How to stop Frying Arduinos using GRBL

All,

I have long had an interest in building a serious CNC mill. I have built breadboard layouts using Arduino Unos and 2M542 Stepper motor controllers running reasonably small steppers at 12V. I have had successful tests running the stepper motor using GRBL and source rabbit. I also built a small CNC Pen drawing machine and was also able to get it to work with GRBL and source rabbit. These all use a 12V power supply

I just spent a couple of years building a CNC Mill, and a couple of months building the electronics wired carefully into a case. This is designed for seriously strong Stepper motors. I used a 24-30V power supply and a larger DM542 stepper driver. I first connected a tiny Casun 428shd001-24B stepper 4 wires (a-, a+, B-,B+) to the X axis driver.and fired up source rabbit. I was able to get it to vibrate when bumping it forward, and nothing when I bumped it backwards. I then connected a somewhat larger stepper (probably still not a perfect voltage match) and as soon as I tried to bump it forward using source rabbit the main IC on the Arduino popped, and smoked.

I checked the wiring, wired in a new Arduino with GRBL and connected the Stepper motor to the Y driver. As soon as I bumped the Y axis in Source Rabbit, the new Arduino popped and smoked the main IC. Now I have destroyed 2 Arduino Uno boards.

My questions.

  1. is there any electrical connection between the stepper motor side of of the stepper driver circuit (gnd, +V, A+, A-, B+ B-) and the arduino side (ena -, ena+, dir-, dir+, pls- pls+). Do I have any concerns that on the stepper side everything is about 30V and on the Arduino side it should be 5V) ?

  2. Other than frying Arduinos is there an organized method for checking the circuit to see where the problem is?

  3. what is the recommended steps for finding the problem?

Thank you in advance

George

Without an accurate, detailed schematic, help is impossible. Read this for a start:
Help with posting
And:
More about creating a schematic of your project including how to upload an image.

most likely you have 30V on your arduinos 5V. check your wiring with a dead unit and measure.

Hi,
We need a schematic, in particular how you have your power supplies and stepper driver and motor connected.

Thanks.. Tom.... :slight_smile:

Loose stepping motor wiring, especially on logic breadboards, is a quick and sure fire way to destroy parts.

GRBL probably has nothing to do with it.

I then connected a somewhat larger stepper (probably still not a perfect voltage match) and as soon as I tried to bump it forward using source rabbit the main IC on the Arduino popped, and smoked.

Steppers are current driven, not voltage driven, so the only issue would be if the new stepper was
high-impedance (most these days are not, only a ohm or so). Even so it would just not perform well,
since the driver limits the current.

I suspect you blew the stepper driver (through hot-plugging the motor winding connections (never do this!).
Disconnecting a stepper when the driver is powered up causes high energy sparking and this puts high voltage
spikes on the pin and typically immediately destroys the driver chip.

When the stepper driver blew it likely shorted the high voltage supply to the Arduino (when semiconductors
fry they often become short circuits internally).

You can help protect the Arduino by adding protection on the Arduino logic outputs (standard
circuit is resistor and 2 shottky diodes to the rails). Then any current is limited by the resistor
and routed to the 5V/GND rails through the diodes.