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Laser Scanning Display Project

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ElectroNick:
Yeah, 10Hz isn't going to work for sure  :( I have a nice driver that does approx 10kHz (or in other words, 100µs pulses) - and even that was too slow, so I had to ditch the driver.

I would guess that if there's a capacitor in the driver's circuit, it's the culprit. Nevertheless, I would advise you to set the more expensive and harder to get green laser diode aside and play with reds first until you're absolutely confident about the circuit/hardware/software.

Georg:

I got a new idea: to switch between different levels of volt. I addad 2 Ohm parallel to my circuit. I thought the laser may switch between dark and bright. As you see atleast something can be seen now... Also more dots after the other results in a brighter laser light. But is not really nice, because the lines in dark mode a still visible and the brightness of the dots is different.
Red laser is ordered ...
BTW: the 30mW green laser needs aprx 300mA - the 10mW red laser needs 35mA!! Strange - there must be a different physik behind it!

ElectroNick:
Looking at your last picture, I just had an idea - it may actually be beneficial to show empty lines as dimmer bands of light so that the eye can follow them on the wall and probably better pick up the actual characters on those lines. Perhaps not  as important if the picture is static, but if the text will be changing, and I hope to get to that point eventually, if may be easier to follow.  I don't know, gotta try though.

As far as specifics of green laser diodes (modules?) current - I haven't got one one yet but I would presume that there's not all that much difference between green and red, as in LEDs. (unlike between red and blue / UV - those have different voltage). I think it's just different drivers have different efficiencies. 

ElectroNick:
Happy New Year to everyone following this thread!  :D

There has been some progress lately, thanks to the free time afforded by the holidays, so I decided to post an update.

I think I have found the best way to spin that HDD motor! The solution was there all along, I just put it off thinking that others may be easier to implement. The practice, however, showed that quite the opposite was the case. I decided to use the dedicated sensorless BLDC  controller chip that was right there on the PCB of one of the HDDs which I broke apart to get the motor. It was a slightly older, circa mid-late 90s Quantum (I think) HDD, and the IC  Philips TDA5143T was right on its controller PCB, free for the taking. I actually almost thrown it away, I'm glad I decided to look at the PCB second time before throwing it away.

TDA5143T (see attached photos) is a 20-pin SOIC IC. It is very easy to handle because SOIC, although surface mount, is still large enough of a footprint to easily use soldering iron on. I just happened to have a 20-pin SOIC-to-DIP adapter, so I guess you might want to get one if you are using TDA5143T - will make breadboarding easy.

It is very easy to control, only 4 external parts needed - the small ceramic or poly capacitors, value of which defines the RPM and the length of the spin-up period. It starts extremely reliably using its own built-in algorithm and works all the way down to approx 3.5V - important for me because I want to power the entire device from a 5V adapter. Using a 2.5" laptop HDD drive motor you can see on the picture draws about 150mA @ 5W - perhaps it could even be possible to power from USB?

So, anyway, now that I think I got the spinning part of the project done, I got encouraged and created myself yet another 3D model of the mirror holder, this time with surfaces at 1/10° to each other (0.25° surfaces created lines too far apart on the wall 10 feet away). As usual, the model is available from Shapeways here : https://www.shapeways.com/model/1605919

I will continue working on the project as soon as my new mirror holder arrives.
     

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