Jumping into the self-build fray

[Galvonaut]

Thanks for the balancing info. I will see how my pennies go. I've still loads of components to buy!
I may well want to use it as a beamer - so the upgrade would be worth it I think.

Glad to hear temperate isn't an issue.

I've skipped a step in my build progression - and hope I can pull this off - going straight from single colour to PBSed RGB pairs. I am going to have one of each pair using a bounce mirror so that alignment on the PBS cube might be easier (fingers crossed).

[frostypaw]

I am curious about how to align into a PBS cube nicely. I had difficulties getting the lenses into positions where they didn't jiggle and move the beam about with single diodes, bounce mirrors could really help. Eyeing up other's builds it doesn't seem like it's that hard though so all very interesting

Almost ready to start building again here. Got some lovely silicone wire and actual diode press from Jeff/laser den with some free mini-heatshrink which is grand. My abnormally tough thumbnails were a surprisingly effective diode press but hey it's christmas etc. New Simpledrives from BBE which look very nicely made and positively zoomed over from Russia, and a new blue from DTR who was as speedy and pro as ever. The PL520 turns out to be available at a very reasonable rate from RS so might do that that way... Going to fix some little connector blocks on the back of each diode sled and wire up via those for strain relief too - belts and braces. Just pausing after finding someone with all the lasorbs in stock so I can put those in too then back on it, can't wait!

[frostypaw]

It's back up and running! dunno why the sound lags on this video, can't fix it either but you get the idea



The Simpledrives are a joy to work with, no problem with nice smooth colour fades with all the diodes. So pleased, and they're so neat and tidy. Cheers to BBE I've had a bit of strangeness about how quickly the diodes are responding to the modulation so going to re-set them up tomorrow or later but I've worn out my tiny-screwdriver muscles and patience for now and it's really fussy detail compared to all the problems there were before - far from convinced it's not down to having the lasorbs in the path. Wish I had an oscilloscope sometimes. Will be ptfe tape time too to fix the alignment and get final focus spot on.

Things I have learnt recently:

1. The stanwax ilda board dual colour led remote e-stop thing is really cool and satisfying to use even if you don't really need it. Must find more uses for dual colour leds. Do you need some Galvonaut?

2. The wiring diagram for the DB9 connector for the stanwax board is not as you are looking at the board as stated in the manual, but as you are looking at the cable. The other way around leads to much misery, head-scratching and fiddly little soldering and wiring of the tiny tiny tiny cable wires twice cos you did it upside-down.

3. Running the mains through it's relay as suggested was a little over-exciting. Caused 50hz wobble on the galvo output and terrifying noises if the DAC was outputting as the e-stop tried to close resulting in some sort of scream from the relay and no output. This might be an inrush current issue and correct functioning to protect the board, but alarming. Wired it switching the 12v output side instead - silky smooth.

4. It's normal for projector galvos to sing when doing nothing (miles back in pl's history that one) don't spend several days chasing ground loops and reading everything in the world about it first. If the dot's still, just chill.

5. 5mm aluminium *feels* stiff, it isn't. Might frame it with ally extrusion and see if that makes it more rigid and flat.

6. Big hole, small bolt, large washers. Or a better drill.

7. Dust, so much dust. A cover is a priority.

Oh and higher power laser pointers are quite satisfying but also meh, so you point it at some things then the sky and feel really paranoid for a while and then what exactly do you do with it? And why the hell would anyone ever want more than the brightness of 250mW of 445nm for *anything*? It is, with delightful irony, pointlessly bright.

here ends the crazy person long post.

[ghosttrain]

You mean 5mm for the optical plate right, not the walls?

BTW, nice beam alignment

[frostypaw]

Oooh yes, i wasn't planning on hitting anyone over the head with it

Considering the low amounts bouncing around inside which terminate themselves nicely I'm wondering about using a smoked acrylic for the walls so you can still see it flashing around, then still give it a solid roof to catch the galvo mirror losses

[frostypaw]

The strange diode glow issues remain... the bias point should be set to the moment the diode starts to lase right? i.e. proper interference speckle in the spot not just 'light' right?

