Author Topic: PWM vs TTL (:  (Read 12497 times)

rasfh

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PWM vs TTL (:
« on: July 31, 2017, 01:22:32 PM »
Hello people. Can someone explain for me, what the difference is between pwm laser and a ttl laser?

Right now I have a eleksmaker a3 2500 mv pwm laser, with a mana se board.
Is it possible to connect a ttl laser to this mana se board?
And how can it be done?

I hope someone can help me (: Thanks.
 


Zax

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Re: PWM vs TTL (:
« Reply #1 on: July 31, 2017, 02:45:18 PM »
The Mana SE has 2 ports, "motor" for a 2-wire laser (commonly called a PWM laser) and a "laser" port for a 3-wire laser which has a TTL signal pin (S). So yes, you can directly connect a TTL laser to the Mana SE board.

These aren't really the correct terms as TTL and PWM are used in both cases but for the "PWM" laser the TTL/PWM signal drives a MOSFET so the output is a switched 12V PWM signal. TTL refers to a 5V logic signal and PWM refers to the method of switching the signal.

rasfh

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Re: PWM vs TTL (:
« Reply #2 on: July 31, 2017, 03:14:08 PM »
Okay thanks (: So if I have a 2 wire laser, I would still be able to adjust the laser power? From 0-255.

Right now I have a 3 wire laser (which must be TTL). How is this so different from pwm?

Zax

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Re: PWM vs TTL (:
« Reply #3 on: July 31, 2017, 04:21:46 PM »
The 3-wire is better as you are directly controlling the laser driver with a TTL/PWM signal.

The older 2-wire lasers can be used with PWM to get variable power but often it won't be linear or may not work below a certain threshold.

rasfh

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Re: PWM vs TTL (:
« Reply #4 on: July 31, 2017, 04:30:56 PM »
So if I connect a 2 wire laser to the "motor output" on the mana se, I would be able to control pwm with T2laser? Or should there be more connections.

Zax

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Re: PWM vs TTL (:
« Reply #5 on: July 31, 2017, 04:37:03 PM »
Yes. If it's a non-TTL (2 wire) laser then you must use the motor connector.

You will usually get better results using Velocity Mode or Dithered.

rasfh

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Re: PWM vs TTL (:
« Reply #6 on: July 31, 2017, 04:51:21 PM »
Okay, but i don't understand how that should work as (pwm) because there is no continuity between the motor out on mana se and the microcontroller?

But there is between D11 on the microcontroller and the (s) pin on laser output on the mana se.

Zax

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Re: PWM vs TTL (:
« Reply #7 on: July 31, 2017, 06:09:12 PM »
Pin D11 from the Nano is a TTL / PWM signal, it switches the motor ground pin using the MOSFET.

PWM works like a dimmer switch for a lamp, quickly turning the circuit on and off. If you measure the output from the motor pin with a multimeter it will appear to be a variable voltage from 0 to 12VDC but is in fact always 12V just switched too fast for the meter to detect a change, but with an oscilloscope you can see the PWM signal.

Zax

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Re: PWM vs TTL (:
« Reply #8 on: July 31, 2017, 06:11:39 PM »
The S pin is directly from the Nano D11 pin, that's all it is, a TTL/PWM signal but it needs a compatible laser module.

The motor circuit is a ground switched 12V output so you won't measure any continuity unless you measure from the MOSFET gate. The source and drain are the motor ground to power supply ground, making the circuit.

rasfh

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Re: PWM vs TTL (:
« Reply #9 on: August 01, 2017, 05:30:36 AM »
Okay, it makes sense now. Thanks for help! (: