TTL on a cheap Chinese driver troubleshooting

Hello, I recently bought a Chinese laser for my first laser cutter conversion from a 3D printer. The driver has clearly marked pins for the TTL input and the +12v. After researching, it seemed like the most common setup was running the 12v port to the power supply and connecting the TTL pins into a port that has PWM (I used the classic D9 port).

Testing the laser, however, I would plug the board into the 12v supply and the laser would instantly turn on. The TTL port made no difference to the laser.

I understand this is a common issue but everyone seems to take a different approach.Sometimes it's the voltage, sometimes you need resistors, sometimes it's a wiring issue or a bad board. Knowing me, I could have just missed something really obvious.

Does anyone have advice on the next steps I should take?

Thank you

For safety reasons you could add a relais between 12V and laser-driver ( add a keyswitch for total peace of mind). That way you can software-control when the laser driver get's powered.

... this chinese drivers are not really "standardized" - they can behave randomly ... but could be, it's meant to short the TTL input to GND to get the laser OFF ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Supply the laser driver with its own 12V power supply

Trigger it with TTL connection

Pin 11 or 12 of arduino can be set to PWM TTL

M3 laser ON M5 Laser OFF

M3 S(1 - 255) with set the PWM and power out of laser

there may be a switch on driver for TTL or continous trigger

Thank you everyone for the advice.

o_lampe, that is good thinking and I may do that eventually. But I would like to figure out the driver a little more and consider other solutions first.

cozmicray, I did everything you suggested up until pin 11 or 12. I have been using pin 9 instead because it is fairly easy coming from the cooling fan and should still be PWM capable. Are 11 and 12 any better or is it just preference?

On another note, I realized I should have adjusted the driver using a multimeter and the potentiometers before testing. Who knows what chaos might be going on since I don't know the voltage going through the thing. I'll make those adjustments and see how it goes.

Just a matter of making G-code control the right pin

see

[jtechphotonics.com]

using D9

M106 S255 = Turns the laser on at full power
M106 S0 = Turns the laser off
M106 S127 = Turns the laser on at 50% power
M107 = Turns the laser off as well

Okay, so I checked the driver with a multimeter and it appears that the TTL makes no significant difference on the output to the laser.
I'm considering just getting a new driver but I feel like there must be something I am missing.

By the way, here is a link to the laser and driver. Has anyone worked with these kinds in the past?

[www.ebay.com]

I don't know how you can test TTL trigger with multimeter
It is a switch ------ a voltage applied one state, No voltage the other state

Pulsed by a signal to turn laser ON / OFF

Since you never gave specifics about the Laser / driver

can't help ---- ask seller

Not the TTL itself, the output to the laser diode. I would check the voltage with the TTL on and then off: no change. (I am confident the port is working correctly). I connected the laser and included an ammeter: no change.

And the specifics are in that link (I would give a picture but this site isn't allowing me to upload anything). It is hard to find much more than that but it does all the basics.

I would review your test procedure for a diode driver
this is pulsed DC to diode and ammeter may not show current
and
can you measure this pulse --- perhaps a O-scope


Why does uncle_ding
call this a 15W laser
when spec says

Model Number: LJ450nm1.6w
Output power: ≥1200MW
Operating mode: tunable
Motivation method: electric incentive
Working substance: Semiconductor

I would ask "uncle-ding" for a manual
and
some lazer dust to make it work

.... uh, oh! - "Output power: ≥1200MW"

1200 MegaWatt(!!!) ia a pretty serious laser! ... my diodes with this power specs are more in the milliWatt range

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Haha. That's the weird thing with some of these companies. It's easy to move a decimal place or capitalize a letter without any repercussions. I made the assumption the laser was 1.5 w when I bought it.

Luckily I did find a way of turning the laser off by running the TTL port to the ground of D9. The issue is that this makes it a pull-down instead of pull-up which has certain dangers (such as the laser being on when I start the machine and such). As well, because M5 (or M107) is the command to turn on, I don't know whether I can get any grayscale with the laser. I may just order a new driver seeing as everyone I have found using this driver has had the same problem.

can i ask which TTl pin you attached to D9? I've got the same laser/driver, there's two listed on the board as TTL, one with 2 pins and one with three?

and a side note, is there a practical way to power the module from the extruder heater pin, (and the TTL to another pin?) so that it only turns on when the 'exstrude' is activated, the TTL controlling the power level.(assuming the TTL actually works on mine..or even some other board)


i'm thinking for a stand alone laser cutting purpose the G code could be any stl file with one perimeter and no infill at a very low layer height (move the z homing switch up...) or simply repeating the 'print' for more pass's. just a thought.



the laser has a pot, so the current can be set to 4 amps maybe..
disable/uncomment extruder motor and temperature sensor for the extruder..
using Simplify 3d with two models would give some degree of stencilling/shading by adding infill...or not.

will marlin do this at all?

