Lost steps newly upgraded machine <clearpath, resistors>

[carboncymbal]

It's always best to ask. The manual that I have from Teknic also shows a 1K resistor, so I thought that someone just had a typo when I saw 10K.

I assume that the manual was written for all users of ClearPath servos, so in actuality, it becomes the responsibility of the user to run some tests such that any resistors used keep the current within the specs of whatever he is using. Page 7 of the Acorn user's manual tells us that the Acorn can handle up to 50mA. A 1K resistor would allow 24mA at 24V, so a 1K resistor can be used with the Acorn. A 10K resistor would allow 2.4mA which is below the average current of the Acorn's open collector spec, so that also fits within the specs. As noted below, the ClearPath can still pull more than 2.4mA when the pull-up resistor is mounted in parallel.

The placement of the resistor, as shown in the Teknic manual, creates a parallel circuit. When resistors vary greatly in value, most of the current will flow through the path with least resistance. If there is less resistance through the ClearPath circuitry than there is through the pull-up resistor, then the pull-up resistor acts more like an open circuit than a resistor. If there is less resistance through the pull-up resistor than the ClearPath circuitry, then the ClearPath might not get enough current to function; however, Teknic lists 1K, so they know that a 1K resistor will work in parallel with their ClearPath motors.

The real question is what actually happens with a 1K resistor and a 10K resistor? An oscilloscope shows the answer. The higher the resistance, the greater the "shark fin" or "shark tooth". If I saw a pronounced "shark fin" on my 'scope with a particular length of cable and a 10K resistor, I would try using a 4.7K resistor, or a 3.3K, or a 2.4K. We're looking for results. In a lab setting, we might be able to say that a 10K resistor is best. In the shop, a 10K resistor might be the best or another value might produce a more ideal waveform.

Thanks so much for the detailed description in this post and elsewhere.

Thanks,
Clay

[tkbot47]

It's always best to ask. The manual that I have from Teknic also shows a 1K resistor, so I thought that someone just had a typo when I saw 10K.

I assume that the manual was written for all users of ClearPath servos, so in actuality, it becomes the responsibility of the user to run some tests such that any resistors used keep the current within the specs of whatever he is using. Page 7 of the Acorn user's manual tells us that the Acorn can handle up to 50mA. A 1K resistor would allow 24mA at 24V, so a 1K resistor can be used with the Acorn. A 10K resistor would allow 2.4mA which is below the average current of the Acorn's open collector spec, so that also fits within the specs. As noted below, the ClearPath can still pull more than 2.4mA when the pull-up resistor is mounted in parallel.

The placement of the resistor, as shown in the Teknic manual, creates a parallel circuit. When resistors vary greatly in value, most of the current will flow through the path with least resistance. If there is less resistance through the ClearPath circuitry than there is through the pull-up resistor, then the pull-up resistor acts more like an open circuit than a resistor. If there is less resistance through the pull-up resistor than the ClearPath circuitry, then the ClearPath might not get enough current to function; however, Teknic lists 1K, so they know that a 1K resistor will work in parallel with their ClearPath motors.

The real question is what actually happens with a 1K resistor and a 10K resistor? An oscilloscope shows the answer. The higher the resistance, the greater the "shark fin" or "shark tooth". If I saw a pronounced "shark fin" on my 'scope with a particular length of cable and a 10K resistor, I would try using a 4.7K resistor, or a 3.3K, or a 2.4K. We're looking for results. In a lab setting, we might be able to say that a 10K resistor is best. In the shop, a 10K resistor might be the best or another value might produce a more ideal waveform.

In previous posts, it has been stated that Tekniks is in the process of modifying their manual for fractional HP SDSK's to indicate 10K for 24V. I hope we can assume that they have looked at the waveforms for the lead resistance/capacitance for at least their standard cable lengths that they supply and are satisfied that motor parameters will be met. I understand the usefulness of looking at a waveform to determine the optimum resistor, but I have to believe the average DIY does not have a scope and would want to rely on recommendations like are being made here, or plug in various values and look for step issues. In any event, thanks for your insight.

[blksmth]

Just ordered the C86ACCP After talking to Tom T last week. And now following Marty's new project. CNC4PC says the C86ACCP solves the problem but I didn't ask about which resistor they were using.

[martyscncgarage]

Just ordered the C86ACCP After talking to Tom T last week. And now following Marty's new project. CNC4PC says the C86ACCP solves the problem but I didn't ask about which resistor they were using.

Teknic Engineers reviewed the C86ACCP schematic and said it should work.

[Gary Campbell]

Teknic Engineers reviewed the C86ACCP schematic and said it should work.

But have they tested it? Always be aware of engineers that use the word "should"

[martyscncgarage]

Teknic Engineers reviewed the C86ACCP schematic and said it should work.

But have they tested it? Always be aware of engineers that use the word "should"

Gary and all.
Here is what I know.
Teknic signed off on the C86ACCP
Centroid is going to test the C86ACCP with a long cable.

I am encouraged by what I hear from all three companies.

Marty

[Gary Campbell]

Centroid is going to test the C86ACCP with a long cable

.

Hopefully they will test with a short one too. I had a couple lathes that showed the error and they had cables under 10'

[Richards]

I think that Teknic's testing will be valuable; but, unless we use exactly the same components placed exactly in the same place inside the cabinet and run our wiring exactly the same, our results may differ. That wouldn't show errors with Teknic's tests or with the C86ACCP board; it would only show that our build differs from their build.

Everyone likes the freedom to create their own design, but that freedom comes with a cost. Fixing problems that we create isn't Centroid's problem or Teknic's problem, (or Gary's or Marty's). When any of us builds a DIY controller, we have to assume responsibility for the end-product. Enough users have built reliable controllers with Acorn boards and ClearPath servos that we know that those components work together. Adding a VFD, a bunch of relays, contactors, or solenoids or even failing to properly configure Windows 10, could cause something to be glitchy.

[martyscncgarage]

Nicely put Mike!

[MarkRH]

Tom T.
Thanks for the informative explanation!

Mark,

Have you resolved the issue or are you still having problems?

You might consider looking into emi issues in the panel effecting Acorn.

Clay, sorry I missed your question, have been busy.
Started off adding 1K resistors to both step and dir, seemed to be working fine, after the 10K recommendation I added what I had on hand which was 2.2K, and everything seemed to work fine, bought some 10K installed and it seemed to work fine. I havnt run a bunch of files only a few. In addition I added a EMI filter Line side of VFD, drove a ground rod at subpanel.
Now after reading the new approved diagram for Acorn + clearpath SDSK looks like I'm ordering some 100 ohm resistors and changing the 24v to 5v.
Not sure I like that idea with long unshielded cables, more susceptible to EMI .
I suspect braided shield 8 core cnc rated wire is in the future.

Mark