Help with Gecko 203v on Acorn, retrofitting old ShopBot.

[Cambroe]

Hello,
At my school we have an old ShopBot PRTstandard, the old 4'x8' model. Its controller is long gone, but the Gecko 203v 10 Microstep Drives are still here. We purchased an Acorn board and have been trying to get it all setup, but I haven't gotten anything to actually move yet. I found a schematic from Centroid regarding how to wire 203v's to the Acorn, which involves 220 Ohm pull up resistors coming off the Acorn's Step, Direction, and Enable headers, then connecting to the +5v lead on the included power supply.

The problem arises when I do that: and the power LED on each gecko is no longer green (looks like red & green lights are both on). With or without resistors, I get no motor movement when attempting to jog. It seems that the drives aren't getting any info from the Acorn.

I suppose my primary question is what is the proper way to set this up? Both in software and in hardware. I've worked with steppers before but so far can't figure these out. Below is all of the things I know about the system.

Controller: Acorn Rev3
Drivers (x4): Gecko 203v 10 Microstep Drive
Software: CNC Mill 12

Steppers: A6497-9412KTG
- Base spec of 0.5 degrees per step
- Mounted to unknown gearbox
- Unsure of final steps/revolution
- 25T pinion on X/Y axis

2 steppers on X, 1 on Y, 1 on Z

Any insight would be greatly appreciated, you'll be helping out me, fellow students, and my robotics team

[todd432]

Hi
Here is my 2 cents on 203v witch I have 4 of. Sell em and buy new drives.
I can only get 50 ipm out of mine before they start throwing fits and loosing steps and stalling altogether.

I had mine wired to the Acron header with resistors and now use the DB25 port (no resistors needed).
To see if it would help with the stalling , it did not.

As far as what to replace them with..... lots of choices out there.

Not much help but a little incite with a touch of experience.

[Gary Campbell]

I agree with Todd on tossing the Geckos. That said, a number here have made them work. If you choose to go in that direction go to the website and download the latest schematics: http://www.centroidcnc.com//centroid_di ... y_cnc.html

Use the schematic that shows the Geckos wired to the DB25 header, not H2/H3. Make sure you set the pulse rate to 100K steps/sec by setting Parameter 968 to 12. There are lots of posts regarding this.

When you get your motors turning post back here what you actually used, what the drive settings are and if you have a different pinion (20T) on the Z axis. In any case you will set the steps per rev (on the Geckos) at 2000 steps per rev, but if you change drives it may be 1600 or 3200. Personally I would never set a router at 1/10th microstepping, 3D printer... maybe, nothing with a load on it.

Your ".5* per step" is for a 3.6:1 reduction. 200 native steps X 3.6 ratio = 720 steps per rev. 360/720 yields 1/2 degree per step.

A 25 tooth pinion will need a 0.9167 revs per inch and a 20T will require 1.1459

Let us know what else you need.

[deanq]

I think we have gotten into an era of information overload. There is so much information on so many different drive types and models that information (misinformation) is bleeding over to everyone's feedback for a "fix" to their problem.

First, look at the specs for your drives. then look at the specs and options for your board (acorn). Then look at your systems physical setup (leadscrew, rack/pinion, gearbox, pitch ratio).
You can get everything to work (I have done it), BUT....will it meet your performance expectations?
You can figure it out old school with a calculator or you can put it together and hope it works (calculator is cheaper).

Gecko drives: Max pulse rate is 350KHz. What is the acorn set to? 200 or 400KHz. It needs to be <350KHz (200K).
Drive ratio:Pinion/leadscrew/gearbox (whatever) will it move fast enough with 1/10 microstepping drives?
Your Gecko's will work (if wired correctly) wired from either acorn header.
Will it meet your expectations? Only you and your calculator know for sure. (I didn't even touch on selecting correct size motors)
JMHO YMMV.

[Ken Rychlik]

I have the gecko 201x on a machine and they are working good wired directly to the board step/dir signals. The 203 and 213 seem to have been giving people trouble, but I know they functioned on the bot system. It's easy to miss a wire or connection from the schematic, (I forgot to run the 5v to my drivers at first) so post of pic of your wiring and link of the diagram you are using. It will be much easier for others to possibly spot an error or give advice.

[robtown]

Just completed building a control box from scratch using 203's for my circa 2005 PRT standard.
Had no issues at all... none that I wasn't directly responsible for anyway.
I spent this past weekend cutting 16 sheets of 3/4 ply and around 20 sheets of 1 inch and two inch foam.
When I say "spent the weekend" I mean 2-3 hours on Saturday and 2 on Sunday.
Cut the ply at around 240 IPM in two passes, the foam at 360 IPM.

Not sure why the 203's have such a bad rep around here....

Anyway. Use the DB-25, not the header, to wire your drives and you won't need the pull up resistor.

If you pulled the Geckos off the ShopBot control board, you may need to add resistors to the Geckos, in my case the resistors were soldered directly to the board.

I purchased new cables, but just ended up using the existing ones.

[Dan M]

I think we have gotten into an era of information overload. There is so much information on so many different drive types and models that information (misinformation) is bleeding over to everyone's feedback for a "fix" to their problem.

