Electronics > Microcontrollers

ARDUINO: EMF problems

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Brexei:
Hello everyone,

In the past year i have managed to build my own CNC, using an Arduino mega + ramps 1.6 shield etc.  It works fine, for the moment, but i have a problem with the electronics:

When i power on the vacuum  cleaner (it is an ac motor, with a triac for controlling speed) the Arduino sometimes looses the connection via usb and i have to reset it to fix the problem. Of course this ruins my projects... I should mention that it works perfectly fine when the ac motor is off.

I installed an APC surge protector plug on the Arduino psu and this improved things a lot, but still sometimes i get disconnections when i power on the vacuum or increase speed of the motor.
I would like to ask your opinions about what to do. How can i block the back emf from the motor? Should i install a plug on the motor cable, so it blocks the emf from getting to the other components? Unfortunately i only have one wall power plug in the room where the cnc is.

And a second question:

For powering up the Arduino i am now using a 12 volt led power supply (it is what i had in stock. There is no room for a pc power supply), but i am planning to upgrade to a 19 volt laptop psu, in order to give the stepper drivers more voltage, so they can run faster. I plan to remove diode D1 from the ramps board and power the arduino mega through usb. So, is the laptop psu stable enough for the ramps? (Toshiba brand). Should i put a big >25 volt electrolytic at the input of ramps, for extra filtering and power reserve?

Thanks a lot.

BrokenYugo:
Possible an interference suppression capacitor has failed/aged out in the vacuum, probable if it has a lot of hours on it.

Brexei:
Thanks, i will try to add some ferrites and see if it solves the problem.

However, the back emf from the vacuum cleaner motor also causes the cnc spindle motor controller (inverter) to report an error sometimes! So, the vacuum motor emf also harms other components, apart from the Arduino.

Is there a way to block the back emf going back to the plug?

Also, do you think that the problem is emf travelling through the air that affects electronics, or emf coming back to the power cables?  Difficult to find out...

Most probably, there is no interference suppression capacitor in the vacuum cleaner... It was a carpet vacuum cleaner, VERY loud, so i added a triac controller to control the power (and noise). Can i add a suppression capacitor before the triac board, to stop the emf from returning to the plug? If yes, please suggest one.

Would a plug filter do the same if i pluged the vacuum on one? I mean, will it back-filter the noise to the plug?

Roehrenonkel:
Hi Brexei,
 
is the Arduino & Ramps-PCB in a shielded box?
How do you drive the triac? Via Optocoupler?

Post a picture and wireing-diagram.

Additional cap for the steppers is always good.
Try feeding vacuum- and spindle-motors through separate line-filters.
You may also try shielded cables - ground one end only.

Good luck

janoc:
These are common problems due to EMI (not EMF) from the various motors and supplies.

Common causes and solutions:

- Limit switches wiring picking up noise and causing resets/malfunctions - make sure the wires are twisted/shielded, you can put also a ferrite on the cables.

- Stepper motor wiring emitting EMI - make sure the wiring is twisted/shielded, you can put also a ferrite on the cables.

- Spindle or other motors using commutators (i.e. universal or permanent magnet DC motors) emit EMI because of lack of noise suppression/filters - add them.

- Conducted noise trough the power supply rails - add filters, in the worst case you may want to use optoisolated control signals.

- Make sure your electronics is in a metal box (shielding)

- Make sure everything on the machine is properly earthed - not only for safety but also to provide good return path for the EMI, otherwise it will go through your electronics instead.

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