Basic hookup

[1metalguru]

Hi guys:

I'm currently designing a CNC using the Acorn controller, I don't currently have one so I have a few questions about hookup. The documentation section is pretty overwhelming, there are hundreds of schematics and so on there, it's hard to find what you are looking for.

What I want to do is hook up some standard stepper driver modules, like a DM860 type driver. The outputs on H2 and H3 from what i could find are open collector outputs. These are the questions I have:

1. For the step and direction outputs, I would have to supply a separate 5v supply to all the common + inputs to the drivers, correct? There doesn't seem to be any 5v connections on the acorn board, despite the supplied power supply having a 5v output. I would need to wire the drivers in a common + configuration, correct? The COM terminals on the H2 and H3 connectors I assume are grounds, so I don't see why they are even there, if the outputs are OC, the only way you could hook up an external driver is with a common + arrangement, so these grounds are useless...
2. For the enable outputs on the acorn, why are there 4 separate outputs? Every system I have ever seen before has only one enable output for all 4 drivers. Can the acorn be wired up with all 4 drivers on any one of the enable outputs? I can't see much reason to have individual enables...

I will likely have more questions about VFD hookup in the near future. Thanks in advance for the assistance, guys.

MG

[Gary Campbell]

Find a schematic for Leadshine drives that show the step and direction connected to the DB25 connector. Most stepper drives do not work with the open collector data outputs. Db25 breakouts are a dime a dozen on Amazon, etc.

Don't use the ENA connections as they disable the drive when energized.

Set step pulse rate to no higher than 100k/sec

Set microstep to 3200 (best) or 1600(no less than)

[ShawnM]

Do as Gary recommends, those DM860 drives wire to the DB25 via a breakout board. Do not wire them to the headers.

Follow this diagram:

https://www.centroidcnc.com/dealersuppo ... 976.r4.pdf

There are diagrams for "generic" VFD connections as well as many specific VFD on the market. Easy to do.

[Richards]

Have you downloaded and read the centroid_acorn_install_manual.pdf? Be sure that you spend a few hours reading it before getting too far into your project. Near the end of the manual, you'll find an Acorn specifications chart. The data in that chart shows the voltages and currents allowed. Using that chart and a data chart for stepper drives, proximity sensors, VFDs, etc., makes it fairly simple to connect things together. Centroid's schematics are excellent.

I enjoy reading data sheets and exploring schematics. Not everyone finds enjoyment in that type of reading. The first time I tried reading schematics was for a Durst photo printer. The schematics used European symbols and strange vocabulary. "Quiescent state" was a term that I didn't know. There was no Google and my dictionary didn't have the word "quiescent". It was the beginning of a great adventure. I learned then not to skip past anything in a schematic or data sheet until I understood completely how that worked.

Enjoy your adventure. We're here to help when you get stuck. Before too long, you'll be experienced enough to offer advice to others based on your own experience.

[Upnorth]

Keep in mind it's not as complicated as it seems. You only need to figure out how one thing works at a time. You figure out how one axis works then duplicate it. Same with inputs and outputs. Once you figure out how they work they are easy to hook up. If you find yourself in some odd situation then you will have to figure out a bit more.

I have 3 DMA860 drives and they are hooked to the DB25 acorn output (DIR- and PUL-) I'm using the 5VDC from the acorn power supply for the DIR+ and PUL+ terminals on the drives. I think technically you should avoid using the acorn power supply for this but it has been working for me. I did not use the drive enable terminals.

[1metalguru]

Find a schematic for Leadshine drives that show the step and direction connected to the DB25 connector. Most stepper drives do not work with the open collector data outputs. Db25 breakouts are a dime a dozen on Amazon, etc.

Don't use the ENA connections as they disable the drive when energized.

Set step pulse rate to no higher than 100k/sec

Set microstep to 3200 (best) or 1600(no less than)

Gary:

I don't want to use the DB25 adapter because I don't have room above the board to have that giant thing sticking up. Also seems kind of klunky to me. I don't understand why the terminal block outputs won't work. If they are indeed OC outputs, there should be no problem with a standard stepper driver. You can wire it up as either common positive with OC outputs, or common negative with PNP outputs. Since the input to the stepper driver is just an optocoupler, you can wire it either way. The only issue I can see is that the terminal block outputs are designed to work with 24v, but I would have to put extra series resistors to use 24v with the DM860 driver, AFAIK. I should be able to just use a 5v supply, the OC outputs should pull it low enough to activate. I will have to go back and check the DM860 datasheet to see if it can handle 24v.

