Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: moorea21 on December 29, 2010, 12:00:48 PM
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Hi,
At the risk of starting a war of some kind, can anyone recommend a control board for me that is actually popular and well supported (in terms of advice, updates, etc) by both the manufacturer and cnc forums.
I'm fed up with the pace of progress getting my ncpod based machine running.
My pc has a parallel port, and I'm running 6 axes. Such things as backlash compensation, spindle speed control etc not necessary, but THC would be helpful (not obligatory, though; there's probably a way to work around the lack of it), and I need home/limit for all 6 axes, plus a few supplementary input and output pins.
Anyone any ideas? anyone tempted to sell me something they're not using?!
Rich B
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The original LPT version is hard to beat for form and function AND support.
2 lpt's would do the trick, (;-) TP
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Can you give me a link for that? It's a bit general for me to google...
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There are lots of options. I've always used Gecko drives and have never had a reason to look at any other company. I've been using the Sound Logic BOB, but I think I'll try the CNC4PC C35 next time. The Gecko G540 is a great option if your motors draw less than 3.5A. It is a complete 4 axis setup with built in BOB. I've used two of them so far.
The THC would interface through the second PP.
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Can you give me a link for that? It's a bit general for me to google...
What Terry is meaning is use the parallel port and just add a second port to get extra I/O
I use the SmoothStepper on all my machines as I have servos with high count encoders and the parallel port would limit my rapids unless I used the drives electronic gearing. Personally I dislike electronic gearing so the SS has been a great benefit to me.
Hood
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Okay, thanks Hood. I was thinking smooth stepper, I just think there's a bit of a wait to get one now, and I'm impatient!
I'm also loath to give up on the ncPOD, but it's just more efficient to spend a day sorting a problem out by using the benefit of wide experience online, rather spend weeks redefining the problem to one support guy at oemtech. They are nice guys over there, but there are just too few of them! Time ticks away...
Do you find the smooth stepper people helpful? Is the support fairly prompt, and suitably competent? The documentation doesn't appear to have moved on in the last couple of years.
Anyway, thanks again
Rich B
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To rrc1962:
You mention that your controller is only 4 axis; is there something else in your system that makes it able to handle 6 axes?
Richard B
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The SS is really just a parallel port replacement in the respect that for the majority of things you just set up as you would the parallel port. Documentation hasnt changed but I think Jeff Birt has written a doc although I havent read it myself so not sure exactly whats in it.
The SS does most things but THC and Backlash are two it doesnt yet support, Backlash is being worked on and I suppose it has been for a year or so but Greg had other commitments so his time was stretched thin, hopefully it will get done soon for the guys that are waiting.
Dont think there is much of a wait for the SS but if Greg doesnt have one Jeff or even some of the others that sell them likely will have some in stock.
Hood
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Okay, thanks again.
I'll probably buy one.
Rich
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The thing the LPT version has going for it is it has the widest USER base, SUpport Base, Documentation base AND the cheapest overall solution for the average application.
Also as Art has always said Nothing beats the LPT for being able to do all Mach functions well.
(;-) TP
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To rrc1962:
You mention that your controller is only 4 axis; is there something else in your system that makes it able to handle 6 axes?
Richard B
No. I didn't realize you needed 6 axes.
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Thanks BR449,
Do you have any recommendations for hardware for this?
RB
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You would, I imagine, already have the drives and likely a breakout board as you have been using the ncpod so you dont really need any further hardware other than a computer with a parallel port and a PCI parallel port if you require a second port.
What kind of motors do you have? If just steppers then you will almost certainly be able to get their max speed from the parallel port.
Hood
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I have motors (steppers, nema 23) and drivers, but no breakout board. Can't remember why I didn't need one, but I remember being told either the drivers or the pod do this instead. How much are parallel port controllers/ breakout boards, in general?
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You dont actually need a breakout board but I prefer to use on mainly for the ease of connecting but they also usually afford a little protection if they are isolated and a further benefit when using the parallel port is that most can accept the 3.3v signals some modern ports put out and will boost it to 5v for your drives.
Cost wise they go from cheap to expensive, my personal preference is the PMDX122 which will be around $80 but there are cheaper ones from other makesrs and also dearer ones, for six axis and the I/O you would need 2, if wanting breakouts for each port. There are also dual breakouts, I think PMDX do some and as said there are others that make boards.
