View Full Version : Soldering DB9 connectors on the motor cables for the Gecko G540

Gerald D
Tue 07 October 2008, 13:12
And if you want a 5th drive for an indexer?

Further, the DB9 connectors for the motors do not appeal to me at all. My experience with DB connectors hasn't always been 100%, and then it has been with much lower currents. Would have to figure out what to do with the screen of the motor cable when it gets to that connector. Can a DB connector accept the thickish wire cores we use for our motors?

Tue 07 October 2008, 14:11
I am not saying the G540 is perfect for every applicaton, but just thought Mariss' post might help some in their decision. :) The screen termination is no problem when using metallic backshells. The fifth axis does seem to be a problem. DB9 style connectors can easily fit a 20AWG wire which might be ok for some applications (more expensive connectors with replaceable pins can go up to 18 AWG).

Gerald D
Fri 06 February 2009, 22:59
That DB9 connector also means that some soldering needs to be done. That is another potential can of worms, because it is not the easiest soldering for a beginner. It needs some practice and practicing on those connectors can get expensive. Maybe get some old/spare connectors to practice on first. The tip of the soldering iron should be shaped nearer to a blunt pencil, rather than a screwdriver.

Sat 07 February 2009, 04:04
Soldering DB-xx connectors can be a challenge. I use an adjustable heat soldering iron with a pencil point tip (just like Gerald described). The method that works for me has several steps:

(Always heat the connection, not the solder. When the connection is hot enough, the solder will melt and flow into the connection. Heating the solder, and not the connection, can cause a cold solder joint, which will eventually fail.)

1. Heat each cup and fill with solder.

2. Strip 1/4-inch of insulation from each conductor.

3. "Tin" each conductor. (Heat and apply solder).

4. Trim each conductor to 1/8-inch after tinning.

5. Re-heat each cup with the soldering iron and slide the tinned conductor into place.

Back when the personal computer industry was young, most of us had to learn to make our own serial cables using DB-25 connectors. When I complained about the difficulty of making cables, a good friend sat down with me and showed me the correct process. He used a 15W soldering iron with a pencil point tip, a container of liquid soldering flux and solid core solder, otherwise the steps were the same as I use. (If you can get some "flux", it will make any soldering job easier. DO NOT USE ACID FLUX DESIGNED FOR PLUMBING. USE ONLY FLUX DESIGNED FOR ELECTRONICS. I bought a gallon jug of water-based flux more than thirty years ago. At the rate that I'm using it, it will last for more than one-hundred years.)

If you buy a G540, you'll also have to buy or make the data cable. It has a DB-25 male connector on each end, so you won't be able to use a standard PC printer cable. I just made one from ribbon cable and some push/crimp DB-25 male connectors. I would never use a ribbon connector in the shop because they pick up electrical noise more easily than a standard cable, but for the test bench, a ribbon cable works well.

Sat 07 February 2009, 06:15
Also don't use Electrical solder when you are doing plumbing. I did that and had a really bad leak behind a wall.

Sat 07 February 2009, 09:32
BTW, there is a special for the 540 running at the cnczone, here are the details: http://www.cnczone.com/forums/showthread.php?p=560304#post560304

Sat 07 February 2009, 11:20
The G540 drives four PK296B2A-SG3.6 motors very well.

I've got the test bench configured with a 35VDC power supply, four PK296B2A-SG3.6 motors, the G540 and cables with 3.2K resistors. The 1K + 2.2K resistor combination is the closest match I had on hand to 3K. The G540's current limit resistors require 1K per amp of motor current. The PK296B2A-SG3.6 steppers are rated at 3A, but the PK296-F4.5 is rated at 4.5A. All other electrical specs for those two motors are identical, so I'm assuming that Oriental Motor has de-rated the PK296B2A-SGxx motors because of the gearbox. In any case, I thought that driving the steppers as close as I could to the G540's 3.5A current limit would be a good exercise.

For those who are wondering what the difference is between the PK296B2A-SGxx motor and the PK296A2A-SGxx motor, the PK296B2A-SGxx motor is the PK296A2A-SGxx motor with a dual-ended shaft.

After an hour of running all four motors at speeds ranging from 50 RPM to 1300 RPM (motor shaft speed, the gear box's output shaft is turning 3.6X slower), the motors are at 90F and the G540 is 100F. The G540 is just sitting on a wooden bench without heat-sinking of any kind.

Wiring time, compared to connecting the PMDX-122 and four G20x stepper drives is minimal. It took just over 1/2-hour to build four new cables this morning, including the time it took to install shrink-tubing on the cables and the time it took to install ferrules on each wire.

