rlower Posted January 7, 2011 Share Posted January 7, 2011 Hi, Just wondering if anyone has any suggestions... In a venue we're wiring some power and data points around the room for some newly purchased fixtures.As everything will be running through our trussing, as these points will be semi-permanent I'd like to keep the cables grey, so everything will look a bit neater. Some signal cables below... ~£0.54/m (110 ohm) http://uk.farnell.com/belden/1800b-t5x500/cable-audio-grey-4-5mm-152-4m/dp/1423232 ~£0.39/m (100 ohm) http://www.canford.co.uk/Products/20466/31-078_CANFORD-FST-CABLE-1-pair-Grey We'll be purchasing 500m so theres about £75 difference between 100 and 110 ohm. I know DMX should be 120 ohm, but does if matter than much? Has anyone seen 120 ohm cable thats grey for a similar price? Also anyone seen any grey HO7 style 16A cable anywhere? End of the day, we can just use black cables I doesn't really matter. I would just be nice! Link to comment Share on other sites More sharing options...
smalljoshua Posted January 7, 2011 Share Posted January 7, 2011 If the DMX Points can be made permanent, you can just use Cat5 cable terminated into Wall boxes for the DMX. Josh Link to comment Share on other sites More sharing options...
jonathanhill Posted January 7, 2011 Share Posted January 7, 2011 I know DMX should be 120 ohm, but does if matter than much? Yes, otherwise you will get impedance mismatches and reflected signals, which will probably manifest itself as dimmer or mover 'jitter'.Also anyone seen any grey HO7 style 16A cable anywhere?No, as grey rubber doesn't really exist. Link to comment Share on other sites More sharing options...
rlower Posted January 7, 2011 Author Share Posted January 7, 2011 Thanks for the replies. Every so often the cables will be removed. The plan was grey cables, grey pvc... Anyone seen any grey 120 ohm cable before? Link to comment Share on other sites More sharing options...
Brian Posted January 7, 2011 Share Posted January 7, 2011 I know DMX should be 120 ohm, but does if matter than much? Yes, otherwise you will get impedance mismatches and reflected signals, which will probably manifest itself as dimmer or mover 'jitter'. TBH it makes sod all difference.Terminating it at all with something around the right value is a huge step but whether it's 100, 110 or 120 Ohms after that makes not much difference. Link to comment Share on other sites More sharing options...
matt c Posted January 7, 2011 Share Posted January 7, 2011 Thanks for the replies. Every so often the cables will be removed. The plan was grey cables, grey pvc... Anyone seen any grey 120 ohm cable before?Got 2 30 metre reels under my desk.. Belden make it, but I can't remember the reference number off the top of my head. Try looking on the Belden website. They do a few "chrome" pvc data cables that are suitable. Also try the likes of RS and Farnell. Link to comment Share on other sites More sharing options...
adamharman Posted January 8, 2011 Share Posted January 8, 2011 Also anyone seen any grey HO7 style 16A cable anywhere? The plan was grey cables, grey pvc... IIRC, HO7 actually only refers to the voltage rating although it is commonly used to describe the decent quality heavy rubber sheathed cable (HO7-RNF) which is always? black. If you're happy that PVC is suitable for the job, 3x2.5 flexible cable shouldn't be that hard to get hold of. If you can't find ordinary BS3183Y in 2.5mm grey, then YY cable is usually grey and is made in 3x2.5. Any electrical wholesaler should be able to get one or the other in for you. Link to comment Share on other sites More sharing options...
matt c Posted January 8, 2011 Share Posted January 8, 2011 Belden make it, but I can't remember the reference number off the top of my head Have a look at Belden 8132. It's 2 pair, but I'm sure there'd be a single pair version too. Link to comment Share on other sites More sharing options...
musht Posted January 8, 2011 Share Posted January 8, 2011 I know DMX should be 120 ohm, but does if matter than much? Yes, otherwise you will get impedance mismatches and reflected signals, which will probably manifest itself as dimmer or mover 'jitter'. TBH it makes sod all difference.Terminating it at all with something around the right value is a huge step but whether it's 100, 110 or 120 Ohms after that makes not much difference. Actual 120 Ohm cable in any colour seems very rare, as far as undertsand it Cat5 is around 100 Ohms and a lot of industrial data cables, for RS485 machine control as well as ones marked suitable for AES/EBU seem to be 110, even though RS485 and DMX512 spec says 120 Ohm cable. Is it like the blue mains cable debate, the standard specifies something that dosen`t really exist? Link to comment Share on other sites More sharing options...
Brian Posted January 8, 2011 Share Posted January 8, 2011 There's a useful table of recommended cables in 'Recommended Practice for DMX512'. It lists cables from 80 to 150 Ohms. Link to comment Share on other sites More sharing options...
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