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I am building a solenoid based equipment. The problem with off the shelf solenoids I figure out is they become hot very quickly. & may burn soon too or at least are not optimal for a constant long term vibration solution. I have this question in mind that audio speaker also use a solenoid like mechanism but that don't suffer from same problem. Why ?

As I am also thinking to build one of my own solenoid for my requirements. So if someone please answer me in this context How to build a solenoid that don't tear off too quickly if at all. If one is available off the shelf, it will be more then welcome.

enterprize
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  • Perhaps you can stop/limit the current when the solenoid is fully activated. – Ignacio Vazquez-Abrams Jul 15 '13 at 10:30
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    Why does it get hot? - Possibly because *"A solenoid is sub-optimal for generating ongoing vibration"* as stated in an [accepted answer](http://electronics.stackexchange.com/a/75497/2191) to your prior question. – RedGrittyBrick Jul 15 '13 at 10:34
  • what if a speaker like solenoid mechanism is built as there is no such phenomenon associated with that type of solution. – enterprize Jul 15 '13 at 10:37
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    How much mass is a speaker pushing around and what is it fighting against? The mass it moves is very small and it's moving against air and it's not moving a great distance. How does this tie in with what your expectations for this project? – Andy aka Jul 15 '13 at 10:40
  • you mean if speaker has to push hard, it will also get hot? this kind of question was in my mind but if we look at the time a speaker can work constantly, is a factor to think on this way. & there is no plunger in a speaker solenoid rather coil itself is vibrating. What if we replicate that mechanism for a proper solenoid?I mean the coil vibrates an attached cone like metal plate like cone of speaker. Bec that kind of a solution can work for my project too as I need to push things. – enterprize Jul 15 '13 at 10:53
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    What speaker? What solenoid? What load? Your question lacks sufficient detail to have a meaningful answer. – Phil Frost Jul 15 '13 at 11:59
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    Try touching the voice coil of a cheap 500 to 1000 watt (*those ratings are typically Peak Music Power Output, actual sustained power is way way lower*) subwoofer running full blast. After you get back from the hospital due to eardrum rupture, you might still be nursing the burn marks on your fingertips, if the coil resistance is high enough. The premise that a speaker's voice coil does not get hot while a solenoid coil does, is meaningless without specifying how much power each is driving, and the respective coil DC resistances. Why not use the voice coil of one of those subwoofers instead? – Anindo Ghosh Jul 15 '13 at 12:44

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What you are asking makes little sense. Solenoids and voice coils are quite different things designed for different applications. Voice coils are bi-directional, try to have constant force over the range of travel for a particular current, but that force is usually weaker for a similar size.

Either of these can be made for a particular force, travel distance, maximum input power they can handle, etc. If your solenoid is getting hot, then you are putting too much power into it. See its datasheet. You can likewise make a speaker get too hot or to destroy itself some other way when you apply excessive current.

Again, you are comparing apples and oranges. A gasoline car chugging up a hill will get hot, but tomato on the counter remains cool.

Olin Lathrop
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  • If one were to replace the slug of a solenoid with a permanent magnet, how would that affect its behavior? Energized solenoids grip most strongly when the plunger is in its "energized" position, but if the purpose of a solenoid is to strike something, it would be most helpful to have the strongest force when the object is in its "rest" position. Would a using a permanent-magnet slug achieve that? – supercat Jul 15 '13 at 16:33
  • The power was an issue. I asked this question in general sense too as I have been reading about life time issue of solenoid if they are operated constantly. I have this thing in my mind that a loud speaker also uses solenoid mechanism & speakers lost like an infinite time. Thanks to all people who replied gave me more in depth about that thing too. – enterprize Jul 16 '13 at 12:34
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Food for thought: -

  • What distance does the "solenoid" need to move? Let's say 5mm
  • What force is it acting against? Let's say 10 newtons
  • Does the "return" journey need energy inputted to return it? Let's say same as forward journey
  • How many times a second do you need to repeat the "task"? Let's say 100 times per second

Work = force x distance so to move forward, the work is 0.005m x 10N = 50mJ

It needs to do this twice (forward and return journey) so this becomes 100mJ

It needs to do this 100 times per second therefore power = 10W

If you do your own calculations instead of mine and get a power requirement you're going to be in a better position to decide what you need. Don't forget to take into account the mass of the solenoid plunger - convert this to a force. Also don't forget any other mechanisms that might make the force harder.

If my numbers were correct (and there is no reason they should be because I'm guessing) and you wanted to use the equivalent of a loudspeaker, you'd need to understand how power efficient they are. From my experience a loudspeaker power efficiency of 5% isn't too far off the mark.

This means you'd need a speaker greater than 200W capacity. You'd probably want a power supply of about 300W to cover the unexpected scenarios and things might be getting a little warm.

Andy aka
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  • I don't need 100 time a second vibration. I need vibration pattern to be recognized by the subject i.e. she may count the vibrations in a pattern & recognize time gap gap between two patterns. So may be 2-3 times a second max. For 300 watt probably its like a 10 volt power source of 30 A will do the job. 5-10 mm distance, 10 newton seems ok. – enterprize Jul 15 '13 at 14:50
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    @enterprize only you know the real requirements - my numbers were just guesses. You need to do the calculations and the measurements to be sure. – Andy aka Jul 15 '13 at 14:55