What is the difference between carbon film and metal film resistors and which would be the choice for the geckos?

Carbon film resistors are really old technology. These days metal film resistors are the way to go. Early in the day, carbon comp resistors were cheaper to make and therefore for non critical applications they made sense. These days metal film resistors offer better performance in tolerance, temperature and drift and they are affordable. Use them if you can.

Everything on my MM seems to be operating just fine.

But, one of the Gecko V203's has no green light. When power is first applied to the control box, I get a red and yellow light on the drive. The three other drives have a green light.

This happened during the kitchen project, so I sent the drive off for inspection. Gecko said everything was fine.

Just thought I'd mention this. Maybe just a failed light bulb.

Greg,

If you only got a Red light, then I would agree that the Green side of the L.E.D. was not working; however, to get the Yellow light, both the Red side and the Green side of the L.E.D. have to be on at the same time.]

According to the spec sheet, the G203v should have the Red L.E.D. on when the G203v is first turned on (1 sec), when the G203v overheats, when the Disable input is active, or when there is a short circuit present. The Yellow L.E.D. turns on when the drive is running at full power. Otherwise the Green L.E.D. should be on at all times.

However, if the G203v is driving the stepper motor properly, then having the Green L.E.D. on or off really doesn't matter.

By the way, does the Green L.E.D. come on when you ONLY have power supplied to the G203v? (No motor connections. No step/direction/common connections. No resistor connections.)

Mike,

First, thanks for the help.

I re-checked it this evening. I was in error before. I get a red LED on all four drives when first powered up. No yellow LED is ever present. I was working from memory in the previous post (I should know better :o)

After the red LED, 3 of the 4 drivers go green, and the fourth, shows nothing.

Just to re-iterate, everything seems to be operating fine. I have not cut anything yet, so the motors/drives have not been under much of a load.

The weird thing with stepper motors is that their heaviest load (electrically speaking) is when they are idle. Get them to do some real work and then they get cooler!

:confused::confused::confused:

Back to the Gecko documentation on "basics of stepper motors".

Greg,
Another site to check for info on stepper motors and drivers is
www.pminmo.com. There is a lot of good reading there. :)
Actually, he references geckodrives article as well! :eek:

thanks Heath.

I'm having some issues with my setup as well. I have one PK296A1A-SG7.2 (half-coil), two compumotor LN series motors (full coil), three g203v drivers, and one pmdx-122. I got everything powered up and was even able to get some motor movement, but the thing is, all my motors are real darn slow. I definately do not see pins 3,5,7 flickering. They are always on. Pins 2,4,6 do turn on and off depending on the direction. The gecko green lights are on as well, which is expected.
I think I might know why everything is slow but I'm looking for a little confirmation here. I am temporarily using a variable DC power supply that supplies 20V and up to 20A. I checked while the motors were turning at max jog rate and I'm getting from 0.3A -0.36A on the PK motor, and about the same on the other two.
I have tuned the motors but still they are slow. Is the power supply my problem here?

Evan

The PK296A1A-SG7.2 motor wired half-coil needs a power supply voltage around 45VDC for optimum performance. I don't have data sheets on the Compumotors.

Pins 3,5,7 should flicker on/off with every step pulse. Pins 2,4,6 should either be steady on or steady off, depending on the direction signal.

Things to check:

1. PMDX-122 JP1 connector must be in the bottom position with G203v stepper drivers.

2. Mach3 setup configuration - verify the pins and the polarity of the step and direction signals.

3. Wiring - verify that you have continuity between the PMDX-122 and the G203v stepper drivers.

4. Current limiting resistor - verify that you have the correct value resistor (+/- 10%) for the motor that your using.

5. Mach3 - verify that the feed rate, ramping are set properly.


I have run stepper motors at less than 50% of the optimal voltage with excellent speed, so I don't think your power supply is the main problem. It's hard to know what voltage is actually going to a stepper motor without using an oscilloscope. A digital meter responds too slowly to get accurate readings.

