Dmx/pc Interface

[peternewman]

Okay, I've just rediscovered this thread, and seeing as I now own a pair of the DMX Protocol Converters I thought I might try and answer some of the queries.

 

Has anyone tried the RS232/DMX interface card from maplins yet (cat number RP99H)? Seems quite cheep really at £79.99 inc. VAT and the idea of not having to fault find is very appealing.

<{POST_SNAPBACK}>

 

Yes I have tried it, its very nice ;) I got my pair on eBay for £100, so a good bargain.

 

Am I right in thinking that the Maplin interface would also work as a 4 channel 0-5v demux? It seems almost too good to be true.

<{POST_SNAPBACK}>

 

This is indeed correct, however if you wish to drive things other than dimmers, I'm making a four channel switchpack for example, you will need a transistor. Also note there is a resistor connected on each analogue voltage channel, 430 ohm IIRC, so this must be taken into account. Also rather frustratingly, from reading the manual about the DAC, it could be set to output 10v instead, if they had set it up differently.

 

Peter wrote:

Am I right in thinking that the Maplin interface would also work as a 4 channel 0-5v demux?

<{POST_SNAPBACK}>

The manual for the Maplin board can be found here Link to Maplin board

I have a couple of concerns with it though...

 

1. The serial link to the PC only runs at 9600 baud and uses an ascii protocol , this will introduce a noticeable delay on any changes. Worst case a full update of all 512 DMX channels (eg DBO) will take 3.7 seconds to send to the board.

 

2. I do not think that the unit will transmit all 512 channels. I can't find a definate answer anywhere on that but when reading DMX to send to the PC, the card only extracts the 4 channels assigned to it and sends those to the PC. If it where to be able to transmit all 512 channels it would need 512 bytes of RAM and the micro they use does not appear to contain that much.

<{POST_SNAPBACK}>

 

The board in fact outputs only 112 channels, so an update is not going to take so long. Out of interest how did you get your figure of 3.7 seconds?

 

I think the Maplin blurb says it all:

"Control disco lighting equipment from your PC"

since when were we into controlling disco lights?

<{POST_SNAPBACK}>

 

I can imagine controlling disco lights with it. The software they supply is probably slightly more aimed at disco, as there is no cuestack or submasters or presets. I can also imagine Maplin wouldn't get many sales if they said "Control expensive, high specification moving lights which we don't even sell from your PC".

 

If anyones interested... the datasheet for the maplin DMX interface is here...

http://www.milinst.com/gemodules/1_463.pdf

you can also find the freeware control software on their website, obviously doesnt do anything without the interface but its good for seeing what your gonna be able to do, of course it comes with the source code so you can adapt it anyway

 

It does 112 channels out from a serial interface, or 4 from the analogue inputs (start address can be from 1 to 118)

 

not too sure on its recieving capabilities (didnt read it, doesnt interest me), but I think it'll do four analogue 0-5v outputs.

 

im thinking of buying one, probs butchering it and putting it in a rack mount chassis, at least then I can put 5 pin XLRs on it then! B-) might build a power supply into it too *begins muttering to self*

 

Tom

 

--Edit---

 

Also might be worth knowing, if you gonna buy the one from maplin, you can save yourself about £15 by buying direct from the company that makes them.

http://www.milinst.com

<{POST_SNAPBACK}>

 

It can transmit from RS232 (112 chans) and analogue 0-5v (4 chans) and ceive ( :blink: Thanks Bryson) and output RS232 (4 chans), analogue 0-5v and also 4 servo outputs. On this note you could use it to make your own mirror system for the front of a profile, along the lines of the Chroma-Q mirror. Or for animating parts of the set, a drop of some sort maybe? <safety>Obviously do not use DMX to control things that could cause injury or death as it has no error checking built in.</safety> Another idea would be to use the board as an input to a computer, to cue sound playback or video maybe.

 

If anyone is interested, or indeed posses one of these devices, I have been working on some software for it, which you are welcome to have a look at, if people are interested I will post it on my website.

 

PN

[ace]

I would be very interested! I am in the early stages of developing my own visualization based lighting design software, it would be great to actually get some output from it as well!

 

Chris

[martinw]

Enttec has just released this, which is an open source design for a USB to DMX interface. Their site has schematics, PCB artwork, device drivers and software API, so you can build your own from scratch, buy the bits and build one, or just buy the assembled version, which is pretty cheap.

 

Martin

[tuxlux]

A few things.....

 

As discussed previously in other threads (in lighting), I've had a go at my own DMX interface. From my experience I'd strongly recommend the isolated level drivers maxim do MAX1480 or MAX3480 type things (with complete isolation to supply the power for the 485 interface and optical isolation for the signaling) or similar, though these are more expensive than the non isolated ones.

 

I've started writing software to control it, but am currently having issues with licenses, which I'll hopefully sort eventually. However at over 10000 lines, and not even halfway complete, writing good, useable control software for these things isn't trivial. I'm intending to opensource the code though eventually.

 

From my experience I'd agree that serial is not really suitable, though considerably simpler for quick hacks. I was intending too to take the usb approach, so for starters you couldl use it on macs too.

 

I think what would be good would be a good, reliable system which doesn't cost thousands, but actually works. There is the old phrase you get what you pay for though.

[martinw]

From my experience I'd strongly recommend the isolated level drivers maxim do MAX1480 or MAX3480 type things

I've used those, I thought they were rubbish! The power consumption is much greater that a DC-DC convertor/opto isolators/line driver combo, and they still need lots of support components. They also cost more that the DC-DC/opto solution, and you have to contend with Maxim's notoriously long lead times.

 

Martin

[tuxlux]

ok, sorry - misunderstanding, my fault for not making myself clear. I was suggesting them as I simple one chip solution, and suggestion of isolation being a good idea - not necessarily "the chip of choice for all designs" . My design didn't need that many additional components, but would agree that a DC-DC opto solution is probably better for a decent design.

[ziggy252]

Hi all,

 

I've been working with the Enttec interface for several months. It is quite reliable, and the range of available software is increasing by the week. Hopefully mac support will be available by the end of the year.

 

The interface is based on the FTDI chip mentioned earlier in this thread, and is capable of both transmission and reception of DMX signals (hopefully both simultaneously in a short while).

 

Cheers,

 

Robert Wilkinson.

[phillipberry]

Sorry to be a pain people

 

But

 

Could someone update me with the result of USB to DMX topic

 

Does it work?

Can you make it cheaply?

Will it blow up my laptop and give the misses the chance of saying "I told you so"?

 

Thanks

 

Phillip

[peter]

I bought a ready manufactured Enttec USB>DMX dongle at PLASA - it seems to work fine, although there were some refresh rate issues with Chamsys MagicQ, I believe these have now been ironed out - I haven't had a chance to try it out myself.

 

 

Peter