Despite the fact I just finished watching the entire TNG series...
Believe it or not, this project did *not* start as a "Phaser!"
For months, I've been meaning to assemble this:
into a housing with pushbutton, so as to play with the cat. Pretty simple, really.
Just a laser-pointer, but too broke to buy one pre-assembled.
I recently acquired a lifetime-supply of barely-used AA batteries... And my stupid TV-remote, which I don't use except for the "Sleep" function, required AAA's... I've pulled those AAA's out for testing other things so many times, always forgetting to put 'em back in... and falling asleep with the blasted thing on all night... Now with so many AA's it was time to change this scenario...
Amazingly, with a bit of work, the double-A holder and batteries managed to fit!
So, in the mood for "case-modding," and having dug into the battery-holder box for that project, I saw just the thing for my cat-toy... a 4xAA battery-holder, completely enclosed. My plan was to mount the laser, pushbutton, and circuitry into one of the battery-slots, giving me 4.5V to work with...But, turns out that was a no-go... The stupid battery-door clicks into some plastic that I'd planned to remove (for comfort).
So, looking into the box of project-boxes, I found *The Most Obvious* solution, of all. For some reason I saved a TV-remote for a TV I no longer have. Well, that should be no surprise, the surprise is that I stored it in the project-box box.
Yep, we're talking: It's already got a battery-holder. It's already got buttons, it's already got a hole for an LED, and it's ergonomic!
Was still planning on throwing in an LM317 current-source as a Laser-driver... And was pondering usage of hot-glue, etc. How would I solder to the battery-terminals which were attached to the PCB rather than mounted in the housing. What would I do about interfacing with those stupid rubbery-buttons. Then when I opened the thing it struck me: Just wire the stupid laser-diode right where the IR-LED was, in the original -circuit.
Wired it up, and it worked right off the bat.
That's when the last episode of TNG finished, and the song played in the background with the credits and it occurred to me "holy shnizzle, I just built a Phaser."
- the remainder was done sans TNG episodes, having just finished the series :/ -
This particular remote happens to send the signals in bursts about every 1/4 second. So, the laser pulsates at a visible rate, in addition to the high-speed data-rate and higher-speed modulation.
Actually, it's kinda interesting, if you waive it back and forth you can *see* the data-stream. POV-eh?
But I didn't want the low-frequency pulsation when playing with the cat (she didn't seem to like it). So, first... wire a capacitor in parallel with the base of the LED-driver's transistor. No-Go... 22uF was unnoticeable, and 1000uF...? I dunno, it didn't work at all. Tried it on the other side of the base-resistor, and still nada (maybe the IC couldn't handle the current? But even *seconds* later, it still wasn't lighting). And 1000uF on the collector (parallel to the LED) only served to smooth the pulsating, more of a sine-wave rather than a square.
So I thought about it for a minute...
If the remote is expected to run off batteries for a *long* time, then it probably only drives its outputs when transmitting, so as not to waste power.
The transistor appears to be an NPN, since the LED is tied to +V, and the output of the transistor. So that means to light the LED, the transistor's base must be pulled-high. But, when it's *off*, it's *probably* not pulled-low by the IC, essentially the exact opposite of a typical "open-collector" output (which pulls-low, but floats when high).
So, I cut and scraped a couple traces to one of the buttons,...Read more »