OK - here's a write up on the 1 cell mod. This is from <alt.lasers>:
(this thread:
http://groups.google.com/group/alt....k=gst&q=heruursciences+dorcy#9226f2ddc87c5d28)
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Got the PS3 assemblies in, it appears they are NOT genuine sony oem parts, but an aftermarket part. I tried one in place of the original in a PS3 and it plays music CD's ok, DVD games OK, and when I put a blue ray game in it had a little trouble loading it though it did load eventually. Either there is some special adjustment that needs to be tweeked or that the violet laser is barely stable enough to be used for disk reading. The part number is also slightly diferent The OEM part is KES-400AAA, the parts on ebay are KEM-400AAA.
The mechanics of the thing are a work of art, it was almost a shame to rip the diode out. After a brief shrug I deftly removed the diode with a small phillips screwdriver and scissors. Then i removed the diode from it's heat sink by gently bending the heat sink, the diode pops loose very easily and was cleaned with an exacto knife and a q-tip with acetone.
To test the diode i used a SMD soldering pencil and fine eutetric 63/37 solder to solder wires to it. The solder used by the OEM to solder the diode in is indium bearing low temp solder BTW.
The diode drops about 4.3V at low current, and 4.5V at operating current, it threasholded at about 26ma and at 40ma measures about 10 mW. The output is much more multimode than a typical dvd or cd read diode, and even most laser pointers! No wonder it could barely read the disc!
Now the fun part! The challenge was to build a violet beam laser pointer that can run off a single battery!!
First the diode was de-soldered from it's polyimide piece using a very hot iorn and very fast, it desolders quickly with a 40W soldering pencil in less than a second. It was then put into the colimator assembly from a cheap laser pointer (make sure it has adjustable focus capability) powered and adjusted to collimation.
Then I went to sporting goods stores and bought 1 each of all the single battery white led flashlights i could find in town in hopes to find one with an inverter that is not potted. The winner was a $5 chinamatic one made by dorcy company. The next step was to find out how the driver is working. It is a 2 transistor osscilator with a small choke with the LED across it. It uses the inductive kickback to generate the higher voltage the LED needs, but how high?
I measuered it with an O-scope and the kick was over 50V peak!!!! E-gads much, much, MUCH too high, translated into current that is pulses in the multiple AMP range going to the LED! Guaranteed instant death for ANY laser diodes!
The next thing to do was simulate the laser diode using the white LED and get the pulses to a reasonable level. The first thing is to isolate the pulses using a signal diode and add some cap to buffer it. It so turns out a 0.1uF MMC bypass cap (small size SMD brownish things on motherboards by the dozens) drops the voltage to a more sane 6.4V peak with a more sine type waveform with the LED load, Then a 5.1V zener diode is put across the cap, giving a relitively stable 5.1V across the LED
Next is the part where you use a real laser diode, since laser diodes are current sensitive the current must be limited by a resistor. I used a 25 ohm reostat to adjust the current to lase the red DVD diode in the device at about 35ma for 24 hours to be sure the device works fine and won't kill it. There was no noticible change in power of the DVD diode.
Now for the scary part, I decided to set the current peak to 40mA, and used 15 ohms of resistance in series with the VIOLET laser diode. It WORKS!!! A PURPLE BEAM single AAA laser pointer at 7.5mW of power average current to the diode is about 38mA . I finished it by potting it in the original flashlight case with 2 ton epoxy
I only wish the color was a few nm longer in wavelength as i can's see it that well, in fact the IR laser diode in the thing at 6mW appears at least half as bright as the violet laser to my eyes. As a whole it's about the same brightness as a radioshack first generation 1 mW 670nm pointer. If you're planning to build one of these a sensitive thermopile powermeter is ABSOLUTELY REQUIRED for the sake of the diode!
Anyway I'll probably make a couple more of them and list them for saleon ebay.
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