# DMX motors/ chainhoists



## legacy (May 13, 2007)

Anyone know if there are DMX controlled Winches/ chain hoists. I am in the design stages of three Projector rigs that will require up and down movement. These units will be total units with 3000 lumen projectors and 12 x 9 rear projection. I will need to lower them and raise them by programing.. there will be a total of three units..... I can do it several ways but having a DMX controlled hoist would be lots easier.. thanks


----------



## Footer (May 13, 2007)

AHHHHHHHHHHHHHHH... NO THEY DO NOT EXIST NOR SHALL THEY EVER EXIST. DMX is the worst motion controller ever. There is no redundancy or checksum, therefore there is no feedback or real control. DMX works great for lights, not good for show control. What you can do is get a motor controller that takes DMX cues and through a dead man switch the motors will move, i.e. if the switch is not pressed they will not move. Thats the safest way to do it. Think about it, do you really want to be pageing through cues and have the US truss move?


----------



## JSFox (May 13, 2007)

Since DMX lacks error handling and positive acknowledgement capabilities I'd think you'd have a difficult time finding anyone making any systems for controlling motors with it due to potential dangerous outcomes. There are a number of companies that make motor control and animation systems for this type of thing though but you'll need a specific person controlling it (and watching everything for safety).


----------



## avkid (May 13, 2007)

The closest DMX should ever get to motors is the control light that tells the operator when to go.
DMX should not be used for:
Rigging control
Pyro
DMX is for lighting!


----------



## avkid (May 13, 2007)

http://www.jrclancy.com/


----------



## What Rigger? (May 14, 2007)

DMX bad.

On the other hand, _AMX_ good! Real good!

Edit: I don't even know why I tried sarcasm here. Actually I'm not even sure what I was thinking posting this. If you see this now, or any time in the future- ignore it.


----------



## jmabray (May 14, 2007)

What Rigger? said:


> DMX bad.
> On the other hand, _AMX_ good! Real good!




Please clarify. I am assuming that you are talking about AMX, the automation company. Not AMX the old Strand Lighting Control signal....

DMX may be bad, but AMX is very very very very very very bad.  

Jeff


----------



## stantonsound (May 14, 2007)

DMX is bad, I think that we have established this. (Bad for motor controls, etc...) I agree.

Now, how can this be accomplished? There are several problems with just putting them on a fly system, or on chain motors. Neither is good for fine movements. You can get something in the ballpark, but that is it. Getting something that is exactly in place every time, that is difficult. 

Take a look at the Apollo Right Arm. A projector can easily be mounted to one of these. You can at least move the projector, but it is porbably not what you are looking for.


----------



## legacy (May 14, 2007)

thanks for the GOOD info. Had no idea that this was a problem. GLad I asked. For clarification, the units that I will be fabricating will be self contained. The Screen and projector will be flown together. Range of motion; approx' 14 feet, up and down. There are three such units that I will wont to move seperately at various times in show and out. I did some research and found a variety of control. I really want this to be operated from the light and mix position. This is going to be a Youth church seating 500 and they want something different. there will be a total of 4 screens. three as mentioned and one 16 footer that will lowered downstage (rear screen) for Simalcast and movie nights (with complete 5.1 surround, should be cool) We are the A/V contractors. So was just thinking outside the box and this list is a wealth of been there done that. Thanks for help as I continue my quest.


----------



## icewolf08 (May 14, 2007)

I am going to make another referral to Creative Conners Inc. for affordable motion control equipment. His system does not currently support any type of show control, but the Avista software is easy to operate and provides the operator with real time feedback on all motors and moving pieces. If you call them up, they will even help you design a system that fits your needs.


----------



## JSFox (May 14, 2007)

Mixing church and flying stuff is scary. Some churches have people amply qualified to watch over, use, and maintain these types of systems, many don't. As I'm sure your'e aware, moving scenery can be extremely dangerous. It's control should NEVER be done from a house position but should always be done from close to the scenery and from where the operator has very clear view at all times of all elements and anyone who could be in the path of falling or mis moved elements. If they're a Lakewood, Willow, Saddleback, or similar church with a professional staff overseeing everything this could work well, otherwise you should be very careful lest you end up with more liability than you care for.

Mixing a youth group and flying stuff is even more scary.

