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First, I should clarify: I am not looking for much power or much precision. I am looking for the cheapest thing I can plug into an arduino. I am just looking for stuff I can use for prototyping/proof-of-concepts.

I was taking apart an old CD drive when I noticed there was a linear actuator being used for controlling the head. It seemed perfect for my purposes. When I came across this article I realized that this thing was actually quite precise.

This raised a lot of questions, but the most important one to me is:

Do I have to buy a CD player every time I need a linear actuator?

Where do I get those particular linear actuators found inside a CD player? I assume they are cheaper than the CD player itself.

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    \$\begingroup\$ What country are you in? Here and in many countries old CD playersrolling tyhem, then take some wire, magnets are thrown out in their thousands daily.Many are still functional. BUT for experimenting you can "easily" build your own linear actuator. Look at how they work, look at web articles on controlling them then use some wire and some magnets and a few bits of junk and make one. The main cost is time. Surplus CDs are probably easier/chea[per/better. HDDs also have them inside. Very powerful sheet magnet as well. \$\endgroup\$
    – Russell McMahon ♦
    Jan 24, 2012 at 0:27
  • \$\begingroup\$ Motor + threaded rod + threaded nut = linear actuator! Not a very good one, but it is cheap... \$\endgroup\$
    – Faken
    Jan 24, 2012 at 0:55
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    \$\begingroup\$ @Feynman Mods out here have a prejudice against sourcing (or "shopping" as the call 'em) questions. Ergo negative votes. more on that here: meta.electronics.stackexchange.com/questions/933/… \$\endgroup\$
    – Nick Alexeev
    Jan 24, 2012 at 2:48
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    \$\begingroup\$ Again - what country are you in? Location makes a lot of difference. They are thrown out at zero cost in many countries - and probably in yours too. \$\endgroup\$
    – Russell McMahon ♦
    Jan 24, 2012 at 2:58
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    \$\begingroup\$ I am in the US. And thank you for telling me about the shopping question. I noticed other shopping questions rated decently with good replies, so I would not have figured that out myself. \$\endgroup\$
    – Alex Eftimiades
    Jan 24, 2012 at 14:19

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I don't know what is in your CD player, but it sounds like you are asking in general how to create linear mechanical motion that is electrically controlled.

The most obvious answer is a solenoid. Look around and you will see many different types. These are basically a magnetic plunger moved by the magnetism of a coil.

There are also devices known as voice coils, which are the same concept as a solenoid except that the coil is intended to move. They are called voice coils because this is the mechanism used to make loud speaker cones move.

There are also such things as linear motors. These are like rotary motors with the magnetic poles sortof unwrapped in a line.

Of course rotary motion, such as produced by a electric motor, can be turned into linear motion mechanically. A rack and pinion arrangement is one way. There can also be lever-arm driven mechanisms, which are in turn driven by geared down motors.

Getting accuracy is a separate issue. A basic solenoid is generally intended to be on or off. Voice coils can position quite accurately as a function of current when working against a known mechanical spring force. If a stepper motor is used, then the rotary motion is known open loop, and this can be turned into known linear movement. Otherwise, you will need some kind of mechanical position sensing and closed loop feedback to control the actuator. There are again many types of that, but that's getting too far afield of your question.

Added:

Whoever downvoted this answer, please explain what you think is wrong. Phantom downvotes don't benefit anyone since nobody knows what you object to. It also doesn't give anyone a chance to decide whether you might be wrong.

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  • \$\begingroup\$ Thanks for the response. I suppose linear motors are probably my best bet. I just talked with a college who has been working with hobby electronics much longer than I about the CD player actuator. He seems to think (to my surprise) that the market for such an actuator just is not high enough for any to be sold individually. I suppose I am going to have to stick to getting them from CD players. \$\endgroup\$
    – Alex Eftimiades
    Jan 24, 2012 at 15:29
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If you need the high precision of the screw drive found in CD players, you'll need to duplicate that mechanism with a leadscrew. Look for a NEMA14 or NEMA17 bipolar stepper motor (depending on how much torque you need), attach a shaft coupler to it, and add an ACME-threaded leadscrew. Threaded rod isn't really suited for this purpose, but leadscrews are. Leadscrews have dozens of types of nuts available for all kinds of applications. The Allegro 4988 breakout boards will make driving the motor very easy.

This is a common setup on 3D printers, that use a pair of NEMA17 steppers to push a movable gantry upwards a couple hundred microns at a time. 5-to-8mm flexible aluminum couplers are available for a dollar each at everyone's favorite auction site, and 8mm leadscrews are available from several online retailers. The A4988 is the chip used to drive the NEMA17s, and they are actually driven by an Arduino on the RepRaps.

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  • \$\begingroup\$ bugger this question is old \$\endgroup\$
    – Bryan Boettcher
    Jul 17, 2012 at 22:44
  • \$\begingroup\$ Note that acme screws, while often more precise still have backlash. Only rolling contact ballscrews (the nut is a sort of helical ballrace, with an external channel to route the balls that roll out one end back into the other) are truly zero backlash when preload force is applied between paired nuts, however low friction polymer nuts can come close. Also, the cheapest grade of acme rod, and indeed the cheapest ballscrews, are for force applications, not precision positioning, though hobbyists may try. Cheap components are made by rolling the threads, better ones by precision grinding. \$\endgroup\$
    – Chris Stratton
    Aug 20, 2013 at 4:13
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I came across this recently which is great if you're willing to spend some time and DIY: http://www.youtube.com/watch?v=sI8tvjdhYxw

Basically he takes a glue stick, attaches a regular servo to the bottom of it and replaces the internal pot with a linear one attached to the gluestick

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    \$\begingroup\$ Can you bring a bit more information over, this is still mostly just a link, it would be nice to have a bit more. \$\endgroup\$
    – Kortuk
    Jul 17, 2012 at 22:40

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