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Thread: Back EMF smoke in controll panel

  1. #37
    Gold Member TomKerekes's Avatar
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    Default Re: Back EMF smoke in controll panel

    Hi Joe,

    Thanks for clear descriptions.

    I made the energy dump circuit boards with terminals blocks to wire the LED so it was easy to do your test.

    With an LED connected directly to the return energy dump circuit board and the gecko drive powered on the LED was off not lit. I had disconnected the wires to the LED that were 44" long. I touched one of the disconnected LED wires to the ground connection of the LED on the return energy dump circuit board, it did nothing. As a second test I touched one of the disconnected LED wires to the positive terminal of the LED mounted on the return energy circuit board and the LED on the return energy dump circuit board glowed, I did it numerous times, every time I touched the wire to the positive the LED would glow. Your test proved that the wire is acting like an antenna.
    Hmmm that pretty much blows my theory. I'm surprised a 44inch piece of wire can pick up (or radiate) enough energy to light an LED. I'm curious and certainly open to suggestions what is going on. I suppose shielded cables to the LED would solve the problem. Are the LED wires bundled together or close to other things like Stepper Motor wiring or other Gecko Drivers Supply wiring?

    With the spinning cubes, you double the size did you double the weight?
    The 2 inch cube is more than double the weight than the 1 inch cube. Hint: the answer is surprisingly big

    Regards

    TK
    http://dynomotion.com


  2. #38
    Registered john-100's Avatar
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    Default Re: Back EMF smoke in controll panel

    having seen the results of tantalum capacitors setting fire to the PCB in an ASTON 4 character generator ( used a TV station's graphics department )

    I would use solid aluminium electrolytic capacitors instead of tantalum capacitors

    Is the Gecko drivers power supply negative connected to mains supply earth / ground ??
    assuming you are using a metal enclosure do you have a braided strap connecting the door to the enclosure ??

    John



  3. #39
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    Default Re: Back EMF smoke in controll panel

    Quote Originally Posted by TomKerekes View Post
    Hi Joe,

    Thanks for clear descriptions.

    Hmmm that pretty much blows my theory. I'm surprised a 44inch piece of wire can pick up (or radiate) enough energy to light an LED. I'm curious and certainly open to suggestions what is going on. I suppose shielded cables to the LED would solve the problem. Are the LED wires bundled together or close to other things like Stepper Motor wiring or other Gecko Drivers Supply wiring?

    The 2 inch cube is more than double the weight than the 1 inch cube. Hint: the answer is surprisingly big

    Regards
    I did some more testing, using the old method of smell and touch. I found one of the 4 gecko drives was running hot, I had a gecko G201(same as a G210 but with out the half step option board) and swapped it with the gecko that was running hot. Now instead of 4 LEDs lit connected with the wire mounted on the cabinet door I had one LED lit. I moved the gecko drive that had the LED lit to a different axis and the problem moved with it. I think I have 2 bad gecko drives that are feeding noise back into the system. One bad one that is running hot and one bad one that is sending noise into the system.

    I am sending the two drives back to gecko for testing and repair.

    I have a couple of thoughts about the return energy dump circuit. If I am correct and the bad drive that is not getting hot is sending noise into the system its a good thing that the LED was glowing telling me the drive is corrupting my system with noise, good feedback once you know what the glowing LED means. Also I know from failures that if the LED stays on the return energy dump circuit has failed. And if all is well the LED will flash on during quick deceleration letting you know the return energy is being shunted to ground.

    I find it strange that when the LED was mounted to the circuit board and not on long wire leads that it appeared there was no problem. I am confidant that the two drives are bad one I could hardly touch it was so hot.

    Now what do I do with the capacitors I ordered, do I still install them as a precautionary step. I now think that there was a lot of noise on those wires so would adding the capacitors give me a little protection or take away the ability to know if the drives are back feeding noise into the system by filtering the noise that was making the LEDs glow?

    All in all I think this is a good circuit for knowing a little more on what is going on in the system. Just over thinking the whole thing.

    Once I get a fourth drive that is either fixed or replaced I'll post results.

    Tom let me know your thoughts if I'm back on the right track, and yes I did have a ground wire from the cabinet to the door and the negative of the power supply is case grounded.

    Joe

    Last edited by mirocha; 09-05-2017 at 09:50 PM.


  4. #40
    Gold Member TomKerekes's Avatar
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    Default Re: Back EMF smoke in controll panel

    Hi Joe,

    I think you are on the right track.

    The Supply Bypass Caps I recommended may not be necessary. Sorry if I sent you on a wild goose chase. I tend to always add them if I can't convince myself they are not absolutely unnecessary.

    What gauge wire is your supply wiring btw?

    Regards

    TK
    http://dynomotion.com


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    Quote Originally Posted by TomKerekes View Post
    Hi Joe,

    I think you are on the right track.

    The Supply Bypass Caps I recommended may not be necessary. Sorry if I sent you on a wild goose chase. I tend to always add them if I can't convince myself they are not absolutely unnecessary.

