rskelton Wrote:
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> I've been looking at similar setups off of ebay as
> well. After some more digging, I found the ILDA
> specifications here (PDF link). The "show card"
> basically looks to be a card with various
> preprogrammed displays, as well as having
> breakouts for TTL laser control and interfaces to
> the galvanometer amplifiers.
Yep, I think I see how it all hangs together.
> The ILDA spec shows that four pins, +X, +Y, -X,
> and -Y could be used to get direct XY control over
> the galvos. They take a +/- 10v analog signal, and
> that's spit into the amplifiers on the galvos and
> translate to mirror movement.
Agreed, if we create bipolar signals to feed to each galvo controller, then that allows the most direct access. The ILDA standard goes to 16 bit resolution, I don't what sort of resolution is required here.
> I guess where I'm
> lost is how to go from the standard reprap method
> of "send N pulses at frequency F to go distance A
> on the X axis at S speed" to "send analog voltage
> V with a ramp rate R from the previous voltage to
> go distance A on the X axis at S speed". I know I
> gotta go through a DAC, but that's where I get
> lost.
For me, that is the easy bit :) Where regular Reprap would output a step pulse to a stepper, we can just increment (or decrement) the current position and output the new position to the DAC. Getting a clean +/-10V output may take a little electronics, not really my field but I can probably find that somewhere.
I think this is very doable. We are helped by the ILDA standard here.
> I'm also starting to maybe lean towards a super
> lightweight delta bot, since I have the experience
> and the equipment to make most, if not all the
> moving parts out of carbon fiber and CNC'd
> aluminum. It still would be slower, but it would
> be way less work, and arguably less expensive,
> than fiddling with moving optics and writing
> custom firmware.
I admit I didn't realise how fast the laser scanning is in SLA. Deltabot would work, but I think maybe too slow for high resolution?
Cost wise, galvos might cost $120 but saves two axes.
Either way, I would quite like to play with those galvos, even I just end up with a pretty light show! Would the setup be transferable to 400mW laser? I guess it might need different mirrors, I would probably use a lower power laser for testing it out.
-------------------------------------------------------
> I've been looking at similar setups off of ebay as
> well. After some more digging, I found the ILDA
> specifications here (PDF link). The "show card"
> basically looks to be a card with various
> preprogrammed displays, as well as having
> breakouts for TTL laser control and interfaces to
> the galvanometer amplifiers.
Yep, I think I see how it all hangs together.
> The ILDA spec shows that four pins, +X, +Y, -X,
> and -Y could be used to get direct XY control over
> the galvos. They take a +/- 10v analog signal, and
> that's spit into the amplifiers on the galvos and
> translate to mirror movement.
Agreed, if we create bipolar signals to feed to each galvo controller, then that allows the most direct access. The ILDA standard goes to 16 bit resolution, I don't what sort of resolution is required here.
> I guess where I'm
> lost is how to go from the standard reprap method
> of "send N pulses at frequency F to go distance A
> on the X axis at S speed" to "send analog voltage
> V with a ramp rate R from the previous voltage to
> go distance A on the X axis at S speed". I know I
> gotta go through a DAC, but that's where I get
> lost.
For me, that is the easy bit :) Where regular Reprap would output a step pulse to a stepper, we can just increment (or decrement) the current position and output the new position to the DAC. Getting a clean +/-10V output may take a little electronics, not really my field but I can probably find that somewhere.
I think this is very doable. We are helped by the ILDA standard here.
> I'm also starting to maybe lean towards a super
> lightweight delta bot, since I have the experience
> and the equipment to make most, if not all the
> moving parts out of carbon fiber and CNC'd
> aluminum. It still would be slower, but it would
> be way less work, and arguably less expensive,
> than fiddling with moving optics and writing
> custom firmware.
I admit I didn't realise how fast the laser scanning is in SLA. Deltabot would work, but I think maybe too slow for high resolution?
Cost wise, galvos might cost $120 but saves two axes.
Either way, I would quite like to play with those galvos, even I just end up with a pretty light show! Would the setup be transferable to 400mW laser? I guess it might need different mirrors, I would probably use a lower power laser for testing it out.