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

Discussions

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...

Murf

12 years ago

Thanks for you help everyone :P

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.