As far as using the Enable outputs, the Enable pins on the driver disable the driver when pulled low, so when the output is active it would pull the enable line low, which is correct. Enable input low on the stepper drivers activates the reduced motor hold current for the the driver, when it is activated it locks the driver in position by applying half current to the motor windings, when Enable is high it applies full current to the motor. I need this function. There are no driver enable outputs on the DB25 connections. I am assuming the software will allow the Enable output polarity to be set either way for Enabled state. Every other system I have used uses the Enable line to put the driver in motor locked standby state.

MG

[Gary Campbell]

Gary:

I don't want to use the DB25 adapter because I don't have room above the board to have that giant thing sticking up. Also seems kind of klunky to me. I don't understand why the terminal block outputs won't work. If they are indeed OC outputs, there should be no problem with a standard stepper driver. You can wire it up as either common positive with OC outputs, or common negative with PNP outputs. Since the input to the stepper driver is just an optocoupler, you can wire it either way. The only issue I can see is that the terminal block outputs are designed to work with 24v, but I would have to put extra series resistors to use 24v with the DM860 driver, AFAIK. I should be able to just use a 5v supply, the OC outputs should pull it low enough to activate. I will have to go back and check the DM860 datasheet to see if it can handle 24v.

As far as using the Enable outputs, the Enable pins on the driver disable the driver when pulled low, so when the output is active it would pull the enable line low, which is correct. Enable input low on the stepper drivers activates the reduced motor hold current for the the driver, when it is activated it locks the driver in position by applying half current to the motor windings, when Enable is high it applies full current to the motor. I need this function. There are no driver enable outputs on the DB25 connections. I am assuming the software will allow the Enable output polarity to be set either way for Enabled state. Every other system I have used uses the Enable line to put the driver in motor locked standby state.

MG

I only advise new guys on what my experience from building a few hundred controls has proven to work. I never care if they follow my advice.

[1metalguru]

Gary:

Well, aren't you just a ray of sunshine. Just because someone doesn't want to do it your way, they are wrong.
If you don't care if anyone follows your advice, why bother to give it? I think I'll manage just fine without it.

I am not a novice at this. I have built over 150 machines, and serviced a lot more. I have over 40 years experience in the Electronics industry.
I am a novice with the Acorn board, which is why I'm on this forum. I don't yet have my board, which means I can't experiment to see what works and what doesn't. I would like to converse with people who are willing to share ideas and brainstorm alternate methods, instead of just spouting rote information - "Well, this is the way we've always done it".

MG

[cncsnw]

I think if you browse this forum long enough, you will find lots of people who have tried to run stepper drives using the open-collector outputs.

You may find that many of them have struggled with loss of position due to dropped steps.

You might find more than a few whose problems were solved by moving to the DB25 connector.

Gary is not recommending what he does because "we've always done it that way". He is recommending it because collective experience, after much experimentation, has shown that it works better that way.

[1metalguru]

I think if you browse this forum long enough, you will find lots of people who have tried to run stepper drives using the open-collector outputs.

You may find that many of them have struggled with loss of position due to dropped steps.

You might find more than a few whose problems were solved by moving to the DB25 connector.

Gary is not recommending what he does because "we've always done it that way". He is recommending it because collective experience, after much experimentation, has shown that it works better that way.

Hi cncsnw:

Thanks for the info. It does not seem that it would be prudent for Centroid to include an interface on their board that doesn't work... In the manual it says it is to be used for servo drives, which would be exactly the same interface as a stepper driver anyway. I am still going to try it, but if possible, could you point me towards any posts that could back up your opinion?

I really need the enable signals, I feel that is a fix to a different source of error. Generally, there is only a single enable output that is tied to all the drives, rather than an individual signal for each channel.

And thanks for your interest.

MG