Automated Movement of Props/Scenery (Stepper Motors?)

Hello! Hope you're all doing well and healthy.

I'm working on a one-man show that takes place inside of a dreamworld. We want objects and scenery to be able to move on and off stage autonomously. This can range from a hospital-bed-on-wheels, to flats, to flower-patches, to 6" tall miniature houses. Unfortunately, we don't have the budget to hire a large backstage crew to run all these rigging cues using ropes or pulleys, so we're thinking about how to automate. We will have one person backstage.

My first thought was to rig up a bunch of Stepper Motors to DMX, but I've never worked with them. I do have some experience with Arduino, but I'm wondering if any ready-made solutions exist. Would I place objects on wheels or slippery mats to make them able to glide in? Do you just connect the objects to the motors using fishing wire? Is a DC motor better?

The objects would move in 'flat' aka parallel to the lip of the stage. We're also ready to adapt the materials to be as light-weight as possible since nothing has been officially sourced or built yet.

Any advice would be super helpful.

Thanks!
J
 
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If you can't afford manpower its going to be a tough push to be able to get a reliable automation system.

The first step would be figuring out how many axes of movement do you need. To keep costs down being able to reuse an axes is ideal. Like one track midstage to handle 3 scenes and another track upstage of it to handle another 3 scenes. Now you can make 6 looks with two axes.

Most of the time a deck track is made up of a loop of steel wire rope with a 'dog' in the middle of it. The dog never passes the onstage pulley, offstage the cable winds on and off of a winch at the same time. This video has some clips to watch. You'll need to solve these problems if the effect is humanation or automation.
 
If you can't afford manpower its going to be a tough push to be able to get a reliable automation system.

The first step would be figuring out how many axes of movement do you need. To keep costs down being able to reuse an axes is ideal. Like one track midstage to handle 3 scenes and another track upstage of it to handle another 3 scenes. Now you can make 6 looks with two axis.

Most of the time a deck track is made up of a loop of steel wire rope with a 'dog' in the middle of it. The dog never passes the onstage pulley, offstage the cable winds on and off of a winch at the same time. This video has some clips to watch. You'll need to solve these problems if the effect is humanation or automation.
@JerSegal99 If you ever saw any of the full-bore productions of "The Rock Musical Tommy" they had 6 full width tracks within the dedicated deck (Two DS. Two MS + Two US) for a grand total of 24 axis of AC servo drives + 3 90 volt, non-positional DC motors; 1 for the main traveller and two for the propellers which flew in for the bomber scene.

The shop I was with built all of the scenery and automation for 'Tommy' Offenbach (a suburb of Frankfurt am Meine, Germany) in 1995 then repeated it all again for London, England's Shaftesbury Theatre in 1996. We built all nine pin ball machines three times; initially for the second US National Tour, which also played several stops in Canada.

One of each pair of stage tracks housed a tiny Emerson AC servo within the its 'dog' to permit some pieces to enter with their narrowest dimension fitting between the masking legs then rotate to a better angle once within view.

One of each pair of tracks was spec'd to have 12 x 2.4 Kw dimmed circuits within its 'dog' while its mate was only spec'd to include 6 x 2.4 Kw dimmed circuits. We designed, built, and had approved, totally custom connectors; we supplied 12 circuits within all six tracks, once we designed, fabricated, and received approval for the larger connector, it was easier to build 3 more identical than to go through the approvals process a second time.

Once we'd passed Germany's TUV's rigorous inspections, the Brit's accepted our connectors with barely a look.

If your deck tracks span ~45' feet of visible travel, plus ~12 to 15' off stage into the wings on either side for presetting and striking your various pieces of automated scenery, you're talking pretty butch V-grooved drums to neatly / reliably / repeatedly grip and store that much ~5/16" aircraft cable. Include the costs of aircraft quality muling and idler sheaves and you need pretty deep pockets.
Toodleoo!
Ron Hebbard
 
Hopefully you realize this, but DMX512 should never be used to control things that are safety-critical. If any of this scenery could be expected to cause injury if it moved unexpectedly at any time, you should definitely not use DMX512 to control it. Some of your set pieces may indeed be light and soft enough that they pose no threat to safety; but others, such as the flats, could be rather dangerous if they struck or pinched you.

