[windtigertim]

Hi, this is my first post.

I have built a CNC mill using the eBay TB6560 4 axis driver board.

I recently bought a 12 Volt LASER diode and driver board capable of burning/etching into timber/dark plastic..

I am not worried about PWM etc. I just want the LASER to turn on/off with a Z axis movement.

I can build a TTL triggered relay to interface between a pin and my laser driver board.

What I am wondering is how do I physically wire my LASER Diode & Driver to this particular board?

Are there any outputs plugs on this board that i can directly wire to, or do I need to solder a wire from the printer port connector?

Any help would be appreciated,
Cheers

[doorknob]

There should be a relay on the board (with NO and NC output terminals brought out to a connector) which is normally used for spindle control but which presumably could also be used to control your laser diode driver.

[edit: Correction - see my post below - the spindle relay wiring does not normally expose both a NO and a NC contact along with a common terminal, rather one of the outputs is hardwired to the common, so it is effectively wired as SPST]

[windtigertim]

Thanks doorknob.

Yes there is a spindle relay output on the board. To be able to use that relay would be ideal !!

However, my next question is this:

How do I configure the spindle relay to trigger with the z dir signal?

Cheers

[doorknob]

I'm not certain that I understand your goal - are you also intending to use the Z dir signal to control the direction of the Z axis, or is that signal not in use?

I have not hooked up the spindle relay control of my board, but my understanding is that it is controlled by one of the pins of the DB-25 connector, which goes through an optoisolator.

So if you are not using the Z dir signal to control the Z axis, you could simply use the spindle control relay pin instead of the Z dir pin.

If you are using the Z dir pin, then you would probably want to make an electrical connection between the two pins of the DB-25 (which you could probably do by soldering a jumper wire underneath the board, or by building an "interposer" DB-25 board between the LPT cable and the input connector of the board, and make the electrical connection there).

I have not tried doubling up two opto inputs on a single LPT output pin - my guess is that you would be able to sink enough current (with an active low signal) to handle that, but that may depend on the characteristics of your LPT port. Also, you would have to make sure that the "sense" of the Z axis control would be in sync with when you wanted to switch the relay (unfortunately, the spindle relay output does not give you a choice of NO vs. NC connection unless you modify the wiring of the relay by cutting a circuit trace and bringing the extra terminal connection out to an added header pin or other type of connector, because it normally has one of the output terminals connected to the common terminal, but if you're willing to make that modification then you could change the "sense" that way).

[edit: If you are using the Z axis and you need to change the "sense" of the relay control vs. the Z axis direction, another way to do it would be to simply swap two of the motor wire connections for the Z axis motor, for example, the A- and the A+, so that for a given Z axis dir signal value the motor actually turns in the opposite direction.]

[windtigertim]

Thanks, thats all very helpful information.

I shall definately do some tinkering around later this evening and hopefully will come to a solution.

For now I shall attempt clarify my setup and goals.


1. I have built a fully operational 3 axis CNC mill that I am happy with. Currently I manually turn on my VFD and am content with keeping it that way.

2. I would sometimes like to 'bolt on' my Laser diode for the occasional etching / burning.

3. When using the laser, I do not want the Z axis to move up/down - and instead want the laser diode to fire on/off. (That way I can keep the focal point fixed at an optimal burning height).

4. I have read on these forums that a simple way of triggering the laser is to use the Z-dir signal, so that a 'down' movement triggers the laser ON, and an 'up' movement turns the laser OFF.

5. A purely software method of switching between my two modes (CNC Mill vs CNC Laser) would be ideal.I don't know if it is possible. But perhaps just a reconfiguration of Mach 3 ports and pins each time i switch modes??


6. Failing this, I like your idea of an 'interposer DB25 board', and that also seems quite simple and practical.

I shall do some playing tonight and let you know how it goes.

Thanks a lot for your help.

[HorridHenry]

12 Volt LASER diode and driver board capable of burning/etching into timber/dark plastic..

Whats the power output of the laser?

I experimented a few years ago with a defunct DVD writer laser but it needed a tweak to up its power a little before it started to have any effect of buring on wood,I did get it to light a match though. lol

[windtigertim]

Doorknob - thanks a lot for the 'interposer board' idea. I ended up making a DB25 'interposer' cable which took the 'Z-Dir' pin from the computer to the 'Spindle Relay Pin' on my TB6560 Driver Board.

I hooked this up to a DPDT switch which I mounted on my Driver board box. With one flick of the switch I can toggle between LASER Mode and MILL Mode now.

I chose a DPDT switch so that the 'Z-Step' pin can also becomes disabled when changing to LASER mode. I do not want my Z-axis to physically move at all when burning with the laser obviously - as this would mess up the focal point of the laser.

I am very happy with the result - it couldn't get much simpler.

I have attached a Pinout diagram which I used for my setup. It may be useful to anyone else who wants to acheive a similar machine using a TB6560 'eBay' driver board..

HorridHenry - I beleive this laser diode was around 350mW (or that's what the eBay seller claims it to be)... Burns/engraves into MDF and black plastics quite nicely when fixed at the exact focal point..