Pulseboard and motion controller from PCBway

A project log for G-EDM

Sinker EDM with drill chuck and multi-toolhead for cutting and drilling metal

gedm-devgedm-dev 05/26/2023 at 03:000 Comments

PCBway delivered some boards for this project and what should I say except that they are awesome.

I haven't expected this quality. The boards don't feel like the PCBs found in most products but more like Aluminum. They have a very nice finish and haptic.

And the most important part: They work. :D

Both boards are 4 layer PCBs with a ground plane and power planes.

Big thanks to PCBway. They did a very good job.

Let's take a look at the boards:

And a look at the mostly finished boards. They are beautiful.

This is the pulseboard. It is an improved version of the old prototype that comes with a high speed optocoupler to isolate the PWM signal and a trimmer poti to adjust the feedback voltage. It has a Zener diode for gate protection and one on the vSense feedback to protect the ESP.

Tests showed that it delivers up to 100khz more or less reliable. 50khz works good. Above 50khz switching losses start. But at 50% duty cycle it delivers the 100khz. It is hard to debug without an oscilloscope. The multi-meter used is everything I have to measure the frequency and above 50khz it sometimes looses track of the frequency.

I'm currently working on two other boards. All of them use different ways to get the sparks. One is a high side switch and one is again a low side switch with a discrete gate driver circuit and a pack of integrated mosfets on the PCB that will make the build process easier.

The new motion controller is a beauty too. It reduces the number of PCBs in the controlbox from two to one. In the prototype the ESP32 breakoutboard was mounted below the motion controller. Both boards are now merged into one tiny 4 axis board that offers dip switches to set the microsteps for X,Y and the Spindle. Only Z uses software controlled microsteps. The ESP has no Pins left except one Input-only pin.

The software changed heavily and the motion is now controlled with the fastaccel library that uses hardware generated step signals and can fire step pulses at 200khz.

After testing all the connections on the soldered control board with a multimeter it was time to get the display running. Compared to the previous prototypes this was super easy.:

And a little look at the x axis. It is already wired an running. Did some test with a 5kg load and the stepper had no problem at all to drive the axis at all possible microstep settings.