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CNC INFORMATION
Scroll below for G540 motor cables.


HOW TO CONNECT DRIVER CABLES TO STEPPER MOTORS:

For 5 Amps and below, use 22 gauge wire. For 7 Amps and below, use 20 gauge wire. It doesn't HAVE to be shielded, but shielded four conductor twisted-pair wire doesn't hurt either.

First, I'm going to assume that you are connecting motors in Bipolar Parallel wiring. That is usually the best method.

There will always only be four wires in your cable (and maybe a fifth drain wire for ground) no matter HOW many wires come out of the motor. On four wire motors, it's easy--Just connect wire to wire, matching up colors as you can.

But on eight wire motors wires must be paired up. Now you don't want to just cut your cable ends same-length and start splicing wires together. This would make a large ugly bump at the connection point, and would also leave too many connections pressed together where they could eventually short out.

What you WANT to do is STAGGER the connections. To do this, you must cut the motor cables at staggered lengths--Say 4 inches, 6 inches 8 inches and 10 inches. (On an 8 wire motor there will be pairs of wires cut to these lengths) Then cut your cable ends the same way. Now You can slide on some heat-shrink tubing for each wire, splice the wires, solder the connection, let it cool, slide heat shrink over joint and heat with heat gun or hair dryer to shrink it tight.

Now when I say splice, I don't mean just twisting wires together. You want to make a "Western Union" splice:

http://www.mmxpress.com/technical/connections.htm

The example below uses a four-wire motor. Had it been an eight-wire motor, each wire on the right would be doubled. Anyhow, the whole process should look something like this:

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Only don't use black tape as I did here--Use the superior heat shrink tubing instead. (available at Lowes electrical aisle)

Use a larger heat shrink tubing to cover all of the splices up to the motor, and you've got a nice cable.



MAKING G540 MOTOR CABLES

First you may want to build a simple wiring jig. I built mine out of wood scrap, so it's not pretty but works well.
You will need three pieces of wood and some drywall screws, a couple of female DB9 connectors and 4 small screws:

First cut a short length of 2x4. Mine was a scrap 4 3/4 inches long:
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Next, using a 3/4 inch spade drill, make a couple of 1/2 inch deep holes. The centers for mine are set back 3/4 inch from front edge and are 2 1/4 inch apart.
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Now you will want a long strip of wood. I used a 38 inch long scrap of 1 x 4, but 2x4 is probably fine.

Cut a one inch long slot, 1/4 inch wide, in the top and then screw a thin strip of wood next to it. I used a split scrap of 1 x 2 firring strip. This is a clamp for the cable wire, to hold it up while you are soldering the connections,
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Buy a couple of female DB9 connectors from Radio Shack, and fasten them into the 3/4 inch holes using short 1/2 inch screws from Lowes. Notice that they are facing different directions--One has the wide side to the back and one has it to the front. This is so you can solder the front row of connections on one side, flip it around and then plug into the other mount to solder the back row.
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It is very easy to melt the entire connector. Having it mounted into a female connector helps to cool it, but you should only use
a 15 watt soldering iron. Notice I have marked the wire socket numbers on the top and the wiring colors on the front.

Drill two 1/8 inch holes and screw the short 2x4 to the strip. Mine is fastened 9 inches from the top.
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Insert and tighten one screw and then square it up. Now insert and tighten the other screw.

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Here is the finished product:

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I just clamp mine to the side of a bench. You might want to make a base for it.

Next: Doing the actual soldering:

SOLDERING IRON:

Only use a 15 Watt, pencil-tip iron. Radio Shack has a decent one for only $9:
$8.99

15-Watt Soldering Iron with Grounded Tip - RadioShack.com
15-Watt Soldering Iron with Grounded Tip
Model: 64-2051  |  Catalog #: 64-2051

15-Watt Soldering Iron with Grounded Tip is an ideal choice for integrated circuit work.
SOLDER:

Use only the skinny electrical solder with rosin core flux--here from Radio Shack:
$2.19

Standard Rosin-Core Solder (0.5 Oz.) - RadioShack.com
Standard Rosin-Core Solder (0.5 Oz.)
Model: 64-017  |  Catalog #: 64-017

This Rosin-Core Solder has the standard 60/40 formula for electronics work. Diameter is .032”....


FORCEPS:

These are like scissor-handled tweezers that lock onto what you want to hold--like a thin wire. They probably have
them at Radio Shack.

http://www.allheart.com/forceps.html

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It's also a good idea to buy about 4 extra male DB9 connectors while you are at the Shack--Just in case. If you don't need them, they are easily returnable.

 If you are already an expert solderer, then skip ahead.

SOLDERING 101:

The first thing you have to do is "tin" the soldering iron. This means you heat it up, melt some solder onto the tip, wipe it around with a folded up paper towel, (be careful, soldering irons get very hot) and then unplug it. Even when soldering, you will want to wipe the tip every few minutes. If you don't, then the tip will get black and won't transfer heat very well.

