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IndustryArena Forum > CNC Electronics > Gecko Drives > G540 Schematic seems wrong
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  1. #1
    Join Date
    Mar 2012
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    13

    G540 Schematic seems wrong

    Hi all,

    I don't know if this is a warning or a request for help .

    I am trying to track down a input problem where I have 3v on all my inputs (disconnected) (no load).

    Looking for the 12v regulator on the circuit diagram seem hopeless as well as i cant find the component .

    The isolation chips are drawn in an obscure way and not many component values are whats on the chips .

    There is aground drawn on the schematic which seem to be invented by the artist.

    all these things are important when chasing the missing 12v source.

    Has any body tackled this or is there abetter schematic as far as fault tracing goes?

    I contacted the makers last week and no reply ...so it seems my Chinese controller will have to come out of the cobwebs to any more cutting.

    Please help if you can ..I am experienced with fault /repair and can usually work with no diagram but this has me floored.


    PS This has been a working machine until l I hooked up a motion controller (which has the same ins and outs )

  2. #2
    Join Date
    Nov 2012
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    1267

    Re: G540 Schematic seems wrong

    The schematics I just googled has IRF540, 2N2222 and 78L12 in the 12V circuit. Is that the one?


  3. #3
    Join Date
    Mar 2012
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    13

    Re: G540 Schematic seems wrong

    Yes, That's it....try and find it on the PCB,

    I am unable to ....perhaps Im getting old .

  4. #4
    Join Date
    Nov 2012
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    1267

    Re: G540 Schematic seems wrong

    Those are rather large components, they should be hard to miss. Any photos of the board?

    P. S. Your picture attachments may not be visible to others since you only have 11 posts. To share a picture, you would have to use an external hosting site such as imgbb.com.

  5. #5
    Join Date
    Apr 2004
    Posts
    134

    Re: G540 Schematic seems wrong

    Schematic drawing style is "unusual". The unregulated power source comes from the right side. The IR540N functions as a pre-regulator to feed a safe voltage into the 78L12. The IRF540N will be a relatively large thru hole package if the part number shown is correct. If not listed correctly, the next most likely package is a large surface mount one. The 78L12 could be an 8 pin SOIC or a three leg small thru hole transistor style package. The PN2222A really does have only two connections and is being used as a zener to provide the bias voltage to the gate of the IRF540N so that its output is only a few volts above the 12 volt output of the 78L12 regulator.

  6. #6
    Join Date
    Mar 2012
    Posts
    13

    Re: G540 Schematic seems wrong

    Quote Originally Posted by morestuff View Post
    Schematic drawing style is "unusual". The unregulated power source comes from the right side. The IR540N functions as a pre-regulator to feed a safe voltage into the 78L12. The IRF540N will be a relatively large thru hole package if the part number shown is correct. If not listed correctly, the next most likely package is a large surface mount one. The 78L12 could be an 8 pin SOIC or a three leg small thru hole transistor style package. The PN2222A really does have only two connections and is being used as a zener to provide the bias voltage to the gate of the IRF540N so that its output is only a few volts above the 12 volt output of the 78L12 regulator.
    Thanks for the help ,
    I have reached that point myself but the actual component location is still eluding me as it is possible that the 12 has been disabled by something.


    Things will be more clear when my new parallel port card arrives so that I can go back to "standard" and check if something is amiss with the motion controller.

    I like many others a re finding that the pp xp machines are dying due to pcb deterioration and caps drying.

    I had 3 die in one week .

    Win7 32 Is where I'm heading right now .

    I promise to conclude this thread with what it was when I know .

  7. #7
    Join Date
    Mar 2012
    Posts
    13

    Re: G540 Schematic seems wrong

    Update!

    Yes the schematic is wrong as compared to the wiring diagram .

    Many component values on the schematic are in correct .

    I have a spare unit and i was able to repair some of the tiny tracks and components around the power and fault led driver circuits.


    In the process I noted that the out put pins on the schematic are different from the ones on the hookup diagram.

    This will only be a problem for you if you are trying to repair the pcb or do something different with the outputs.

    For example pin 16 we know is the charge pump , yet is is listed on the schematic as an output .

