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Large Solenoid Actuator driven Display

Hello, I am new to this site so I hope you won’t mind if I ask a few questions that I am sure are going to sound quite amateurish to most of you. 

I am an American living in Berlin working on a collaboration between two art research institutes here.  I have been given the task of putting together a proposal for a dynamic moving display. That will be featured next year as part of a conference on kinesthesia. 

My back ground is not in computing or robotics, I am simply putting together a list of materials (and their cost) that would be necessary to make this project work.  And I am responsible for finding collaborators that can help put it together. 

I found this website when I was researching solenoids.  If you have any experience with solenoids I would greatly appreciate any advice or knowledge that you would care to pass on.

So let me try to explain what we would like to do and what I think I might have figured out so far – please be patient and bear with me.

The dynamic display I spoke of can be thought of as a much larger version of this pin-art-clock

http://gadgets.boingboing.net/2008/11/25/1980sstyle-pin-clock.html 

However the display would not be used for numbers but instead for larger art-related images.  Instead of metal pins the display would use much larger plastic knobs (for lack of a better word).  The idea was to use individual actuators to individually lift up each of these knobs so that you could create a series of unique images , symbols, impression, etc.  I hope this makes sense the way I am describing it.  In theory it should be able to handle quick successive displays resulting in a seamless image concept.  To get a better idea of what I mean take a look at the following youtube vid. 

 http://www.youtube.com/watch?v=KRCeKkcTjWw&feature=related

Each knob would have to be able to be raised and lowered independently of the others and in quick succession because the images would in effect be streaming across the display.  The display would be quite large (2 to 3 meters in length and width) with several hundred knobs and corresponding actuators in order to achieve higher resolution.   The knobs would be constructed out of light weight plastic.

I located these companies for solenoids:

http://www.dormeyersolenoids.com/solenoids.html

http://www.ledex.com/

http://www.solenoids.com.tw/about.htm

I thought a small, electric - AC, linear, pull-type solenoid should suit the purpose.  The only problem is that the shaft extension length on most of them is quite short.  I was thinking that for best resolution it would be good to have a difference between the raised and lowered knobs/pixels of at least 2 to 4 cm.  However, most of the solenoids that are capable of achieving that are far too powerful (and thus expensive) for our needs.  I realize that it would be possible to devise a lever of sorts to amplify the small movement but that would result in more moving parts and thus a greater chance of breakdown and higher maintenance.  I also looked at the possibility that I saw recommended of a camshaft with suspension spring but I think this would be too bulky to place side by side and would not possess sufficient speed.

And  I thought that this microcontroller, or something like it, that I found on this forum might be what  would be needed to independently control the solenoid actuators.

http://www.societyofrobots.com/axon/

So what I would like to know is what kind of solenoid would you recommend for something like this (does not require large force, does require large shaft movement of 2 to 4cm)?  How do I determine how long it can remain on (in a contracted position) and how long it has to rest (heat dissipate) before it can be activated again.  Is is possible to get an electric solenoid that is able to be activated in quick succession (1 to several times per second) for several hours without damage?  What would be the best means of control several hundred solenoid actuators independently?  Would the microcontroller I posted above work, and if so would I need several of them to control a large number of solenoids or is one scalable – if I do need several is there a way to link them to create a seamless image? What should I take into account when deciding on an operation voltage?  Finally what would you expect to pay for the type of solenoid that I described above?  Also any suggestions on the best way to hook up a power supply would be appreciated.

I will definitely have more questions, but I thought this would be a good place to start.   I hope you will be able to help – and patient enough to make it to the end of this long posting J

Cheers,

Ryan

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Each ball would have a corresponding needle valve -

" There would be no way to direct and control the air pressure from a single tank." <-- um, you can - that was the point.

Picture is worth a lot of typing ... so here

 ballsculpture.jpg

microcontroller, wires, needle valves, hoses, a single tank and a single compressor  would be the list of parts.

The limitation would be on the microcontrollers ability to provide enough PWM signals - it could be multiplexed but you begin losing individual control (resolution) of the ball movement.  But that would be an issue depending on what images you want to make

I realized that my previous picture of needle valves are not electric - here is a more appropriate picture

 

PSV_Valve.jpg

I have only seen the bernoulli effect in action with something like a reverse vacum cleaner that was supplying a large and constant flux of air.  I assume that the design above would allow for a quick flux of air and then the ball would settle back quickly on the nozzle.  

 

I just thought of this too.  If you had a horizontal piece you would need a much larger range of movements in order to create an "image" because in effect you would not be creating an image or silhouette but instead an outline (much as they created an outline of a BMW in the Kinetic piece.  

Actually I did consider that, and still am.  The only draw back I thought would be that it would at to the amount of moving parts and thus lead a larger chance of eventual failure.  If this screen was in regular use you would expect the bearings of the fulcrum to wear out rather quickly (at least compared to the life of the solenoids).  I also thought it would dramatically increase the cost and complexity to put a lever of sorts on top of ever solenoid.  Maintenance would also be tricky.   But it is definitely a possibility and might in the end result in a lower cost then a more expensive solenoid with a longer shaft.  

Oh, and I just thought of this.  the less expensive solenoid type is the pull version.  The pull version is also good because it would minimize the chances of onlookers being "poked" with an ejecting solenoid.  A simple lever would in effect reverse this pull action.  

 Interesting possibility though. 

In order to get a larger "throw" from a small solenoid, have it actuate the end of a lever. If you have a solenoid that moves 1 cm when powered, have it press the end of a 6 cm lever, say 2 cm away from a fulcrum, turning point. The other end of the lever, 4 cm away, will move 2 cm. It will be half as strong, but perhaps the "knobs" are light weight.

Rinse and repeat for tightly fitting many solenoid actuated levers together.

I'm wondering if it might be easier to use electrically controlled pneumatics? If you had lots of small electically controlled valves, and each one would allow air to blow into a "pixel". Each pixel would be a light weight ball contained in a glass or plastic tube that allows some air to pass. So if air is flowing, the pixel ball floats up. if not, the ball drops.

Then you wire your microcontrollers to the valves, and you can make the pixels go up and down at your command.

No matter what approach you take, you are going to need to address a lot of outputs. How many pixels are we talking about here?

Nice idea, but the problem is that it should be wall mounted. If you use balls you require gravity to pull them back down which would limit the configuration to a horizontal mount. 

Around 100 to 200 "pixels"  This is where price (and to some degree weight) begins to play a role.  If possible more would be added to enhance the resoltion capactiy of the piece but right now I am using this as a starting point.   

Tricky. I was thinking of a horizontal display.

You could still probably do it, if you have valves that either directed air out to the "pixel" or sucked air in. Availability, cost and size of the valves would be your limitation, but it would work in theory.

Good luck with this project. Please be sure to post a link when it gets started and even better when it gets finished!

Thanks for your interest ignoble.  If this project gets the go-ahead I will definitely post the results.  Right now I am still trying to put together a price proposal and then that has to be submitted to the committee along with collaboration partners and estimated time of construction.  I am optimistic but I will take a while.

 

Thanks for you suggestions.   

Talking about the first picture you posted: You wouldn't have to use a solenoid/actuator for every pin you see. You could use instead one per segment and divide each digit into 7 segments (just like the digits you see on alarm clock), thus connecting all those pins that belong to the same segment to just one actuator, that, i believe, could make things much easier.