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Changing polarity Answered

Hi everyone, the problem I have is probably wither really simple or really complex.. .but either way here goes: I have scavenged an old CD-ROM drive for parts, namely, the motor and gears which move the CD-ROM door in and out (depending on the direction the current/voltage is flowing). I want to setup a system where upon flicking a switch (either SPST, SPDT, etc, whatever is needed) in one direction, the tray ejects, and when flipped the other way, the tray loads. In essence, I want the current/voltage running in opposite directions depending on the position of the switch (Up, one direction; down the other direction, and center, off). If necessary some indicator LED's and additional switches could be used... but I don;t really know where to go from here.. .any help would be GREATLY appreciated. Peter

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westfw

12 years ago

Just for completeness:
The simplest polarity reversal capability comes from a DPDT switch, as described by several people and documented in This Instructable
The easiest electronically-controlled version would be a DPDT relay wired the same way.
The "solid state" reversible motor driver is usually called an "H-bridge", and tends to use about 6 transistors or a moderately expensive IC (this means more than $1 and usually less than$10 except for very fancy or high power drivers.)
The typical CD drive has a single-chip wonder-device that usually includes the three-phase spindle-motor driver, plus less complex H-bridge drivers for the tray, the head, and the magnetic "fine positioning" that the head does. Usually by the time a drive hits the junk bins, these chips are "obsolete" and no longer sold or documented by their original manufacturers, but you can look here for a representative sample of the sorts of things that are done.

If you've got multiple power supplies or battery packs, you can make simpler motor reversal schemes...

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Murf

12 years ago

Thanks for you help everyone :P

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NachoMahma

12 years ago

. All you need is a DPDT sw with center off. Wire your + and - supply to the the two center lugs. Wire one of the pairs of other lugs to the other in an X pattern. Run either side of the X to the motor.

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Weissensteinburg

12 years ago

There's an instructable on doing this, ill go look.

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lemonie

12 years ago

The drive would have had a button(?), do you need the switch for a specific purpose?

L