Monday, February 14, 2011

Extending the motor wires

I made a mistake prepping the motor wires with the 3mm bullet connectors.  Unlike a plane (which I am used to), the motors on a quad sit quite a ways away from the ESCs.  So, when I went to wire everything up, there was a several inch gap between the connections.

So, I stripped the shrinkwrap and unsoldered the bullet connectors, and extended the wires.  There were a dozen of the things to do, so I did one first to check for fit, and then did the remainder in a batch, assembly-line style.  I made them a tiny bit longer than they needed, so that we would have some wiggle-room (literally) for the ESCs.  Next time, I'll try making it an exact fit.

I didn't try reusing the bullet connectors... they were kinda messy on the outside after soldering.  I wonder if there's any way to clean solder of lots of pieces at once?  I was also surprised at how heavy a dozen connectors full of lead solder weigh.  I tried using the minimum possible solder on the new connectors.  It made it a bit more tidy as well.  It seems just as strong... I wasn't able to pull it off by tugging at it.

I took photos... partly because I thought it might be useful for someone not super-experienced with solder, but mostly because I thought they would look pretty cool.

Cut all the wires to the desired length, strip and tin the bullet side.  You don't need much solder, since these are being placed in the connector cup. Just make sure the wires are saturated.  One of the previous posts has some details about using the board to hold the connectors.  Strip the insulation so that the exposed wire is just as long as the internal connector cup.

 Nicely attached to the connectors.  I was careful not to get any solder on the outside, which allows 3.5mm shrinkwrap to fit right over the connector.
3.5mm Shrinkwrap on the bullet connectors, ready for the heat gun
Nice looking shrink wrap job, huh?
 Now strip and twist the ends that will be connected to the motor leads.  It will be stripped a bit longer than the connector side, since this will be a wire-to-wire connection.
 Tin the wires.  Notice that we add a bit more of a solder blob (but still not too much; we don't want a big ball of solder in the middle of our wire).  We do the same thing to the motor leads as well.  When the wires are joined, the two solder blobs will be what flows between the wires.  Dont forget to add the shrink wrap before you solder, or you will have to unsolder and do it all again.  On the other hand, maybe that's good practice!
 Here's a set of wires soldered together...
 ... and shrinkwrapped.  Get a heat gun, it really does make a nicer looking connection than using a lighter or any other ghetto method.
 There are tons of techniques for soldering wires together, you can find some really great tutorials on youtube.  I like using an alligator clip to hold the two wires together.  When you heat the wires up, the solder melts, and the jaws of the alligator clip mash the two wires together nicely.

If the solder sticks to the alligator clip, touch the soldering iron to the outside of the clip and it will come right off.  Don't tug, or the two wires will come apart.
 Here's the finished set of motor wire extensions.  Doing them assembly-line style speeds things up a lot and reduces errors.  I wasn't looking forward to doing this, but it wasn't bad at all.  Maybe I'm just getting a bit more used to soldering as well.
Here's the finished result, held in place with blue tape.  Note the extra bit of slack... next time, I'll mount the ESC in its permanent position and try to do it so there's no slack at all.  And by "no slack", I mean "just enough slack so there's no strain on the connections".

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