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  #1  
Old 07-28-2010, 09:34 PM
aceggert aceggert is offline
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Default Pulsing Circuit for DC Solenoid

I am an artist that is getting into kinetic sculpture, and my latest idea is to use solenoids to make strings of pennant flags bounce up and down (whereas, in the past, I've used motors to make them do other things). I was thinking of using a DC push/pull solenoid with a long stroke to make the end of the string move, and I've been told that I need to build a pulsing circuit if I want the solenoid to continuously move up/down.

First, I was wondering if there are any simple tutorials on the web to build such a circuit. I am hoping to have the bouncing get continuously faster and more frequent, until the flags are bouncing around like crazy, and then calm back down again until they come to a complete stop for a little while. Should I use a micro controller to control this or is there an easier/other way?

Second, is a DC solenoid even the right tool to use in this application? Or is there such a thing that moves up and down continuously without the need of a pulsing circuit?

Thanks for your help!
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Old 07-28-2010, 10:08 PM
tom66 tom66 is offline
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You can use a 555 timer to control the solenoid. In astable mode, you can configure the on/off cycles. Bonus is a small parts count and a simple design. Post if you need some help designing this circuit...
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Old 07-28-2010, 11:42 PM
mcgyvr mcgyvr is offline
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why not just use a motor to wind and unwind the string on a shaft or bobbin or something?
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Old 07-29-2010, 05:00 PM
sage.radachowsky sage.radachowsky is offline
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Alicia,

First, I want to say I think your work is awesome. I looked at your website and it's really inspiring to me. I've come from the other end of the spectrum -- from being an engineer to more and more desiring to use that for art purposes. For example, I want to make little firefly devices that blink and communicate with each other and eventually synchronize in groups, like real fireflies do... also, there's a small gallery in Boston that shows works like this very often... Axiom

On this topic, I think that a microcontroller is the way to go. For me, that is the simplest way, but of course it depends on how much experience you have with microcontrollers. It can be done in analog, with a double oscillator, where one oscillates very slowly, and varies a set point that results in the second oscillation speed changing, so it gets faster and slower through hours of time. You'll also need a circuit to determine the pulse width, as I'm guessing you want it to pulse, not stay on.

I really think a microcontroller is so much easier for this. It's also more versatile, if you come up with other ideas while you're working on it, like other timing patterns or sensor responsiveness.

A microcontroller can switch a logic-level MOSFET that then controls the solenoid. Be sure to use a snubber diode to protect against voltage spikes when the solenoid is turned off. They are coils and they have a kickback voltage that can damage the MOSFET if you don't use the protection diode.

Do you need to control the solenoid in both directions, in other words to reverse the polarity of the current? If yes, and if solenoid is a 2-wire device, then you can make an H-Bridge, or use an off-the-shelf one. If it's a three-wire device then it may be that you just need to control two MOSFETs to "push" or "pull" it.
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Old 07-29-2010, 10:06 PM
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Bernard Bernard is online now
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If you do not have solenoids yet, look at The Electronic Goldmine, # G 16036 for US$ .99, long throw spring return, 12 to 24 V, 3.3- 4.2 Ω. solenoid. Should be able to control rep. rate & amplitude. Now the questions:
How many strings, how long, horizontal or verticle, how heavy?
A thought: So that the solenoid does not have to support the tension of a string, stretch string with spring, twang at junction & right angle to string with solenoid. Rotary solenoids can also be used, with arm attached amount of throw can be selected by arm length. Sounds like fun & is do-able. I would be stuck with discrete parts but 555's are old friends.

Last edited by Bernard; 07-29-2010 at 10:13 PM. Reason: correct text
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Old 07-30-2010, 05:56 AM
aceggert aceggert is offline
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Thanks to everyone for posting helpful feedback! Especially to Sage for such kind words about my artwork. (Sidenote - If you ever want to collaborate on a project, please contact me. I love your firefly idea. Also, I just moved to Portland, Maine, so I'm sure I will be in Boston sooner or later and I will definitely check out Axiom. Thanks for the tip.)

To give a little more information about the project, I plan to string the pennant flags horizontally from freestanding poles that are about 10 feet apart (like the way you would hang a clothesline). I plan to make 3-4 vertical rows of the flags, creating a sort of "wall" of bouncing flags. I might actually make two "walls", creating a "corridor" that people could walk between. I had planned to attach the end of each length of flags to a solenoid, therefore attaching 3-4 solenoids to each pole.

That said, I will start doing research on all those recommendations given above, beginning with the solenoid from the Electronic Goldmine and the 555 timer. I am going to look for ways to work with an Ardunio micro controller on this, so if anyone has any more advice in that direction I will gladly take it. I have no experience with pulse width modulation, and I generally figure things out by following tutorials on youtube.

Your very sincerely grateful electronics novice,
Alicia
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Old 07-30-2010, 09:33 AM
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Hello,

Welcome to the forum.

You could take a look at the eBook, see the tabs on the top of the page.
Did you also look at the useful websites thread:
Useful websites for electronics (Ver. 2)

For 555 circuits you can take a look at Bill_Marsdens pages:
LEDs, 555s, Flashers, and Light Chasers

There are more 555 links over here:
http://www.educypedia.be/electronics/digitatimers.htm

When you want to take a look at the arduino, take a look at this site:
http://www.arduinotutorials.com/

Next to the arduino there are also the AVR,PICS and Basic stamps:
http://www.educypedia.be/electronics/avr.htm
http://www.educypedia.be/electronics/circuitsmic.htm
http://www.educypedia.be/electronics...basicstamp.htm


Bertus
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Last edited by bertus; 07-30-2010 at 09:42 AM.
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