Edited 3 time(s). Last edit at 08/12/2018 08:51AM by munchit1.

hmm a penny dropped..

the extruder 'control' can be set from 0-255 in marlin, so its a pwm current to the extruder pin, pulsing the primary part of the laser driver board circuit, followed by the TTL pulsing...may cause problems, may not, hey ho...

maybe set the extruder pins to analog? i dunno.(analog as in constant DC...no doubts the power supply to the laser board is pwm of some sort or another..theyre small, so maybe no transformers in there, it's all go innit lol).


where can i get to know about the set up of marlin and the 3d printer control boards? i've googled ma titz off....

hmmm so i'll randomly plug leads in here and there.. thanks guys lol

Munchit1,

Sorry for the late response. As to the simplify 3d thing, I highly prefer LaserWeb or just about ANY software that is actually made for lasers. It is much more customizeable and has many options. It's just a matter of generating Gcode.
I understand the PWM SXXX commands (XXX symbolizes your laser intensity). The issue is with all the drivers I use, the laser appears to just be always on. I can ground the positive TTL input to turn it off but it inverts the commands and suddenly M106 means off. Not to mention PWM goes out the window. There must be something simple I am missing but I don't see it.

And I am not seeing a third marked pin on mine. There is one port for analogue, CN3, but that's not what we want.

Quote
jdargot
And I am not seeing a third marked pin on mine. There is one port for analogue, CN3, but that's not what we want.

just rechecked and yours isn't the same as mine after all.. ahh well, wishful thinking on my behalf.



[www.ebay.com]

Edited 1 time(s). Last edit at 08/22/2018 04:08AM by munchit1.

Quote
jdargot
Munchit1,

Sorry for the late response. As to the simplify 3d thing, I highly prefer LaserWeb or just about ANY software that is actually made for lasers. It is much more customizeable and has many options. It's just a matter of generating Gcode.
I understand the PWM SXXX commands (XXX symbolizes your laser intensity). The issue is with all the drivers I use, the laser appears to just be always on. I can ground the positive TTL input to turn it off but it inverts the commands and suddenly M106 means off. Not to mention PWM goes out the window. There must be something simple I am missing but I don't see it.

i dont think youd see the pwm by naked eye so to speek, the tv's are at 25-30 frames a sec and you dont notice them flickering. (25-30 hertz)

This is becoming Abbott & Costello

Munchit has laser A with Driver B being hooked up to printer controller C
Jdargot has laser D with Driver E being hooked up to printer controller F

What printer control board are you guys using? Ramps on Mega 2560? or what
What firmware, what software?

you may want to look at

[www.shapeoko.com]

Once I know your controller and have good pics of laser driver
I may be able to help

some pics and the board a mega/ramps 1.4, and not rigged up yet, having ferkles printing parts due to a failing heater bed at the mo, all go innit.(googling for a 240v pad..)

note on the driver board theres a third TTL pin on the power lead (jack plug lead), so +12v,-12v and a TTL. two other pins for the TTL posative and negative.

Edited 1 time(s). Last edit at 08/23/2018 08:13AM by munchit1.

ferkles?

Don't need heated bed to do PLA????

Marlin firmware ?

TTL
low < 0.8 volt
High 5 volt

Everything about TTL and laser control

[endurancelasers.com]

Have you looked at

[www.eleksmaker.com]

Quote
cozmicray
ferkles?

Don't need heated bed to do PLA????

Marlin firmware ?

TTL
low < 0.8 volt
High 5 volt

Everything about TTL and laser control

[endurancelasers.com]

Have you looked at

[www.eleksmaker.com]

i looked on eleksmaker for about an hour, very pritty....hmmmm

Sooooooo update a while later for anyone who is still interested. It took me upgrading to a CO2 cutter and fooling with the wiring there to finally figure out what was going on.

So most commercial drivers have a 0-5V PWM input and a ground input. But I realized when trying to control the laser with a potentiometer that you are actually controlling resistance between ground and 5V running to the PWM pin. Visually, your middle pin of the potentiometer goes to PWM, one side goes to ground, and the other goes +5V. So as you dial down, you have a certain intensity resistor going between ground and the PWM. I never fully grasped it before, but that was why I could only ever turn it off by grounding the PWM pin.
Realizing this, I put a 10K resistor between the ground and the PWM. This is often recommended anyway for keeping the laser from surging on startup. I personally had to go down to a 4.7K resistor, as the 10K was too high to make a difference. But since then, things have worked wonderfully. It follows on/off commands, and the gray scale seems... somewhat linear.

Thank you all for the advice. I'd be curious to know if others have had the same issue before.

So CO2 is a whole new ball game -- not a diode laser!!!!

The trigger is a TTL link

" TTL (Transistor-Transistor Logic). For a TTL input this means that anything
below 0.8 volts is a “zero” and anything above 2.4 volts is a “one,”
and that it presents a load of less than 1.6ma to the driving circuit"

Your resistor is limiting the current thru the TTL switch.

The pulse width is determined by the driving controller -- how long to keep it ON / OFF.

Many circuits are only good to 12KHz -- takes nano seconds for TTL to settle!