As an alternative and perhaps even less expensive and more versital how about building a large rear screen lite by something like a Christie Roadster. A good switcher or NLE can place images anywhere and everywhere within the image area, move them around, zoom them, explode them, whatever. Or perhaps go with a digital LED backdrop to do the same thing. HES DL2's could also be used to do this and more from a front projected standpoint.


----------



## stantonsound (May 14, 2007)

JSFox
I completely agree with you. Rigging in general is a very dangerous undertaking. You know the old saying, "If at first you don't succeed, don't be a rigger...". 
There are some churches that can accomplish this and much, much more. I moved to Charlotte from NYC and I was amazed by the churched here (THE BIBLE BELT!). One of the first churches that I walked into was more than 300,000 square feet. There is a 48 channel front of house console and monitor console, and a JBL vertec line array hanging above the alter. There are more S4's in this church than in any other venue in town. It is more of a theatre than a church, with trussing flown overhead with chain motors. 
One of the other churches in town has an elevator built in so the alter can be raised and lowered, allowing it to be used for various purposes. 
There are big churches, but this is not the norm. These churches that I refer to have a professional staff and it is their full time job, 40 hours a week. The building was designed to accomplish this, and it is done safely.

I am the LD for a local high school, and their auditorium is rented out every Sunday for church services. This is actually very popular in NC. The church group that comes in offers 3 services every week and had approx 2,500 people attend every week. They buy the school just about any lighting and sound equipment they ask for. They just put in a new lighting console, and gave them 24 S4 Pars in the last month. They have 4 professional techs that they hire from IATSE plus a student TD from the High School that they pay to run just lights every Sunday. They staf another 3 people to mix and record sound, and 3 for video recording/projection/live web broadcast. 

(note: The attached photo is not in Charlotte, but it is the Crystal Cathedral in Garden Grove, CA. It is the only sample pic I could find online).


----------



## Jezza (May 14, 2007)

If you do decide to go with automated scenery, take a look at Joker. They make very good systems for standard theatrical linesets but might also support control of chain hoists or specialized winch and control systems to do what you are describing. Their control interface is very user friendly and has a million safties built in. Take a look.


----------



## beltsvillecrucib (May 14, 2007)

At the last load in I did, we installed three very large projection screens. Each screen was within about 16'-18' sections of large truss. Each screen further had a motor attached to it that would lower and raise each screen. The truss was bolted together, permanently flown with house winches and the motors that raise and lower the screens will be controlled by DMX I believe. However, there is also a control at the Stage Manager's position just off stage. DMX goes to a distro for the screens above stage and gets spit out to each screen along with power.

The truss/motor/screen system was specially designed for the house by some company out in California, can't remember the name right off the top of my head.


----------



## soundman (May 14, 2007)

That goes agienst the DMX standered put into place by USITT http://www.usitt.org/standards/DMX512_FAQ.html#FAQ_09


----------



## jfitzpat (May 14, 2007)

I would readily agree with the comment above that rigging/flying involves serious safety concerns and should not be undertaken lightly.

I would also agree with the statements that DMX is a terrible native format for safety related control. Frankly, I've always thought that the complete lack of error checking makes it pretty lame for lighting, but after two decades, that is a debate I am willing to let go... 

Still, a fair amount of 'unsuitable' equipment (pyro, flame jets, lasers, moving staging/rigging) are regularly controlled via DMX. And it is probably worth examining how it is done with reasonable safety - if, for no other reason, folks do not try to come up with simple DMX solutions.

First, it is important to understand when you are looking at, say, terrifying propane jets at a huge concert, the DMX control is not 'direct'. That is, it typically isn't a simple DMX->relay board. Typically, the pyro, flames, lasers, etc. have a controller of their own. DMX is used to 'trigger' one system from another. The dedicated control system often supports specific safety interlocks and additional operator over rides. This can be fairly involved, for example one setup I can think of involved pressure mats to account for everyone on stage. Another had an operator arm specific charge groups. That is, DMX provided the precise timing of the fires, but a human armed the effects just moments before while visually inspecting clearance.

