Mach3 CNC interface

[DTJ]

My hand rolled parallel port interface board is up for replacement and it seems more sensible to buy than make.

What's wrong with this one? I don't know how they do it for AU$8 delivered.


http://www.ebay.com.au/itm/CNC-5-Axis-MACH3-Interface-Board-With-Optocoupler-Adapter-Stepper-Motor-Driver-/141149835880?hash=item20dd2f9268:g:TpsAAOSwHgVW76K~

My system is currently 3 x steppers running open loop. Does anyone have any suggestions on a better unit or see any problems with this one?



Does anyone else think a sub forum for CNC / machining / fabrication would be useful?

[andtfoot]

From a quick look at the link, that board needs separate motor drivers to run. Have you got those already?

Otherwise, I don't know enough to comment on that one in particular. I use a Gecko G540 without any issue, but it's definitely on the more expensive end of the scale for a hobbyist.

[H.O]

If you're sticking with the LPT-port then I'd say that board is as cheap as you're going to get. It doesn't specifically say but it looks like the outputs are buffered which is great. They're NOT opto-isolated which, if your drives already are, isn't a problem at all.

Suggestions for a better one? No, not at that pricepoint, that's for sure. But places like PMDX and CNC4PC have many different break-out-boards for CNC.

If you want to get away from the LPT-port then you could look at the stuff from PoLabs, like the PoKeys57CNC or the Smoothstepper (the Ethernet version!) from Warp9. There are many different external motion controllers available - at various prices of course.

[DTJ]

From a quick look at the link, that board needs separate motor drivers to run. Have you got those already?

Otherwise, I don't know enough to comment on that one in particular. I use a Gecko G540 without any issue, but it's definitely on the more expensive end of the scale for a hobbyist.

Yeah, my drives (old but pretty high quality ex industrial Parker Automation driver) only need step / direction signals.

I just checked out the gecko, it looks quite good for the price.
http://www.geckodrive.com/geckodrive-step-motor-drives/g540.html

[DTJ]

If you're sticking with the LPT-port then I'd say that board is as cheap as you're going to get. It doesn't specifically say but it looks like the outputs are buffered which is great. They're NOT opto-isolated which, if your drives already are, isn't a problem at all.

Suggestions for a better one? No, not at that pricepoint, that's for sure. But places like PMDX and CNC4PC have many different break-out-boards for CNC.

As much as I hate the parallel port I want to stick with it as its simpler to fault find when something goes wrong.

I'm not sure there is any opto-isolation in  my system, I'll have to check the docs for my driver units.

I'll check out the links you posted. Thanks.

[Muttley Snickers]

I'd be happy to get one of these and see how it goes at that price even though I'm not a fan of devices that incorporate A to A USB connections, just not a common lead around these parts. I'm currently running just a basic parallel to terminal strip breakout board with an additional inline surge protector which from memory was an optical isolator, also running Parker Compumotor OEM650X drives in dumb mode with the daughter boards removed along with a Meanwell PSP 1000-48 vdc 19 amp power supply, we have been more than satisfied with this setup.

Here is the surge protector we are using, it uses MOV's and not opto isolators as mentioned earlier.
http://www.radioparts.com.au/product/30577701/pj7701-rs232-surge-protector-'d'-db25-plug-to-db25-socket#.V2NRHdJ94dU

[H.O]

There's nothing saying you must have opto-isolators. Properly wired it'll work just fine without. My comment was just a note/reminder that the board itself doesn't have any - on its outputs.

[DTJ]

Thanks HO, I can see that isolation would be good insurance.

I think I'll order one of the boards this arvo.

[SloaneRanger]

I just got one of those boards (Mach 3 driver board).  USD$5.52 on eBay!

Can't figure out why it has an Octal Bidirectional Transceiver ('245) on it.  It actually has two of them.
I would expect a  Schmitt trigger buffer.


Is there a schematic for it?  All my googling has not turned one up.



I assume those are 4-pin JST-XH connectors for the stepper drivers.  But why +5V and no gnd?

[DTJ]

Is there a schematic for it?  All my googling has not turned one up.

I assume those are 4-pin JST-XH connectors for the stepper drivers.  But why +5V and no gnd?

I'm awaiting delivery of mine.

If you find a schematic please pop a link to it here.

No ground is interesting. Does the EN line when high disable the drive & when low act as a ground?
Maybe the +5 is to facilitate pull up resistors?

[H.O]

I don't have one of these boards and I don't have a schematic so this is all based on previous experience and speculation.

The transceivers are simply buffereing the output signals and they're using transceivers (instead of basic buffers) because of the convenient pinout - been there.... They may also be using the transceiver chips EN pin to gate the outputs OFF.

Many step drivers with integrated opto-isolators (ie most of the Chinese "packaged" drives from Leadshine (and clones)) can work with both sourcing and sinking outputs (it exposes both the anode and cathode of the LED in the opto-isolator) it's just a matter of how you're wiring it. For output buffering like this I tend to use 74ACT series because I know it's capable of both sourcing and sinking 24mA but I don't remember if 74HC family is better at sinking than it is at sourcing which may be the reason they opted to do it this way.

If you have drives that need sourcing outputs I'm sure there's ground available somewhere on the board.

[ebclr]

The fact that have not isolator is a good thing and by design, because it's better to have nothing than a low speed opto , also they used optoisolator on the digital lines

[masawee]

normally all thats breakoutboard have include optoisolated chip all in/output. and need stepper driver board, etc, hy-div-268n-5A i use many cnc and other stepper project, can use little to big motor, dip switch can select current whick motor u have. 0,2-5A scale.
need connect breakoutboard step,direction pin and enaple. have ready to use, ofcourse too power and motor