Lost steps newly upgraded machine <clearpath, resistors>

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tkbot47
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by tkbot47 »

martyscncgarage wrote: Tue Feb 23, 2021 8:45 am
tkbot47 wrote: Tue Feb 23, 2021 8:34 am Tom T., I asked this in Marty's build thread as well, but is Teknic now saying that those of us who bought SDSK motors a while ago and are using 1K resistors now should switch them to 10K for proper performance?
Tom
Tom answered this. It's not a matter of performance, it's more a matter of heat generated by the 1k ohm resistor. Check your resistors, change them out if heat is an issue. The performance should be the same.

Marty
Marty,
I must have missed where Tom mentioned heat, but it makes sense. I have not noticed any issues, but I have not checked the temp of the resistors. Won't hurt to change them out to 10K though. I only use them on the longer cables.
Tom
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by martyscncgarage »

tkbot47 wrote: Tue Feb 23, 2021 10:59 am
martyscncgarage wrote: Tue Feb 23, 2021 8:45 am
tkbot47 wrote: Tue Feb 23, 2021 8:34 am Tom T., I asked this in Marty's build thread as well, but is Teknic now saying that those of us who bought SDSK motors a while ago and are using 1K resistors now should switch them to 10K for proper performance?
Tom
Tom answered this. It's not a matter of performance, it's more a matter of heat generated by the 1k ohm resistor. Check your resistors, change them out if heat is an issue. The performance should be the same.

Marty
Marty,
I must have missed where Tom mentioned heat, but it makes sense. I have not noticed any issues, but I have not checked the temp of the resistors. Won't hurt to change them out to 10K though. I only use them on the longer cables.
Tom
No worries Tom. I am hopeful that CNC4PC's C86ACCP with it's built in resistors and soon, terminal blocks for landing the individual wires from the Teknic cable finally resolves the issues users have been having with Clearpath SD motors and Centroid Acorn. Including simplifying wiring.

Marty
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by Muzzer »

The LEDs in the optos convert current to light, so the requirement is to discharge any stray capacitance (charge) in the cable and / or the LED. Either that or the Clearpath optos themselves are rather marginal on speed. The actual forward voltage is simply a function of the forward current.

Like the DMM Tech drives, the Clearpath step / dir inputs don't quite seem to perform quite as fast as specified. It really shouldn't necessary to be experimenting with resistors to make them work consistently.
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by tkbot47 »

martyscncgarage wrote: Tue Feb 23, 2021 11:14 am
tkbot47 wrote: Tue Feb 23, 2021 10:59 am
martyscncgarage wrote: Tue Feb 23, 2021 8:45 am

Tom answered this. It's not a matter of performance, it's more a matter of heat generated by the 1k ohm resistor. Check your resistors, change them out if heat is an issue. The performance should be the same.

Marty
Marty,
I must have missed where Tom mentioned heat, but it makes sense. I have not noticed any issues, but I have not checked the temp of the resistors. Won't hurt to change them out to 10K though. I only use them on the longer cables.
Tom
No worries Tom. I am hopeful that CNC4PC's C86ACCP with it's built in resistors and soon, terminal blocks for landing the individual wires from the Teknic cable finally resolves the issues users have been having with Clearpath SD motors and Centroid Acorn. Including simplifying wiring.

Marty
Marty,
Out of curiosity, where does Teknic officially state to now use 10K? the link in Tom's post to the manual still goes to v3.09 of the manual, which still says 1K. I looked through their online faqs, and there is no mention of it. Is our forum the only place it is mentioned? I hope I'm not missing something here - I'd like to think I can check their website periodically and get the latest info.
Tom
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by martyscncgarage »

tkbot47 wrote: Tue Feb 23, 2021 11:31 am
martyscncgarage wrote: Tue Feb 23, 2021 11:14 am
tkbot47 wrote: Tue Feb 23, 2021 10:59 am
Marty,
I must have missed where Tom mentioned heat, but it makes sense. I have not noticed any issues, but I have not checked the temp of the resistors. Won't hurt to change them out to 10K though. I only use them on the longer cables.
Tom
No worries Tom. I am hopeful that CNC4PC's C86ACCP with it's built in resistors and soon, terminal blocks for landing the individual wires from the Teknic cable finally resolves the issues users have been having with Clearpath SD motors and Centroid Acorn. Including simplifying wiring.

Marty
Marty,
Out of curiosity, where does Teknic officially state to now use 10K? the link in Tom's post to the manual still goes to v3.09 of the manual, which still says 1K. I looked through their online faqs, and there is no mention of it. Is our forum the only place it is mentioned? I hope I'm not missing something here - I'd like to think I can check their website periodically and get the latest info.
Tom
viewtopic.php?f=60&t=5392&hilit=Tom+T.&start=20

"Dave,

The ClearPath manual is being updated this week with the following information:

* Use 1k ohm resisitors for 5VDC and 10k ohm resisitors with 24VDC
* The Step Input Timing error is being added to the Blink Code chart starting on page 156.