Stepper motors are one possible drive technology, but far from the only reasonable one. Stepper motors have strengths and weaknesses. The main strengths are pretty precise and repeatable control of positioning (provided they aren't overloaded and skip steps) and good low-speed and holding torque. The weaknesses include noise--at least with some stepper drivers, limited speed, and the need for comparatively complicated driving circuitry. These are probably not exhaustive lists. It is well to bear in mind that steppers in themselves, while capable of pretty precise positioning, have no feedback for that positioning and so will happily move things around in the wrong positions all day.

Receiving and interpreting DMX512 with a micrcontroller is straightforward as DMX512 is a very simple serial protocol. You'd need an RS422 (or RS485) receiver chip for the physical interface. DMX512 is asynchronous serial data at 250 kbps, with a break condition marking the start of a packet, then the first byte indicating the type of packet (zero for dimmer data, which is what you'd be using), and then the remaining bytes the data of the packet--in the case of dimmer data, one byte giving the level for each DMX512 channel in succession. Packets with an unrecognized start code should simply be ignored. There are no checksums, no acknowledgements, and generally nothing to verify data integrity. The entire specification is available for download for free.

Controlling stepper motors (via stepper drivers) is also pretty straightforward. While precise details can vary a little bit, generally the drivers have as their main inputs a direction input and a step signal. Pulsing the step signal causes the motor to advance by some (often configurable) amount, either a full step or a fraction of a step. There are often additional inputs (such as an enable/power on) and outputs (such as various fault indications).

Since you have a tech person doing stuff, I think controlling the various things via some sort of a dedicated control panel with switches wired directly to the devices would be much preferable to doing it over DMX512 via a light controller. It might be appropriate to do something simple like using a plain motor and limit switches rather than fiddling with steppers. Hydraulic, pneumatic, or even just spring or weight driven systems might also be appropriate.
 
Hopefully you realize this, but DMX512 should never be used to control things that are safety-critical. If any of this scenery could be expected to cause injury if it moved unexpectedly at any time, you should definitely not use DMX512 to control it. Some of your set pieces may indeed be light and soft enough that they pose no threat to safety; but others, such as the flats, could be rather dangerous if they struck or pinched you.

Stepper motors are one possible drive technology, but far from the only reasonable one. Stepper motors have strengths and weaknesses. The main strengths are pretty precise and repeatable control of positioning (provided they aren't overloaded and skip steps) and good low-speed and holding torque. The weaknesses include noise--at least with some stepper drivers, limited speed, and the need for comparatively complicated driving circuitry. These are probably not exhaustive lists. It is well to bear in mind that steppers in themselves, while capable of pretty precise positioning, have no feedback for that positioning and so will happily move things around in the wrong positions all day.

Receiving and interpreting DMX512 with a micrcontroller is straightforward as DMX512 is a very simple serial protocol. You'd need an RS422 (or RS485) receiver chip for the physical interface. DMX512 is asynchronous serial data at 250 kbps, with a break condition marking the start of a packet, then the first byte indicating the type of packet (zero for dimmer data, which is what you'd be using), and then the remaining bytes the data of the packet--in the case of dimmer data, one byte giving the level for each DMX512 channel in succession. Packets with an unrecognized start code should simply be ignored. There are no checksums, no acknowledgements, and generally nothing to verify data integrity. The entire specification is available for download for free.

Controlling stepper motors (via stepper drivers) is also pretty straightforward. While precise details can vary a little bit, generally the drivers have as their main inputs a direction input and a step signal. Pulsing the step signal causes the motor to advance by some (often configurable) amount, either a full step or a fraction of a step. There are often additional inputs (such as an enable/power on) and outputs (such as various fault indications).

