This is a help request, not a finished design.
I'm looking for a 405 nm @ 2-5 W, PWM LD driver.
Since I'm totally new to the LPF community, I've been looking at loads of
various designs both off-the-shelf and DIY circuit designs. However, now I
feel even more confused and undecided how to go about this. I would very
much appreciate what the experienced LPF member would recommend.
Background:
I'm planning to build a CNC-like laser cutter/etcher, using a
RaspberryPi-3. What will make this cutter non-usual is that it will
attempt to cut some materials only normally possible with professional
machines, using much higher powers. This will require using the highest
available power laser diodes. (I assume as of today, that these are
rated around 3-5W of optical output power.)
The Rpi3 already have a HW driven PWM built-in on GPIO#1 (header
pin-12), while all other GPIO can also be configured as software PWMs.
Thanks to the PiFM project, we know we can drive the HW driven PWM up to
at least 100 MHz, so I'm considering the possibility of using this. However,
this option may also overload the processor, that also need to control the
CNC steppers...
The project will ultimately be Open Source and published with full DIY
instructions.
So the LD driver design specifications I'm looking at is something along the lines of the following.
Other useful criteria:
All close-to-LD parts are kept close to LD, while other parts of the
driver are kept off the moving CNC board. Connected by moving a light
and flexible 3 lead cable.
Questions:
1) What is better, using the Rpi to generate PWM control signals
(over GPIO) or to use off-the-shelf components to offload MC for
CNC operation?
(The Rpi3 already have a HW driven PWM built-in on GPIO#1 (header
pin-12), while all other GPIO can also be configured as software PWMs.
Thanks to the PiFM project, we know we can drive the HW driven PWM up to
about 1 MHz.)
2) What are the best and cheapest design options using PWM components?
(LM555, 74AC14, MAX3667, HV9925 etc)
3) What design options would keep the number of components to a minimum?
4) How can you best control the PWM driver? (Through a DAC or something else?)
5) What is better for the LD, that the PWM pulse shape is a square-wave, sine-wave or something else?
6) Will the LD always be lasing at lower PWM duty cycles (at high frequencies)?
(Assuming f=1MHz, what is the minimum duty cycle for lasing?)
7) Can you improve LD start-up performance by using a zero/baseline current/voltage offset?
(For example, by letting the LD current idle at some constant but very low value?)
I'll surely have many more questions as the fog clears... But these are already overwhelming for most people.
I would appreciate anything or any suggestions that could help me get started...
I'm looking for a 405 nm @ 2-5 W, PWM LD driver.
Since I'm totally new to the LPF community, I've been looking at loads of
various designs both off-the-shelf and DIY circuit designs. However, now I
feel even more confused and undecided how to go about this. I would very
much appreciate what the experienced LPF member would recommend.
Background:
I'm planning to build a CNC-like laser cutter/etcher, using a
RaspberryPi-3. What will make this cutter non-usual is that it will
attempt to cut some materials only normally possible with professional
machines, using much higher powers. This will require using the highest
available power laser diodes. (I assume as of today, that these are
rated around 3-5W of optical output power.)
The Rpi3 already have a HW driven PWM built-in on GPIO#1 (header
pin-12), while all other GPIO can also be configured as software PWMs.
Thanks to the PiFM project, we know we can drive the HW driven PWM up to
at least 100 MHz, so I'm considering the possibility of using this. However,
this option may also overload the processor, that also need to control the
CNC steppers...
The project will ultimately be Open Source and published with full DIY
instructions.
So the LD driver design specifications I'm looking at is something along the lines of the following.
Code:
Specific:
- LD wavelength: 405 nm
- LD output power: .5 - 5 W
Features:
- LD current [A]: 0 - 5 A
- LD voltage [V]: 1 - ? V
- PWM Frequency [MHz]: 0 - 1 MHz
- Duty Cycle [%]: 5 - 95 %
- MC digital/TTL control signals
- TTL / CW mode
- ESD protection on LD side
- Reverse polarity protection
- Variable baseline voltage (zero offset voltage)
- Over voltage protection
- Under voltage lockout
- Current Limit / Short Circuit protection
- Low current cutoffAll close-to-LD parts are kept close to LD, while other parts of the
driver are kept off the moving CNC board. Connected by moving a light
and flexible 3 lead cable.
Questions:
1) What is better, using the Rpi to generate PWM control signals
(over GPIO) or to use off-the-shelf components to offload MC for
CNC operation?
(The Rpi3 already have a HW driven PWM built-in on GPIO#1 (header
pin-12), while all other GPIO can also be configured as software PWMs.
Thanks to the PiFM project, we know we can drive the HW driven PWM up to
about 1 MHz.)
2) What are the best and cheapest design options using PWM components?
(LM555, 74AC14, MAX3667, HV9925 etc)
3) What design options would keep the number of components to a minimum?
4) How can you best control the PWM driver? (Through a DAC or something else?)
5) What is better for the LD, that the PWM pulse shape is a square-wave, sine-wave or something else?
6) Will the LD always be lasing at lower PWM duty cycles (at high frequencies)?
(Assuming f=1MHz, what is the minimum duty cycle for lasing?)
7) Can you improve LD start-up performance by using a zero/baseline current/voltage offset?
(For example, by letting the LD current idle at some constant but very low value?)
I'll surely have many more questions as the fog clears... But these are already overwhelming for most people.
I would appreciate anything or any suggestions that could help me get started...