Archive | May 2012

Belt Tension

I’ve found a way to tension the belt.




I just wrapped a bit of steel wire around it.

The laser finally works!

I found the failed power supply and pulled off the LM317 to put together a power supply on my breadboard according to the schematic in the last post.

And it works!
















Here’s a video. (By the way, GNU Media Goblin is a worthy project. You should check it out. Use it, run it, or donate to help it move along.)

LD is Fine. PS is screwed

Recent messings around have concluded that the laser diode is perfectly fine. The wiring of this 808nm diode is different from the 445nm. Instead of being unused, the case pin is actually the anode(+) and pin #2 is the cathode(-).

Furthermore, the laser diode driver that I bought is crap. It’s basically just a resistor. It puts out about 4mA at 2vdc when the bench is first turned on and gradually increases thereafter. If you’ll recall, I need about 2vdc at a constant 300mA. So that thing is junk.

I’m just going to get a LM317 and a potentiometer. I have all the other components necessary to make a good current regulator.

LD datasheet

I don’t know why I haven’t looked at this until now.

Apparently this has just been sitting in my projects folder since I got my diodes. It turns out that the operating voltage is 1.9V and the operating current is 370mA with a max of 2V and 400mA.

That LD power supply I bought has been pissing me off, so I think I’ll try my hand at building another one when I have some pocket change.


Jeez I suck at DC.

Whadya know, I’m on Hackaday

[Check it out.](

People in the comments are concerned about the current rating of the LED, and rightly so. Turns out the phone charger I’m using puts out about 3A. That seems insane to me. I wouldn’t think a cell phone could handle that kind of current.

The LED is rated for 750mA and I happen to have another phone charger here that meets that exact requirement.


WHY did I not post the Arduino code to this page?!

It appears to have gotten lost when backing up my hard drive and switching distros. Oh well. It’s not like it was that impressive or hard to duplicate…if you know what you’re doing…which I don’t.

Replacement 8mm projector bulb from super bright LED and old cellphone charger.

One of my other hobbies is small-format film. Showing them, making them, etc. By small-format, I mean 8mm, Super 8, and 16mm movie film.

It started with a $25 8mm projector from a flea market and grew into a small of obsession from there. I bought a few cameras and some films off of Ebay. I had some fun one Halloween showing a bunch of horror shorts to some friends.

One of my better finds was this 8mm-super 8 projector. That’s right. It plays both 8mm *and* super 8 film! If you don’t know the difference, I invite you to skim through [this Wikipedia page.](








I don’t think there’s anything “magical” about watching something on real film. I find it somewhat comforting that my brain is being tricked by having successive images reflected into my eyes at 16 frames per second and *that’s it*. That’s as far as the illusion goes. It is literally one image coming right after another. Don’t get me wrong. LCD screens and even CRTs are fucking cool. But film is simple and almost primordial. And what illusion there is is fragile. If the film gets jammed it will burn a hole in the frame. Learning to switch reels is a dance considerably more athletic than learning a new UI. It’s like being an auto mechanic, but instead of just fixing cars, you’re presenting a work of art.

And, yes. “I was a Teenage Frankenstein” is art. I don’t care what you say.

Unfortunately, these old projectors use incandescent bulbs that get *really* hot and occasionally explode. That’s what happened to this poor guy. What’s worse is that nobody makes these bulbs any more. You can find them for sale, but they are pretty damn expensive and in very limited supply. So, in my attempt to keep film alive, I bought [this fella]( from Jameco Electronics and opened up an old cellphone charger. This is what happened:









You might notice that this LED comes attached to it’s own heat sink. Regardless of the voltage applied,  this thing generates enough heat to burn itself out. It’s a good thing the projector has a built-in fan to keep that old monster of a bulb cooled down.

A couple cool things about cellphone chargers: they usually take in 110-120VAC and put out 3-5VDC (perfect for this LED) and they use [PWM](, which makes them really small and light.

Luckily the operating voltage for the projector bulb is 120VAC, so I won’t need to do any modifications. All I have to do now is fit a square peg into a round hole.









Basically, I just need to make a nice case for this so it doesn’t hit anything conductive and short out. Those two squares of solder on the bottom left of the circuit board are the AC in, so I need to get . Pretty soon this is going to be a pretty satisfying hack!