Second, for anything remotely life threatening, DMX is seldom used in a conventional channel->value->result fashion. The standard is typically enhanced in two ways. First, DMX one (often two) channels used by the safety system are typically repurposed for error checking. Take one I can think of off the top of my head. It uses 4 DMX channels to set off fire jets. Instead of a conventional DMX channel/fixture map, you get:

Toggle
Charge
Action
CRC

It actually resembles conventional DMX usage very little. It is more like it is borrowing 5 bytes of bandwidth on the RS-485 connection to implement a control protocol. The 'Charge' and 'Action' are close to what you might expect. Pick a 'charge' (0-255) and tell it to take an 'Action' (prep=001, arm=122, or fire=165).

However, you would be hard pressed to work the two channels with a simple DMX board. The prep, arm, and fire values must come in order, and no other values must be received (any value other that 1, 122, or 165 tells the system to look for 'arm' again). Similiarly, the 'charge value' cannot change during the sequence, otherwise the controller again goes back to idle.

If the thing being controlled were scary, but safe (ex. big fire blast, but never near anyone), this scheme alone is pretty good (sequence in time). However, in this case, a higher level of error protection was required, so two additional mechanisms are present. The 'toggle' an 8 bit counter. The bottom 2 bits must to match the 'action', and count in order (idle, prep, arm, fire means a count of 00, 01, 10, 11). The top 6 bits count 'command cycles'. Mathmatically, this does not improve the error checking that much, but it does make the messages longer, and more unique, which helps with the other form of error checking - the last byte is a CRC, based on the first 3.
Again, any error, packet count, action to count modula, CRC error, resets the state engine and alerts the effect operator.

The above is just one example, but it shows the sort of solutions that get used. In this case, you can use a the cue stack in a memory board to 'run' the system (using a little tool to calculate the CRC and toggle values). However, bit errors, programming errors, or just breaking cue order all have a mathmatically very high probability of stopping the jets and alerting the safety operator.

Again, my point isn't to encourage people to use DMX for safety related control. My point is just the opposite. When DMX has been safely used for this sort of thing, a lot of work and extra precautions normally go into it. 

-jjf


----------



## soundlight (May 14, 2007)

I would ask why you would want to move the projectors? It seems pointless. If you're going to do that, you also have to have cable reels at the top to take up the VGA or RGBHV cable that you'll be using for that, as well as power, and possibly a control signal depending on the projector. I'd say that the projectors could stay stationary unless they're actually going to be blocking someone's view. But for screens moving up and down, use the AMX control system (www.amx.com) to do what you're looking for. The AMX system will also be able to control the powering up and down of the projector, the signal input selection, the powering up and down of signal sources, etc. It's an amazing system. There are panels in all of the lecture halls here at Bucknell, and the system is amazingly flexible, and very, very easy to use.

But, you may have a reason to move the projectors. But it could add very significant cost.

EDIT: Looking back over the thread and reading it twice more, I realize that it may be necessary to fly the projectors due to the RP nature of the project. But if you can make them fixed, do it. Keystoning can do wonders.


----------



## JD (May 14, 2007)

Regarding Pyro control, before my first retirement (in 1990) I used to control Pyro from the board. (pre-DMX days) Even then, several layers of safety were used. The last and key element was a "dead man" switch on the stage monitor board. Our stage manager / monitor mixer had to hold the switch down to engage the system. He knew the approximate times for the effect and would maintain visual contact with the effect. If something got in the way or he lost view, he simply let go of the switch and the system was disabled. There was an indicator light on my board that would light when he was on the switch. In the 2000 shows we did, there were about a half dozen times I can remember the light going out right before the effect was scheduled.
I also would not recommend using DMX for lift control or pyro. Even if DMX was an error checked system, things can happen in live shows that are not visible from a distance. Anything that occurs over people's heads, or in areas that can affect people should be treated like a bomb waiting to go off.


----------



## icewolf08 (May 14, 2007)

On the other hand, and this does not circumvent the need for being able to see what you are doing, you may be able to find a system that supports MIDI Show Control (MSC). Most lighting consoles can output MSC commands and you may be able to trigger motion control via MSC. This is a protocol that was designed for the task.


----------



## jfitzpat (May 14, 2007)

JD said:


> I also would not recommend using DMX for lift control or pyro. Even if DMX was an error checked system, things can happen in live shows that are not visible from a distance. Anything that occurs over people's heads, or in areas that can affect people should be treated like a bomb waiting to go off.



I think that they are really two different things. Tons of big fireworks shows are pre-programmed to tape each year. In the highest tech ones, the very precise firing control is even required. The pre-programming gives a very tight, well coordinated firing - but it does not negate the need for proper safety personal and observers.

