Yea, I guess your right. Since 1/2 the coil is outside the gap the only non linearity is the suspension.

 

strantor: Ah, thanks! Ugh, I emailed H2W Technologies (seems to be the biggest company for voice coil actuators) and found out they're all hundreds of dollars :'( Such a shame, because that would have worked!

ronv: I would be feeding it an amplified music signal, so it's more like AC. Oh seriously?? All hobby servos? Jeez, I need to learn the NE555 more haha. Thanks!

MaxHeadRoom: I'm a bit confused as to what these are and how to use them. I'm guessing these are "analog servo drives"? Also, the models spec sheet shows they need to be powered by 20+VDC and have power ratings measured in KW. Even if this fits all of my needs, it seems this is something much too heavy duty & expensive for what I'm doing. I'm just working with low power devices on breadboards haha. Anyway, I still don't know what these things even do, and overview information on the internet seems scarce.. thanks for the suggestion though!

shortbus: No, you're right! Mine is no bigger than an inch. And that is what I also thought to do, but I think the movement of a speaker cone is just soo small that it still wouldn't work. For example, I have $40 desktop speakers, and when I put my finger on the dust cap of one of the satellite speakers while it's blaring music, I can feel that it still has no more displacement than my phone does when it's vibrating, which is not nearly enough. I'll need at least 2mm of displacement. While I do believe that my subwoofer outputs enough displacement, I wouldn't feel very happy about either cannibalizing my $40 speaker system, or putting such a gigantic speaker driver on my desk amidst the breadboards. Please tell me if you know perhaps of some cheap, midrange speaker that outputs enough displacement, that I could buy and take apart for its voice coil actuator!

 

Hmm, well you fooled me with the few cycles per second comment in your first post. Maybe you meant a few thousand?
Anyway, you might have a go with the actuator out of an old disk drive and some springs to center it. It should do a few hundred cycles/second.

PS.
The speaker needs to keep the cone to center the coil.

 

I'm "working" on diy voice coil linear actuators for my project. If you can wait several months I might have something for you.

 

I worked on something like that over in the engineeriing lab several years ago. it wasnt a solenoid, but a motor with a high ratio planetary gear drivng a screw. it was set up so you fed it pulses, and it moved a specific amount with accurate enough pulses. it was used to move optical bench componants. unfortunatly, that was quite a few years ago, and I dont remember the brand name.

 

ronv: Oh that's my bad. The thing is, I'm going to feed it a music signal but will be content if the actuator has low accuracy and can only keep up at a few cycles per second (and miss out on the vast majority of the other cycles). I can see how I was confusing - sorry. Oooh, okay, yeah, the HDD actuator so far seems to be the best option that fits my needs, unless I learn to use servos with the 555. Because of your last last post, I've looked at how to use the 555 with servos, and it seems surprisingly doable. Basically, it seems you've given me the two best recommendations - thank you!! Since I left all my dead HDDs at home 200 miles away (I'm in college), I think it's time for me to learn the 555...

strantor: Haha I'll be waiting! Please make them cheaper. It seems to me the only high-displacement ones on the market are high enough quality to produce good music and thus very very expensive - I'm shocked that there aren't any non-music, cheap application coil actuators!! I imagine I'll be still be interested in any cheap coil actuators for months, so let me know if you don't forget this chat and there is one, haha.

alfacliff: It seems you are describing a servo, haha. I know what you are talking about - thanks for the mention, I'll look into it

 

Here's the thread where we were discussing voice coil actuator designs for my prosthetic hand. Once my wife gives birth (sometime between now and 3 weeks) and after she recovers and I get my tinker time and money back, I'll be reopening that thread and maybe it will be of use to you.

http://forum.allaboutcircuits.com/showthread.php?t=93489

 

Also, the hdd arm actuator is a voice coil. I think its called a rotary voice coil or something like that. Trivia, I learned in the course of reading.

 

When reading to find this stuff I saw something that called out from my younger days. The movement from an analog gauge. Older cars, pre-computer era, used a moving coil type gauge for everything but the speedometer, one of those movements would be very adaptable to the laser mirror.

OK, for Konduction and Strantor, some ideas -



http://www.consult-g2.com/course/chapter11/chapter.html

http://www.rcgroups.com/forums/showthread.php?t=164711#post1446348

http://rack1.ul.cs.cmu.edu/rotaryvoicecoil/

Lots of ideas and math for designing them - http://rack1.ul.cs.cmu.edu/rotaryvo...auR_bYbIdZVWnQh-JWCJzWA&bvm=bv.61535280,d.aWc

http://www.instructables.com/id/Electromagnetic-Actuator/

http://optics.ph.unimelb.edu.au/atomopt/shutter/shutter.html

 

that actuator I was taloking about had only two wires. so not exactly a servo, no feedback. just moved a very small amount with each pulse. it would have much more force available than a voice coil areangement, unless the voice coil was big with a very large magnet.

 

Strantor: Ah, okay cool, thanks! And an early congratulations - you must be excited!

shortbus: Ooh, thanks! I've actually seen a few of these already while trying to make a solenoid, haha.

alfacliff: Oh, my mistake. I'm guessing you don't remember what this device is called?