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There are countless projects online that start with "harvest the stepper motor out of an old CDROM drive." Many of these projects look super fun, but I don't have a pile of old CDROM drives around gathering dust.

What are the stats on these ubiquitous CDROM steppers, so I can find an equivalent one to order? Or if anyone already has a favorite model they use for these projects, I'd love to hear it.

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  • \$\begingroup\$ They're tiny worm drive motors, used for positioning the read head. No actual stats on one though. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Apr 12, 2015 at 18:40

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Here's an example of a typical sled motor http://robocup.idi.ntnu.no/wiki/images/c/c6/PL15S020.pdf Note that it only does 20 steps per revolution. The small size and low cost of a CDROM motor mean that you can't expect high resolution from the motor. That is provided by the lead screw.

Also, not all such motors do 20 steps/rev. 24 is also a common spec. You'll just have to test your motor to see what it does, but that should be pretty much the ballpark number.

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  • \$\begingroup\$ By "That is provided by the lead screw" I assume you mean that the attached worm gear reduces the angular displacement of each turn, so that the head can be accurately positioned? Not a criticism, I know nothing of this, just checking. \$\endgroup\$
    – Dan
    Commented Apr 12, 2015 at 21:06
  • \$\begingroup\$ It's not a worm gear. It's a lead screw. The spiral thread meshes with linear movement, not a rotary one. The profile is a perfectly straight cylinder. A worm gear has a concave circular profile, which allows the secondary gear to rotate. In this case, a needle pin engages the single thread and pushes the optical head (the sled) radially in and out - in a straight line. \$\endgroup\$
    – WhatRoughBeast
    Commented Apr 12, 2015 at 22:05
  • \$\begingroup\$ Edit to previous comment. "Radial" refers to movement with respect to the CD, not the lead screw. \$\endgroup\$
    – WhatRoughBeast
    Commented Apr 13, 2015 at 0:33

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