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Need help in identifying connections for CNC board? Answered

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I need help please anyone.

I have bought another CNC shield recently, goes by the CNC Shield ver 2.7 name.
The board has www.lubandiy.com printed on one corner.
There are 8 optical isolators on the board for the limit switches and a socket for a Nano.
Also there is a heavy duty hexfet near the laser connections.
I am not able to find out much about this board, even though I have asked the seller and even a few other sellers that are on ebay.
I went to the website as shown on the board, but it is all in Chinese and after trying to use Google translate was still not able to find out any further information.
The board looks well made and seems to have a lot of good features, but lacks the needed info to be able to put it to good use.
I am not sure if the board has a laser TTL built in or not, it is possible due to the hexfet being there,  There are two heavy duty connections (two pin each marked + - ) and a small connection with a xh2 socket that could be for a laser or maybe a fan.  Can't get any further info on it.


If anyone can help with info, please let me know so I can start to use the board with my machine build.
I have managed to program a Nano with GRBL 1.1f and it works OK when testing the board on a dry run, no motors connected or laser.

12 Replies

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regpye (author)2018-01-20

I found these images that may help others with this board.

Seems like the three wire boards may be a little different.

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regpye (author)2018-01-13

It gets stranger.

I disconnected the fan from the TTL board and connected it directly to the GRBL board., that way the fan is always on.

I connected the power in on the TTL board to the laser out on the GRBL board and disconnected the signal wire on S-EN

I have a 2W LED connected to the TTL board to simulate the laser and it is working, flashing on and off as it is doing an engrave. Tested it with the framing macro that has low light and the LED lights up dimmed as it should.

I wonder if I should bite the bullet and test with the laser now??

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Downunder35m (author)regpye2018-01-13

If you feel happy with the results so far then move ahead ;)

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Downunder35m (author)2018-01-12

With these unknown boards there is only one real way to test it and that is by simulating and measuring.
The motors are sorted, same for the endstops.
Yellow jumper block at the bottom is to change the direction of the motors and might have something to do with the stepping depending on what motor sriver you use.
The laser connection should be just power, same for the fan next to it.
The actual laser firing happens using either the spindel drive or spindle direction pins on the yellow header where the enstops are located.
Depending on how GRBL is set up one of these pins gives the PWM signal for the laser control.
Since most laser diodes run with 12V it makes sense to have the dedicated supply on the board, should even be possible to turn it on and off using the right output pin.

Running GRBL with nothing attached to the board will always work but you will never know if it works ;)
Wite some simple code that allows you to connect a simple button to one of the enstop connections to trigger an output signal and another one to cycle through the output pins.
Using the serial monitor you can also do it from the PC and see which output is active.
Write down all input and output pins you can find this way.
Requires a half decent testing device like a multimeter though.

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regpye (author)Downunder35m2018-01-13

Thanks for that info, I have made a few tests and found out a bit more.

Do you have one of these boards yourself? The small yellow block you say is for reversing the motor direction, that could also be done with GRBL I would say.

I am not sure about your suggestion of writing some code for testing the endstops, could you expand on that please.

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Downunder35m (author)regpye2018-01-13

Don't have one of these boards...
You might not need the directional pins but in some cases you need to define them in the code, so having pins for it means you might not need to change the code to reverse an axis ;)
All comes down to being able to use the software out of the box without the need to make modifications other than the stepping.

Seems you board is meant for the use with GRBL as otherwise you would not get the LED simulation working the way you did.
So again:
The laser power is to power the laser module,
the spindle outputs (depending on how you define them in GRBL) are for the laser TTL or PWM input.
If the laser power can not be switched off (checking for pin-outputs ;) ) then it works like this:
Board is powered on and laser module as well.
In you code you define the homing, power and whatever you need.
Either the spindle speed (PWM) or the spindle direction (TTL) will be responsible for your actual engraving.

I did not mean to write code to test the endstops, I was talking about some basic code to run through the output pins at least.
This way you should be able to find out if the laser power can be switched off or if it is permanent.
It also pays off to know what pins do what rather than only knowing where the pin is on the board.

