Important Gecko 540 info - news to me!!

[DonFrambach]

I just read a very interesting thread in the Taig subforum of Benchtop mills where Maris Freimanis of Gecko says:

"Never place the current set resistor on the motor end of the DB-9 connector cable! The resistor MUST be placed on the G540 end and on the connector. Otherwise the motor cable wires will inject a lot of noise into the current set pins and cause erratic motor behavior, incorrect phase current and audible noises from the motor.

Mariss "

This is in post #57 of this thread:
http://www.cnczone.com/forums/taig_m..._problems.html


I have been using motors from CNCRoutparts.com where the resister is installed in the motor pigtail. I then used used extension DB9 cables also for CNCRouterparts.com to connect the motors to my Gecko board. This is exactly what Mariss says not to do.

The best solution I see for me is to make my own cables.

[DonFrambach]

In post #61 of the same thread Mariss says in response to being told about the CNCRouterparts pigtails and extension cables:

"Wow! I had no clue this is being done; the result can be terrible motor performance. ...

Mariss"

[Markwind]

here is more info on this g540 cable subject,

http://www.cnczone.com/forums/gecko_...le_issues.html

http://www.cnczone.com/forums/gecko_...es_motors.html

[ahren]

All,

I have talked with Gecko over email regarding this issue. The short of it is that Gecko is working on addressing this on their end. Marcus asked me not to talk too much about it until they finish testing, so that's all I'll say for now. On our end, I am working on an attachment that will go in between our cables and the G540 that contains the current set resistor, but does not pass through pins 1 and 5. I doubt this will be needed for long, as Gecko typically moves pretty fast, but I will be offering these as soon as they are available to customers who have experienced problems.

I do want to emphasize that while having the current set resistor on the motor end can potentially cause issues, it is by no means always (or even usually) a problem when using our cables. Many of the problems people have experienced with "molded cables" are not due to where the resistor is, but due to the fact that people have used cables with insufficient wire gauge or connectors. Our cables are molded just for us to our specifications, and are made with high quality 20 AWG wire and rated connectors.

Best regards,

Ahren
CNCRouterParts

[maspeir]

Oops... Never mind...

[wireb]

Here is a EE 2 cents

Yea that makes total sense. You want your current sense wires as sort as possible and shielded from everything else if possible.

The I sense voltages are typically in the low double or even single digit mV (0.001V). At those low voltages noise is a big deal. The only good news is the termination resistance is so high you need some major noise to affect short traces.

Few years back designed a electronic load box for a project at work and had all sort of weird feedback issues with it. Turns out they layout for the sense lines just happened to form a tuned circuit on a harmonic of a local radio station Once we figured that out you could tell from the traces when they were playing load music vs dead air / soft stuff... Few cap value changes later and everything started behaving again.

One thing folks could do for the existing cables and motors is grab a breakout box (they are about a inch or two long with a male and a female connector on each end) that matches your cables and just disconnect the sense lines and add another resistor in the box. Then just plug this directly into the geko and all your existing cables into it. Easy upgrade if your using molded cables and cannot crack the ends open to add the resistor where it needs to go.

[CNC Lurker]

Originally Posted by ahren All, I have talked with Gecko over email regarding this issue. The short of it is that Gecko is working on addressing this on their end. Marcus asked me not to talk too much about it until they finish testing, so that's all I'll say for now. On our end, I am working on an attachment that will go in between our cables and the G540 that contains the current set resistor, but does not pass through pins 1 and 5. I doubt this will be needed for long, as Gecko typically moves pretty fast, but I will be offering these as soon as they are available to customers who have experienced problems. I do want to emphasize that while having the current set resistor on the motor end can potentially cause issues, it is by no means always (or even usually) a problem when using our cables. Many of the problems people have experienced with "molded cables" are not due to where the resistor is, but due to the fact that people have used cables with insufficient wire gauge or connectors. Our cables are molded just for us to our specifications, and are made with high quality 20 AWG wire and rated connectors. Best regards, Ahren CNCRouterParts

Thanks for posting. There are a few on here that have stated the resistors are incorrectly placed and I was hoping you would respond. I noticed the steppers get too hot to touch after being on for about 20 minutes.

This is without pushing a load. By that I mean they're not pushing the router along the rails since they've only been tested on my desk. I don't know what a "normal" temperature should be for them. I'll have to add that I don't even know if the temperature has anything to do with the placement of the resistors, but I've wondered if that was the cause or not.

[Markwind]

thanks for that information, good to know gecko is working on a fix, I was close to a G540 purchase, but it sounds like I might as well wait for a revised version

does anyone know what is the latest version number of the G540 is?

[cornbinder23]

All the information on placement of the current limiting resistor is in the G540 manual, the "Problem" with noise is not a very prominent one or we would see more posts regarding issues with the G540, as Ahren stated it is usually when someone is using sup par components, the G540 comes with its own set of good quality DB9 connectors and it is really not that hard for end users to make their own cables and place resistors in the DB9 backshells, decent quality stepper cable can be had by the foot on ebay or sourced somewhere else
On my cnc mill I have the cables going from the motors to a bulkhead box exiting the flood coolant enclosure then to the G540 so I have a hard connection at the motor, DB9 connector at the bulkhead, Db9 connection exiting the box and the DB9 connection at the G540 and havent had one problem with noise, I even have the limits and home switches running through the same bulkhead.
So unless you are going to use Ahrens racy red stepper cables (which I havent read any users having problems with those) just make up a set that comply with the instructions that Gecko provided with your G540, although those molded cables are downright sexy!!! (did I type that out loud?)
BTW I know most of the users here know this info already but I am bored and just wanted to type something

JTCUSTOMS

[Arbo]

Interesting to hear. I have never had any issues that I have noticed, and I do it the CNCrouterparts way.

[DonFrambach]

My router uses motors and cables purchased from CNCRouterParts. The resister is placed on the motor pigtail. I just replaced one of the cables with a custom cable placing the resister next to the G540 and removing the resister from the motor pigtail. Preliminary testing tonight revealed no difference in audible motor noise and the motor seems to work just fine (as it was with the CNCRouterParts cable arrangement).

[DonFrambach]

I let my machine idle for about 30 minutes. The stepper with the resister location changed to next to the G540 is cool. The other two steppers are quite warm. Don't know if that will affect performance or durability but resister location does seem to make the motors cooler. I'm going to go ahead and make cables for the other two steppers.