It looks to me like the G540 would be a good stepper driver for a MINIMAL system (assuming that the DB-9 connectors continue to carry the required Amps).

Edited: My G540 is one of the "custom" units that Pablo referred to. I has a non-standard nut on the DB-9 female connectors to suit a particular customer's special needs. If I use this G540 in production, I will have to use a non-standard length screw and some spacers between the DB-9 female and DB-9 male connectors.

Sun 01 March 2009, 23:46
Also don't use Electrical solder when you are doing plumbing. I did that and had a really bad leak behind a wall.

Depending on where you where in the world and when this was done, it is likely you introduced LEAD into this water supply. The fact that this leaked may have been the biggest favor physics could have done you.

************************************************** **

In the more general theme, I do a lot of connector soldering at work and would like to mention a couple of 'tricks' I use to get a professional finish. The easiest way to find the right pieces and sizes is to walk into a full service electronics shop (On the off chance you live in my neighborhood, I highly suggest these guys: http://www.metro-electronics.com/ ), tell them what you are doing (making a db-9 cable with a resistor bridging 2 of the pins) and then tell them you want to insulate each of the pin-wire connections with shrink tubing. Also, you'd like to add some strain relief the end of the cable(s) with the db-9 shell clamp. Lastly, admit that while it may be a little overly cautious, you want to seal each resistor with 'GC Electronics Insulating Coating'. You realize that once you've covered each wire with shrink tubing there will be no exposed wiring under the clamshell, but you never want to question the integrity of this project ever again once this phase is behind you.

In preparation to shopping at whatever store you choose, make a list of the things you will take with you and the stuff you want to leave with. Do bring one of your steppers with you; if you have more than one size of motor to wire, bring an example of each. This will come in handy for choosing the larger of your shrink tube sizes. Bring a printout of the G540 manual (http://www.geckodrive.com/upload/G540%20REV3%20MANUAL.pdf).

Bring a copy of this post: don't be afraid to show it to the employee.

Remember, they don't expect you to be an expert, but it will really brighten their day if you are not an idiot: you'd be surprised how often people expect counterfolk to provide salvation without preparation or information.

If you have chosen the right shop, an employee will grab an unsoldered male db-9 connector out of a box and walk around the store with you, describing each step in the process of creating the perfect connector. As you prepare to leave the store, you should have:

1 male db-9 for each axis (plus an extra... you'll probably screw one up by slopping solder around the cup... Newbie!),

1 shell assembly for each male db-9,

1 female db-9 (you'll thank me later),

2 sizes of shrink tubing (the smallest size should just fit over the solder cups, the other should just fit over your motor wiring...you DID bring a motor with you, right?),

1 straight through db-9 extension cable for each axis (your motor wiring is only a few inches long, right?) that allows for complete axis movement from the motor controller to the motor in question.

1 resistor (or parallel resistor network, if needed to obtain exact resistance value) for each axis.

If you need solder or an iron, you can get that here, too. If the shop is any good, they'll try to sell you a small can of Caig DeoxIT. I recommend you take it. If they have it and you do not, I also recommend a small pair of bent-nosed needle nose pliers.

Keep the receipt. You'll need to explain to your accountant (and your spouse) just where all the money went in this project. There is also a chance you'll not use one or more items.

Fine. The day for attaching your db-9 cable ends to the motor wiring has arrived. Grab the female db-9 connector (you are really going to wish you'd followed my advise and bought this) in your vise with the pins pointing away from you. Clamp the vise jaws lightly onto the plastic surrounding the solder cups. The full mating surface of this connector should now be available to slip a male connector into place with it's solder cups facing you. This little trick does 2 things for you. First, it allows you to apply more heat to each solder cup than strictly necessary (Newbie!) because even though the plastic holding your pins in place will begin to ooze and flow, the pins stay in one place thanks to the female connector's mating pins and the cooler plastic surrounding them. Second, it relieves you of the responsibility of knowing just how much vise pressure it takes to deform the male connector's metal faceplate (not much!).

Follow Mike's steps above (nicely done) to step 4. Now, cut a 2 inch piece of the big shrink tubing and slip it over all of your wires and as far away from the connector as you can. Then slip a short piece of your smaller shrink tubing around each of the motor wires. Each piece should be long enough to completely cover the solder pin and any exposed wiring. If you've followed the directions above, an inch apiece should be more than plenty. As before, slide these as far from the solder cups (and the heat they are about to receive) as feasible. Once this is done, follow with step 5 from Sir Richards' description. At this point, using those small bent-nosed pliers to feed and hold each wire until the solder sets would be a treat. When step 5 is behind you and all wires have a strong mechanical bond with the correct (Newbie!) solder cup, wait for the cups to cool before sliding the shrink tubing all the way to the base of each cup. Use your heat gun to shrink the tubing in place. Don't have a heat gun? Use a lighter... but have a care not to let the heat dwell in any one spot: you might burn through the material. Then, slide the bigger heat shrink tube forward. Using the db-9 shells you bought at the store, measure out where the clamps will grab your wire bundle. You want the shrink tubing to straddle this spot evenly. Apply heat using the method of choice.

