The Paranormal Unicorn Posted October 27, 2014 Share Posted October 27, 2014 Hello all, I wasn't exactly sure where to ask this question, but I think this is the most appropriate place. I'm currently working on a rotating LED bar (imagine LEDs attached to a single clock arm) to use as a fixture. The strip will accept 90 channels of DMX to control the LEDs, but I have been told that controlling stepper motors with DMX is a very bad idea. So my question is: what are my options for controlling rotating motors? And is there lighting software out there that can visualize rotation? Thanks in advance,stefan Link to comment Share on other sites More sharing options...
Tom Baldwin Posted October 27, 2014 Share Posted October 27, 2014 Controlling stepper motors with DMX is exactly what happens inside moving lights... not sure what the person who gave you that advice was trying to say! Do you want to control position, rotation, or both? Either way, think of a gobo wheel in a moving light - a specific gobo can be selected, or continuous rotation of the wheel is possible, cycling through all gobos in turn. Link to comment Share on other sites More sharing options...
richard Posted October 27, 2014 Share Posted October 27, 2014 the issue might be that you are controlling continuous rotation (rather than a position) so DMX is more tricky, however I would just treat it like a rotating gobo - so you have a mode channel (which selects either index (position) or speed (continuous rotation) and then a second channel which controls the afformentioned position/speed. You might want the second channel to be 16 bit, but that's probably dependent on how precise the motors are. Richard Link to comment Share on other sites More sharing options...
nickb12345 Posted October 27, 2014 Share Posted October 27, 2014 Controlling chain hoists and motors that move largs pieces of set (revolves etc) from DMX is a bad idea as if they move at the wrong time they can cause injury or damage to equipment. All about the risk assessment but if we are talking about a small clock arm then DMX control will be fine (just like in moving lights). If we are talking about something bigger then maybe not so much, but you probably wouldn't be looking at stepper motors for large pieces of set etc. Nick Link to comment Share on other sites More sharing options...
The Paranormal Unicorn Posted October 27, 2014 Author Share Posted October 27, 2014 Well thanks for the quick replies. Yes, the information I was getting was about winches, not rotary motors. The stepper motors I'm looking at using have 200 steps, though the resolution can always be upgraded with a gear train. The 2 channel solution seems like a good one. Ultimately, the aim would be to create an array of these, so the next problem would be content creation and visualization. It's possible to create everything in vvvv or MaxMSP, but it would be preferable to use existing solutions. Are there any packages out there that would be able to visualize such a thing? I know that there are procedural pattern generators for winches and hoists, but I've never seen something similar for rotary motors... http://www.kinetic-lights.com/ Link to comment Share on other sites More sharing options...
Jivemaster Posted October 28, 2014 Share Posted October 28, 2014 Milford Instrumants ( http://www.milinst.co.uk/index.php ) and others will supply stepper motor controllers to rotate things like clock hands. The issue with DMX is that it is not considered suitable for safety critical tasks so some things it could do it shouldn't. The issue I see is getting control for the LED light unit through the rotating spindle Link to comment Share on other sites More sharing options...
the kid Posted October 28, 2014 Share Posted October 28, 2014 The issue I see is getting control for the LED light unit through the rotating spindle Would this be why we have not seen more 360 heads. Someone at plasa a few years ago had continuous 360 pan and tilt, but not seen them anywhere or the idea been taken up by manufactures. Link to comment Share on other sites More sharing options...
Jivemaster Posted October 28, 2014 Share Posted October 28, 2014 Good DMX needs good cable and good connectors, I doubt it would pass well through any slip ring system, BUT the power could be sent through slip rings and the DMX by some kind of RF protocol or an induction loop system. If I read the OP right then there is more to consider than just using a stepper motor to move a clock hand, but it's all possible. Link to comment Share on other sites More sharing options...
The Paranormal Unicorn Posted October 28, 2014 Author Share Posted October 28, 2014 The LEDs I'm using are of the WS2811 variety. There are plenty of boards out there to convert DMX to WS2811, so the DMX signal doesn't have to actually pass through a slip ring. The DMX is converted before the slip ring and the WS2811 information only has to travel 5 cm or so to the LEDs. My question about the software remains unanswered though. Are there any software packages that can visualize rotating elements? I know that many of them offer moving trusses and pipes but I haven't seen anything yet that offers 360 degree rotation. Link to comment Share on other sites More sharing options...
Shez Posted October 28, 2014 Share Posted October 28, 2014 The stepper motors I'm looking at using have 200 steps, though the resolution can always be upgraded with a gear train. You'll likely want to look in to microstepping. Many moons ago at uni I had to do a presentation all about that but have sadly forgotten most of the details now. Essentially, it gives you much finer and smoother control than 1.8 degree steps. Link to comment Share on other sites More sharing options...
top-cat Posted October 28, 2014 Share Posted October 28, 2014 Controlling chain hoists and motors that move largs pieces of set (revolves etc) from DMX is a bad idea as if they move at the wrong time they can cause injury or damage to equipment. Not necessarily true. Look at things like the Wahlberg DMX Winch, it can be done safely and properly. Most of Kinesys' control equipment has options for DMX input. The key is that if you are moving people or equipment, (a) your DMX system is designed with that in mind and has some failsafes built in (IE having to send multiple simultaneous values to the equipment, so that a glitch in one value does not make it do something wild - this is how many DMX-based Pyro systems work), and (b) you have additional safety measures in place to prevent an accident occurring if DMX fails. This can be 'spotters' with E Stops, for example. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted October 28, 2014 Share Posted October 28, 2014 You'll likely want to look in to microstepping. Many moons ago at uni I had to do a presentation all about that but have sadly forgotten most of the details now. Essentially, it gives you much finer and smoother control than 1.8 degree steps. But microstepping also means that some steps have less torque than others and your motor may lose position. Its much better to use gear reduction and full stepping. Or you could use one of these if they weren't discontinued. There is one on ebay... Link to comment Share on other sites More sharing options...
fliggygeek Posted November 17, 2014 Share Posted November 17, 2014 The issue I see is getting control for the LED light unit through the rotating spindle Would this be why we have not seen more 360 heads. Someone at plasa a few years ago had continuous 360 pan and tilt, but not seen them anywhere or the idea been taken up by manufactures. There are a lot of 360 moving heads out there, and these days only power is done with sliprings, you can now buy sliprings that have power transmission and then through the centre they have essentially an optocoupler that can flawlessly transmit the data at almost any speed. Link to comment Share on other sites More sharing options...
the kid Posted November 17, 2014 Share Posted November 17, 2014 I have not see anything that does 360 non stop most seem to do 540 Link to comment Share on other sites More sharing options...
fliggygeek Posted November 17, 2014 Share Posted November 17, 2014 I have not see anything that does 360 non stop most seem to do 540 Ayrton MagicBlade -RAyrton MagicPanel 602Ayrton MagicPanel -R Theres three I know of off the top of my head, theres more, Morpheus lights were touring some nice arc wash units with continuous pan at least on the recent Springsteen tour. Theres a bunch of 5R beam lights with continuous as well, ovation and adj have models etc. The ayrton and morpheus are the most significant, the led units demonstrating super high data throughput to the head, and the arc lights demonstrating large current supplied to a continuous movement head. Link to comment Share on other sites More sharing options...
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