If you still have problems after re-checking everything, please post your Mach3 pin-outs and speed settings so that we can cross-check things with you.

I would also check

Mach 3 motor tuning configuration - Check the velocity on all motors.

1. PMDX-122 JP1 connector must be in the bottom position with G203v stepper drivers.
JP1, JP2, JP3 are all in the bottom position; JP4, LP5, JP6 are all in the top position. "Outputs Enabled" is lit, and "pin17" is lit. Direction led is lit when moving in one direction and off when moving in the opposite direction

2. Mach3 setup configuration - verify the pins and the polarity of the step and direction signals.
Step/Dir pins are all wired correctly (checked 3 times)
X Axis: Enabled, StepPin#3, DirPin#2 DirLowActive Disabled (red X mark), Step LowActive Disabled (red X mark)
Y Axis: Enabled, StepPin#5, DirPin#4 DirLowActive Disabled (red X mark), Step LowActive Disabled (red X mark)
Z Axis: Enabled, StepPin#7, DirPin#6 DirLowActive Disabled (red X mark), Step LowActive Disabled (red X mark)

3. Wiring - verify that you have continuity between the PMDX-122 and the G203v stepper drivers.
I have checked continuity and all is well here

4. Current limiting resistor - verify that you have the correct value resistor (+/- 10%) for the motor that your using.
Resistors are correct, PK296 motor (unipolar) is 33k, the compumotors (2.2A/phase) are 22k

5. Mach3 - verify that the feed rate, ramping are set properly.
The compumotor motors are driving direct ballscrew, so disregarding them for now, and focusing on the X Axis with the PK296:
I have 20/20 pinion and I'm working in Inches:
1 revolution of the motor gearbox output shaft makes 3.1416" of travel .
or 1 x pi = 3.1416"
2000 pulses from computer will turn the motor one turn. Motor must turn 7.2times for one revolution of gearbox output shaft.
7.2 gearbox would make 14,400 pulses for one turn of the output shaft.

divide the pulses from computer by inch travel:

14400/3.1416= 4583.66 Steps/Per



With these settings, I'm only able to get about 21 IPM's of Velocity while tuning in Mach3 before skipping occurs.

Have you verified the current limit resistors with an ohm-meter - I have made mistakes with colour bands before.

DOH! I checked again and I grabbed the 3300 and 2200 ohm resistors instead of the 33000 and 22000 ohm resistors. That did it for the motor velocity issue as they are getting up to speed nicely now. But I still do not see the LED's on the Step pins of the pmdx-122 flickering.

Evan, welcome to the club of the wrong resistors! :)

You won't see a kilohertz flicker - realise that you don't even see a 60Hz flicker from a lightbulb. Remember, us club-members don't have the best of eyes. ;)

Gerald,
If you use metal film resistors, then some type have numbers on them for easier identification. Also more stable than other resistor types. :)

I would still check them with an ohm-meter for this application ;)

Thanks Gerald. Next time I check with an ohmmeter I'll try and actually read the display. Thanks for the quick replies.

Evan

Gerald,

Today I mounted Geckos (G203V) on Alu plate, two of them (pin1) does not show continity with Alu plate or back plate, it means there me be ground voltage difference with another two which are showing continity.
I even scratched back plate and checked continity with pin 1 but no continuity.
I am providing seperate power for each Gecko and shilding of each power cable is grounded to Alu plate.
Should I go with it or if there is any issue?

Bob, do not worry if there is continuity between the Gecko's case and the alu plate. The power ground for the gecko runs from pin 1 straight to your power supply negative pole, and from that negative pole there should be a wire to the alu plate.

The gecko case is hard anodised, which makes a pretty good insulator, except where your mounting screws might manage to break the insulation/anodising. Gecko needs the insulating property on the inside of the base plate, because there they have some semiconductor devices pressed against the plate as a heatsing.

The power wires feeding pins 1 and 2 need not be shielded. They are commonly unshielded.

