CNC Stepper Drivers

I recently changed the stepper drivers on the MPCNC engraver/router/plotter. Previously I was using a Gecko G540 but I want to save this for another project.

Three TB6600 stepper drivers were purchased and a new power supply was wired up.An Arduino Uno is breaking out the signal coming over USB from EstlCAM. A 3D printed holder supports the Arduino, a daughter board plugs in the top and the inputs/outputs are taken to some three custom 3D printed terminal blocks.

These use M4 hardware to fasten crimped lugs.

The board was laid out, assembled, wired then tested…
and nothing happened.

A quick test with the oscilloscope found that the Arduino was sending the correct signals to the drivers. A quick sketch in Arduino gave a modified signal to the drivers and was able to drive the motors. This proved that the drivers weren’t faulty, although reducing the duty cycle and increasing the frequency, similar to the signal that EstlCAM was sending (short high pulse), started to produce missed steps and a stalled motor.

The drivers were wired up with a common +5VDC to the opto-coupler inputs, as per the screen-print on the driver, but in talking to a colleague we theorised that the transistor was becoming saturated and not able to trigger with the short duty. Looking at the G540, which had worked using a common ground, the wiring was modified and soon the controls were working successfully again.

 

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