Thanks,
Tom T"
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by tkbot47 »

martyscncgarage wrote: Tue Feb 23, 2021 11:37 am
tkbot47 wrote: Tue Feb 23, 2021 11:31 am
martyscncgarage wrote: Tue Feb 23, 2021 11:14 am

No worries Tom. I am hopeful that CNC4PC's C86ACCP with it's built in resistors and soon, terminal blocks for landing the individual wires from the Teknic cable finally resolves the issues users have been having with Clearpath SD motors and Centroid Acorn. Including simplifying wiring.

Marty
Marty,
Out of curiosity, where does Teknic officially state to now use 10K? the link in Tom's post to the manual still goes to v3.09 of the manual, which still says 1K. I looked through their online faqs, and there is no mention of it. Is our forum the only place it is mentioned? I hope I'm not missing something here - I'd like to think I can check their website periodically and get the latest info.
Tom
viewtopic.php?f=60&t=5392&hilit=Tom+T.&start=20

"Dave,

The ClearPath manual is being updated this week with the following information:

* Use 1k ohm resisitors for 5VDC and 10k ohm resisitors with 24VDC
* The Step Input Timing error is being added to the Blink Code chart starting on page 156.

Thanks,
Tom T"
Ah....missed that one. Evidently, the manual is not updated yet. Thanks for the link, Marty. I've been running the 1K for about a year now, glad to see that it wouldn't have caused damage, just maybe some heating issues.
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by Richards »

It looks like there are still some concerns about resistors and Teknic ClearPath servos.

Here's part of what Tom posted:
teknic_servo wrote: Thu Feb 18, 2021 6:51 pm . . .
The Centroid Acorn uses 24VDC open collector outputs, so installing 10k ohm resistors across both the step and direction outputs for each axis of motion is appropriate. This resistor promptly drives the signal to an “off” state between steps. In contrast, a driven TTL signal (this is a different hardware architecture than open collector signals) is less prone to this behavior because the circuitry “drives” the signal to ”on” and then “drives” the signal back to ”off”. This type of signal is referred to as a “driven signal”.
. . .
Best regards,
Tom T. - Teknic Servo Systems Engineer
Various resistors can be used. Ohm's law helps us decide the value of resistor to use.

Using a 1K resistor:
24V / 1000 = 0.024A and 0.024A X 24V = 0.57W which means that even a 1W resistor would be too hot to touch.

Using a 10K resistor:
24V / 10000 = 0.0024A and 0.0024A X 24V = 0.057W which means that a 1/4W resistor would stay near room temperature.

The function of the resistor is to snap the voltage HIGH after the Acorn sends an active LOW signal. Tom described the situation. Without the resistor, the voltage "floats" back to the HIGH level. The time it takes to float is determined by the capacitance of the wiring. Before microprocessors and even before the famous 555 timer chip, timing circuits were built using resistors and capacitors. Kodak used that principle for over a decade on its S-Printers. A 911 light sensor tube acted as a resistor, depending on the amount of light passing through a negative. The keyboard had pushbuttons to select a capacitor. Kodak used vacuum tubes to amplify the voltage. When the "shark fin" pattern reached a specified voltage, shutters and filters were activated. That behavior was essential for an S-Printer, but it is exactly what needs to be eliminated in a servo drive signal. An oscilloscope shows the "shark fin" or "shark tooth" timer caused by capacitance on a long cable. The oscilloscope also shows that the "shark fin" or "shark tooth" pattern is squared up when the specified resistor is used.

It was very common before 7-segment displays were used on desktop calculators to use PIXIE tubes to display numbers. PIXIE tubes required more than 5V, so Open Collector logic was used. In the case of the Acorn, an Open Collector allows the user to choose the voltage he uses to send pulse streams to the servo drivers. Using 24VDC is better than 5VDC in a electrically noisy environment. In my opinion, there is nothing wrong with the Acorn board or the ClearPath servos. The flexibility that an Open Collector circuit gives us comes with a possible requirement to "snap" the signal back to its OFF state (floating HIGH).
-Mike Richards
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by tkbot47 »

Mike,
I understand the need for the resistor. My concern is that we were told 1K was the correct value for some time now, without any stipulation as to the voltage or heating. I just wanted to make sure that the 1K I''ve been using for over a year has not caused any damage to either the Acorn board or the motor driver circuits.
Tom
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by martyscncgarage »

tkbot47 wrote: Tue Feb 23, 2021 12:54 pm Mike,
I understand the need for the resistor. My concern is that we were told 1K was the correct value for some time now, without any stipulation as to the voltage or heating. I just wanted to make sure that the 1K I''ve been using for over a year has not caused any damage to either the Acorn board or the motor driver circuits.
Tom
Well, we've answered, your machine works. Given the new information, I suppose it wouldn't that big a deal to change them out for the 10k resistors....or you decide whether or not to leave sleeping dogs lay.... ;)
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Re: Lost steps newly upgraded machine <clearpath, resistors>

Post by Richards »

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.
-Mike Richards
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