You can read more about the Gecko grounding here:
http://finance.groups.yahoo.com/grou.../message/10408

and here:
http://finance.groups.yahoo.com/grou.../message/12440

Oops, I mean to say two drives (pin 1) show continuity with Alu plate but other two does not show continuity. That continuity comes through back plate of Gecko. Should I also provide path for ground via back plate to Alu plate?

Alternatively should I screw power -ve to Alu plate then star connect to Gecko's pin 1 ? (Like attatched file - borrowd from unknown cnczone link)

As in first link at #10413 para 1, Mariss said Sorry for my mistake, my Gecko power cables are unshilded, I unthoughfully recalled step/dir/common cable as shilded power cable while posting.

Thanks for the links. And hope that I am not causing any confusion here.

I have caused confusion by giving those links! :(

This picture should answer your questions. +ve wire is all red, -ve wire has black stripe on red. Capacitor -ve is the star point for all the wires going to all the pin 1's. Capacitor -ve also connected to alu plate:

http://www.mechmate.com/Forum/messages/832/893.jpg

After connecting like this you can measure Gecko pin 1 to alu plate - it will be a good connection. You need do nothing more to ground the geckos.

Thanks Gerald,
Everything about grounding is crystal clear right now.
I should have checked pics more thoroughly.

No problem Frank.

You can also omit the resistor across the capacitor. A single gecko across the capacitor does a good enough job of draining the capacitor when you switch off. Four geckos across the capacitor does an extremely good job of draining the capacitor. In this circuit, the resistor is a waste of time and space.

Frank, your fan wiring is unusual, unless you have a non-standard fan that runs off the transformer's secondary voltage.

Also, there is a serious error in my photo above. The ground wire from the PMDX to the alu plate should not be there. The PMDX-122 must NOT be grounded inside the control box. The reason is that the parallel cable from the PC grounds the PMDX to the PC's ground.

Gerald,

I ground my computer's case to the common ground on the frame of my CNC. The power supply inside the computer is grounded to the case via the power supply's mounting screws, so all things (computer, control box and CNC router) have a common ground point.

As you mentioned, because the PMDX-122 is grounded via the computer's parallel port, a secondary ground wire is not needed and may actually cause a ground loop.

Mike, is your computer case also grounded to your computer's incoming mains power? For us that would be normal (that our computer cases are "mains" grounded), and that is why I wouldn't connect the computer case to the CNC control box case.

I am taking the supply to my computer through the control box (off the main isolator) so it would share the same ground/earth as the control panel, much like Richard above, anybody see any problem with that?

We had ours like that for a while, then an inteference problem crept in. Moving it to completely different supply breaker improved the interference issue. We resolved the interfence by taking our mains E-stop circuit out of the screened cable that was doing all the other signals. But we havn't moved the PC supply back to the control box isolator. I am fairly sure that the PC running from the control box isolator would be fine.

I have dirct power line fan.
My PMDX is completely isolated from grounding. Even parallel cable does not have shielding (I wonder if it should be there). Signal cable shieldings bolted to Alu Plate.

Then your left diagram above is incorrect.

Oops again.
This is borrowed photo for reference. See #103.

Can someone tell me what function a Gecko GRex-100 Controller have in a simple way, and what is the advantage of having this?

It is a USB supported 6 axis controller that is at end of cycle for production and will no longer be supported. It was addressable and could be networked, but for the MM use, no advantage.

Ok!
Thanks :)

Mike, I'm starring at the gecko manual here and not sure what there looking for for the Resistor equation. I'm using PK296A2A-SG7.2 motors, so my amps per phase are 2.1 amps wired Bipolar?

What is "I" stand for and what is "?" in the equation.

R (in kilo-ohms) = 47 * I / (7 ? I) [/i]

I'm just trying to figure out this simple equation...I must be missing something simple here.

Thanks.

Travis, I is the current in amps. The equation as stated had an error.
From the gecko manual
R (in kilo-ohms) = 47 * I / (7 – I)

So, for 2.1 amps:

47 times 2.1, divided by, 7 minus 2.1

= 98.7 divided by 4.9

= 20 kiloOhm