PMDX-132 instead of the PMDX-122
 

Gerald, I've been researching the BOB and I'm wondering why the PMDX-122 seems to be the preferred BOB for the MechMate over the PMDX-132. I've read your posts about proper wiring and it would seem that with the 132 and it's lack of need for BOB to Gecko wiring, that it would be the better choice for that purpose.


It also has a built in power supply (120 and 240) so you don't need an external one. It also has a few other advantages - additional capacitors for the Geckos, an additional relay output, direct support for their spindle speed controller, fused power supply for Gecko's and the overall package of Gecko's and BOB would take up less space.

The only disadvantage I see is that the price is $100 more but when factored against something like 10-12 thousand, it's not much more. The cost savings for the smaller controller box size and lack of need for additonal power supply would also off-set that cost.

It is exactly because the 132 has so much more than the 122, that I don't like it. If a 132 goes faulty, it is a big thing to repair or replace. The 122 is much more replaceable, and can be replaced with BOBs from other suppliers if needs be. Remember that my perspective is from sitting on the tip of Africa, where supplies are not always a phone call away.

(You can't reach the Gecko tuning screw with a 132)

I can understand the issue of replacement if you live outside of the USA. If you were located inside the USA, would you lean more toward the 132 over the 122?

I don't think so.

Stepper motor drivers (Gecko G20x) generate (lots of) heat. Trapping that heat directly beneath a circuit board is not good for either the stepper drivers or the circuit board. Granted, there is some clearance, but I would much rather have the stepper drivers sitting on their own heat sinks without anything blocking the air flow.

Now that I have added the picture, it strikes me that a central concept for this board is a parallel printer cable input - something that is rapidly becoming obsolete. That board is a big investment in dying technology.

Is anyone using a USB "BOB" yet? I've been tracking the Smooth Stepper thread but there hasn't been a post in quite a while. Also, there isn't a forum on the Smooth Stepper board and their Website hasn't changed in ages. Has development been stopped or delayed? Same with the NCpod. Can anyone shed some light on why the perpetual delay in a viable and reliable USB alternative to the Parallel Port?

Smoothstepper is alive and well. There is a forum on the website but you need to be registered and logged in to see the link. Not very much happens on that forum, because the Smoothstepper is fairly invisible once it is installed.

The ss can be inside your PC case if you choose and the cables would plug into it on one end and the other end would mount in the back of the case and look identical to parallel port(s) plugged into a PCi slot.

(copy and paste in: http://www.machsupport.com/forum/ind...ic,6406.0.html)

Here is Grandpi's MM running on a true USB system from TechLF of France.

I'd use the basic 122,

I didn't. Instead of using the PMDX at well under $100.00, I simplified my install and used a set of boards that featured direct plug in installation for Geckos, eliminating field wiring.

Right. I eliminated maybe 50 hard wired point to point connections, saving maybe an hour or two in stripping and installing wires. Instead, I spent three days endlessly resetting jumpers, begging for tech assistance which came several days after I finally stumbled on proper settings in direct contradiction to what passed as a manual. Had I used the basic PMDX I could have posted a couple messages on the forum and most likely had expert assistance in a few hours.

When my setup takes a @#$%, I won't even attempt to fix it. I'll chunk it and install the tried and true setup.

Chuck

There seems to be some conflicting information on the heat that the Gecko's generate. Here is a comment from Gerald where he mentions that the heat from the Gecko's isn't that great:

http://www.mechmate.com/forums/showt...57&postcount=5

And another prior post you made about this subject:

http://www.mechmate.com/forums/showt...5&postcount=15

It's confusing when someone says "generate (lots of) heat" and for the same product (Gecko), say "the heat never builds much higer than room temperature". It would also seem that the heat sinking in the Gecko is on the base, away from the circuit board.

The PMDX-122 and PMDX-132 both, according to the PMDX website, both are based on parallel ports. The later discussion about the smoothstepper seems to miss the fact that their website (http://www.pmdx.com/PMDX-132/) says:

"+The 26 pin ribbon cable port also allows direct connection to compatible pulse generator boards like the SmoothStepper."

So, I think one could generally say that both the 132 and 122 both are "dying technology".