PCI parallel port I am not sure, in the UK you would be talking £10 to £20 so it would probably be the same in $ for you.
Hood
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Okay, so if I have a smoothstepper I have to have breakout boards, but if I use the parallel ort I could theoretically just wire my drivers directly to the port on the pc? Is that correct?
From reading on the site, I'm not clear how many axes the PMDX122 supports...
I'm in UK, too! Do you know what the shipping charge is likely to be for the smooth stepper? They're all on holiday at the moment, apparently.
Rich B
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You could wire directly to the PP, but if the drives create any spikes it will fry your PP. Breakout boards are opto-isolated to prevent that. They also provide opto-isolated inputs. They are well worth the little bit of money they cost. You should have a BOB with both SS and PP.
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So I ought to use breakout boards if I have SS or PP.
On running Mach's driver test, my PC was rated good to excellent for pulse, so does this mean I don't really need an off-board controller/pulse generator?
My (motion control products msd415) drives have , and I quote: " TTL compatible and optically isolated input signals". I will mail them to ask, but does that mean I don't need a breakout board? It's starting to sound like all I need to do is tear up an old PP cable and wire my drivers to it. For 6 axes, I'll need another parallel port though, right? Would a PCI parallel port work identically to my on board one? No issues to look out for?
I ought to check that my PC is producing 5V not 3.3V to the parallel port. No idea how to do this, can I do this in xp sp3? A link to a walkthrough would be a help.
I think that's all!
Thanks for advice so far, I really appreciate this,
RB
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I'm pretty sure that the opto-isolation in the drives is there to protect the drives, not the PP. I tried going direct to the PP with Gecko drives a few years back and popped the PP within about 5 minutes. Since then, I've always used BOB's. All it takes is a little stray voltage to a PP pin to blow the port. These are low voltage signals, so it's not hard to get that, especially when working with plasma.
You would need an extra PP and BOB. A PCI card will work the same as your on-board PP.
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Then that's what I'll do! Thanks, I think I've got a shopping list to write.
RB
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Not sure on shipping, its been a while but its not hugely expensive.
What does the graph look like in the driver test, is it smooth or does it have spikes?
Hood
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These are the worst spikes I saw during the test, apart form one of much higher amplitude right at the start, which happens every time I run the driver test (4 times now, to be sure)
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That should be fine :)
Hood
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Good, thanks
Credit card at the ready!
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Another vote for smoothstepper here. Works just like 2 LPT's, except with only 1 usb connection and cleaner and faster pulse rates.
I've had excellent results with the Kflop board as well. It has an insanely fast pulse rate and is very powerful and flexible, but the setup can be quite daunting at first as it requires you to tune your motors through their proprietary software before using mach.
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Here's another option. Less money since you have to buy two of them. I'm going to try one on the next machine we do that uses individual drives.
http://www.cnc4pc.com/Store/osc/product_info.php?cPath=33&products_id=270
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Erm...
"Less money since you have to buy two of them".... do you mean that, because this has 8 outputs, I only have to buy one, and I don't need to but the parallel port PCI card?
RB
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No. It only has 4 axes so you still need two board and another PP. The others are auxiliary inputs and outputs. You'd be into two of these for about what you'd pay for one of the PMDX boards.
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From what I see you would still need 2 and yes you would need an extra port if going the parallel port route for the amount of axis/IO you want. Also that is not optically isolated although in my book thats no big deal, to me the buffered outputs would be the important thing if using the PP.
If thinking of SS route then both CNC4PC and PMDX have boards that are capable of supporting all inputs/outputs of the SS (2 parallel ports worth plus an extra 6 Inputs) and the SS plugs into them.
Hood
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I was looking at motion control products mcp25 BOB's. If I can get a discount out of them (bought a few things before) I should get 2 of them including postage for about £50, and no VAT or duty or long wait, etc.
Anyone used these before?
I think the SS route is out for me, due to cost, and it not being necessary for my steppers.
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Thats just a straight connector, no buffering, no isolation but it would make it easier than connecting by soldering.
Hood
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Hmm... that's an expensive way to avoid soldering, then. Is there a good enough cheap BOB available from UK? I'm guessing cheap and buffered are mutually exclusive... how important is this in comparison to isolation? or do Bob's generally have both, rather than just one of these features?
