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Added Resistors the Z

Discussion in 'General Talk' started by GrandpawB, Jul 19, 2014.

  1. GrandpawB

    GrandpawB Veteran
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    The NEMA 17 stepper on my Z axis was over heating. The manufacture said I was over powering it and that I needed to add 2.4K resistors. I got the resistors and soldered them in line to each of the four wires on my Z stepper. Now I have no movement at all. Did I do this wrong? Any suggestions out there? :banghead:
     
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    I think I'd have probably only put in two. When you think about it, a 4-wire stepper is functionally two circuits, each with one wire in and one wire out (thus making 4 wires). So by adding in resistors at both ends of each circuit, you have functionally added 4.8K of resistance to each circuit.
     
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  3. Tweakie

    Tweakie OpenBuilds Team
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    Adding series resistance to a stepper motor to reduce it's current consumption is most inefficient, the actual series resistance (and as Rick has said only two are required) can be calculated from ohms law (R=E/I) and the actual value, in your case, will be less than 1 ohm but remember that their wattage (W=V*A) needs to be huge.

    Perhaps go back to the manufacturer and ask for clarification on exactly where the 2.4K resistors are to be fitted (it is certainly not in line with the stepper motor connections).

    Tweakie.
     
  4. GrandpawB

    GrandpawB Veteran
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    So, do you know where I'm suppose to add this 2.4K resistor? I use Geckodrive equipment so I have the DB 9 connectors and the G540 drive. Thanks.
     
  5. Rick 2.0

    Rick 2.0 OpenBuilds Team
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  6. GrandpawB

    GrandpawB Veteran
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  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    That's what is shows on the diagram.
     
  8. GrandpawB

    GrandpawB Veteran
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    I'm no Mr. Electronics by a long shot but I was under the impression that only pins 6 7 8 9 (Red Blue Black Green) were being used. Not to be argumentative, I know you're trying to help, but I don't understand what a resistor between 1 and 5 will do. :banghead:
     
  9. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    That makes two of us. But that's what it shows in the diagram so it must affect something in the circuit somewhere.

    ZR.jpg [
     
  10. GrandpawB

    GrandpawB Veteran
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    Sorry, there's no attachment.
     

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    • 3329.JPG
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  11. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Take a refresh. You caught me in the middle of revising the attachment.
     
  12. Brian Slee

    Brian Slee Veteran
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    Basically what it is doing is adding a parallel circuit in order to reduce the amount of current available to the stepper.
     
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  13. mr.eman

    mr.eman New
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    What's odd to me is that they're telling you to use a 2.4K resistor. I've seen two different prewired commercial db9 cables made for use with the G540 and they have either a 3.3K or a 3.5K resistor. Here's a links to the 3.5K resistor version from cncrouterparts.com.

    http://www.cncrouterparts.com/cnc-motor-cable-p-45.html
     
  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Thank you for the explanation.
     
  15. GrandpawB

    GrandpawB Veteran
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    I was told by Geckodrive support , based on the equipment I have, to use a 2.4K resistor. However, The G540 is sealed so I can't get to the solder points and the orange DB9 cables are molded. So I don't understand how I'm suppose to solder a resistor from pin 1 to pin 5. Do I cut off the molded connector and connect another DB9 with a removable jacket? :banghead:
     
  16. GrandpawB

    GrandpawB Veteran
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  17. mr.eman

    mr.eman New
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    The molded cable in the link I gave you already has the resistor built in. However it has a 3.5K resistor and is set up for a 3.5A motor. I did some more research today to find out why you were told to use a 2.4K resistor. Everyone I've talked to has used 3.5A motors to get the max out of the G540. They told me if using smaller motors, you need smaller resistors based on 1.0K to 1A motor size which is the reason I wasn't sure why you were told to use a smaller size. Based on that, I'm assuming you're using 2.4A motors in your build. With that in mind here's a couple of more links I think will help. The first is just a photo of the correct wiring showing the location of the resistor should you decide to try and wire it in yourself. The second is an actual db9 core you can purchase which has an adjustable resistor already soldered in. You simply wire your motor to the correct pins, put an ohmmeter on pins 1 and 5 and adjust till you have 2.4K resistance. Place in a plastic db9 backshell and you're ready to go.

    http://gvcc.home.bresnan.net/CMILL44.JPG

    http://www.soigeneris.com/ez_g540___set_of_4-details.aspx
     
    #17 mr.eman, Jul 21, 2014
    Last edited: Jul 21, 2014
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  18. GrandpawB

    GrandpawB Veteran
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    Thank you. Very helpful. Was going to order from Soigeneris.com but the shipping is almost as much as the set of 4 connectors.
     
  19. killabigfats

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    Just wanted to say thanks for your participation on this topic. It helped me clear up and verify some things before i wired in my motors.
     

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