Blaize110 Posted June 8, 2008 Share Posted June 8, 2008 I have recently been working on a piece of hardware to control out school's 4 Betapacks via DIN from a computer. Someone else has made a previous attampt at this using USB and DACs and it cost over £100 and it still temperamental. I am looking to build something a bit cheaper. I have looked into PICAXE chips sending a digital signal and then using an RC circuit to take an average. These could then just be sent numbers from the computer. After discovering that the chips were too slow, I am now experimenting with sending the same signal out of the parallel port pins. This method would involve 3 parallel ports as I can only easily control 8 pins per port. However the computer is fast enough that no RC network is needed and all it needs is op-amping up to 0-10V. I was just wondering, while this is still all in experimentation, if anyone else has had similar projects or could offer any advise, it would be greatly appreciated. ThanksRory Link to comment Share on other sites More sharing options...
Ben Langfeld Posted June 8, 2008 Share Posted June 8, 2008 Would it not be simpler to just buy a demux and a USB DMX dongle for the computer? Stick with industry standard stuff... Link to comment Share on other sites More sharing options...
niax Posted June 8, 2008 Share Posted June 8, 2008 Would it not be simpler to just buy a demux and a USB DMX dongle for the computer? Stick with industry standard stuff... Simpler yes, but significantly more expensive. What you are saying should work, although finding 3 parallel ports on a computer might be hard and their speeds might be soft-limited. Always remember that when dealing with computers you should isolate the output from the port, just to protect the computer from any electrical strangeness. Link to comment Share on other sites More sharing options...
bruce Posted June 8, 2008 Share Posted June 8, 2008 Simpler yes, but significantly more expensive. Only if you place no cost/value on your time. Link to comment Share on other sites More sharing options...
Blaize110 Posted June 8, 2008 Author Share Posted June 8, 2008 Simpler yes, but significantly more expensive. Only if you place no cost/value on your time. No, in fact I enjoy having a project to work on. Especially as I am just about to finish my exams and I have an extra long summer holiday to look forward to. Link to comment Share on other sites More sharing options...
bruce Posted June 8, 2008 Share Posted June 8, 2008 If it's just a "for-interest" project, then go ahead. But bear in mind that as (I guess) you are a student at the school, and are not going to be there much longer, what you're building is something that is very non-standard, and unsupportable. The next person to come along will probably curse you, and chuck the lot in the bin! If you go for a USB-DMX-demux solution, you've got something which has some future-proofing... Link to comment Share on other sites More sharing options...
Jivemaster Posted June 8, 2008 Share Posted June 8, 2008 http://dj-online.co.uk/acatalog/PC_to_DMX_Interfaces.html has some good dongles and good prices. So you can have USB to DMX. there is a basic software included free also! Some ae isolated to protect the PC from live DMX lines. http://www.milinst.com/DMX/dmxtext.htm Some ideas for DMX to analog though not cheap maplin L92BL may assist your thinking or planning. The variously branded DMX Multi-exchanger from Germany, may be a cheap way of getting DMX to analog. However What is so wrong about a small box with some slider pots and sending a 0 - 10v signal directly to the dimmers? It's the only solution below £100 Link to comment Share on other sites More sharing options...
Brian Posted June 8, 2008 Share Posted June 8, 2008 I have looked into PICAXE chips sending a digital signal and then using an RC circuit to take an average. T... After discovering that the chips were too slow...You might want to look again. A quick look at the manual shows a PICAXE is quite capable of doing 24 channels of AtoD. Link to comment Share on other sites More sharing options...
Jivemaster Posted June 8, 2008 Share Posted June 8, 2008 Search http://www.audon.co.uk for anything that will take USB directly to several 0 - 10 analog outs. Trouble is that many pic chips have only two analog outs to enable at most! Link to comment Share on other sites More sharing options...
Blaize110 Posted June 8, 2008 Author Share Posted June 8, 2008 However What is so wrong about a small box with some slider pots and sending a 0 - 10v signal directly to the dimmers? It's the only solution below £100 We already have a Zero 88 Sirius 24. This is just something that I was doing in addition. I am hoping that as it is cheap, if I can make hte software as user friendly as possible, it will be used my future generations of the technical crew. It will also be able to incorperate the 2 pulsar mobile dimmers and 2 more betapacks that are moved into the hall for larger productions. You might want to look again. A quick look at the manual shows a PICAXE is quite capable of doing 24 channels of AtoD. The problem I found was the limits of the programming. It was hard to get it to loop thorough all the channels and maintain a constant square wave signal to prevent the lights going out. The capacitor needed to even out the irregularities then meant that the channel would take 20 seconds to turn off. As far as DMX goes, I had considered making a USB->DMX converter myself that is compatable with freestyler as that could be used for when we hire in movers but the demux seemed the complicated (if making) / expensive (if buying) The problem with this whole project is that we get very little budget for the crew and this isnt a priotity so anything bought would leave me out of pocket hence I am looking for a cheap solution Link to comment Share on other sites More sharing options...
roryfm Posted June 8, 2008 Share Posted June 8, 2008 Kelly Kohls has D2A and A2Ds on his website here, including source code, hex and schematic - obviously pricing it etc may mean it's not viable, but in case you haven't come across it before it may be worth a look. However I do second everyone elses opinion of it's not really worth building all this stuff yourself. Good luck either wayroryfm Link to comment Share on other sites More sharing options...
Blaize110 Posted June 8, 2008 Author Share Posted June 8, 2008 Thanks for everyone's advice. I think I will go ahead with what I am building at the moment for fun and hopefuly get some use out of it just because of the cheapness of it (only a few op-amps needed). But will bear all this in mind for future possible projects. Link to comment Share on other sites More sharing options...
maeterlinck Posted June 8, 2008 Share Posted June 8, 2008 If you're wanting to build this yourself (and why not as long as it's safe and working) then it's probably easiest to use projects that other people have designed and released the designs under some form of open licence. As suggested if you're going to do this then it makes sense to do it to some for of industry standard. A USB to DMX transceiver is a good way to get control out of your computer and will allow connection of newer equipment. Then look at a DMX demux. Have a look at these sites: USB to DMX @ http://www.usbdmx.com Demux (and others) @ http://www.hoelscher-hi.de/hendrik/english/demux.htm Good luck and let us know how you get on! Link to comment Share on other sites More sharing options...
Blaize110 Posted June 8, 2008 Author Share Posted June 8, 2008 Its the demux that really stopped me going down that route as it seemed complicated to build with many DACs just like the attempt made at this interface previously. I am also a bit lazy and so dont want to make too much work for myself. As far as I can see, the only disadvantage with using parallel ports (I'd have to buy some extra parallel PCI cards) is the large numbers of cables coming out of the back of the computer... Link to comment Share on other sites More sharing options...
musht Posted June 8, 2008 Share Posted June 8, 2008 If you really want to DIY, look up sample and hold: http://en.wikipedia.org/wiki/Sample_and_hold but another vote for buying boxes http://www.thomann.de/gb/botex_me72_multi_exchanger.htm Link to comment Share on other sites More sharing options...
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