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Anybody have experience with small solenoids?

  1. Mar 17, 2005 #1
    Hey Guys,
    I'm new here, this is my first post. I am a member of other message boards, but they are primarily for fun. I think this board may acutally help me out with some of the work "opportunities" I run into now and again.

    First, I should tell you that I'm a ME, not an EE, so although this may sound simple to you, it's a stretch for me. I'm working on a project that requires a very small solenoid. By "very" small I mean that the max diameter is about .125". The length is not as important, so I'd say it could be 1" long. It will be powered by DC batteries. We're still trying to determine how much power will be available to actuate the solenoid. The plunger only needs to move .1" or so.

    So, now my questions:
    - Does anybody have experience with small solenoids?
    - Are there any suppliers that make them this small?
    - Are there any suppliers who can custom make them this small? (and have experience doing so)
    - Can I design this myself and build it using simple magnet wire and a power supply?
    - What type of core/plunger material will generate most force?
    - Is it better to fill the entire coil void with plunger, or can there be an air gap/space between them?

    As you can see, I'm a total rookie with respect to this particular component. Any guidance or help you can lend me would be greatly appreciated.

    Thanks, in advance.
  2. jcsd
  3. Mar 19, 2005 #2
    does it need any special outer case ? or can you just leave it with the wire exposed?
    Looking at a solenoid i took apart recently i see that the plunger part seems to be made of steel, with an aluminum rod comming out of one end and a nylon rod comming out the other..
    i would make it myself if i were you.. because it seems to be a special part that you need..and the smallest one that i have seen before is about .375 '' dia.
    your plunger would need to be about .060'' ..
    what kind of force is required by your solenoid ??
    does it need to actuate something , like a microswitch?
    or does it need to be normally off??
  4. Mar 21, 2005 #3
    The solenoid will be housed inside a Titanium housing, so it doesn't need any additional housing. It would need to be normally off, and I'd prefer pulsed power to energize.
    The solenoid will be moving a small pin as a "release" mechanism. The force required to move the pin has yet to be determined, but will be very small.

    I'm leaning toward building this solenoid myself within the housing that exists. By doing so, I can make it .23" diameter and have the coil around some other things on the inside (not effected by field created). I'm hoping this will give me more room for the solenoid, and more room for wire density.

  5. Mar 21, 2005 #4
    how fast does it have to respond ,when energized?
    pulsed power is the way to go , because you could pulse it with a lot higher voltage ,than the coil could withstand for a sustained amount of time..
  6. Mar 21, 2005 #5
    response time.

    I would think that it should respond or complete it's movement (approx. .10") within 15 seconds. Any longer and the user will become impatient.

    I, too, like the pulsed application of power. I don't want this device to get too warm since it's inside the human body...
  7. Mar 21, 2005 #6
    thats very different , i was thinking it was something else..
    i suppose that if you create a decaying exponential pulse you could keep from shocking your patients with the Ldi/dt from the coil when you turn it off..
  8. Mar 21, 2005 #7
    Please explain "shocking the patient with Ldi/dt"?

    I have some experience with generating muscle motion from low freq. AC and DC current due to inadequate filtering of the output on an Electro-Cautery unit, but how does an inductive coil shock the patient?
  9. Mar 21, 2005 #8
    all i meant was if you abruptly interrupt the current flow through an inductor ,you could create a large voltage ..V=Ldi/dt..
    but if you use a decaying exponential as your pulse there should be no problem..and since you have plenty of time (15 seconds is a lifetime..)
    so your pulse would rise up to your 'ON ' voltage then decay at a slower rate..
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