RB
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Afraid I have no idea what boards are available from the UK :(
Hood
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Quick google brought up this, how good or bad it is I have no idea. http://www.slidesandballscrews.com/uniport-breakout-board-p-179.html?cPath=54
Hood
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Looks quite interesting, good documentation, too. Still not as cheap as chips, though.
Saw this on Ebay, CNC DB25 Breakout Board Adapter Stepper Motor Driver.
http://cgi.ebay.co.uk/CNC-DB25-Breakout-Board-Adapter-Stepper-Motor-Driver-/150540689910?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item230ceca1f6#ht_4039wt_912
About half the price... maybe worth a try; what could go wrong?!
Anyone recognise this product?
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Its from Hong Kong but otherwise looks ok.
I made the mistake of buying cheap with my drives and BOB when I first started out and it ended up meaning I had to go buy stuff that worked properly, so I wont do that again. At £25 suppose you dont have much to lose.
Only other thing is it says its opto isolated but doesnt give specs and doesnt say whether step/dir outputs are, sometimes having double isolated step/dir can cause issues and I think you said your drives did have isolation.
Hood
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I could short across the step dir optos? Obviously whatrever wraranrt ther was goes out the window.
I like how you said "Its from Hong Kong but otherwise looks ok." Damning with faint praise?!
What can go wrong with cheap Bob's, and what went wrong with yours?
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and no VAT or duty or long wait, etc.
Was why I mentioned Hong Kong, not anything to do with its origin in respect of quality or anything else.
What went wrong with mine was they were crap, the BOB sucked up noise from anywhere and everywhere, even soldering caps all over it failed to cure it. The drives had lovely alu heatsinks on them but if I touched them to anything metalic the steppers would start rotating all on their own. I isolated the drives from the cabinet and got things going eventually but if it hadnt been for the great advice and help I recieved from John Prentice I would have thrown in the towel.
John sent me up a Gecko to try and from a max of 400mm/min withthe drives I had it instantly allowed me to get 4000mm/min and that was without anything else being changed, so as soon as I could afford it I bought some Geckos, I had already swapped out the crap BOB for the first PMDX122 that I have had.
Hood
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See what you mean; I noticed the delivery time for these is about a month... not so great.
Maybe I could make my own? is it doable with veroboard, and a gang of opamps with a gain of, say 1.5 to act as buffers? Opto couplers on all lines except step/ dir... I can solder okay, what spec amps and optocouplers might be okay? Or am I heading towards noise problems, too? Could noise be negated by mounting the Bob(s) as separate boards, each very close to my drivers? Loath to spent more on electronicky stuff than I have to. Maybe shooting myself in the foot, of course.
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I dont know enough about electronics to be anything other than dangerous ;)
Hood
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I don't think shipping from the US would be that bad. It's a small and light package. Priority mail, flat rate, small box looks like about $14USD.
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I just emailed pmdx.com, asking for a quote. They charge handling and insurance, and my lovely government will need their palms greasing, as usual...
RB
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If you get it sent to a home address then 90% of the time it rolls right through without customs charges.
Post has never taken more than a week for me from either Gecko or PMDX but this time of year with the backlog it could be more. Then again if customs are busy they will tend to concentrate on suspect packages and ones with higher value ;)
Hood
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BTW if going PMDX then maybe the dual board would be a better option.
Hood
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Just looked, the last PMDX122 I got cost £60.61 and that was Feb 08. the one before was Dec 06 and that cost me £61.68 and the one before that was Apr 05 at £59.73.
Hood
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That sounds fine, I'll look at the PMDX126, then. Will it have issues with the optocoupled step/dir on my msd415 drivers? I'll Email PMDX on this, too. Happy new year when it happens, btw!
RB
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The PMDX will not likely have optos on the outputs (havent checked though) so should be no trouble that way.
Hood
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There don't appear to be optos on outputs.
Apparently I need 2 db25 m2m cables, and a db25 female to idc 26 pin adaptor, too... Ebay cheapest for former...
http://cgi.ebay.co.uk/PC-Parallel-Switch-Box-Cable-Lead-DB25-Male-2m-/300340091375?pt=UK_Computing_CablesConnectors_RL&hash=item45edaa19ef#ht_1010wt_1141
...pmdx for latter.
RB
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Just check with them that they are direct connection cables, I think they are but there is a chance they could have some pins crossed.
Hood
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Ta, will do
RB
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They seem to be okay.