Since you have a tech person doing stuff, I think controlling the various things via some sort of a dedicated control panel with switches wired directly to the devices would be much preferable to doing it over DMX512 via a light controller. It might be appropriate to do something simple like using a plain motor and limit switches rather than fiddling with steppers. Hydraulic, pneumatic, or even just spring or weight driven systems might also be appropriate.
Mechanical brakes are a MUST; spring applied, powered to release.
Why (I can hear you asking).
E-stopping / powering down a drive motor is one thing when it's moving things laterally.
Brakes become ABSOLUTELY necessary if / when drives are lifting and lowering scenery overhead.
Unpowered motors without automatically applied mechanical brakes all too often unwind proving gravity's not only an interesting theory; it's an irrefutable LAW.
When we built 'Tommy' for Germany, TUV insisted our E-Stop HAD to remove ALL power IMMEDIATELY.
We proved to them it was more dangerous / hazardous / potentially injurious to simply cut the power: It was MUCH better; faster, safer, to command the drives to deccelerate as quickly as safe, then power down / set the spring actuated brakes before totally removing ALL power.
Once we'd demonstrated this to TUV, they agreed but insisted E-Stops could only use mechanical / non-electronic delays.
This proved to be no problem: Sprecher Shuh (Sp?) the European manufacturer of our contactors, had two models of pneumatic delays in their catalogue; one pneumatic delay delayed a contactor's closing, the other delayed a contactor's opening.
Standard catalogue items, already TUV approved: Done deal.

EDIT: @JerSegal99 In both the Tommy' productions I was involved with, the 6 deck winches were driven by Emerson 4120 AC servo motors and their associated drive electronics as were the elevator which came up from the basement and formed a weight bearing part of the show deck when down / out of sight.

The full width lift-bridge with its ~20 heavy, vacuum tube CRT, video monitors was powered by another Emerson 4120; the other 16 AC servo drives were all manufactured by Emerson Electric, ~12 Emerson 455's and 4 much smaller / lower torque drives; three within the track's rotators and one more to rotate the miniature pin ball machine which flew overheard during one or two scenes.
Toodleoo!
Ron Hebbard
 
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Look into Creative Conners and their automation systems. You can either buy their system or rent it for just this show.
 
Yeah, just to reinforce what @RonHebbard said: one person running automation is not acceptable. Automation is not just a simple proposition of "move on, move off, stop here, stop there." What happens to the person onstage in the event the automation operator is suddenly incapacitated? Who pushes the E-stop?

You're asking a lot of questions @JerSegal99, which is good. But you've also played the "I have no money, I need to do this on the cheap, and I don't know how" and that is problematic from a safety standpoint and a money standpoint. Automation isn't really a thing you can get right via the internet, and the trial and error you're going to have to go through without someone knowledgeable on the ground with you to design it, install it, wring it out, etc...is going to be as expensive, if not more so, than finding someone well versed in this sort of thing. Proceed with caution and care of your safety and budget.
 
Hello! Hope you're all doing well and healthy.

I'm working on a one-man show that takes place inside of a dreamworld. We want objects and scenery to be able to move on and off stage autonomously. This can range from a hospital-bed-on-wheels, to flats, to flower-patches, to 6" tall miniature houses. Unfortunately, we don't have the budget to hire a large backstage crew to run all these rigging cues using ropes or pulleys, so we're thinking about how to automate. We will have one person backstage.

My first thought was to rig up a bunch of Stepper Motors to DMX, but I've never worked with them. I do have some experience with Arduino, but I'm wondering if any ready-made solutions exist. Would I place objects on wheels or slippery mats to make them able to glide in? Do you just connect the objects to the motors using fishing wire? Is a DC motor better?

The objects would move in 'flat' aka parallel to the lip of the stage. We're also ready to adapt the materials to be as light-weight as possible since nothing has been officially sourced or built yet.

