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hboy007

Sun Aug 14 2011, 03:50PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

Maybe some of you know GRIN (graded index) lenses. They are mainly used for beam shaping of laser diode bars but I need a GRIN cylindrical lens for a project. I really, really need one.

The easiest thing I could come up with is this:
The refractive index of epoxy resin can be tuned with additives within some range:

now all you've got to do is get two phases of resin to mix before curing. This can be done by printing a gradually changing mixture layer by layer with a rapid prototyping machine (but I don't think that'll work).
A simpler approach could be to start with 2-3mm of resin of mixture A, then soak a membrane (everything from filter paper to clay or glass fibers, you name it) with mixture B, put a bit of mixture B on top, evacuate it to get rid of gas bubbles, then press the membrane down. This will mix both phases as they pass the channels of the membrane.

Depending on the thickness and adsorption properties of the membrane, a graded concentration of Phase A will emerge on the other side of the membrane.

It if is possible to generate a stack of layers of resin , they could be pressed through a membrane to smear out the layer boundaries.

Maybe it is possible to spray epoxy with a fine nozzle and a high velocity gas jet, then one could simply use two stepper motor driven injection pumps and a mixing column in the feed line for the spray nozzle. Maybe even some piezoelectric Diesel injection system will work when care is taken and the nozzle is cleaned with petroleum after use.

Conundrum

Mon Aug 15 2011, 09:00PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Nice idea, I may have to steal it

JOKING!!

But yes the folks trying to make laser etchers using used printer mechanisms are having issues with beam homogenity, so finding two suitable lenses with the right profile then glueing them together should be able to iron out any problems with the beam.

I am working on a way to use those small mini fans used on many laptops as a bidirectional servo.

It seems that if you reverse the signals to the Hall sensor the fan spins in reverse, BUT you need to pulse one input to +V to get the fan to start.

Putting a PIC 12x between the fan drives and Hall outputs would allow this to work well, and any compatible fan can be hacked to do this.

The software ought to be easy, just High Z the outputs to stop the motor and drop current to low levels, and periodically pulse it to maintain relative position.

Use a simple toothed gear set from a dead analogue clock (cheap from charity shops) and voila.

Even count number of pulses seen in each direction so you can not only do +/- 180 degrees but speed control and continuous rotation with the same servo.

Control servo using MCLR with the relative pulse width determining the position.
If you have it set up so pulses outside the normal range are interpreted as 0-full speed and 0+full speed then the same line can be used for wakeup AND position control.

Use a pulse counter to set the speed to a linear factor of pulse width on MCLR, possibly
also have a built-in limit switch derived from a laser mechanism magnet glued to the smaller wheel so it has auto-home functionality.

Another idea related to rTMS hacking, use a stack of carefully designed multi-wire "Litz" PCBs with 0.3mm thick layers of bismuth between them to make a vertical "tape head"- like setup able to generate powerful 1-D magnetic pulses with a narrow beam for stimulating the visual cortex.

The idea here is that a single coil would need huge dV/dt to make it generate a good quality pulse. But using lots of smaller parallel coils driven with the same signal on their own small capacitors would generate a large pulse.

-A
-

Forty

Tue Aug 16 2011, 05:06AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

semi-infinite stage coilgun.
take two lengths of straight plastic pipe and two semicircle joints. build an optically triggered, dc powered (no capacitors, just a lot of batteries or something) coilgun around one straight section. rig up the second straight section parallel to the first and with a pivot at one end. arrange the semicircle joints to form a loop with the straight sections (picture: racetrack.) set up a solenoid to fling open the pivoted section. put a ferromagnetic ball inside. fire the solenoid after the coilgun gets the ball up to speed. laugh.

Forty

Sun Aug 21 2011, 12:31AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

party trick/emp mayhem
place a long, well insulated photoflash capacitor bank along the inside of a leather jacket's sleeve (loose fitting+rigid exterior would hide the bank), with a charging circuit +battery pack in the inner pocket. run well insulated wires to a glove which contains an induction-launcher-type pancake coil in the palm. run an scr trigger switch to the cuff of the opposite sleeve. enjoy flipping cans and coins out of the palm of your hand, and frying any electronics you happen to "rest" your hand on.

hboy007

Sun Aug 21 2011, 08:45AM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

maybe not suitable for plasma spray coating

but for spray deposition of a material that can be sintered, e.g. copper+tin powder mixtures.
The four rotating discs form a self-cleaning, variable aperture for the spray jet. Using a FR4 substrate covered with a hot melt adhesive, one could print traces of variable width and thickness.

Thinking of laser PCB etching devices, an electromagnetic diaphragm (as Canon calls a circular aperture combined with a stepper motor) with an adjustable diameter of 0.2-5mm may be used to control the beam of an argon laser or a focused arc lamp to achieve variable writer beam size.

Tetris

Sun Aug 21 2011, 07:34PM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

If we can have ICs with such thin circuits, why not put a twist to "PCB"and have literal PRINTED circuit boards? In essence you buy a special printer and special paper and you can buy circuits off the internet and you can use OLEDs for a display at the moment. If we can do this to ICs why not be able to etch with a special printer?

Conundrum

Mon Aug 22 2011, 06:09PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Would work, unfortunately OLEDs are very moisture and UV sensitive.

IIRC they are printed in a moisture free environment and then encapsulated with a moisture scavenger so they don't degrade as much.

Come to think of it, OLED "paint" would be badass where the OLED emitters are paired up and encapsulated in UV cured resin with little magnetic iron particles on one side only.
Apply field and it self assembles while wet, voila instant OLED display.

You could generate multiple colours by having red and green/blue on the poles, so you have a 3 colour display.
Won't be HD but would be ideal for adaptive camouflage and large area displays.
Scrape it off the glass etc and re-dissolve in solvent to recycle.

Bonus hack:- putting 2.4 GHz 0.1mm2 Rx antenna chip in each pellet so that it lights up on command.
Wifi tattoos anyone? (g)

-A

Inducktion

Mon Aug 22 2011, 07:05PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

I actually had a similar sort of idea, Highvoltagechick, but instead of using OLED's, why not use a solder inkjet dispenser? Then you just, make a sort of black and white tracing of the PCB you want to make, hit print, and the solder would be dispensed accordingly.

Problems being, getting the solder hot enough to melt, as well as getting the solder to stick to whatever you're printing to. Perhaps, make it so the printing area is relatively airtight, then heat everything up inside to a good temperature, soldering temperatures to be exact. (what effect would this have on the PCB plastic?)

Chip Fixes

Mon Aug 22 2011, 11:19PM

Registered Member #3781 Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701

You could use cold melt solder, it melts at a much lower temperature but takes a while to harden. Otherwise they have those conductive ink pens, you could just use the conductive ink? I am not sure how stable the ink would be long term though

hboy007

Tue Aug 23 2011, 10:57AM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

cylindrical condenser lenses for cheap: apply a thermal profile to a sheet of PMMA (use an array of NiCr wire or project IR light > 2,2Âµm onto the sheet), then pull out slowly.
Maybe some changes to the heating pattern and FEM calculations magic will be needed to get the correct aspherical lens shape but cost will be really low. If you don't care about induced birefringence and loss of polarization, this is how to.

easier way to get a lens (plano-convex): buy an acrylic tube, cut out a section of it, close the sides and pour MMA resin into the curvature.

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