ins_atge@jhunix.HCF.JHU.EDU (Thomas G Edwards) (05/30/90)
About a year ago, I purchased a .5 mW helium-neon laser tube at a hamfest. Unfortunately, the guy didn't have a power supply, but for $30 for the tube, I figured I could make my own. I went around the hamfest and found a 120V to 630V transformer. I also got enough pieces for a voltage quadrupler with 1000V capacitors and 6500 PIV diode packages. It turned out that the laser did not fire when I hooked up the circuit. I tried different balast resistors, but still nothing. Much later, I decided to work on the project again. I finally bought a VOM with a 1000V scale. I also came into a 120V-30V transformer, a 120V-6V transformer, and a variable transformer for 400 cycles. So, I kludged together the following circuit: 120V to 30V transformer feeds the variable transformer (not getting it too warm at 60 cycles). The variable transformer feeds the 6V-120V transformer. That feeds the 120V-600V transformer, which finally feeds the quadrupler. I slowly turned up the variable transformer, and the laser lased at around 700V input to the quadrupler (thus only slightly overpowering the 6V-120V and 120V-600V transformers). I woudln't reccomend anyone to copy this circuit, seeing how there are multiple overvoltages and the variable transformer must be kept at a fairly low voltage, but it is an example of how one can work with a bunch of free and inexpensive parts to put together a laser system. total cost was around $60 (not including VOM). I spent last night bouncing the laser around with mirrors around my room, down the hall, out the door to the late-night barbecue on our porch. Lighting up neigborhood stop signs from the second floor window is also fun. And finally, we passed the laser beam through various multi-faceted glass dishes we had for interesting refraction results. Now all I need are two galvometers... -Tom
grege@gold.GVG.TEK.COM (Greg Ebert) (06/01/90)
In article <5395@jhunix.HCF.JHU.EDU> ins_atge@jhunix.UUCP (Thomas G Edwards) writes: > >I spent last night bouncing the laser around...... > >Now all I need are two galvometers... > Try mounting a mirror fragment on a speaker. You can get x-y positioning with your stereo. Better yet, get several DC motors with separate voltage control. Place a mirror slightly off-perpendicular with respect to the axle. Zig-zag the beam between 3 or 4 motors, and finally onto you wall. Vary the voltage on the motors to your heart's content. You can get some incredible patterns. For maximum enjoyment, crank-up some Pink Floyd, have a few drinks [or whatever :-) ], and enjoy.
cgordon@vpnet.chi.il.us (Gordon Hlavenka) (06/02/90)
>Now all I need are two galvometers...
No, it works well with an old speaker. The trick is to glue a mirror onto
the voice coil, but just a bit off center. You also want some "slop" in the
mounting. I find RTV works very well. When you play sound into the
speaker, you get wonderful patterns.
For more precision, remove most of the speaker cone and mount the mirror
firmly onto a rigid stick which pivots on the rim of the speaker frame.
This gives _mostly_ linear response. With two of these and some playing,
you can do circles. With LOTS of work you can do small amounts of text or
simple line art. But I mean _small_ amounts and _simple_.
There are companies that sell positioners for laser drawing. With these you
could build a laser TV projection system or something... But that's
probably out of your price range for a $30 laser.
Interesting app:
A friend has a 4-acre lot, and often has unauthorized hunters on the
property. He bounces the beam around two corners to cover 3 sides of the
lot. When the beam is broken loudspeakers in the brush tell the hunters to
get lost. Of course he has to keep the brush trimmed back, the mirrors get
knocked around / dirty, and he warns off a LOT of animals. But it's fun to
play with, and that's the whole point after all...