Tinning the tip is the ONLY time that you will put the solder directly onto the tip. The usual method is: Put the hot soldering tip onto what you will be soldering, Then when that is hot enough, touch the solder to the heated part--NOT the iron itself. Solder is not like caulking or glue. You can't just flow it over the wire or whatever and expect it to hold. Solder must BOND with the part, and that means both must be at the same temperature. Failure to bond means a Cold Solder Joint. CSJs neither hold  nor conduct electricity well.

So the idea is to heat the part hot--but not hot enough to melt the insulation around it, and then let the part melt the solder. A little preparation will make this happen easily.

1) Strip the wires about 1/4 inch from each end and  tin them. (Heat the wire and melt a little solder into it before trying to attach it to anything.)

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2) Cut the bare tinned wire to about 1/8 inch long.

3). Fill each cup of the DB9 connector with solder. (On the wide-side, you only need fill cups 1,5 and for shielded cable, cup #3.) Heat a cup, melt in the solder, move on to the next one--NO WIRES YET! Do NOT let the hot tip touch anything else--the plastic insulation will melt instantly. Do not over-fill the cup. Do not create solder bridges between cups.. If you heat the cup too much it will BREAK RIGHT OFF--thus ruining the connector.
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4) If you are using shielded cable and intend to solder the bare drain wire into pin 3, Slide a length of heat shrink tubing onto the wire until only 1/4 inch is exposed. You DON'T want a bare ground wire flopping around in those tight quarters.
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5) Drape the cable down over the locking notch and lock it with just enough room to comfortably reach all of the connector cups.

6) Wipe and re-tin the hot soldering iron tip between soldering cups.

Notice that the G540 has a little schematic beside each connector. This tells you exactly what goes where. Pins number 3, 4 & 5 are grounds. Pins 1 & 5 are for the current limit resistor to connect between. Pins number 6 & 7 are one phase of the motor and 8 & 9 are the other phase. Remember there are always only four colored wires in the cable, no matter HOW many wires come from the motor. Figure out in advance which wires are which and mark the color that corresponds to each pin onto the wiring jig or a post-it note.

Let's start with the resistor. It doesn't matter which end is which, it can go either way. Push a DB9 connector onto the right-side-jig female socket. Cut the resistor wires about 3/4 inch long on each side and bend them so they span between the two outside cups. (1 to 5)

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Lightly hold the lead about 3/8 inch back. with the forceps. Hold the tip of the resistor lead onto the number one cup and touch the hot soldering iron to the cup. When you see the solder in the cup melt, push the wire down until it is all the way in and remove the heat. Hold the lead still for about 5 seconds while the joint congeals and unclasp the forceps. Now hold the OTHER resistor end with the forceps and repeat--only on cup number 5.


There, you've soldered two cups already.

Now for the wires. You should have cut the wires so that the drain wire is about 1/2 inch longer than the others. Bend that drain wire up out of the way and save it 'til last.

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You will have cut the wires so that they fit into the plastic shell like so:
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The length of cable at bottom is for the strain-relief clamp that is applied later.


Don't forget to trim the tinned ends of insulated wires back to 1/8 inch long.

Remove the DB9 connector from the right side of jig. Turn it around and connect it to left-side of jig. The 4 cups facing you are (from left to right) numbers 9, 8, 7 and 6.

Each pair, 9-8 and 7-6 is a coil, and from left to right they are A+, A-, B+, B- respectively. Choose your motor wires accordingly and translate them to cable wire colors for attachment to DB9 connectors.

Cut some heat-shrink tubing, of a size large enough to easily fit over the cups, into 1/2 inch lengths for each of the four motor wires. As you solder each wire, first slide one of the heat-shrinks way up onto the wire. Keep this away from soldering heat.

Just as with the resistor, hold each wire on the cup with the forceps, heat the cup with soldering iron tip, and push the wire down in when the solder melts. Remove heat and continue to hold wire still for 5 seconds. Do this with each wire. If you have a drain wire, move the connector to other side of jig, push back the drain wire heat shrink tube and solder that wire to pin #3.

Check all connections. They should be shiny and smooth. If any of the connections is dull and rough, that is a "cold joint" and must be reheated and remelted. Check for loose wires, solder bridges between cups, tiny stray wire strands that might later short between cups.

After everything is inspected and cooled, slide the heat-shrink tubes down around each cup. The HS tubes should completely surround each cup, and extend all the way down:

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Using a heat-gun or hair dryer, heat the tubes until they shrink down tightly around each cup and around
the drain wire:

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Since all of the other wires and cups are now insulated by heat shrink tubing, we needn't worry about
resistor wires, just bend them to fit into shell.

Now we're ready to install shells.

First install strain-relief onto cable and tighten screws:

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Next install back shell. Adjust resistor to fit:
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Now is the time to install the long hold-down screws. Notice there is a little metal reinforcement that goes
under each screw. If you want to moisture-seal this connector, you could immerse the cable top in silicone seal.
Now put the shells together and fasten with screws/nuts:

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And there's one completed cable.
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