norty303 Posted May 1, 2015 Share Posted May 1, 2015 I have been using some of these and the 12 way versions very satisfactorily - excellent for the money, and pretty sturdy and heavy too. Which ones please Paul, the first link or second? I'm about to press 'buy' on an order in the next hour or so, so it would be good to know which is working well for you. Cheers ;) Link to comment Share on other sites More sharing options...
MarkPAman Posted May 1, 2015 Share Posted May 1, 2015 I'd guess that he means the Stairville, as there does not appear to be a 12 way version of the Cameo. :unsure: Link to comment Share on other sites More sharing options...
richardash1981 Posted May 6, 2015 Share Posted May 6, 2015 Just put my sdc-6 on the scope - frame length is 1.2ms and it only sends out 6 channels. channels 1-5 are at 60usec intervals but Channel 6 is spaced 140usec after channel 5. Sync break is 120usec and the following mark is 40usec. Frames are sent every 98ms, i.e. frame rate is 10.2Hz. Differential output is 4.4V when running from the mains PSU.Finally got round to doing the same job on my Phillips Sixer, and much as d_korman describes, except I was getting 6V differential into a 120R terminator (but with no other cable/load). It certainly only sends 6 channels (and as a result, the data packet is shorter than the minimum frame length of 1204us in the standard), but I found that the timing of the bytes varied from packet to packet:tek0006 tek0007 (few more images on Flikr if anyone is interested)The long (~150us) gap, which is OK by the standard, moves around, sometimes between channels 5 and 6, others between 4 and 5! I can see why this might upset some receivers which expect compliant input, and it seems a bit lazy - I wouldn't expect it to be hard to make the UART send blanks to make up the minimum packet length (24 channels I think). Boosting the refresh rate would be harder, but essential to stop LED fittings from strobing on fades. Link to comment Share on other sites More sharing options...
timsabre Posted May 6, 2015 Share Posted May 6, 2015 Errr... that's totally horrible DMX and I'm not surprised things don't receive it. If there is an idle time between slots/channels then it should be high, otherwise the byte before does not get a stop bit, which will give a framing error on a lot of devices. The line can't continue low at the end of the byte. So in your picture 0006, the long low is the breaktime, then the next low period is the startcode, the next 3 lows are slots 1-3, but then slot 4 is stretched to a massive length with no valid stop bit. To borrow a picture of what it should look like...http://www.element14.com/community/servlet/JiveServlet/showImage/2-6779-5874/Figure%252B2%252B-%252BDMX%252BFrames.jpg Link to comment Share on other sites More sharing options...
richardash1981 Posted May 6, 2015 Share Posted May 6, 2015 Can you check I didn't cross the scope probes over and invert the lot? This is what it looks like zoomed out:tek0008have I got everything upside down if it idles low between frames? I think I have, which means that in 0006 the break starts off screen, the wide low (which should be high) is a 120us MAB. This makes the line idle high, as it should do, and means I mixed the XLR pin-out up when clipping scope probes onto my dismantled terminator. This is also correct for the desk sending zeros, which is what it was doing at the time (flickr has some non-zero data captures as well). Link to comment Share on other sites More sharing options...
timsabre Posted May 7, 2015 Share Posted May 7, 2015 Yes it's upside down, duh I didn't think of that. So it must be the short 6 channel packet that's upsetting things. Link to comment Share on other sites More sharing options...
Brian Posted May 7, 2015 Share Posted May 7, 2015 ...short 6 channel packet that's upsetting things. Short but spec compliant. Link to comment Share on other sites More sharing options...
timsabre Posted May 7, 2015 Share Posted May 7, 2015 ...short 6 channel packet that's upsetting things. Short but spec compliant. I've come across quite a few devices which need to receive one more channel than they actually use, or they don't work. This usually shows up when you put the device at the top end of the DMX that is being sent, so for one of those disco controllers that sends 128 channels, if you put a 4 channel fixture at 125 it might not work. Link to comment Share on other sites More sharing options...
