A few weeks ago the most adorable little Päckchen arrived on my doorstep from Germany. Inside was the EasyLase USB interface by JM Laser. The EasyLase is a USB device that has a 25-pin ILDA compatible DB-25 connector to output analog signals for laser projectors. It incorporates 12-bit DACs for the X-Y channels for superior resolution.
In testing so far, it seems like it is going to be great, but there is plenty of coding to do yet to achieve the greatest performance. The card has plenty to give, and extra features like DMX512 In/Out--one less thing I need to buy!
Thus far, because the projector isn't quite finished yet, I've been testing with a Tektronix 2440 Oscilloscope. My friend Sean helped code a 3d Torus demo. It worked quite well, but I'm still having trouble with FTDI's D2XX driver for OS X version 0.1.0, perhaps the next version will solve some of the problems I'm having. Specifically, read and write calls are hanging when I know they shouldn't.
A while back I had the pleasure of speaking with a gentleman named Craig from the ECE Machine shop here at my university. I had the opportunity to talk to him because I was picking up some parts that he had machined for me out of solid aluminum!
Key features include all-aluminum construction for optimal heat-dissipation as well as strategically placed mounting holes for circuitry or additional heatsinks. The should also provide flexible mounting surfaces for the galvos. It will be necessary to use thermal epoxy to glue the coils to the surface for maximum thermal conduction.
I really anticipate these will provide high-performance platforms for the rest of the components.
I spent quite a while building the prototypes. They include the cheap bearings I bought at the hobby store, a steel axle, and the N50 cylindrical magnets.
The acrylic models gave me a good idea of the tolerances involved, but it was clear I needed more precision. I used the dremel to finish the prototypes, drilling holes, and tapping some of them for 2mm screws. Unfortunately my drilling was not precise enough for production work.
I never install the coils more than just for test-fit in the acrylic prototypes. Amplifiers would be needed before any performance testing would be possible anyway. Eventually the prototypes proved useful in demonstrating design to the machinists that would build the aluminum pieces for the final version.
Electricity can be scary. As can be lasers. When working with high voltage and lasers always be sure to post appropriate warning signs. "But what if I don't have the appropriate warning signs," you plead. (Of course you are asking this, because of course you are commonly working with these, and other sorts of dangerous things...) The answer is simple. Make your own by following these simple steps:
- Find appropriate warning sign on Google Images
- Re-implement graphics in Adobe Illustrator
- Mask, X-acto, and paint; repeat for each color
I followed this procedure exactly and produced a great warning sign for the power supply mentioned in a previous post.
I recommend using a good german font, like one from the DIN Schriften family, and being careful with the masking. I covered the box in masking tape, printed my design, and taped the printed template. Next I used an X-acto knife to cut out areas of exposure for a given color. I repeated for each additional color, layering as I went.
Speaking of Power Supplies…Every summer I spend way too much on eBay. Case in point:
Its a Power Designs TP 343B triple output power supply. Extremely well built on the outside, surprisingly modern on the inside, with ICs and such. I'm quite happy with my first real lab power supply. There will be at least one more post about summer eBay purchases within the next few weeks. I can make this guarantee because I have already made the purchase.
I started working with lasers in 2003 when I bought the above Siemens LGK-7630 HeNe laser off eBay for like $15.00. It was lots of fun; rated at 6.0mw; manufactured in march of 1984, and tested 6.4mw (according to a sticker) in 1986; apparently removed from an old Xerox product of some sort.
Shortly after getting my second laser, the Argon Ion one, the power supply on the Helium-Neon failed catastrophically. This isn't such a surprise for a $15.00 laser, but I couldn't find a suitable replacement at a reasonable cost for a long time. Having the JDSU 2214 around made it even less of a priority.
Fast forward to 2006; development on LaserLine and the galvanometers is getting serious, so I need an easy to operate beam that I can switch on and off with no fuss so I can focus on development of the scanning hardware and software. No maintenance; instant on, quiet operation. Perfect.
Meredith Instruments (via eBay) happened to have a Melles Griot 05-LPM-948-065 Power Supply at just the right price. It does somewhere between 1.85 and 2.45 KV at 6.5ma; quite reasonable for the 15" LGK-7630 tube (well, the enclosure is 15", I'm guessing the tube is 13" or 14").
A quick trip to Fry's provided me with some parts for the enclosure; other parts were found in my basement. Plenty of Dremel work was required for the IEC power plug and 1A breaker, but they look nice. Now I just need a source for a key switch, because it is a class IIIb laser, being above 5mw. Black paint should really make it look better too.
The beam profile on the HeNe is so much rounder and consistent than any laser pointer I've ever used. (The dimmer 2nd beam in the top picture is laser pointer to which I was comparing beam profiles.) The picture below illustrates the quality Gaussian profile, but also illustrates the noise around the outside. I'm thinking much of it can be attributed to a dirty external surface of the OC. Pretty good for 22 years though...
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