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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > parallel to usb? + can i "convert" open loop to closed loop steppers?
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  1. #21
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    Jan 2005
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by A_Camera View Post
    Yes, there is a cheaper way, and that is the UC100 way. Why buy a dinosaur PC, go through the troubles of using parallel port when for an additional $60 you can use the PC you most probably already have? Apart from that, if you have an old PC you can still use that with the UC100 because it is definitely MUCH better than using a parallel port, just like OlfCNC is saying.

    But sure, on a very tight budget a free (or almost free) PC with a free software and a free OS is better than a commercial software like Mach3 and Windows10. The disadvantage is that with no Linux experience life can be a PITA with LinuxCNC.
    A couple points.

    UC100 is not just $60. The UC100 hardware is $120, and then their software is $60. So the minimum cost to go with the UC100 solution is $180.

    The LinuxCNC option is not as hard as people make out. It is available on a Live CD iso, bundled with the Linux operating system. From the live CD, installation no more difficult than answering a few simple questions. Once installed, for a stepper system there is a stepper configuration wizard that takes you step by step through setting up a stepper controlled machine.

    Whether or not a UC100 type system is "much" better, or better at all is a matter of opinion, and is also machine dependent. Take my machine, a G0704 mill/drill. The highest practical feed rate that you would want for that machine is about 200 IPM, With my 0.2" pitch leadscrews, and 8 microsteps/step, I need a 27 kHz step rate, which is easily achievable with a parallel port. It works great and has not presented any real problems in about 4 years of hobby use. So what exactly is "much" better about using a UC100 type solution for my situation? As I see it, going to a FPGA, UC100, or anything else only makes my wallet lighter.

    An analogy for parallel ports being dinosaurs would be my 1996 Honda Civic. Sure it is an old car by today's standards, but it is very reliable, runs fine, and gets me where I want to go. I am frugal and could afford to go down to the car dealer and buy a brand new car and pay cash for it, but I don't because I don't see the cost/benefit to do so. My friends all ask me why I don't get a new car and my response is "Other than make my bank account smaller, what will a new car do for me that my old Civic won't?" If/when my old civic starts giving me problems then I will think about a new car. So, is a new car, "better" ? It depends on how you look at it. Printer ports are the same way. In my opinion, if it does the job, I don't care if it is a dinosaur.

    All this is moot since the gentleman that started the thread has stated that he wants to use his current computer that doesn't have parallel port. That is his choice and he has his own cost/benefit parameters to assess. I can't fault him for that, just like I can't fault my friends that get new cars about every 3 or 4 years.

    As far as USB solutions, the UC100 does seem like a decent route and not too terribly expensive. The absolute cheapest USB solution is GRBL on an arduino that I mentioned before. If you want turn key and more complete g-code support then the UC100 is obviously better. GRBL doesn't take too much to get going, but has some limits on g-codes available, and is currently limited to about 30 kHz step rate.

  2. #22
    Join Date
    Sep 2014
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    51

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    as I believe I've mentioned earlier in the thread, I've already got a Leadshine MX3660 (that connects to PC through parallel port)

    if I go with UC100

    it's just: PC<usb-UC100-parallel port>MX3660>stepper motors (and limit switches etc.)?

    I was thinking running Mach3 on the PC but with the UC100 using UCCNC is also an option?


    and I'm very happy for your help on this matter!

  3. #23
    Join Date
    Dec 2003
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    24216

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by teglberg View Post
    is there any encoders that can be attached to the motors so that I can convert them to closed loop steppers or do I need all new closed loop steppers? or is there better ways - let me hear your thoughts on this
    Personally if going to the extent of putting encoders on a stepper, why not go the preferred method of servo in the first place?
    To me, encoders on steppers is a little like the phrase of 'Putting lipstick on a pig!"
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #24
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    May 2008
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    4068

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by Al_The_Man View Post
    Personally if going to the extent of putting encoders on a stepper, why not go the preferred method of servo in the first place?
    To me, encoders on steppers is a little like the phrase of 'Putting lipstick on a pig!"
    Al.
    Actually the easyservos which is a 3 phase stepper with encoder work great . But you need the driver for encoder feed back. Just putting encoder on stepper will do nothing .MX3660 has no input for encoder.
    XZero cnc

  5. #25
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    Dec 2003
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    24216

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    These do not appear to be traditional stepper motor, also I am a little suspicious of any servo motor site that makes a statement such as "Compared with servo systems, easy servo systems have much higher low-speed torque that servo systems lack, no overshooting, and no hunting."

    No:1 A DC servo, and most DC/BLDC motors have maximum torque at zero rpm, and remains fairly flat through the rpm range, just look at the torque/rpm curve, the servo systems I implement, when tuned do not "overshoot and hunt"!.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  6. #26
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    Jan 2005
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    1943

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by Al_The_Man View Post
    These do not appear to be traditional stepper motor, also I am a little suspicious of any servo motor site that makes a statement such as "Compared with servo systems, easy servo systems have much higher low-speed torque that servo systems lack, no overshooting, and no hunting."