    My guess is that they don't want any duplication by other interests.
    It was a shame that they did not respond to my request for an accurate diagram but it is understandable.

    It is a good thing that there are other options that work using breakout boards and tb6600 drivers that work ALMOST as well .for a much lower price .

    Im still happy with the gecko units I have as at the time in 2014 there were many really bad chinese units that are now almost sold out .

    The weakness in my units was the ultra fine pcb tracks which corroded away over time due to exposure to condensation in a large open workshop over the years.

    I hope that the tracks may be made bigger in the future as there is really no need to make the units so small .

    If you have g540 in an open air workshop you can expect the effect of small tracks and condensation to end these units lives prematurely.

    I do take responsibility for not installing doors on my large workshop.

  8. #8
    Join Date
    Apr 2004
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    5728

    Re: G540 Schematic seems wrong

    I've been trying to get my G540 to put out the analog 0-10v output to modulate a VFD, but it doesn't seem to be working. Everything is hooked up and the motors move if jogged from the keyboard, but when I command the spindle to go on with a M03 S10000 command, nothing happens. I don't detect voltage from the pins on the terminal; is there something else that needs to be done or set up before that function is triggered?
    Andrew Werby
    Website

  9. #9
    Join Date
    Apr 2004
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    134

    Re: G540 Schematic seems wrong

    The G540 requires a 10V reference FROM the VFD to be connected to pin 9 of the G540 terminal block. It does not produce a voltage by itself, it returns a voltage on pin 8 that is a regulated fraction of the 10V on pin 9 from the VFD.

  10. #10
    Join Date
    Apr 2004
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    5728

    Re: G540 Schematic seems wrong

    Thanks for the reply! I have 3 wires connecting the VFD and the G540 but I'll check to see if they're correct. Does the M03 command trigger the 10v signal from the VFD, or is it supposed to be on all the time, and waiting until the M03 command triggers the G540 to send something back?
    Andrew Werby
    Website

  11. #11
    Join Date
    Apr 2004
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    134

    Re: G540 Schematic seems wrong

    The 10V from the VFD should always be there.

    When the speed is commanded to zero or an M5 is executed, the PWM signal will go away and the output voltage from the G540 should be close to zero. Actual start and stop is normally assured by using a relay configured for the Run signal from Mach. The contacts of the relay would be wired to the Forward Run input on the VFD. Inputs on the VFD are typically configured by editing the parameters in the VFD to tell it where to look for the Run signal and Speed setting input. Defaults are typically buttons on the VFD front panel and you must edit parameters to accept signals in the VFD terminals for external controls.

    When an M3 is executed with an S word with, lets say 50% speed, then the relay should be activated and the output voltage should be about 5 volts.

  12. #12
    Join Date
    Apr 2004
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    5728

    Re: G540 Schematic seems wrong

    After reading that, I did confirm the presence of the 10v signal at the VFD. Should I set the spindle up in Mach3 as a PWM device? By default, it seems to be step and direction. I think it must be the relay I'm missing, unless there's one built into either the G540 or the VFD. I've got the parameters of the VFD set for automatic rather than manual triggering, but I'm not sure how the relay is supposed to work. Do I need to build a separate box with a solid-state relay in it, and wire it in between the G540 and the VFD? Or do I (somehow) find the right pins coming out of the parallel port and use them to switch the relay before it gets to the G540?
    Andrew Werby
    Website

  13. #13
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    Apr 2004
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    134

    Re: G540 Schematic seems wrong

    Yes, you should be using PWM mode for the output from Mach. You must also set the max spindle RPM to the correct value so that Mach knows how to compute the %PWM.

    The typical configuration is to use a DC relay whose coil voltage matches the motor supply voltage and drive it from the terminal 5 or terminal 6 open collector output on the G540 as shown on page 8 of the G540 manual. Using a relay that has a coil rated for the same voltage as the motor supply voltage avoids needing a separate power supply for the relay. The contacts of the relay connect to the Forward run input on the VFD.

    For VFDs with isolated control inputs you may be able to connect the Forward run input of the VFD directly to the G540 output, but you should consult Geckodrive before trying this.

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