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I have removed a stepper motor from a DVD drive which looks like the following: http://forums.parallax.com/attachment.php?attachmentid=102789&d=1373845076

As seen, there are 4 pins in a rectangular arrangement and the problem is that I currently do not have access to a multimeter therefore, cannot check for continuity within the coils to determine which pairs related to which coil.

Within the shown arrangement, is there a "rule of thumb" or an educated guess for determining which pair of pins relate to each coil? I know that in a linear setup where 4 pins are all one beneath another, the "rule of thumb" is that the top two pins are for one coil and the bottom two for the other, is there a similar rule for these???

Also, would I damage anything if I accidentally connected this up wrong? I mean if I connected the coil backwards or mismatched wires between the two coils?

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4 pins would most likely be a bipolar stepper motor. Two pins per coil (often two coils in series, but seen as one coil), two coils (or coil pairs):

enter image description here

Grab a small battery (AA) and see which pairs make the stepper twitch. Those are your two coil pairs.

How do you know if you have the coils connected the "right" way? Well, what is the "right" way? With a bipolar stepper you drive the coils in both directions at different times, so it's just a question of which way you drive them when. If you don't drive them in the right way in the right sequence then the motor won't "step", it'll just shake.

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  • \$\begingroup\$ Don't leave the battery connected. The internal resistance is probably rather on the low side. If you can, use a resistor in line, somewhere around 100Ω. \$\endgroup\$ – Simon Richter Aug 5 '18 at 21:46
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I have found myself without multi-meter many times, most recently my meters are still in our camper, which is in storage, and I haven' the time to go for it, so what I did was simple. I needed to check connectivity so I took a small 2AAA cell battery holder I had laying around from some project or another, the holder was complete with a small switch. I grabbed a piece of circuit board and soldered a yellow LED to the end of it, then took the black wire and soldered it to the - side of the LED, then I soldered a couple of male pins to the board, and connected the red wire to one side, the other side I connected to a 220 ohm resistor, then to the + side of the yellow LED. This leaves an open between the two pins, now I simply plug in a pair of DuPont type leads female to male onto the pins, and use the male side as probes to test for conductivity. If the LED lights, you have connectivity, if not then it is an open circuit. I keep this laying on my desk for quick checks. It is not as safe on solid state components but for finding wingdingsenter image description here on a motor it is just what you need, also for tracing ground faults and such.

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  • \$\begingroup\$ I think this would be better as a comment, as you haven't tried to answer the actual question at all. You could have summarized the idea in a comment, and the photo doesn't really add any helpful information. \$\endgroup\$ – Elliot Alderson Aug 5 '18 at 23:22

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