Gordon S. Hlavenka cgordon@vpnet.chi.il.us
DISCLAIMER: He's lying.ins_atge@jhunix.HCF.JHU.EDU (Thomas G Edwards) (06/05/90)
In article <2667547f-214.1sci.electronics-1@vpnet.chi.il.us> cgordon@vpnet.chi.il.us (Gordon Hlavenka) writes: >No, it works well with an old speaker. The trick is to glue a mirror onto >the voice coil, but just a bit off center. You also want some "slop" in the >mounting. I find RTV works very well. When you play sound into the >speaker, you get wonderful patterns. I tried mounting a mirror on a small speaker by taping one side of it to the rim of the speaker, and letting the rest of the mirror hang over the coil region. Very neat effects. Now all I need is to replace it with a front surface mirror to allow the best reflection. I mounted a mirror on a shaft of a DC motor (mirror is perpendicular to shaft on the end), and noticed that the reflected laser beam forms a circle on the wall (I thought it would form a small line...I forgot that the mirror would be off-axis in two different ways). I have had fun projecting it onto the wall of a nearby building. -Tom
bldrnr@Apple.COM (Brian Hurley) (06/06/90)
Ack, a speaker with a bit of mirror on it? In some areas it is possible to find early Pioneer LDP 1000 laser disc players that have a HeNe laser, several red-spectrum surface mirrors, a 10mm x 10mm beam splitter, and a pair of galvos with surface mirrors attached. These little dudes are used to position the beam on the surface of the disc. They are about 8 ohms impedance and work quite well when driven from LM386 audio amps. The LDP 1000's are usually found at surplus places for between 25 - 99 dollars depending on where you find them. I have a little rig that I have built that uses a Macintosh SE as a sound source, and a delay pedal(from my electric guitar) to display all kinds of neeto patterns. Don't expect a lot of bandwidth out of the galvos. Above about 500Hz, they are worthless, nonlinear, and given to making like fuses if driven too hard. For my $99 it's been a heck of a lot of fun. Your milage may differ. - Brian bldrnr@apple.com
siegman@sierra.STANFORD.EDU (siegman) (06/06/90)
In article <5452@jhunix.HCF.JHU.EDU> ins_atge@jhunix.UUCP (Thomas G Edwards) writes: > >I mounted a mirror on a shaft of a DC motor (mirror is perpendicular to >shaft on the end), and noticed that the reflected laser beam forms >a circle on the wall (I thought it would form a small line...I forgot >that the mirror would be off-axis in two different ways). >I have had fun projecting it onto the wall of a nearby building. > 1. The mirror should be (MUST be) just slightly OFF perpendicular to the shaft. 2. Bounce the beam off TWO such mirrors in a zigzag "shallow Z" configuration. Include variable-speed controls on both motors, and be sure to include a reversing switch for one of them. Interesting "circular Lissajou figures" are the result. Also interesting: the difference in patterns when you reverse one
jharkins@sagpd1.UUCP (Jim Harkins) (06/07/90)
In article <2667547f-214.1sci.electronics-1@vpnet.chi.il.us> cgordon@vpnet.chi.il.us (Gordon Hlavenka) writes: >The trick is to glue a mirror onto the voice coil, but just a bit off center. You might also try taping aluminum foil or saran wrap to your speakers. I used to have a laser and had nothing but fun with it. Too bad my He-Ne tube quit lasing and I'm too cheap to buy another. -- jim jharkins@sagpd1 I hate to see you go, but I love to see you walk away.
kp74615@kaakkuri.tut.fi (Karri Tapani Palovuori) (06/07/90)
In article <808@sagpd1.UUCP> jharkins@sagpd1.UUCP (Jim Harkins) writes: >Too bad my He-Ne tube quit >lasing and I'm too cheap to buy another. Try immersing it into pure Helium (from balloons, for example). This is a known (desperate) method to repair 'aged to death' HeNe -tubes. If the reason for malfunction in your case (in your tubes case ;-) ) is the slow leaking of helium through the tube walls, this could work. A day or so should be enough to let some He 'leak' back into the tube. Remember that the atmospheric pressure (which you should use) is MUCH greater that the partial pressure of He in the tube, so also the change is much faster. >-- >jim jharkins@sagpd1 > >I hate to see you go, but I love to see you walk away. Karri Not in my case, I hope.