Seeking advice about parameters for small, DIY backyard laser projector

[ryanlightsitup]

Also "TTL" and "analog" are functions of the driver, not the laser itself.

Ah okay. That is in line with the labelling of what I have been seeing around. And makes sense!

I'll have to do some research, and while I really love the idea of building with the individual diodes, perhaps my first attempt would benefit from a few premade components. It is only my first after all! There may be many more.

[kecked]

You know I do wonder if Pwm over TTL would work. I can't see why not. Would be a lot bettter control on the low end too.

[HankLloydRight]

Welcome Ryan!!!

Any chance you like quad-copters or SCUBA diving?

[ryanlightsitup]

You know I do wonder if Pwm over TTL would work. I can't see why not. Would be a lot bettter control on the low end too.

You know, it couldn't hurt to do a little experiment once I get the stuff I've ordered! I'll let you know how it goes.

[ryanlightsitup]

Welcome Ryan!!!

Any chance you like quad-copters or SCUBA diving?

Thanks for the warm welcome! I am into a great many things, though both of those have escaped my attention so far, though, I am getting dangerously close to looking into quad-copters as I have always wanted to get some awesome photos from above. Everyone here seems pretty fun and knowledgeable too. I have a feeling I'm going to learn a ton here!

[HankLloydRight]

Thanks for the warm welcome! I am into a great many things, though both of those have escaped my attention so far, though, I am getting dangerously close to looking into quad-copters as I have always wanted to get some awesome photos from above. Everyone here seems pretty fun and knowledgeable too. I have a feeling I'm going to learn a ton here!

Oh yes, you'll learn a lot! Also, keep the second week of August open.

I'm surprised that nobody has yet mentioned the slippery slope of eventually spending all your free cash on lasers.

Ask me how I know.

Or better yet, ask Bradfo69

[dkumpula]

You know I do wonder if Pwm over TTL would work. I can't see why not. Would be a lot bettter control on the low end too.

If you are talking about getting apparent levels that are below the diode's threshold, yeah, I agree. My concern would be having the driver respond to each PWM peak with a slight spike to the diode (as we've seen with many drivers over scopes) that would result in stress/damage to the diode over time. Also if the PWM signal frequency was on the low end, wouldn't this result in crappy video like PWM'd LEDs?

I seem to recall that BBE's drivers can handle PWM input and apparently this is not uncommon output from some DACs, although I don't know which ones.

-David

[ryanlightsitup]

My concern would be having the driver respond to each PWM peak with a slight spike to the diode (as we've seen with many drivers over scopes) that would result in stress/damage to the diode over time. Also if the PWM signal frequency was on the low end, wouldn't this result in crappy video like PWM'd LEDs?-David

This is where my non-familiarity with laser diode will come into play, but when working with constant-current high-power LEDs, you can use something like this driver (https://www.sparkfun.com/products/13705) that uses a chip (AL8805WS) that is designed to give a constant current based on the resistor value, but also has a PWM pin allowing you to do the full range of PWM.

You're right though, if it's anywhere near how an LED works, the very low end will be kinda crummy. I am not familiar with the stresses that they can endure though. They have the schematic available on how to use that chip, and it's available on digikey. I'm already getting a bunch of these components for some 3w LEDs, so might as well try it out too.

Unrelated question that maybe someone can answer that I have been having a hard time trying to find the answer to. When looking at galvos, I often see their ratings subject to their degree spread (like 20kpps at 20*). So, I am trying to calculate the size of a projected image based on this but I cannot figure out if 20* is from one side to the origin in the center, or the full sweep. To put it another way, if I am running at 20*, is the arc at the largest I can make it (left to right) 20* or 40*?

[dkumpula]

Unrelated question that maybe someone can answer that I have been having a hard time trying to find the answer to. When looking at galvos, I often see their ratings subject to their degree spread (like 20kpps at 20*). So, I am trying to calculate the size of a projected image based on this but I cannot figure out if 20* is from one side to the origin in the center, or the full sweep. To put it another way, if I am running at 20*, is the arc at the largest I can make it (left to right) 20* or 40*?

The stats are usually expressed as optical scan angle which is twice the mechanical scan angle. Bill Benner has an excellent book on the topic, Laser Scanners Technologies and Applications. You can get it on Kindle using the link provided for a single dollar!

Be wary though that the stats from Chinese suppliers are frequently overstated or simply copied from whatever galvo they were attempting to copy at the time. There are several reviews and discussions of a variety of scanners on PL if you do some searching.

Have fun!

-David

[neobenedict]

Worth noting, I have nothing bad to say about phenix. Both times I've ordered from them they were extremely helpful and the shipment arrived in a few days. The scanners I've used are of good quality and I have no complaints thus far. And they're perhaps 1/5th the price of what it would be to order from pangolin.