Now is the time for the resistor. Technically, as I mentioned above, the leads from this component should be the only pliable exposed metal in the entire shell 'space' at this point and as such you can afford to leave them un-insulated. Bad idea. These cables are going to flex. Any exposed metal has a chance of wearing through a wire's insulating coat and producing a short. If you are very unlucky, it will produce an 'intermittent short'. I have diagnosed a lot of electronic faults: I loathe the word 'intermittent'. Loathe it. Insulating all moving parts against future electrical contact is a VERY justifiable expense, both in terms of material cost and man-hours invested. I urge you to learn from my mistakes and coat this resistor's leads and it's solder cups (once it is securely soldered in place) with the stuff in that expensive little bottle of 'GC Electronics Insulating Coating' I mentioned above.

Once this is all done, just assemble the shells, spray all mating pins with DeoxIT and move on with the balance of your life, secure in the knowledge you have done all that can reasonably be done to arrange a bright future for your CNC electronics.

A final note on the subject of db-9 (or db-[any number], really) shells may useful here: these often come with grommets of varying sizes to secure the cable or wire harness feeding the connector, but the 'right' size for a given project may not be included. In these cases, it is possible to build up the harness or cable with shrink tubing of increasing diameters. With a bit of planning or experimentation, this might even look fairly presentable. You do want good contact between the shell and the cable to minimize or eliminate the rubbing your cables will experience every time they move.

- Kalo

Gerald D
Mon 02 March 2009, 00:11
Thanks Kalo, you have explained very carefully why I have this big resistance to DB connectors for a self-build project!

Mon 02 March 2009, 01:41
This I understand: to be fair, though, any _soldered_ connector should have this much stress attached to it's construction. Even the XLR connectors from Neutrik (far superior for our purposes... but still a little iffy at the high-power end) should be approached with this sort of worst-case planning, in my experience.

Gerald D
Mon 02 March 2009, 02:29
Let me re-phrase that: . . . . I have this bigmoderate resistance to DBany connectors for a self-build project . . .

Marc Shlaes
Mon 02 March 2009, 07:06

Where were you 4 months ago when I learned to solder DB9s??????

EVERYTHING he says is right on.

I learned each of those things the hard way. You would have saved me a bunch of frustration.

Very well stated.

Mon 02 March 2009, 10:12
I hear what you are saying, but I do have a suggestion I think may help a lot of projects with this whole connector issue (though not the g540 itself, sadly). For power-hungry connections, I have had zero problems with this product:

www dot andersonpower dot com/products/standard-powerpole dot com

Anderson PowerPole family (hmm... somehow my links got through last time, but blocked on this post. Someday...)

Granted, I haven't tried using them for high-power data connections, but I'm willing to bet they'll do well. The finer stores will also sell the locking pins that will keep an assembly in one piece.

If you can find these in your neck of the woods (actually, a place named after fishing tackle is probably on the beach, right?), you should really give them a go. If your local shop doesn't carry them, try some ham radio buffs; very popular with these folks.


There was this girl, see... I lost track of time, forgot about my bros completely...by the time it was over, I couldn't find my watch. Sorry, dude. I'll have your back next time, promise.

- Kalo


Oops, found an(other!) error in my first post: When the female db-9 is mounted in the vise, the pins should be facing you, the solder cups should be facing away.

Mon 02 March 2009, 21:56
Hi all,
This my first post. Found out about this site last Monday and canít stop reading!! Must Build MechMate!! :D I have done nothing all week, because I have been up every night till 5am!

Thinking of using the g540 on my MM for 3 reasons
1) Itís almost $400 cheaper (vs. 4-203v's and bob)
2) I am in CA with Gecko (so shipping is cheap if it has to be sent back a couple of times)
3) Itís almost $400 cheaper, I could buy 2 and still be ahead

I am planning on building MM with the PK299A2A7.2 as per recommended, anyone foresee any other reason for not using the g540? as yet, other than the DB9 connectors.