There's something odd but different going on, the red channel seems to behave differently depending on the workload. Low point number frames and i get diode glow and slow modulation so white spots are cyan, higher point numbers and it behaves perfectly. Much twiddling left to do I guess!

[dkumpula]

The strange diode glow issues remain... the bias point should be set to the moment the diode starts to lase right? i.e. proper interference speckle in the spot not just 'light' right?

Bias needs to be set BELOW the point of lase - and in my experience even lower to the low end of the LED glow point, because when the diode "warms up" and its completely dark, you'll start to see some very low-level and distracting lasing.

There's something odd but different going on, the red channel seems to behave differently depending on the workload. Low point number frames and i get diode glow and slow modulation so white spots are cyan, higher point numbers and it behaves perfectly. Much twiddling left to do I guess!

I'd guess your frame is displaying beam points without many repeats (if any). A diode only responds so fast, so if you are rushing by only displaying a point with no repeats or multiple on-points in a row, you may get very little to no lase from one or more diodes. I believe most of the red single-modes are relatively slow compared to single-mode blues and greens. You'll also want to set grey-scales so that all the diodes ramp up in even-white levels.

In addition, tweaking your scanner / laser optimization settings can correct several issues with images that begin or end too hot (e.g. giving you a circle with a bright point at the begin or end of the draw) / start too late (e.g. giving you a blank spot in your circle) / display unwanted blanking trails (requiring extra post-blanking off points), etc. 'Optimal' optimization settings will vary per projector and also vary at different scan speeds.

Alternatively / additionally, if you are using the StanWax / DZ colour correction board, this type of problem may require adjustment to your rising and/or falling levels for one or more colors. Note that this board also has bias control, which affects the modulation voltage. If this bias setting exceeds the driver's beam suppression levels (frequently 0.25V or less; I believe the simple-drive is set at 0.1V), you'll essentially be forcing the driver to always be on. Generally, all-diode builds don't require a DZ colour correction board as long as your drivers have bias control and your software has color linearity control. They can still be useful for very fine tuning for very picky builders - count me as one of those.

-David

[frostypaw]

Ah thanks David - your pickiness is much appreciated here after all what's the point in precise beams without precise colour right? that's how I set them up in the end - instructions are a fickle beast in laser world. The driver instructions say to set the bias at the point where it starts producing a laser beam but as you say much better responses when it's set to where it doesn't produce any sort of glow at all.

You saying about the single mode reds being comparatively slow sounds like what I'm experiencing, at least I know I'm not going mental now! It is like the red's rise-time is just a shade laconic, once there's lots going on in the frame it wakes up and everything is spot on. Setting up using the frame with the 7 colour fades and the master brightness slider I've got everything pretty lovely for normal busy output at least.

I'll see if I can get some pictures if I can't whup it into shape today. Thanks

edit> here's the weirdness. perfect when busy, but feeling blue when not

[Galvonaut]

Great tips Frostypaw - thanks

I think I might have some dual colour LEDs laying about somewhere but thank you for offering. Are you using these in the e-stop?

The output of your projector looks amazing!

[frostypaw]

No problem, i had a slew of normal and rgb ones around but not one dual-colour bi-directional type! Yup for the e-stop remote, I didn't really need to build one for this at home but will be very useful for anything larger.

The output is lovely - I've not been doing this long enough to do anything like the pros here manage yet these diodes are so amenable that I've been able to get the beam dimensions identical (at least at my projection distance) so there's no fringing at all. Got the colour almost sorted too by strictly setting at specsheet levels then tweaking the bias and gain on the awkward frames, gonna ask if folk have ones they recommend over in the appropriate forum. Dim white lines/dots seem to bring out all the gremlins

dk's advice about the output settings was great too - adding a couple of post-blanking-off points gave the slightly slower green time to catch up - but the relationship between scan speed, the size of projection, the blankshift and all the other settings is a bit of a mystery box and I must have been through ten different setups getting there

how is your parts collection coming along?