krone punch down terminals to terminate the solid core stuff, it fractures in soldered or screw terminals. Link to comment Share on other sites More sharing options...
mutley Posted November 10, 2008 Share Posted November 10, 2008 The only issues you may have using Cat5 are crosstalk and interference. In a normal situation, the twisted pairs in the cat5 are carrying balanced signals much like a microphone cable: one wire is the inverse of the other. Any interference picked up by the cable should be equal in both wires and therefore cancelled out at the other end. However, in lighting control, each wire is it's own signal, without it's "complimentary other half", and so any interference remains present. With the input impedance of a dimmer's control circuit being so high, that interference won't be 'restrained' (like the 50 ohm impedance of coax helps minimise interference) and so the interference would be regarded as a signal voltage. Also, if there are any major changes in level on any one wire, over what is probably a long run, that signal may be carried onto neighbouring wires like a capacitor (crosstalk). I would still give it a try, but avoid running the cat5 near any power cables, fluorescent lighting, dimmers or switch-mode power supplies (eg; laptop charger, phone charger, etc). If you do experience either of the problems shown above, try putting a resistor of about 1k to 2.2k on each wire to signal ground. This will give less than 10mA of load on each wire at a full scale voltage of 10v, but should help reduce any unwanted noise on the line.Alternatively, it you can get it at a reasonable price, try going for FTP (foiled twisted pair) instead of UTP (unshielded twisted pair), and ground the foil screen to shield the wires from outside interference. Link to comment Share on other sites More sharing options...
david.elsbury Posted November 10, 2008 Share Posted November 10, 2008 It's not FTP. The acronym you want is STP, for Shielded Twisted Pair (as opposed to Unshielded Twisted Pair) Link to comment Share on other sites More sharing options...
mutley Posted November 10, 2008 Share Posted November 10, 2008 It's not FTP. The acronym you want is STP, for Shielded Twisted Pair (as opposed to Unshielded Twisted Pair) You're probably right, but CPC call it FTP: B-) http://cpc.farnell.com/CBBR7493/cable-wire...-power-cbbr7493 (They sell some STP too!...) Link to comment Share on other sites More sharing options...
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