But let's assume your board is fully conform to the GRBL standards:
Connect the hardware including the laser and do some dry runs with simple code, like axis movement, simulating to hit an endstop, different laser power levels...
If all works as planned than you only need to worry about the stepping for your final setup.
If endstops constantly show as "hit" and fail to indicate any change you might need a pullup resistor so the board knwos what's going on.
If they show the opposite action you can try the yellow connector for the endstop logic and check if the logic is correct with a jumper present.

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regpye (author)Downunder35m2018-01-13

I tried connecting the laser power to the laser connections on the board and also using the S-EN connection on the yellow strip block for the TTL connection. When sending a file out the board will pulse with lights and the TTL controller board will also pulse with lights at the same time.

I had the laser itself unplugged from the TTL board for safety and added the 2W LED instead. The LED did not light up and I noticed that the cooling fan switched on and off at the same time as the pulsing of the on board LEDS, so that indicates to me that there needs to be a constant 12 volts applied at that power connection.

I will figure out about the endstops after getting the laser section sorted, I can run without endstops, but would rather have them so I can setup jobs better for repeat positioning.

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regpye (author)2018-01-12

The latest on this board.

I checked and found that the servo works on PWM and there is a s-EN pin in the yellow strip of pins that the endstop pins are among.

It activates when using M3 and M5 turns it off.

I connected a 2W LED across the laser output pins, positive and negative and didn't worry about the PWM pin at all.

I have a small macro that I use with LaserGRBL that will run the laserhead around an image that would be engraved so that you can determine the actual work area. To this I added a M3 S1 at the beginning to turn on the laser at very low power and added a M5 at the end of the macro to turn the laser off again. That way I can see the laser location and see if it is working.

G0 X[left] Y[bottom] F1000 M3 S1.5

G1 X[right] F1000

G1 Y[top] F1000

G1 X[left] F1000

G1 Y[bottom] F1000

G0 X0 Y0 F1000

M5

I loaded a small file and ran the macro and on the screen could see the position of the laserhead and at the same time the LED that simulates the laser turned on at low power and off again at the end of the script.

I then ran the full file as if doing the engraving and the LED pulsed on and off at high brightness while simulating the engraving.

It was a little hard to get an accurate voltage reading across the LED, but it appeared to be around 12 volts most of the time.

Maybe I should be looking for a laser that doesn't have a TTL or PWM board .and just has a 12 volt connection. I think all of these come with a built in constant current circuit built in, but I may be mistaken.

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steveastrouk (author)2018-01-10

If all else has failed, buzz out continuity from your unknown pins to the nano socket. You know the yellow and red sockets are for standard stepper motor drivers, don't you ?

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regpye (author)steveastrouk2018-01-10

Thanks for your reply steveastrouk,

Yes I know about the stepper driver sockets, they are not a problem.
I have a nano already programmed with GRBL 1.1f that will work in the board under software, I can actually simulate the cutting under software with no driver attached and no laser attached.
I connected a meter across the laser power outlets and found that there is a constant 12.5 volts there on all 3 sets of outlets that are only two pin outlets marked + and -. I am able to connect a 3W LED across either of those pairs of outlets and when I send a file for engraving, the LED will light up and stop at the end of the file.
It appears that the connections may be for a laser module and the either PWM or TTL is already built in to the board, but I don't want to risk blowing my laser module that is some 6 times the cost of the board without knowing what I am actually connecting to.
The voltage seems too high for a laser module at 12.5V, I may be wrong, but without specs on the board it is all hit and miss.

I did find the the jumper at the 12v supply is to bridge for a switch. The power in socket can have a switch across two of the pins, but if using the barrel connector the jumper must be placed to allow power to go to the board.

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steveastrouk (author)regpye2018-01-11

I doubt it would be intended for direct drive to a naked laser module, more a trigger signal for something else.

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regpye (author)steveastrouk2018-01-11

If there was a signal connection I would agree, but the only connections are all positive and negative, each pair will drive a 12v LED and there are no other connections for a TTL signal. It seems very strange that a manufacturer would put out a board with very little information about how to use it, makes the board almost useless.

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