Author Topic: TTL laser vs PWM (Analog?)  (Read 1846 times)

Stormin Norm

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TTL laser vs PWM (Analog?)
« on: July 27, 2019, 07:44:37 AM »
So if my research proves true, TTL laser control uses the laser's full power but kicks it on and off very quickly to do the grayscale control, right? (Plus speed settings of course)

PWM, or analog lowers and raises the power to the laser to control how strongly it burns, giving levels of grayscale. (Plus speed settings of course)

First, I havn't seen a definitive answer as to which is better.  But it seems that stronger lasers are usually TTL, right?

Now, here are two pictures of the 3000mw laser and control box that came with my cheap-o ebay engraver:

Note the guts of the control box. Black/Red is Ground/+power going to the control box, feeding from the GRBL motherboard.

Yellow-Red are output to the laser, Blue/Green output to the fan.

Notice that there is an unused pin on the little board, labeled TTL...  Anyone think it might be as simple as running a 3rd wire to the GRBL motherboard to use the TTL control output, or do you guys think this might fry something if the laser/controller maybe isn't set up to use the TTL option?



Zax

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Re: TTL laser vs PWM (Analog?)
« Reply #1 on: July 27, 2019, 07:59:09 AM »
I very much doubt the driver can provide "analog" power control to the laser, it's just the input that allows a variable voltage to control the PWM output to the diode.

The Nano doesn't have an analog output, it supports TTL/PWM which is what you would use.

A laser diode is a LED (light emitting diode) which is a current driven device so to run it analog would require a complex variable current limiting and variable voltage output, very unlikely. This is why you see LED's flicker on camera as PWM is almost exclusively used for brightness control. I suspect trying to run them analog would have severe life time issues due to in rush current.

As that controller is working without an input to the TTL it's probably "backwards" where a high input would be OFF (very wrong but I won't get into that) so you would require an inverter.
« Last Edit: July 27, 2019, 08:02:29 AM by Zax »

Stormin Norm

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Re: TTL laser vs PWM (Analog?)
« Reply #2 on: July 27, 2019, 08:13:19 AM »
 :o :o

I'll pretend I totally understood all of that, and will water it down to:

"Don't mess with anything since it works now"

ggallant571

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Re: TTL laser vs PWM (Analog?)
« Reply #3 on: July 27, 2019, 08:22:00 AM »
I would guess that you are using the power MOSFET on the controller board to switch the +12 ON/OFF.
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Stormin Norm

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Re: TTL laser vs PWM (Analog?)
« Reply #4 on: July 27, 2019, 08:43:18 AM »
Probably so.  This controller board has 2 types of laser outputs.  A 2 wire named "laser" and a 3 wire named "PWM Laser"

(I had thought I had seen ttl, but as it turns out, I did not.)

So currently, I'm just plugged into the "Laser" output, since I only have 2 pins/wires to work with.  Again, it's working, so I'm calling it good.

Zax

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Re: TTL laser vs PWM (Analog?)
« Reply #5 on: July 27, 2019, 10:58:00 AM »
What controller board is that?

It is using the MOSFET, so it would be an update to use the PWM output (it's probably TTL but you would need a volt meter to verify). That could be input to the laser module also set in TTL mode.