The investment doesn't seem that great - by the time I purchase connectors, mounts, extra space in my control box, purchase additional relay and extra power supply that the additional ~$100 isn't that great. $100 really doesn't seem like a big investment in light of spending $10-12,000 on the total cost of the build.

Thanks for your input guys!

Steve, some people put the PMDX-132 on standoffs (as per pic) and hang the geckos under that, with no firm connection to a heatsink. (It is tricky to line up / fix the geckos on a heatsink so that the PMDX-132 plugs straight in). . . . and then they have high current motors . . .

The ShopBot G4 has the geckos plugged side by side on a motherboard and there they are prone to tripping out because of temperature . . . .

Talking in terms of lot and little is all relative and subjective - geckos are known to overheat when confined.

How do you plan to tune the setscrew on your geckos if you use a PMDX-132?

Yes, the PMDX-122 is also dying technology, but it is a much smaller investment. And we have proved it over and over again. And there is support here from others that are using it.

I called and asked them about the issue of alignment of the Gecko's and the board and he sent me a drawing I can print out and then use as a template to mark the holes perfectly. I've attached the drawing he sent me.

I asked him about this issue while I was on the phone and he said it just takes a few seconds to remove the board mount screws, then unplug the board from the Geckos, make the adjustment and then plug it back in. He mentioned that setting the Geckos is a one-time thing.

That is not a practical solution - while the board is unplugged, the motors are dead. . . . you cannot tune to a sweet spot on a dead motor.

I am at the breakout board / stepper driver purchase stage and am debating the choice of the PMDX-122 with four G203v Vs. a G540. The price difference is substantial ($299 for the G540 vs. $769 for the PMDX-122/Combo) Any thoughts on this? Thanks

Joe,
If the motors you have chosen match the G540 then that might be an option for you. The thing I do not like about the G540, is that the drivers are not stand alone. I chose the G203V and Pmdx122 combo since all the parts are separate. If you had a problem with one of the geckos, you could easily put in a spare if one was available. The 203s also have every type of protection imaginable, where the G540 does not. I liked the idea that I would probably not be able to kill a 203v with stupidity or a mistake. :) You could with a G540. Marris told me on the phone once that the V is for vampire, just cannot kill them. :) Is it worth the extra, depends on the person doing the buying. :)

Heath, while I mostly agree with what you say, I think it's important to note that the G540 is made up of a case, a motherboard that serves as a BOB, and four separate individually replaceable driver boards. Now, those drivers aren't the vampires, so you might be able to kill them; however this is a a situation where each builder should weight their own confidence and comfort. Having been inside my G540, I'm pretty confident in asserting that you'll have no significant difference in serviceability or component swapping between the G540 and pmdx solutions; in either case you'll either have spares on hand, or not. You'll have to apply a screwdriver to about a dozen screws, swap an electrical component, and apply the screwdriver in the other direction - pretty much the same effort in both cases.

G540 and PK296A2A-SG7.2 compatibility
 

Heath: I have ordered the OM PK296A2A-SG7.2 motors which I believe are compatible. Can you confirm this?

Thanks

Brad,
Thanks for that clarification, I was not trying to sound biased, but I guess I did. :) I forgot also that another reason I went with the combo was that I want to run an indexer, so the G540 for me would not have the capability for the fifth driver.

Another option for you Joe is to give Mariss a call at geckodrive, he will gladly go through any questions you have on comparing his products, I know he did for me. :) They are a really good company, I think either way you choose to go you will have a good driver solution. People here have had good success with both options.

Joe, If you wire those motors half coil they should be fine with the G540. Those are the same motors Brad is running if my memory serves me right. :)

you can search the best option o can search the economy option.

The economy option is one pmdx... in this configuration case, Work.
The best option is one controller board Like This... work in this and in much more other configurations, like servos, 8 axes, etc...

You can weigh your needs and possibilities before choosing.

I am not arguing that Gecko isn't the best, but there are more options.

http://www.driver-motor.com/ProductContent.aspx?ID=59

The above are working well for me with geared fuller steppers and a PMDX-122.

Jeff: How much were these? Thanks
Joe