Again, I can't stress enough how important safety can be with these things. I've got a rough patch of skin on my forearm that reminds me of a local stage hand with 3rd degree burns over much of his body (several of us got minor burns trying to extinguish his burning clothing with packing blankets) and I have a small thin scar on my right wrist that is from a broken reed switch. An early 'moving trussing' system would count links on chain hoists - it got confused in an early rehearsal and while folks futzed and tried to react, the rig experienced 'load multiplication' on a massive scale. I got stabbed by a gel frame from about 75' away - fortunately, no one was killed or seriously injured.

-jjf

Edit: Not to pick on MSC, but MIDI is also a unidirectional protocol without error checking. I'd have to dig up the MSC spec again to confirm, but I believe that it uses a universal SysEx (System Exclusive) message to send show 'commands'. I don't recall error checking being added to the command structure. Without that, and without an ack/nack mechanism from devices (not possible with MIDI topography), I would not use MSC for safety sensitive control applications without taking the same sorts of precautions and enhancements I described above.


----------



## JSFox (May 14, 2007)

You may also want to check out John Huntington's book. Not sure if it's been updated since last time I flipped through it, but some good info.


----------



## icewolf08 (May 14, 2007)

jfitzpat said:


> Not to pick on MSC, but MIDI is also a unidirectional protocol without error checking. I'd have to dig up the MSC spec again to confirm, but I believe that it uses a universal SysEx (System Exclusive) message to send show 'commands'. I don't recall error checking being added to the command structure. Without that, and without an ack/nack mechanism from devices (not possible with MIDI topography), I would not use MSC for safety sensitive control applications without taking the same sorts of precautions and enhancements I described above.



I do not claim to be an expert on MSC, but the way commands are transmitted is inherently safer than a protocol like DMX. In a MIDI system commands are transmitted only once as opposed to a constant repeating data stream like DMX. Therefore if a device sends a command (say a lighting console to a computer running SFX) the command is transmitted only once (Cue X Go). If there is any data loss or the receiver can't interpret the command nothing happens. Some devices require more than one MSC command, like "Load Cue X" followed by "Cue X Go".

Compared to DMX for many situations this is an ideal setup. If there is a bit error in a DMX stream you might not notice if a dimmer kicks to full for one 44 thousandth of a second, but that is enough to trigger a relay or a cue.

MSC is very widely used from amusement parks to Broadway to Vegas shows. I know, from working in the cruise industry that lighting, sound and pyro are tied together via a combination of SMPTE timecode from the click track tape and MSC from the lighting console.


----------



## What Rigger? (May 15, 2007)

jmabray said:


> Please clarify. I am assuming that you are talking about AMX, the automation company. Not AMX the old Strand Lighting Control signal....
> DMX may be bad, but AMX is very very very very very very bad.
> Jeff


Hey Jeff, nice catch! I'm talking about AMX as a way of communicating between (for lack of better terms) "show control" and "automation". My current gig uses this as a way of keeping one of the elements of the gig synch'ed up and running safely. SMPTE also figures in, but as I've had to say before to folks, I can't say much more. Current conditions of my employment forbid me to speak in specific terms. Sorry.
Perhaps Fisher Technical's website can add further illumination to the issue: www.fishertechnical.com


----------



## jfitzpat (May 15, 2007)

icewolf08 said:


> In a MIDI system commands are transmitted only once as opposed to a constant repeating data stream like DMX. Therefore if a device sends a command (say a lighting console to a computer running SFX) the command is transmitted only once (Cue X Go). If there is any data loss or the receiver can't interpret the command nothing happens.



The most likely form of error is a line bit error. Without a checksum or CRC, how does the receiver know to discard the command instead of executing a corrupt one?


icewolf08 said:


> If there is a bit error in a DMX stream you might not notice if a dimmer kicks to full for one 44 thousandth of a second, but that is enough to trigger a relay or a cue.



Read my post above, most the approaches that I am aware of do not use DMX this way. Much as MSC uses a SYSEX message to embed a different protocol message on the MIDI uart stream, most applications that I am aware of use bandwidth on the DMX stream to implement a more robust protocol for certain types of control applications. 


icewolf08 said:


> MSC is very widely used...



DMX is widely used as well, but it is still a lame protocol. 

