https://www.centroidcncforum.com/
Wouldn't this be most beneficial to the product supplier? To ensure that their product is properly mounted and doesn't break with normal useWould be nice if one of are users proficient with CAD and 3D printing could design and make some brackets for it.
Anyone? Anyone
Tom,teknic_servo wrote: ↑Fri Feb 19, 2021 5:40 pm "Interesting that they don’t require resistors on this yet they do normally. Can anyone explain why that would be?"
carboncymbal,
Not sure if you say this post on a different thread so I added it here to ensure coverage.
All-
I’m an engineer at Teknic and came across your comment about step input timing errors and noise interference.
The ClearPath motor inputs are optically isolated and current limited. This design provides exceptional noise immunity even in the most difficult EMI environments like plasma CNC machines and applications that use a VFD. The optical isolation hardware of the ClearPath motors provide enough noise immunity that shielded and twisted pair cables between the CNC motion controller and the ClearPath motor are not required.
You might wonder, “if the noise immunity of the ClearPath motors is so good, then why is there a possibility of getting step input timing errors and why are the termination resistors required?” Great question!
The minimum length of time for a step to be “on” is 715ns. In addition, the minimum length of time for the “off” period between steps is also 715ns. The ClearPath “step input timing error” occurs when the “on” time of a step is shorter than 715ns, and/or the “off” time between steps is shorter than 715ns.
Typically this error is elicited when one or more of the following conditions occur:
- The controller has open collector outputs and the resistors specified in the ClearPath manual are not installed correctly, or not at all. Here is a link to the fractional hp ClearPath manual:(https://www.teknic.com/files/downloads/ ... manual.pdf)
An open collector output “drives” the signal to a true logic state but then the return signal “floats” back to its false logic state. This floating nature of the open collector signal means that the signal might not be “off” for at least 715ns required between steps before the next step is sent. This behavior is often exacerbated by capacitance in the control system, whether due to long cable runs or the electrical design.
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”.
- The controller output voltage is lower than the minimum 4VDC required for the ClearPath motor and is unable to reliably turn on the optical isolated inputs. For example, some controllers only output a 3.3VDC signal.
- The controller's maximum step pulse output frequency is higher than 700kHz, or the step pulse time is less than 715 nS. These settings are typically configurable in the controller.
(https://www.teknic.com/files/downloads/ ... om=100,0,0)
- Shared return paths for outputs. The V+ and GND wires for each controller output should travel the entire distance from the controller to the motor and then back to the controller. Some systems have limited I/O connections so the output signals go individually out to the motor, but then they share a common return path back to the controller. For example, three output signal wires could go out to the motor but then the return wires are tied together and only one return wire comes all the way back to the controller. This can cause problems related to noise immunity.
As a side note, we’ve recently reviewed the Acorn schematics with Centroid and they will be updating their schematics to include this 10k termination resistor. This should address the issue that you mentioned.
I hope this helps you and other users. If you have any other questions regarding the ClearPath motors, please feel free to use Teknic’s "Contact Us' form (https://www.teknic.com/contact) or give us a call at 585-784-7454.
Best regards,
Tom T. - Teknic Servo Systems Engineer
Tom T.teknic_servo wrote: ↑Tue Feb 23, 2021 12:23 pm Tom K,
It comes down to the current rating of the resisitors. The 1k ohm resistor used with 24VDC at a high duty cycle could get warm to hot. If you have run your system for a substantial period of time and do not see any heat related issues with the resistors, you could be fine. That said, it would be safer in the long run to change the resistors to 10k ohm.
Thanks,
Tom T
I have an Avid CNC with 4 Nema 34 SDSK's with one Teknic IPC5 power supply and have not had any issues with not having enough power.teknic_servo wrote: ↑Fri Feb 26, 2021 2:03 pm As far as how many power supplies you need for your machine, most systems only need one power supply.
Hope this helps,
Tom T.
A little thread creep here, but I am planning on using 4 of the CPM-SDSK-3421S-ELN servos on a 4'x8' AVID Pro machine. I will mostly be cutting 1/4 to 1/2" acrylic (although the more I read, some wood project would be fun). I am not too worried about transition speed and will be limited to about 200 IPM for a cutting speed (for acrylic). If you think 1 power supply has a chance of getting it done, I will just leave space for another one and get the 2nd one if needed. Thanksteknic_servo wrote: ↑Fri Feb 26, 2021 2:03 pm TaylorPilot,
Great question. A bulk linear power supply has the advantage of stored energy for high accelerations and simulataneous multi-axis movement. Their downside is that the voltage is typically not stiff and the voltage will often droop when power is pulled from them.
A switching power supply has stiff voltage that typically doesn't droop but very little (or no) stored energy. This means that you are essentially pulling electricty right from the wall through the power supply. When too much energy is drawn from a switching power supply, it will suddenly "brown out" or black-out" during operation. The voltage recovery period and performance is often erratic.
Teknic's IPC-5 ("Intelligent Power Center") has stiff voltage (+/- .5VDC) like a switching power supply, stored energy for high accelerations like a bulk linear power supply, AND regenerative energy management. I could discuss this topic in more detail but we have written a motion article that discusses the power supply topic in depth. Here is the link:
https://www.teknic.com/selecting-power-supply/
As far as how many power supplies you need for your machine, most systems only need one power supply. Usually only the biggest machines with the most powerful N34 motors, with the most demanding cut requirements use two power supplies. You can start with one IPC-5 ($248 ea) and test your machine for performance. If you find out that you need to supply more energy to meet your motion objectives, you can decide to add another IPC-5 or return the one you bought within 90 days for a full refund (minus shipping).
Hope this helps,
Tom T.