Need help with laser driver and TTL signal

[BRobbins]

I am trying to attach a laser diode to my CNC running MACH3. I purchased this driver to use with a 1w laser.


I have configured MACH3 so that I can use M3 and M5 commands to turn off and on and use pin 17 for + and 25 for -. Confirmed with meter that I get 5V when on an ~0 when off. I can hook up a small 5mW laser to these pins and control on/off as well as use the spindle command to control the intensity. That part works. When I hook up the pins to the TTL connector on the driver board, power it, and use the same commands the voltage at the laser connector doesn't change regardless of how much I initially trim the voltage pot. It stays on all the time. I was hoping that I could turn off and on the laser with this setup.

Any ideas?

Thanks

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[dharmic]

Laser diodes, like any other type of diode, do nothing until they hit a particular voltage and then (like a switch) they open up the floodgate and go very low impedance. So when the thing is on, regardless of power, you won't see a great deal of variation of the diode voltage. And, to a large extent, it's irrelevant.

What you want to be measuring is the current, which means hooking up your meter (be sure to make sure the meter's in the right mode with the probes in the right sockets) in series with the diode instead of across it and measuring that.

Also, these cheapo drivers seem to come in three flavours:
- TTL (can't modulate output power with these, they're either on or off)
- PWM (modulate with a PWM output from MACH3 and your BOB, it's a digital 0-5V square wave where the duty cycle of each pulse determines the value of the output).
- Analog 0-5 or 0-10V where a steady voltage controls the output power.

I bought my diode with a TTL driver under some illusion that I'd be able to run PWM control through it but, as soon as the power went up over about 1%, it just started flickering on and off. Useless. Replaced it with a proper PWM driver and moved onto the next issue - my particular BOB doesn't have any PWM support. Lol. Next step, I have a UCCNC UC400ETH controller sitting on my desk with a breakout board for it on the way. When that gets here I'll switch over and hopefully get control of both my spindle (analog) and laser (PWM).

[BRobbins]

Thanks for the reply. Was hoping to use this as a PWM with Mach3 but would even settle for on/off. Seems to be on all the time whether or not TTL voltage is 0 or 5.

[dharmic]

You shouldn't need two pins for it, one either at 5 or 0 from the BOB and the other connected to BOB ground should suffice. My TTL board had a pullup on it, so that if the TTL input wasn't connected it defaulted to "on" state.

[Dean448]

On the Mach3 side those M commands are too slow to do anything practical. The delay will cause burning at the ends of the cuts. Check my past posts.


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[dharmic]

One step at a time, I thought

But Dean448 is right. Once you've got on/off control you're going to want to get rid of the M3/M5 and replace them with M11 (on) and M10 (off) to get rid of pauses.

[BRobbins]

Thanks. I've been following the issues with M3/M5. As soon as I can on/off that's my next step. Hopefully a lot easier.

[Bx3mE]

I had the same issue... I had a ground loop due to connecting the diodes housing to the frame...


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[BRobbins]

I had the same issue... I had a ground loop due to connecting the diodes housing to the frame...


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What was the fix? Working now?

[dharmic]

Fix is most likely to ground the frame properly. I know on mine (OmioCNC) they, for some reason, decided to keep everything isolated. Frame isn't grounded. Spindle isn't grounded, nor is the VFD, nor are the stepper drives and the USB BOB is floating too - sitting on rubber spacers and an insulated sleeve around the USB socket so it doesn't ground on the case! Horrible, horrible electrics which caused some real weird problems. Fixed 'em by wiring the machine frame to mains ground but one day I will need to go through and properly star point ground the whole lot.

[Bx3mE]

Yes working now... Heat dissipation fr.o.m. Dioderna goes via housing so everything in contact with it or its cooling finns bill be conducting diode psu - voltage. This causes pwm or other signal to likely drop voltage making the signal invisible to the recieving circuit. Fix can be adding optocoupler or isolate the diode/housing. I used 3D printed holder and plastic screws.


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[Bx3mE]

Try to just make a bench test placing the diode with housing on some isolated material to see if this might bee the issue...


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[dharmic]

Hah, same here (3D printed mount) which is why I probably never had the issue

[Bx3mE]

Lol I just remade the electronics to fancy pansy on my Kissel mini.... Awesome printer which after modification is far better than stock ultimaker and lost only 150$ plus 300$ for modifications lol


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[BRobbins]

Thanks to all for your help and suggestions. Will post if successful.

[BRobbins]

Finally had success by using this laser that came with driver.

445nm 2000mW 2W Blue Laser Module TTL Signal Outer Driver CNC Cutter Engraving | eBay

Worked right away and was able to control on/off and power with PWM from MACH3. For those who commented about the issues with delay start using M3/M5 commands you are correct about an extra burn at the start. I played around trying to get M11/M10 to work with no success. Perhaps my version is old and I have no internet access in the shop to update. Instead, I was able to issue an M3 command at the start of the code along with an S0 which turned the laser on with no power. Then, throughout the code, when I wanted the laser on instead of an M3 command, I just used an Sxx to what ever power I wanted and S0 to turn it off. At end of program, used M5 to turn off. Worked like a charm. See pictures below of test panels and set up.

[dharmic]

The S method is a new one on me, thanks for sharing - I like it!

[biqut2]

Finally had success by using this laser that came with driver.

445nm 2000mW 2W Blue Laser Module TTL Signal Outer Driver CNC Cutter Engraving | eBay

Worked right away and was able to control on/off and power with PWM from MACH3. For those who commented about the issues with delay start using M3/M5 commands you are correct about an extra burn at the start. I played around trying to get M11/M10 to work with no success. Perhaps my version is old and I have no internet access in the shop to update. Instead, I was able to issue an M3 command at the start of the code along with an S0 which turned the laser on with no power. Then, throughout the code, when I wanted the laser on instead of an M3 command, I just used an Sxx to what ever power I wanted and S0 to turn it off. At end of program, used M5 to turn off. Worked like a charm. See pictures below of test panels and set up.

I have the same laser, how did you end up wiring yours up?

[BRobbins]

I have the same laser, how did you end up wiring yours up?

Hooked up power to a 12volt wall wart

I'm using this laser as a alternate to my spindle on my CNC for which I control with Mach3 through Gecko 540 controller. Between the Gecko and parallel port on my computer I use a breakout board. On the breakout board I connect the high side of the laser TTL wire to pin 17 and the other to pin 25 (ground).

[biqut2]

Thanks for the fast reply.That pretty much reflects how I have mine hooked up. I've sorted everything out except for when I issue an S command there is a momentary pause that leaves a dot on my engraved lines. I've turned off spindle delays, turned of backlash compensation, turned up acceleration to ridiculouslyhigh levels and can't seen to get rid of this little pause. I am using the spindle speed/PWM to vary th laser power which works fine except for the pause. If you have any idea whats cauing this youd be saving me much banging of my head against the wall.