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How did those lightscribe things work?

I had been reading about pcb direct exposure a while back, and now I am wondering if something like that could be cobbled together from the remains of an old cdrom drive... Unfortunately I have no Idea about (rotational-)position sensing/jitter..

I suspect the hall sensors from the bldc would not work too well because of the disturbances generated by the stator coils... so what's the alternative? optical?

The cheap integrated reflective (Omron EE-SY193

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stuff has a phototransistor and may not be fast enough... and I have no Idea what's the jitter to expect.... If the delay were reproducible that would be just fine.. but is it? Should I rather try to build it from discretes (pin diode+ir)?

Reply to
Johann Klammer
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CDROM is such a small scale. Laser printers are a better fit to the task.

With the right gear train, it's pretty good (helical gears, some friction load, and step down from the raw motor speed). The main reason for feed irregularities in laser printers was the drum journal bearings going egg-shape (two stable but different centers). The drum bearings were part of the replaceable cartridge, so you got new ones on a regular schedule.

Thus, use a laser printer (preferably one that has a straight-through feed path option) to make a negative, then contact print from that. For fine-pitch boards, it's gonna take a world-class printer, though (2540 dots per inch works out well). I've done it with paper negatives (long exposure through the paper), but the best material is a plastic film, like drafting mylar.

Reply to
whit3rd

my laser printer was never really up to the task (weak contrast), hence the idea to improvise...

Reply to
Johann Klammer

I've used an ink jet printer with the option that prints on a CD. Use acrylic ink instead of standard. Insert pcb instead of CD. Works real good. Google on inkjet print pcb

Reply to
sdy

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