Forgive me if I sound jaded, but I made many of the same arguments when MIDI was standardized that I made when DMX was standardized. And the response to no error checking, no duplex support, etc., was similiar. Much as DMX was only envisioned replacing the 0-10V snake from front of house, MIDI was envisioned connecting two keyboards together. A bit error, the wrong note plays, no big deal...

Two technical advantages that MIDI does have for these sorts of applications are:

1. It is opto isolated by specification.
2. It uses a dramatically lower baud rate (31250).

However, most complex theme park installs that I am aware of use proprietary protocols for master show control. Show control implies smart clients (ex. lighting board reading MSC and producing DMX). MIDI's electrical specification makes even rudimentary remote device management and monitoring (like the RDM specification) impossible in a multi device rig.

-jjf


----------



## PadawanGeek (May 16, 2007)

You could also use something like an ETC Unison.


----------



## Kelite (May 17, 2007)

<Current conditions of my employment forbid me to speak in specific terms. >
I've got to remember that one!


----------



## TimMiller (May 19, 2007)

i'd personally try to stay away from running chain hoists over AMX. Esp on wireless. Maxx technology did an install over at second baptist and they love to use AMX. They have AMX running 4 chain motors that lift up a big piece of truss with screens in them. Well one sunday the wireless remote lost signal with the reciever and the motors kept on moving and they smart people at maxx tech did not set up any limit switches. They had to run up and kill the power to the motors. The truss was about 1/2" before it was going to go through the roof.


Now on another note of using AMX
How about using some projectors that has lens shift. So you just lens shift them to every position. Lens shift can easily be carried out using an AMX system.

Also as far as using DMX for lasers.
There are quite a few high output lasers on the market that use DMX. Last one I used was a 30 watt. There were interlocks around and mirrors carefully place so no matter what happened the laser beam would not shine into the audience.


----------



## jfitzpat (May 21, 2007)

TimMiller said:


> people at maxx tech did not set up any limit switches...
> 
> There were interlocks around and mirrors carefully place so no matter what happened the laser beam would not shine into the audience...



I think this sums up nicely what I was trying to say before. Safety generally involves a multi-part system with some redundancy. A communication protocol is just one part and, in of itself, may or may not matter.

-jjf


----------



## Old School 512 (Jun 29, 2017)

Footer said:


> AHHHHHHHHHHHHHHH... NO THEY DO NOT EXIST NOR SHALL THEY EVER EXIST. DMX is the worst motion controller ever. There is no redundancy or checksum, therefore there is no feedback or real control. DMX works great for lights, not good for show control. What you can do is get a motor controller that takes DMX cues and through a dead man switch the motors will move, i.e. if the switch is not pressed they will not move. Thats the safest way to do it. Think about it, do you really want to be pageing through cues and have the US truss move?


 
I most definitely agree! Back in the late 80s umm early 90s ahh whatever. When you actually had to know electronics and how to mod them fast. I built a black box to control 2 CM 1 ton winches in my shop and tested them in the warehouse in a controlled 10ft rig. Oh the disaster it was almost funny but in real life it would kill people. There was no protocol for the winches except relays on the death box. Even having both motors hardware patched to the same channel was a failure. 1 Though they look and are rated at the same speed that is not always the case after running them up and down a few times they would start to tilt the test truss. 2 no safety at all at that time locking out a channel on a console could be done but overwritten causing umm death. Please take it from a couple of techs that tried this IT Does Not Work don't bother trying you can end up killing people. I changed my design back then to not touch the winches but as was stated before. It operated a red and green light that a human using a lift controller operated. I did expand it but those were the solder and duct tape days. Today buy or rent a real motor controller with mechanical safety covers over the actuator switches. I am sure many here could lead an interested party to a proper system. My last install was with JR Clancy equipment a bit pricey but I cannot put a value on the fans under practically tons of aluminum and live power. Oh my DMX to motor controller it sits on a shelf to remind me and teach others the importance of lift control.


----------



## Pie4Weebl (Jun 29, 2017)

It took me way too long to realize I was reading a 10 year old thread.


----------



## Old School 512 (Jul 4, 2017)

Pie4Weebl said:


> It took me way too long to realize I was reading a 10 year old thread.


I have done that before. I think we all have, todays technology has to have a prebuilt answer for you check Applied ( http://www.appliednn.com/index.php ). They may have an appropriate answer for you.


----------