Any advice would be super helpful.

Thanks!
J
@JerSegal99 Similarly to needing to have spring actuated (electrically released) brakes and having them applied prior to powering down your drives, you also need be certain your drives are powered, stabilized, and prepared to support their loads BEFORE you release your spring applied brakes.
Toodleoo!
Ron Hebbard
 
Curious as to why all this kind of tech isn't designed using worm gear boxes? Worm gears essentially are a one way system.. you can drive the shaft but the shaft can't drive you.
Would take a lot of the complexity out of braking systems etc..
 
Curious as to why all this kind of tech isn't designed using worm gear boxes? Worm gears essentially are a one way system.. you can drive the shaft but the shaft can't drive you.
Would take a lot of the complexity out of braking systems etc..
@jtweigandt When /if the goal is to unwind 40' in ~3 seconds, including smoothly accelerating and deccelerating (Flying in 5 decent sized windows for example) that's a lot of rotations of your worm gear.
Yo yo drums are popular and, to a degree, automatically provide acceleation and decceleration.
Toodleoo!
Ron Hebbard
 
Steel low profile wagons with push sticks have been my experience when you want a show to seem automated but using inexpensive and reusable materials. Usually end up with 2 per side that are 10-15' long and your designer makes all the pretty sets fit nicely on the wagon and your backstage crew swaps out what the set on the wagon between scenes.

In beauty and the beast we had the initial houses for the village scene built as forced perspecive on the wagons, then they flopped off and were replaced with trees, belle's house facade and all kind of stuff.
 
Thanks for all your responses everyone! Really appreciated. I think it's become clear that I'll need to hire someone to manage this system for the production. Definitely have the health and safety of the team as the priority, so no worries there. Was hoping there might be a simple and cheap (and safe) solution that existed that I wasn't aware of.
 
Thanks for all your responses everyone! Really appreciated. I think it's become clear that I'll need to hire someone to manage this system for the production. Definitely have the health and safety of the team as the priority, so no worries there. Was hoping there might be a simple and cheap (and safe) solution that existed that I wasn't aware of.

It only hurts if you don't ask.

There is a whole bunch of effort, thought, considerations of various types - behind stuff that looks easy and is relatively 'safe' under the circumstances, but in theater it's usually carefully choreographed chaos.

In a previous decade I worked as a deck electrician for a month of Wicked!-ness. When I wasn't actively running my cues, my time was spent avoiding being trampled by the cast (running off stage for quick changes) or being hit by scenic automation moves. There was a point in Act 2 where I counted 6 measures on a song intro to move to where the wardrobe dressers were leaving because a large, heavy thing was about to occupy the space I'd been standing in. I had to work that out with the Automation Carpenter and the tour's SL asst carp, or the thing couldn't move and the SM would be ever so cross with all of us...

Think about this: most of what makes elevators (Lifts, for our UK/EU friends) complex are the interlocking safety mechanisms - moving the car up and down is relatively simple. Making that safe for the general public, like not closing the doors on a passenger, or moving the car without both inner and outer doors fully closed, is where things start getting complicated. Moving scenery isn't especially complicated, but moving it safely brings an order of magnitude more thought into the picture.
 
I like that idea of push/pull with a long, low profile stick. That's solved a bunch of these sorts of problems around here before.
 
Thanks for all your responses everyone! Really appreciated. I think it's become clear that I'll need to hire someone to manage this system for the production. Definitely have the health and safety of the team as the priority, so no worries there. Was hoping there might be a simple and cheap (and safe) solution that existed that I wasn't aware of.
Motors, cheap, and safe are three words that do not go together. I think you would be much better off using a human powered approach. I bet with a little digging you'll be able to find some volunteers who would be happy to crew your show for fun and gas money. There are lots of people out there who do tech work at community theaters for nothing or a very small stipend just as a fun hobby. Go find them.
 

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