First, look at the specs for your drives. then look at the specs and options for your board (acorn). Then look at your systems physical setup (leadscrew, rack/pinion, gearbox, pitch ratio).
You can get everything to work (I have done it), BUT....will it meet your performance expectations?
You can figure it out old school with a calculator or you can put it together and hope it works (calculator is cheaper).

Gecko drives: Max pulse rate is 350KHz. What is the acorn set to? 200 or 400KHz. It needs to be <350KHz (200K).
Drive ratio:Pinion/leadscrew/gearbox (whatever) will it move fast enough with 1/10 microstepping drives?
Your Gecko's will work (if wired correctly) wired from either acorn header.
Will it meet your expectations? Only you and your calculator know for sure. (I didn't even touch on selecting correct size motors)
JMHO YMMV.

Completely agree, I spent a lot of time doing calculations and talking to different vendors engineers and asked guys with more experience than me a lot of questions(Thanks Marty, Gary and Keith). And guess what, my machine works exactly as expected actually better than expected!

I also spent a lot of time on the phone with Marcus and he was nice enough to walk me through setting up the gr214v drivers. I'm running 25000 steps and 400KHz per Marcus.

My router runs smooth with no lost steps, and eats up everything I've thrown at it so far. I'm honestly surprised at how well my router works considering it was my first build. Moral of the story is as you said a calculator is a lot cheaper than crossed fingers.

Dan

[Richards]

The Gecko G203v differs from other Gecko drives in that its "common" signal is DC ground. On that drive, the step signal goes active on the leading edge of the step pulse. In other words, the drive signal must go HIGH in relation to the drive's COMMON. Unless I've missed something, the latest schematics from Centroid (V4) for the G203v shows how to connect the G203v drive to the H2/H3 headers. Note carefully how the drive is connected. +5V is fed to the Step, the Direction and the Disable signals after passing through a 220 ohm resistor (that limits the current to about 10mA because the LED in the optocoupler uses about 2V of the 5V and the Acorn's sinking circuit uses some more of that voltage). When the Acorn SINKs current, the Step, Direction and Disable signals go LOW, which is the opposite of the active signal state. In effect, a step pulse occurs on the trailing edge of the Acorn step signal when the Step pulse signals goes from 0 to +5V.

(As far as I know, the G201x can have the COMMON pin tied to either +5V or to GROUND. If it is tied to +5V, then a SINKING signal from the Acorn will generate a step pulse.)

For testing purposes, do NOT connect anything to the G203v DISABLE pin. If that pin is active, it disables the drive. You can also leave the Direction terminal disconnected. Of course the motor will only turn one way, but you'll be able to verify that the motor is turning. Unless you know the AMPS being pulled by your motor, you can use a 10K resistor connected to the current limiting resistors terminals. That will limit the motor's current to about 1A, which will be sufficient to show motor activity. (Use the proper resistor from the G203v manual for production cutting.)

I just hooked up a G203v per the V4 schematic to an Oriental Motor 3.6:1 geared motor using the Black/Green leads for one phase and the Red/Blue leads for the other phase which may be what you have if you're using original Shopbot motors. The Yellow and the White wires usually don't exist on those motors. After changing the step rate to 100,000 PPS as per Gary's instructions by setting parameter 968 to 12, the motor worked just fine on the test bench.

[Richards]

I ran some tests this morning on a Geckodrive G203v to DB25 connection using a DB25 breakout board that Gary Campbell sent me. I first set the PPS to 100,000 by setting parameter 968 to 12. That gave me a good 4.5uSec pulse width for the G203v. The pulse shape matched what the G203v needs, i.e., inactive = GROUND, active = +5VDC. So far, so good. As you can see from the photos, I connected an Oriental Motor PK296B2A-SG3.6 motor to the G203v using the Black/Green and Red/Blue wires. The G203v step signal was connected directly to the S1+ terminal on Gary's breakout board. Common on the G203v was connected to Ground on the Power Supply's ground plane. I used a 33K current limiting resistor to limit the current to about 3A to the motor, although in series wiring, the motor draws much less current. Power to the motor was +48VDC furnished by two 24VDC power supplies wired in series (the same power supplies that I use when running the DM542 stepper drivers). Direction and Disable were NOT connected for this test. I only wanted to verify that a G203v would run properly when connected to the Acorn's DB25 connector.

The gcode used was G1 F500 X50. It ran perfectly. At F100, the motor movement is a little rough, which is to be expected from that motor when the motor is wired series. (I normally wire that motor half-coil which is black/yellow and red/white, but to keep the test as close as possible to what a Shopbot user would face if using the stock 3.6:1 motors furnished by Shopbot, I used series wiring.)

NO resistors are necessary, just as Gary told us. NO signal inverting is necessary for the G203v, just as Gary told us.

Bottom line: if you have some G203v drives that you want to use, just use the Acorn's DB25 connector, set PPS to 100,000 by setting P968 to 12 and run the motors.

[Cambroe]

Sell em and buy new drives.

I will certainly consider this depending on the results after testing out the solutions proposed below. Thank you!