3. Connecting the CNC Controller Board to the new Schmitt Trigger PCB
Now the circuit track to tap into has been identified, we need to connect the wires of the 74HC14 Schmitt Hex Inverter Trigger board you just made. Using the following photograph for reference, CAREFULLY solder
- A power 5+V supply on the CNC motor driver board
- A ground on the CNC motor driver board
- A contact for EACH “noisy signal” from corresponding optical isolator outputs (ie: one wire for each axis).
- A contact for EACH pin 3 track for the Toshiba TB6560 chips (ie: one wire for each axis).
A picture is worth a thousand words, so follow this diagram carefully for reference (Fig 6).
4. Cutting the Original Copper Tracks
We have to make one cut of the original copper track per axis. Again, you are looking at the lighter colored blue material of the circuit board that is the conductive Copper, not the darker color. We now need to cut the original connection between the optical isolator output leg and the TB6560 chips pin 3.
For a 4 axis board, you will need to make four very careful cuts on the circuit board tracks as shown in the photograph with a sharp blade, pocket knife or electric grinder. There is one cut to make per motor axis.
In cutting the connection, you need to ensure you break the copper contact completely, not just scratch the top layer off the protective lacquer. Test the track is properly cut by testing the ends with a multimeter afterwards. Careful of neighboring circuit tracks!
With this YOU’RE DONE ! The board should now work properly.
5. Now Check, Check and Re-Check !
Check and re-check all components, connections and wiring before testing with the board connected to your CNC machine. Do not test with the cutter operating or near the limits of the machine table until you are certain all is working as it should!
Your CNC machine should behave very differently to what it once did!
The Modification Outcome: A Very Satisfying Solution!
My CNC machine now works fantastically! This was a very satisfying repair project, which is part of the reason I am so enthusiastic to share my experience with others. It is hoped that this guide makes it easier for people to modify their boards for similar results too.
My modifications produced a CNC cutter with no more missed steps from my stepper motors. I also found I had gained some extra torque from the motors and that the motors also run far smoother and quieter both in axis travel and in hold.
Credit Where Credit is Due
There is no way I could have started out this hacking project without initial assistance from the guys contributing to CNCZone’s forum. While these sites put me on to the the idea of what work was required, I initially found them a little confusing, Information was scattered and the original photographs were a little rough. The soldering points unclear. Once I had the solution nutted out however, the job was easy.
In the end, despite initial problems, I do not regret buying the Chinese CNC controller board at all. It saved me money, got my CNC project off the ground sufficiently and the stepping problem ended up being another great learning “side project”, if nothing else. The more I know about my CNC machine operation the better!
Anyhow, if you are having problems due to this same board design, I hope I have provided help.
Best of luck and happy CNCing (or 3D printing, laser cutting, plasma cutting or plotting 😉 )!