Hi MHopp and Chase,
I am an application engineer here at Teknic and wanted to help clarify some points about both the wiring and motion control capabilities regarding the ClearPath fully integrated servo systems.
First I’ll address the wiring and voltage level discussion.
- ClearPath’s logic inputs (8-pin Molex connector) are compatible with both open collector (sinking or sourcing) and driven outputs.
- The inputs are optically isolated, current-limited, and accept a voltage range of 4-28VDC as stated in Appendix D of the ClearPath User Manual.
- We advertise 5-24VDC on the website since these are commonly used voltages, but as you can see there is some engineering margin built in.
- As long as your signals are nominally above 4V, the input will assert with no issue.
- See the ClearPath manual for the input’s minimum current requirements to make sure your board meets spec. For 5V inputs, ClearPath requires a minimum of 8mA.
Control Options
Next I’d like to clarify some comments about ClearPath’s control capabilities. ClearPath is an integrated, brushless servo motor with a high-resolution encoder, vector-torque control servo drive, and DSP-based controller. We simultaneously close the loop on position, speed, acceleration, and we even close the loop on torque (hence the “vector-torque control” mentioned above).
With the integration aspect aside, one unique thing about ClearPath is that it comes in 3 series: SD (“Step-and-Direction”), SC (“Software Control”), and MC (“Motion Control”). Each series has a unique interface and therefore there are reasons to choose one over the other which I’ll describe below.
SD Series
Let’s start with the SD series. These models are commonly used in 3D printing and CNC devices. In fact, these are important market segments for Teknic. If you search YouTube for “ClearPath servo” you’ll see many examples of people using SD models on their machines. Applications range from custom, in-house routers or 3D printers to high-volume equipment manufacturers developing state-of-the-art CNC machines. (Note, the OEMs tend to be more tight-lipped about whose products they’re using but some digging may reveal a few). All of these machines, whether hobbyist or OEM, use the same motion command structure… step-and-direction.
Step-and-direction
This is a common command structure that originated with stepper motor controllers. The step signals are a variable frequency pulse train which inherently contains position, speed, and acceleration command information. Whereas step-and-direction used to only be available on expensive, sophisticated indexers, it can now be found on low-cost, open-source platforms. Teknic designed ClearPath-SD to accept these same control signals, therefore providing people with a cost-effective upgrade path to a high-performance, servo system without having to drastically change their controller hardware and code (which can be time consuming).
Smoothieware board capabilities
While I’m not an expert at the Smoothieware board, a cursory look shows that it is capable of translating G-code to step-and-direction outputs which is perfect for use with the SD series. The Smoothie appears to provide 3.3V logic, but has wiring configurations using the Open-Drain (or an external level shifter) that can produce the required logic voltage for ClearPath. One thing you should double check on the Smoothieware forums is that the board can output enough current for ClearPath (a minimum of 8mA at 5 VDC).
Other than that, give ClearPath-SD an Enable, Step, and Direction signal and you’re done. It will faithfully follow your controller’s position, speed, and acceleration commands all over the machine, in any pattern your controller outputs. ClearPath-SD can move at any speed to any position with whatever torque is required (as long as it’s within that units physical capabilities).
SC Series
Next, the SC (“Software Control”) series, in addition to accepting step-and-direction, also has a high-speed serial communication interface with Teknic’s C++/C# motion class libraries. With these libraries, you can write object-oriented application code for executing point-to-point or velocity moves, reading/writing parameters (like position, torque, etc.), error handling, and so on. This requires an operating system to run but it does not need to be a full blown computer. For example, our YouTube channel has a whole video showcasing the SC library running on a BeagleBone Black single-board computer with embedded Linux. Our GitHub page contains the necessary information to replicate this setup on your own.
MC Series
Now, this is where things can easily get mixed up. The MC (“Motion Control”) series comes with a list of operating modes. Each mode allows you to pre-program only the parameters and moves you care about controlling. Some modes are good for just making velocity moves (conveyors, pumps, fans), some are good for controlling just torque (force, tension), and others for positioning moves (point-to-point, pick-and-place, indexing, etc.). Some modes are more flexible than others to provide a wide range of options.
The MC series has a built-in controller which lets you start/stop pre-programmed moves using any 5-24VDC digital I/O source (again, this is really 4-28VDC). This could be from a button or sensor to a microcontroller or PLC. As Chase said, this unit has a very simple interface, and purposely so. It’s easy to use in part because it strips out any motion features you don’t care about in your specific application. Note, this series was not designed for CNC applications and therefore cannot do path following. But for simpler applications that still require precise, smooth, and/or repeatable motion, this is a good option to consider.
Summary
Finally, MHopp, I think you’re on the right track with the SD series for your application. This only requires hooking up to an Enable, Step, Direction, and HLFB (optional) signal architecture and doesn’t require any software library or serial communication interface. Because of the simpler interface, easier implementation, and slightly lower-cost, the SD series is by far our most popular product for in-house 3D printing and CNC projects.
I know this response is long but motion control is a deep topic so I hope it helps. Please feel free to send additional ClearPath question to support@teknic.com.
Best regards,
Kevin Smith