Brian Posted May 7, 2015 Share Posted May 7, 2015 I've come across quite a few devices which need to receive one more channel than they actually use, or they don't work. It's amazing how much bad DMX firmware is out there. It's not as if it's (that) difficult. Link to comment Share on other sites More sharing options...
Impact Pete Posted May 7, 2015 Author Share Posted May 7, 2015 It's a cheap desk but it should work! no excuses really I'm more bothered that I spent ages trying to fault find what turned out to be the desk rather than any patching in my dimmer rack thanks for everyone putting in the time, I have a new one in stock in my shop that I'm not keen on selling now if they don't work! Link to comment Share on other sites More sharing options...
timsabre Posted May 7, 2015 Share Posted May 7, 2015 It's a cheap desk but it should work! It is looking like a problem with the dimmer pack rather than the desk. As the desk will work an LED fixture, and a desk which outputs more channels will work the dimmer. I would suggest the dimmer pack is actually looking for more than 6 channels of DMX. Possibly it is the same software from a 12 channel pack or something like that. Link to comment Share on other sites More sharing options...
Impact Pete Posted May 8, 2015 Author Share Posted May 8, 2015 It's a cheap desk but it should work! It is looking like a problem with the dimmer pack rather than the desk. As the desk will work an LED fixture, and a desk which outputs more channels will work the dimmer. I would suggest the dimmer pack is actually looking for more than 6 channels of DMX. Possibly it is the same software from a 12 channel pack or something like that. Oh I must have read the posts wrong, so if it's an issue with dimmers why does all 3 of the 6 channel dimmer packs I have not work with this desk, when it works with all pro desks and even many of the cheap desks I have here to name a few, eurolite, glp stairville showtec etc (all made in similar Chinese factories) Link to comment Share on other sites More sharing options...
Tow Posted May 8, 2015 Share Posted May 8, 2015 [Oh I must have read the posts wrong, so if it's an issue with dimmers why does all 3 of the 6 channel dimmer packs I have not work with this desk, when it works with all pro desks and even many of the cheap desks I have here to name a few, eurolite, glp stairville showtec etc (all made in similar Chinese factories) Your not the only one, as Tim says "that's totally horrible DMX". Which it is, with a strange gap between channel 5 and the 6th (which moves!) and the frame time (440?) is way below the DMX specification minimum of 1204us. Then Tim says "It is looking like a problem with the dimmer pack". But who am to argue, Tim has designed DMX fixtures. If you look at the setup of some DMX desks/dongles there may be an option to set the minimum number of 'Channels' to output, whether they are used of not, defaulting to around 24. Found this: http://en.wikipedia.org/wiki/DMX512 The standard does not specify the minimum number of slots that can be sent in a packet. However, it does require that packets be transmitted so that the leading edges of any two sequential BREAKs must be separated by at least 1204 μs, and receivers must be able to handle packets with break-to-break times a short as 1196 μs.[8] The minimum break-to-break transmit time can be achieved by sending packets that contain at least 24 slots (by adding extra padding bytes, if necessary) or by stretching parameters such as the BREAK, MAB, Interslot, or Interpacket times.[9] Link to comment Share on other sites More sharing options...
Brian Posted May 8, 2015 Share Posted May 8, 2015 Interesting thought....if the packet time is less than 1204us then the item should not have DMX on the label as it doesn't meet the spec. So importers of these units are opening themselves up to claims from consumers via Trading Standards. Link to comment Share on other sites More sharing options...
timsabre Posted May 8, 2015 Share Posted May 8, 2015 Oh I must have read the posts wrong, so if it's an issue with dimmers why does all 3 of the 6 channel dimmer packs I have not work with this desk, when it works with all pro desks and even many of the cheap desks I have here to name a few, eurolite, glp stairville showtec etc (all made in similar Chinese factories) Yes sorry about the confusion earlier, I didn't twig that the DMX traces were upside down, so the DMX was not as horrible as I thought. Still a bit weird with that funny gap between channels but it should work. I am suggesting that the dimmers do not work if they are only presented with 6 channels of DMX. Have you tried it with another DMX desk that only outputs 6 channels, most desks (even cheap ones) will output at least 24 chans. Link to comment Share on other sites More sharing options...
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