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  1. #1
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    Red "fault" light is lighting on my G540.

    It has worked until today when I coupled a rotary drive stepper to it. I have tried to remove the A-axis wire from the drive, but it´s still the same. I can reset Mach3, but when I push the buttons, only the numbers on the screen are running but not the steppers.

    What may be wrong?

  2. #2
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    Re: Red "fault" light is lighting on my G540.

    when the RED LED is on all 4 G250 stepper drivers are disabled
    ( the signal that turns the GREEN LED on also enables the stepper drivers )

    its possible a faulty connection to the A Axis has damaged the A Axis driver and is triggering the E-stop / over current circuit

    I would disconnect all motors and check you can clear the fault ( just in-case its not the A axis that's the problem)
    if you then get the green light , connect one motor at a time until you trigger fault so you know what is the problem

    if the RED LED is on with no motors connected
    contact Geckodrive.com
    they will probably talk you through the disassembly of the G540 and removal of the four G250
    drivers to find the faulty one that need repair / replacement
    that will enable you to use the G540 as a 3 axis driver while your waiting for the fourth G250

    ( the G540's case is just clipped together the motherboard with all of the external connectors is plugged onto the four G250 boards that are screwed to the lower half of the case )

    Click image for larger version. 

Name:	g540coverless.jpg 
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    picture taken from geckodrive web site

    alternatively they will give you instructions for you to return the G540 for them to test

    John

  3. #3
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    Re: Red "fault" light is lighting on my G540.

    I removed all the wires, but the red light was there yet. I have also removed the paralell port cable, but still the same. Can it be that the power supply is damaged and doesn´t deliver enough current?

  4. #4
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    Re: Red "fault" light is lighting on my G540.

    with the parallel printer cable disconnected you will need to switch the charge pump to off ( switch to the right of the printed logo on the G540)

    what powersupply are you using ?
    with no motors connected what is the voltage you measure at the power supply terminals ?

    John

  5. #5
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    Re: Red "fault" light is lighting on my G540.

    The charge pump has always been off. The voltage is 44V and when I took a quick on/off measurement of the current, it meassured 12A, so it should be more than enough. If I open the black box, can I then find out more? Will it be possible to remove some of the drives from the others in order to find the reason?

  6. #6
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    Re: Red "fault" light is lighting on my G540.

    44V is OK (it is within the 18 to 50V limits )
    with no motors connected you should not see 12A going into the G540 even taking into account current waveform will cause an inexpensive multimeters reading to be inaccurate

    with the cover off you will be able to unplug the main board from the four drivers and test the board on its own

    you will see each G250 driver is fastened to the base with 2 screws -
    note the G250 FET transistors and voltage regulator is only insulated by the black anodised coating, be carefull you don't damage the coating

    assuming the main board tested OK
    remove 3 drivers plug the main board onto the remaining driver
    if that works add another driver and retest
    repeat until you find the faulty driver (or all 4 axis are working)

    john

  7. #7
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    Re: Red "fault" light is lighting on my G540.

    I didn´t measure the input current to the drives, but the short cut current of the power supply. I have now removed the drive for the A-axis and the green light came back, so I think something must have been wrong with the rotary stepper motor or maybe the wiring. Are there any ways to troubleshoot that case?

  8. #8
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    Re: Red "fault" light is lighting on my G540.

    have you have used the rotary axis stepper motor before ?

    I expect either the cable has been crushed so 2 wires shorted
    or you have a wire break that could be intermittent with just the insulation holding the broken ends of the wire together

    with the power on ,
    the back EMF generated when a motor coil is disconnected is high enough to destroy the stepper driver H bridge transistors

    while you can have a wire break any where
    the odds are greater where the wires exits the 9 way plug or enter the motor

    with a basic multimeter its not always easy to see the increased resistance of a dry joint
    when the resistance of the cable and motor winding is a few ohms and can be comparable to the contact resistance of the meter probes

    several times at work
    I have had inconclusive resistance measurements while checking multicore camera or audio cables

    cutting the last inch or two ( 25 to 50mm) off each end and soldering the connectors back on solved the problem

    John

  9. #9
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    Re: Red "fault" light is lighting on my G540.

    I used this motor several years ago, but with another driver and I have resoldered the wire to the gecko plug after that, so maybe I have done something wrong there. The wire has also a middle plug connection near the motor which has been disconnected these years, so maybe some of the pins in this plug have been covered with an oxidation.

    Can I test the motor and the wiring with a stable dc current in any ways?

  10. #10
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    Re: Red "fault" light is lighting on my G540.

    do you have the data for your motor ?

    do you have a bench power supply with a variable voltage output and current limiting ?

    stepper motors will not run when connected to a DC supply

    what you can do is either apply the DC voltage as on the data sheet or label to one of the motor coils in turn and measure the current that flows
    or set the power supply current limit to the current stated in the data and measure the voltage across the coil

    for example if the motor data gave the coil resistance as 2 ohms the current as 3A and voltage as 6V

    connecting a motor coil to 6V DC will result in a current of 6/2 = 3A


    if the power supply is set to provide a constant current of 2A the volt drop across the motor coil will be 2 x 3 = 6V



    using a spare 9 way socket to make it easy to connect to the 9 pin plug on the cable
    you can measure the voltage across the motor coils and then at the 9 way D-type plug

    the volt drop across each coil and each pair of wires should be the same

    in addition you will need to check for short circuits between pins 7 & 8 (coil B- and A+)
    and pins 1 to 5 and pins 6 to 9

    did you fit heat shrink sleeving in the wires to insulate the terminals ?

    Attachment 412060

    if you have used a single resistor to set the motor current its easier to insulate the terminals than trying to solder 2 resistors in parallel

    one possible problem you can have when you solder stranded wires to the bucket terminals on the 9 pin plug
    solder can wick up inside the wire and when its flexed the wires break where the solder stops


    John

  11. #11
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    Re: Red "fault" light is lighting on my G540.

    Motor label: KL23H251-24-8B When I tested the wires there was a difference between the coils. I could light a led with one of the coils but not with the other, and I have tested the wires close to the motor, so I believe it must be a damage inside the motor. There was also resistance difference.

    I have another new larger motor: 57BYGH78-401B 1.8 degr. 2.8A 1.8 N.m. Do you think I can use that with the Gecko driver? And do you know where I can buy a new driver for best price?

    ----------------------------
    Edit:
    I used the 8 wire motor in serial connection with the red/yellow and black/orange wires shorted and after cutting of these wires, the motor runs more smoothly and I got a light on the led at that coil that didn´t light before. When I short the red/yellow wires, the same problem occurs, so I found that the motor is wired with wrong colours compared to the specification at http://www.kelinginc.net/KL23H51-24-8B.pdf

    I have found that the red/yellow and green/blue are connected to each of the coils and my problem is now to find out which of them are a+ and a- ...

  12. #12
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    Re: Red "fault" light is lighting on my G540.

    if this is how the motor is connected

    Attachment 412082

    the motor should work

    unless your following instructions to make one of a number of identical machines

    swapping A+ and A- or B+ and B- will reverse the direction of the motor
    easily corrected in software if your using Mach 3 or similar to avoid resoldering the wires

    just make sure you don't mix the A and B wires

    John

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