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I have a hobby project where I would like to use micro stepper motors as shown in the picture below. However, as you might be able to see, the spacing between the pins is incredibly tiny and each pin is much narrower than the 24 AWG wire I was planning on using. In addition, each pin seems to have a single strand of copper wire attached to it presumably attached to the stepper windings.

So my question to us all ... what technique might one use to attach wires to these pins? Assume poor/average soldering skills and "normal" mans hands with normal steadyness (and by that I mean (what I hope are) the normal amount of shakes).

enter image description here

Here is a photo I took myself which shows the scale against a rule.

enter image description here

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    \$\begingroup\$ Inhale, solder, exhale. \$\endgroup\$ Jul 1 '15 at 1:27
  • \$\begingroup\$ What @Stihl said but also wire can be positioned with crocodile clip or clamp or stuff so it sits against pn. Pretin both and maybe liquid flux. Use finest tip available. Heat with tip against touching wire pair is >> heat to non touching pins. \$\endgroup\$
    – Russell McMahon
    Jul 1 '15 at 3:10
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    \$\begingroup\$ @IgnacioVazquez-Abrams If it's anything like shooting a rifle, it should be exhale-solder-inhale. Your heartbeat moves your body more when your lungs are full of air. :) \$\endgroup\$ Jul 1 '15 at 3:49
  • \$\begingroup\$ This would probably work with a flex-PCB which would be very thin and would also serve as the cable. This may well be what the motor designer(s) had in mind. \$\endgroup\$
    – Tut
    Jan 14 '16 at 14:22
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I would probably use a small amount of tacky flux and pre-tin both the wire and the pins.

If you can secure the motor in a clamp with pins facing horizontally, that would be ideal for me (an average solderer).

I would feed the wire with my non dominant hand while resting my palm on the bench top and soldering with my dominant hand.

Hope that makes sense. Pre-tinning will make it relatively easy.

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The pins on each motor seem to be all in a single plane; perhaps you could make a custom circuit board that fits those pins and functions as a breakout board.

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  • \$\begingroup\$ Unfortunately the pins are not in a plane. They alternate in two planes with a tiny distance between each. \$\endgroup\$
    – Kolban
    Jul 1 '15 at 5:18
  • \$\begingroup\$ I'm not saying they're in a line; it's clear pins 1 and 3 are offset from 2 and 4. But, if they all come out of a single plane (which from your picture it looks like they do) then they all could fit into a circuit board. OTOH, it looks like the internal wires are wrapped and soldered onto the pins, so it might be tough getting the pins to fit into the board holes. \$\endgroup\$ Jul 1 '15 at 10:04
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Some guesswork: What is the length of those pins? you wrote about alterating pin pattern (two rows), so maybe they are designed to be soldered dircetly to a PCB? They seem short, so not full through-hole, but rather push-me-somewhat-into-hole style. With tiny PCB you could presolder the points on PCB then press the PCB to motor (or use soldering paste), then heat the PCB from the other side. Hm.. or a plastic connector with four slots.. but my, they are short. No, I'd bet on tiny PCB.

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  • \$\begingroup\$ Thanks very much for the thinking. I added a photo showing the scales to the question. \$\endgroup\$
    – Kolban
    Jul 1 '15 at 14:21
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If the motor and pins are fixed in horizontal plane with a clamp (as suggested by Stihl Alighve), it should not be that hard to hang the wires around the pin and then solder (make a J in the wire end). Support the soldering hand to reduce shaking.

Preferable wrap them a couple of rounds. Cut the excess wire.

Use finest tip possible and a fine soldering wire. Add a tiny drop of soldering wire to the tip and apply to wire pin (some flux might help).

Hard to see exact size, but I guess the motors are about 6 mm i diameter, and the terminal less than 0.3 mm. AWG 34 (0.19 mm) or AWG 36 (0.15 mm) wire is probably needed.

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  • \$\begingroup\$ I have added a photo ... I believe you are correct and that I will have to obtain some tiny wire. \$\endgroup\$
    – Kolban
    Jul 1 '15 at 14:22

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