Wierd application, hypothetical question.

[justin ivan]

Eric,
Everything that you stated about solenoids is indeed accurate, now I don't 
know that much about voice coil actuators at all BUT you are 100% correct a 
stepper motor really is the way to go in this case. Do we have an idea of 
response time required? Solenoid's have a very rapid response time (on the 
order of 15 microseconds or less in most cases). Stepper motor is probably a 
bit slower then this but should fit this app OK
Stepper motor is definately they way to go with this application, there are 
already plenty of circuits designed to control these suckers you just need 
to do a search. One of the things to look is CNC retrofits for milling 
machines.
Justin

>From: Eric Bryant <BRYANTE at ghsp.com>
>Reply-To: diy_efi at diy-efi.org
>To: "'diy_efi at diy-efi.org'" <diy_efi at diy-efi.org>
>Subject: RE: Wierd application, hypothetical question.
>Date: Wed, 6 Dec 2000 13:08:38 -0500
>
> > From: justin ivan [mailto:vlkslvr at hotmail.com]
> > Subject: RE: Wierd application, hypothetical question.
> >
> >
> > I assume that maybe by voice coil actuators you mean as in
> > speakers? Either
> > way, .5 to 1" of stroke for an electormechanical solenoid
> > really is asking
> > for too much if you need any considerable force. I could dig
> > out some of the
> > charts relating to stroke vs force that I have hiding but I
> > don't see it
> > happening.
> > if it were .25 to .33 or so, you might be able to get away with it.
>
>That's the beauty of a voice-coil actuator - you get a nearly-flat force 
>vs.
>displacement curve, while a solenoid will yield some sort of exponential
>roll-off as the armature travels from the pole piece (the shape of the 
>curve
>depending on a lot of factors, of course).
>
>With a solenoid, it's often necessary to use some mechanical advantage in
>order to keep the armature in the higher-force portion of the travel.  You
>start getting non-linearities with increasing mechanical complexity (due to
>lash and so on), so this turns into a difficult motion-control problem.
>
>A voice coil may be a bit easier than a solenoid to work with, but 
>something
>like a stepper motor will give a far-greater power density, and I think 
>it'd
>be more appropriate for this application.  At least that's where I'd
>start...
>
>Eric Bryant
>mailto:bryante at ghsp.com
>http://www.novagate.com/~bryante
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