    No:1 A DC servo, and most DC/BLDC motors have maximum torque at zero rpm, and remains fairly flat through the rpm range, just look at the torque/rpm curve, the servo systems I implement, when tuned do not "overshoot and hunt"!.
    Al.
    Actually, a properly sized stepper system compared to a properly sized servo system will always have additional reserve torque at low speed. The reason is because in order to achieve the maximum feed rate there is a certain required torque. Since the servo has a flat torque curve the 0 rpm torque will be close to what is required at max feed. Conversely, you would have to have a stepper with much higher 0 rpm torque so that at max feed there is still enough torque not to stall. so at speeds below the driving design point, the stepper system will have more torque than the servo, and hence more reserve torque.

    I'm not saying steppers are better, just pointing out how each design differs.

  7. #27
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    24216

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    A stepper motor has maximum torque at zero rpm when the plate rated DC current is applied, as does a servo, the rated stepper torque is whatever the current is as stated on the motor plate or spec, it should never be exceeded.
    These qualities are described in any of the major stepper motor manufacturers technical manuals such as Oriental Motor, Pacific Scientific, Slo-Syn etc.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  8. #28
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    Jan 2005
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    1943

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by Al_The_Man View Post
    A stepper motor has maximum torque at zero rpm when the plate rated DC current is applied, as does a servo, the rated stepper torque is whatever the current is as stated on the motor plate or spec, it should never be exceeded.
    These qualities are described in any of the major stepper motor manufacturers technical manuals such as Oriental Motor, Pacific Scientific, Slo-Syn etc.
    Al.
    Yes agreed, all this is true. Nobody said anything about exceeding any specs. I think you may not be understanding what I was saying.

    For example, if you choose a suitable size stepper for a machine, and for the same machine you also choose a suitable size servo to achieve the maximum feedrate for the axis, you will wind up with a servo that has a torque rating that is lower than the holding torque rating of the stepper. This is due to the facts that a stepper torque drops off and a servo torque doesn't with rpm. If we graph this we get something like the graph below. So you can see at the max feedrate the torque of the stepper and the torque of the servo have to be the same. Now at lower speed, the servo torque is flat, but the stepper torque is higher because of its torque curve. So, the stepper has more reserve torque at speeds below the design point. This will be true for steppers in general, not just the easy drivers mentioned before.

    Attachment 330658

  9. #29
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    Jan 2005
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    1943

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Quote Originally Posted by teglberg View Post
    as I believe I've mentioned earlier in the thread, I've already got a Leadshine MX3660 (that connects to PC through parallel port)

    if I go with UC100

    it's just: PC<usb-UC100-parallel port>MX3660>stepper motors (and limit switches etc.)?

    I was thinking running Mach3 on the PC but with the UC100 using UCCNC is also an option?


    and I'm very happy for your help on this matter!
    I was waiting for someone that has a UC100 to answer, but since it hasn't happened I will give it a go.

    The UC100 is made so that it provides a USB connection to the computer on one end and a parallel port type connection to the machine on the other end. On the parallel pots side you would need to connect to a BOB. Your MX3660 has a BOB built into it, so you can connect the UC100 directly to the MX3660. From there you have 2 options for the software on the PC. Either Mach3/mach4, or the UCNC software.

  10. #30
    Join Date
    Jul 2003
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    1753
    Not mach4.


    Quote Originally Posted by 109jb View Post
    I was waiting for someone that has a UC100 to answer, but since it hasn't happened I will give it a go.

    The UC100 is made so that it provides a USB connection to the computer on one end and a parallel port type connection to the machine on the other end. On the parallel pots side you would need to connect to a BOB. Your MX3660 has a BOB built into it, so you can connect the UC100 directly to the MX3660. From there you have 2 options for the software on the PC. Either Mach3/mach4, or the UCNC software.

  11. #31
    Join Date
    Mar 2016
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    46

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    Good morning, I don't know if I could help you, But need some help too sense you have a UC100. I am wiring up my UC100 to a breakout board that shows only 2 pins for each axis. pin 2&3 for X , 4&5 for Y, and 6&7 for Z. The question is where does pul- (cp-) on the driver connect to on the breakout board. If its the ground, can all 3 drivers be connected to it. if not, please explain, thanks. by the way, I am new to the CNC scene and this is my first post !!

  12. #32
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    Mar 2003
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    35538

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    So you can see at the max feedrate the torque of the stepper and the torque of the servo have to be the same. Now at lower speed, the servo torque is flat, but the stepper torque is higher because of its torque curve. So, the stepper has more reserve torque at speeds below the design point. This will be true for steppers in general, not just the easy drivers mentioned before.
    Servos will have a peak torque for short periods of time, which can be 3x their rated torque. So a servo can have more torque available than a stepper at any speed.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  13. #33
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    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    As per e.g.
    Blue is max continuous running torque throughout the rpm range
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  14. #34
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    Jan 2005
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    1943

    Re: parallel to usb? + can i "convert" open loop to closed loop steppers?

    With respect, you can only count on the peak torque for a short period of time, usually measured in seconds. In this graph I have plotted a peak torque type curve, and added a red star. The stepper can operate where the red start is indefinitely, while the servo can only operate at the red star for a limited amount of time.

    Attachment 330714

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