Also had a thought on the DB9 could you buy 2-DB9 patch cords cut them in half Splice in shielded cables and resistors inside youíre your control box? Much easier to splice than solder ends, I think.
Thanks Gerald and all for this grate site and all your hard work. I donít think I can sleep till I finish this thing

Gerald D
Mon 02 March 2009, 22:52
Pete, the DB9 is not a total horror story - it just takes a little practice with the right equipment. A good soldering iron is the expensive item and is a good investment anyway. May I suggest you buy yourself a DB9 or two today and see what this is all about? After a couple of practice runs (and photos posted here, of course) you should be able to make nice connections.

(Where is Heath? He lives in the world of connectors and is photo-crazy.....how about some pictures inside the backshells of DB connectors? :))

Gerald D
Tue 03 March 2009, 00:00
Some pictures borrowed off the www:

3879 3880

3881 3882

3883 3884

3885 3886

Tue 03 March 2009, 18:18
I wouldn't pay a lot for the connectors to practice on, Gecko sent nice connectors with my G-540.

Gerald D
Tue 03 March 2009, 21:04
For practising, you only need the part in the first photo, and they are sold loose at under $2. My thinking is that you might want to trash your first practice attempts.

Gerald D
Wed 04 March 2009, 00:41
Okay, who is going to do us pictures of neatly soldering a screened 4 core motor cable (plus resistor) into a DB9?

Heath, how does one neatly connect the screen to a metal backshell(pic2)? Kalo? :)

Come to think of it; does Gecko supply metal back shells?

Wed 04 March 2009, 06:32
The screen or shield wire is normally soldered to the metal shell (photo #1) of the DB-9 connector on one end of the cable and then a jumper wire connects one of that connector's mounting screws to the machine's common ground point. It's important to use heat shrink tubing or other insulating material to keep the bare shield/screen wire from shorting against other wires or pins.

Wed 04 March 2009, 17:05
No Gecko don't supply metal back shells, so is done as per Mikes reply.

Wed 11 November 2009, 19:02
Okay, who is going to do us pictures of neatly soldering a screened 4 core motor cable (plus resistor) into a DB9?

Has anyone done these photos? (I have seen the generic ones in Post #16 above.) I am particularly interested in seeing how the Resistor is done. Thanks

Wed 11 November 2009, 19:32
I did but I am afraid of posting them, with me being a noob at solderiing.

Fearing what Mike or Gerald might say...

I will upload what I got but take it easy please....

EDIT: Sorry but this is the only pictures that I have of my soldering of the db-9's. I must of deleted them some time ago...

Thu 12 November 2009, 10:20
Thanks, that is what I needed.

Gerald D
Sat 14 November 2009, 09:14
Am I really that scary? :D:(

Sat 14 November 2009, 12:47
I dont think anyone would complain about those pics. :)

Sat 14 November 2009, 15:29
Scary.... no.

Respected greatly.... yes.


Mon 30 November 2009, 13:51
Seeing how I am totally lazy and a can't solder to save my life, has anyone tried using the db9 breakout boards with the G540. They have the db9 male connector and a small row of terminal blocks to connect the resistor and wires.

Mon 30 November 2009, 15:39
If your interested, www.BTX.com (http://btx.com) has db9 connectors with solderless screw terminals for attachment. They have a gaggle of High Density connectors in screw terminal format. A big plus for my installation business as-of-late.


Tue 01 December 2009, 15:21
Those are exactly what I need. Thanks Sean,

Tue 01 December 2009, 19:27
...always glad to help a fellow ohioian!(sp) I'm from Akron originally! Good luck...I use these connectors weekly and have had great success with them. Make certain you order the "boot" or cover too....

List price on those are about 20 dollars per connection with the cord cap boot. You will only need 4 of these with the G540. A little pricey, but well worth the convenience factor. (plus, easily reusable)


Fri 11 December 2009, 11:41
Sean: Thanks for that BTX link (my soldered DB9 connectors were impossible:)) Joe

Sat 12 December 2009, 06:18
Sean, the db9 connectors sound like a good christmas present idea from the wife. I jury rigged some old db9 cable I had by cutting off the female ends and using terminal blocks for connections. Ex-Akron, want to trade locations? I'm from Barberton originally now living in Norton. Right now it's 3 degrees with a -15 wind chill . My CNC is in the basement and like me it gets cranky in the cold weather. I need to really let it warm up before I ramp up the speed.

Gerald D
Fri 22 January 2010, 01:16
Here is another interesting option:


from http://soigeneris.com/gecko.aspx

Sat 23 January 2010, 12:19
Very nice and at less than $11 US for a set of four, they are much less expensive than the BTX option. Had I known....:) Thanks Gerald