Large number of Motors

Hi all,
I am intending to begin an ambitious project and I urgelly need your help.
I will be working on a kinetic installation similar to the famous “Kinetic Rain” installation in the Singapore’s Changi Airport by ART+COM.
At the beginning, it will be smaller in order to master the different challenges within this project. (e.g: 10 x10 grid)

Now, Here are my concerns:
1- Which Arduino plateform to choose?
2- Which type of motors: servos or steppers.
3- How to drive such large number of motors?

Any additional comments are more than welcome.

Thank you for your help.

Cunning ploy that, posting the same thing three times under different thread titles.
Thought we wouldn't spot the cross-posting?
Wrong.

Duplicate posts deleted.

DO NOT CROSS-POST, CROSS-POSTING WASTES TIME.

Sorry,
There was no bad intention. I thought that my question was valid under the three sections, and I didn't want to loose any valuable recommandation or help.
Excuse me please.

Don't! You are basically asking the same people three times, and they will get annoyed.

If something genuinely falls under two very different categories you could add a pointer
thread from one subforum to the true thread, but your best tactic is usually to make the
subject line concise and clear.

  1. Doesn't really matter at this point. Start with an Uno.

  2. I don't remember this sculpture from my last visit to Singapore. Can you give a bit more detail on what you want to do?
    Servos are great if you need position control and you don't need to spin continuously in one direction. Most servos are limited to 90 degrees of rotation but a sail-winch servo can spin more than one complete turn. It is possible to modify a servo for continuous rotation but then you lose the position feedback.
    Steppers are better for continuous rotation but getting absolute position requires extra mechanical components. They are also much more demanding for motor controllers - you must have a proper stepper driver, where a servo only needs a good power supply and one Arduino pin.

  3. You should look for servo controllers which are controlled by I2C. That way you can put more motors on one Arduino, which has a limited number of pins. I don't know any part numbers off the top of my head.
    Depending on how much data you need to send, you may not be able to update your servo positions as fast as you like with one Arduino. You may end up with several small 'slave' Arduinos controlling blocks of motors which are controlled by a master Arduino. Depending on the data going to the slaves, you may need to pre-load them with the patterns and the master just sends synchronisation signals.

Thanks for your reply. I do appreciate.
Please find here a video about the installation: Kinetic Rain - World's largest kinetic art sculpture @ Changi Airport Terminal 1 - YouTube
Based on this video, what do you suggest to me?
Thanks.

The Kinetic Rain sculpture is explained here: Kinetic Rain - World's largest kinetic art sculpture @ Changi Airport Terminal 1 - YouTube

They use high resulution encoders and likely a BLDC per raindrop, perhaps a budget of $250 per drop.

I would suggest try playing with the cheap little steppers like the 28BYJ-48, which aren't fast and
aren't powerful, but are cheap.

Some idea of your budget would be helpful (maybe you can afford a BLDC, controller and high res encoder
per grid point?!)

Thanks for your reply.
My budget is about $2000 for the whole installation.
I am wondering if the stepper motors will give the same fluent movement?
Another question is about driving these motors. How do I do to control a large number of them.

cherchor:
Thanks for your reply.
My budget is about $2000 for the whole installation.
I am wondering if the stepper motors will give the same fluent movement?
Another question is about driving these motors. How do I do to control a large number of them.

and

At the beginning, it will be smaller in order to master the different challenges within this project. (e.g: 10 x10 grid)

So does that mean $20 per node, or is that only the prototype.

Steppers can be smooth if driven properly with microstepping, but you need one driver per motor.

Finding a cheap encoder to use with DC motor will probably be the cheapest route.

Your budget will really limit the possibilities - remember you need power supplies, microcontrollers,
motor drivers, motors, encoders and mechanical parts.

There may be other ways to approach the problem too, rather than one motor per node.

Perhaps you should purchase a couple of the below stepper motors and drivers and start some basic proof of concept testing.

http://www.ebay.com/itm/2015-DC-5V-Stepper-Motor-ULN2003-Driver-Test-Module-Board-28BYJ-48-for-Arduino-/151580914201?pt=LH_DefaultDomain_2&hash=item234aed3219

So the real problem is economics. Finding a motor and driver combination which is inexpensive will be the hard part. You will have to find a child's toy or something which can be purchased in bulk and already has all of the mechanical challenges solved.

If I was to build something on the scale of that airport one, my budget for plugs on the interconnect cables would be $2000.

Thank you guys,
As you suggested to me, I will be starting by doing a proof of concept featuring a couple of steppers (not servo, is it right?)
Besides that, Can you give further help about how to control a large number of motors? How do I tackle that issue?

There's a number of challenges to be solved on a project like this:

  1. How do you physically mount and electrically connect large numbers of motors?
  2. What driver chips are available for the power (volts and amps) required by the motors?
  3. What chips are appropriate to fan-out the control connections? SPI to parallel? Shift registers? Small Arduino chips on each motor or pair of motors?
  4. What is the central controller? Does it just send sync signals to the sub controllers playing pre-programmed sequences or does it send the actual moves? Hoe does it get the pattern design - SD card?
  5. How do you plan and create the overall design of the movement pattern - a visualizer program for your PC that lets you simulate what it will look like?

The basic issue is make a module that can control one motor and take its command from a
bus such as I2C, RS485 (DMX512 perhaps), ethernet, etc etc.

Then something has to drive the bus fast enough for all the motor modules to get updated
sufficiently frequently...