Strange effect caused by my lathe’s new BLDC spindle motor. Maybe EMI?

[Rimbaldo]

Hi!
I replaced the original brushed 150W motor of my mini lathe with a BLDC 750W one. I managed to replace all electronics inside the lathe so speed controller works normally, reverse, and even I managed to make it all work in CNC using MACH3. M3, M4 and M5 works normally and speed control also, with an encoder.

I’m using MACH 3, a Gecko G540 and an Ethernet Smoothstepper. The Gecko, the Smoothstepper, the brushless motor controller and the spindle encoder have their grounds shared. I just didn’t share the ground with the PC, as it’s not using anymore the parallel port. Although I don’t know if the smoothstepper network plug shares it’s ground with the PC.


When I’m executing a GCODE program, everything works normally from start to end.

But when I want to turn something manually in Mach3, if I turn on the motor manually, and I use the keyboard’s arrows to jog, the movement of any axis is “choppy”, “jerky”. The axis doesn’t move smoothly. If I turn the motor off, then the both axis can be jogged normally with no jerky movements.

And another strange situation is: if I’m jogging using the arrow keys, with the motor on, and I touch the lathe’s bed, then the axis stop moving (I’m keeping any arrow key pressed - so still jogging). As long as I keep touching the bed, I can’t jog. If I take my finger from the bed, then i can jog again.

It didn’t happen when I used the old motor and no smoothstepper.

Any ideas on how to fix these effects? Could the motor create an EMI interference only when doing manual stuff? All CNC GCODE works normally…

Regards, Rodrigo

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[CitizenOfDreams]

Could the motor create an EMI interference only when doing manual stuff? All CNC GCODE works normally…

The EMI could be affecting the keyboard itself. Try typing something in the text editor while the motor is running.

[Rimbaldo]

The EMI could be affecting the keyboard itself. Try typing something in the text editor while the motor is running.

Indeed! All the effects I described happen when I open the notepad and keep some keys pressed, with the motor turned on. The effects are more or less obvious depending on the speed set. Even If I touch the lathe's bed with my finger, than no character get's drawn on the notepad's screen, until I release my finger!

So...

Is there a solution for it???

Regards, Rodrigo

[CitizenOfDreams]

So...

Is there a solution for it???

I would start with bonding all the grounds together - the PC, the lathe bed, the Gecko, the Smoothstepper, the spindle driver.

Next step, try a different USB socket. A USB hub. A different keyboard. A wireless keyboard.

[Rimbaldo]

I would start with bonding all the grounds together - the PC, the lathe bed, the Gecko, the Smoothstepper, the spindle driver.

Next step, try a different USB socket. A USB hub. A different keyboard. A wireless keyboard.

Ok. Grounded PC (wasn't grounded) to lathe bed (wasn't grounded) to controllers. Grounded everything.

Seems to have improved a bit, but still the same effects happen. Touching the bed with my finger seems to make it difficult to the letters appear in notepad. Changed USB ports have shown no improvement. Added a USB HUB also to no effect.

Used two ferrite cores one on each end of the usb keyboard cable, also to no good.

Tried another keyboard (older one) and it behaved much better, but still when I touch the lathe bed, it stops sending the letters to the screen, or it slows it down a lot..

Still didn't try a wireless keyboard, but for this use, a wired one is a better option for safety...

The farther the keyboard is from the lathe (and it's motor), the better it responds, but in my case, it's in a drawer right below the bench where the lathe stands..

I could try to change the usb cable from the keyboard to a shielded cable.. orr a cat 6 cable... don't know if it would work....

Running out of options... is there a way to isolate, filter the EMI from the BLDC motor? Is there a filter for it?

Thanks for the help!

Rodrigo

[mactec54]

Ok. Grounded PC (wasn't grounded) to lathe bed (wasn't grounded) to controllers. Grounded everything.

Seems to have improved a bit, but still the same effects happen. Touching the bed with my finger seems to make it difficult to the letters appear in notepad. Changed USB ports have shown no improvement. Added a USB HUB also to no effect.

Used two ferrite cores one on each end of the usb keyboard cable, also to no good.

Tried another keyboard (older one) and it behaved much better, but still when I touch the lathe bed, it stops sending the letters to the screen, or it slows it down a lot..

Still didn't try a wireless keyboard, but for this use, a wired one is a better option for safety...

The farther the keyboard is from the lathe (and it's motor), the better it responds, but in my case, it's in a drawer right below the bench where the lathe stands..

I could try to change the usb cable from the keyboard to a shielded cable.. orr a cat 6 cable... don't know if it would work....

Running out of options... is there a way to isolate, filter the EMI from the BLDC motor? Is there a filter for it?

Thanks for the help!

Rodrigo

Is your whole machine using the same power source meaning ( 1 ) Power connection for the whole machine, if not then it is likely that you have created a Ground loop.

Your spindle brushless or does it use brushes.

[Rimbaldo]

I have a 48V Switching power supply that powers the Gecko G540, the ESS smoothStepper, and the encoder (through some DC-DC buck converters, to get 5V to the ESS and the encoder and some leds on the lathe. But these DC-DC converters are wired in the 48V supply, with common grounds.

The motor is brushless and comes with it's own controller/supply (220 AC input).

I have connected the grounds (the DC grounds) between the Brushless controller to the 48V supply that powers everything else. And of course the PC has it's own supply.

Testing the Xbox wired controller as a pendant works normally, with no problems. The only thing that looks wrong is the keyboard...

[mactec54]

I have a 48V Switching power supply that powers the Gecko G540, the ESS smoothStepper, and the encoder (through some DC-DC buck converters, to get 5V to the ESS and the encoder and some leds on the lathe. But these DC-DC converters are wired in the 48V supply, with common grounds.

The motor is brushless and comes with it's own controller/supply (220 AC input).

I have connected the grounds (the DC grounds) between the Brushless controller to the 48V supply that powers everything else. And of course the PC has it's own supply.

Testing the Xbox wired controller as a pendant works normally, with no problems. The only thing that looks wrong is the keyboard...

Need to see some photos of the wiring.