Introduction: How to Use the CNC V4 Board (despite Its "quirks")
This cheap (can be found under 10€ with arduino and stepper drivers) board is perfect numerically controlled machinning tools like CNCs or laser engraver/cutter ... or is it?
In theory yes, and in practice with enough time too, but this board seem to have weird design errors and mostly a lack of documentation that makes it non trivial to exploit.
I am actually not sure if the things I will talk about are true for all of those boards, because of the minimal documentation, but it seem unlikely that there are different designs of this board.
I will go through all the problems I encontered and how to fix or circuvent them, and the last step will summarize all the connections on the PCB.
Step 1: Power Input
When you first try this board, your reflex is to just plug a 12v power supply to the power jack, as you can see the label under it say "M .... 2v" ... yes most of the label is hidden under the plug, but It's probably written "Motor 12v" ...
(actually, I removed the plug and it's written "Max-In 12V" so it's a hidden warning)
But doing this will in fact only power the arduino, because you need to place a jumper on "Mot-VOT-Sel" to propagate the power input to the drivers ... and no jumpers are included with the board, so you will need an extra one.
If you want to power the motors with a higher voltage, don't use this plug and jumper because it goes to the "Vin" of the arduino which is connected to an LM1117 rated for 7 to 12v. Instead, solder your power input to the holes on the motor plugs side labeled "Mot-vcc" and "Mot-GND".
and choose a way to power the arduino :
-7 to 12v power supply plugged the the jack.
-step down taking the motor voltage and giving it into the pin on the top of "Mot-VOT-Sel" (closest to "Sel") and one of the GND pins
-just use the USB plug of the arduino itself, easiest and enough if you need to have the machine plugged to a computer to control it anyway
Step 2: Micro Stepping
This is usefull is you use the A4988 drivers, not the fancy TMC2130. (but if you bought this board you probably don't intend to use expensive drivers on it anyway)
Once again, no jumper included, but in fact here, even if you had jumpers, they wouldn't do anything.
This look like a design error : the jumper pins are meant to be connected to 5V, but on this board they are on GND
Because you already don't have enough extra jumpers, and there isn't much reasons to don't want micro stepping, the best way is to solder all of the micro stepping pins to one of the 5V pins.
On the pic you can see in green everything that need to be connected together, and the lines showing the shortest wire to achieve that.
Step 3: Step and Dir Pins
The pic on this step is one of the rare documentation I could find about this board
And it shows that X, Y, Z dir are connected to D5, D6, D7 and step to D2, D3, D4.
it's the other way around...
There are other errors on this schematic, like Vin shown to not be wired to anything, but the last step will summarize everything
to recap :
Xdir --> D2
Ydir --> D3
Zdir --> D4
Xstep --> D5
Ystep --> D6
Zstep --> D7
Step 4: Summary
So I tried to redo the real schematic over a pic of the board here
First pic showing power distribution (+3 unused pins)
Second showing digital and analog wiring (+3 unused pins)
Third showing the physical dimensions of the board (all in mm)