    What gauge wire is your supply wiring btw?

    Regards
    The power supply is fed with #12 from the power supply 70 vd c output each drive is fed separately with #16.

    I will be changing the stepper motors rated at 5.5 amps there will be 4 stepper motors so I am a little concerned the 800 watt power supply may be a little under sized?

    Gecko states if the drive is over 12" from supply you must add a 470uf capacitor on the power input to the drive with leads of no more than 1" . A couple of my drives are over 12" so I am going to add them to all the drives.

    I will be getting the capacitors i ordered .1uf, 2.2uf and 4.7uf ceramic capacitors so I may as well add them to the circuit, since I think any noise is coming from the drives i plan on putting them on the output of the return energy dump circuit feeding each drive.

    I'm thinking when I originally fried the return energy dump circuits I damaged the gecko drives so the wild goose chase is on me.

    Last edited by mirocha; 09-06-2017 at 08:37 PM.


  6. #42
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    Quote Originally Posted by mirocha View Post
    The power supply is fed with #12 from the power supply 70 vd c output each drive is fed separately with #16.

    I will be changing the stepper motors rated at 5.5 amps there will be 4 stepper motors so I am a little concerned the 800 watt power supply may be a little under sized?

    Gecko states if the drive is over 12" from supply you must add a 470uf capacitor on the power input to the drive with leads of no more than 1" . A couple of my drives are over 12" so I am going to add them to all the drives.

    I will be getting the capacitors i ordered .1uf, 2.2uf and 4.7uf ceramic capacitors so I may as well add them to the circuit, since I think any noise is coming from the drives i plan on putting them on the output of the return energy dump circuit feeding each drive.

    I'm thinking when I originally fried the return energy dump circuits I damaged the gecko drives so the wild goose chase is on me.
    I got a used Gecko G210 on ebay for $49 and installed it. All 4 return energy dump circuit LEDs on the control panel door are now working,nice!

    I still plan on adding capacitors on the power input to the Gecko drives just as a precaution to minimize noise from the drives. I have .1uf, 2.2uf and 4.7uf ceramic capacitors.


    What would be a good choice to use, should I add all three, would that cover a wide range of noise or is just 1 a better choice?

    Joe



  7. #43
    Gold Member TomKerekes's Avatar
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    Default Re: Back EMF smoke in controll panel

    Hi Joe,

    That's good news.

    I still plan on adding capacitors on the power input to the Gecko drives just as a precaution to minimize noise from the drives. I have .1uf, 2.2uf and 4.7uf ceramic capacitors.

    What would be a good choice to use, should I add all three, would that cover a wide range of noise or is just 1 a better choice?
    Is that in addition to the 470uF that Gecko recommends?

    I'm not sure which Capacitors would be best. It would depend on the frequency of the noise. The 2.2uF and 4.7uF are similar enough that adding both probably wouldn't make sense. I would think the drive would already have some caps on the input. With bypass capacitors I tend to go for the more the better at the risk of overkill.

    Regards

    TK
    http://dynomotion.com


  8. #44
    Registered john-100's Avatar
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    Default Re: Back EMF smoke in controll panel

    good to see you have it all working

    I guess it a bit too soon to have any feed back from Gecko about whats wrong with your faulty drive

    John



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    Quote Originally Posted by john-100 View Post
    good to see you have it all working

    I guess it a bit too soon to have any feed back from Gecko about whats wrong with your faulty drive

    John
    I'll also be adding the 470uf capacitor Gecko recomends.

    When Gecko let's me know what they found I'll post what they find.

    Thanks Joe



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    Default Re: Back EMF smoke in controll panel

    470 uF for energy, 0.1 uF for RF noise. Pretty 'standard'.

    Cheers
    Roger



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    Quote Originally Posted by RCaffin View Post
    470 uF for energy, 0.1 uF for RF noise. Pretty 'standard'.

    Cheers
    Roger
    Install the 470uf, .1uf, 2.2uf, and 4.7uf capacitors tested circuit numerous times works every time the LED s flash.

    I have been bench testing the stepper motors. After talking to Gecko and going over what motors I was using they told me the stepper motors I was using would not be linear that the impedance was high. The motors were 1600 oz/in 22mH.

    So I bought 1260 oz/in 5.5mH stepper motors.

    Now that I have the return energy dump circuit with the LEDs working I changed out the motors.

    Testing the new motors using the jog button on kmotion the return energy circuit LEDs did not flash,telling me that there was no return energy.

    I added a user button in kmotion and tried raising the stepper motor rpm to see if I could get return energy from the new stepper motors. Entering a "jog(2-50000) did not light the LED. Entering a (jog-55000) gave me a dim flash on the LED. Entering a (jog-60000) gave me full brightness LED flash.

    So I learned a little more, the higher the stepper motor impedance the greater the return energy and according to Gecko the lower the stepper motor impedance the better the linearity.

    Does this make sense?

    Thanks Joe



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    Default Re: Back EMF smoke in controll panel

    Makes total sense.
    Gecko are very knowledgable.

    Cheers
    Roger



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