Reuse Those Servos!
April 8, 2009
I'm kind of new here, so here is my first post. It might seem dumb at first, but I think it's a great idea. I've read a lot of posts about people frying their servos (hint: fritsl's cheap tiny blue ones, said so himself! :), so I came up with a money saving solution. REUSE THE SERVOS! YA!
Servos are expensive after all, and they do have some good gears and they mount easily. So if you fry one, I wouldn't panic too much.
See, why would you want to spend money on this-
"Gearhead motor in Clear Servo Case"
It costs 12 bucks! You could buy a normal servo WITH brains for that kind of money!
But lookey here...
You have just burned out one of your servos and you need a nice geared motor!
TIME TO GET OUT THE SCREWDRIVER! (yeah I know, who in this site owns a screwdriver when we have hot glue?!)
Step 1) Observe.
Yes, it's a VEX servo motor. But it's almost exactly the same as other servos except for the weird connector head. It's male instead of female. Notice the servo is basically three sections: (count them) gear assembly cover, motor body, and controller circuit cover. Vex servos have "female shafts" if that's possible, meaning that you have to stick a metal rod into the output axle hole. And also, they have these wacko mounting holes that project from the body. Just google a pic to see what I'm talking about.
Step 2: Remove Screws.
I skipped a step or two, but I'm sure you guys can figure out how to unscrew some bolts. Some servos have really tiny screws, like this one, so having a precision screwdriver is necessary. You might also need a glasses- screwdriver, (most creative name I could invent) that are used for re-tightening screws on glasses. They're small. But not hard to find, as a local pharmacy probably has has them, got mine for about 2 USD.
Also, my camera ran out of juice right now, so that last pic you just saw was taken with my 1080p hi-def Sony camera. You lucky dogs! Too bad I had to compress the photo to, like, 50 kilobytes from 2.4 megs.
Step 3: Taking off the gear cover.
To take out the circuitry, you might have to take out the gears as well. Sorry for my hand being so shaky, I'm not a very good photographer. Oh well, so much for 1080p. :(
Step 4: Bust it apart! YA!
You see? I have decimated my servo carefully down to the core. Don't worry, I can put it back together! I think...
I don't know if you can see, but there are two tiny screws right by the motor shaft poking up through the black box. Tiny.
Step 4: Pull out the guts.
AWESOME! Try this awesome trick out (IF YOU HAVE A WORKING SERVO, AS THIS TRICK REQUIRES WORKING CONTROL CIRCUITRY.) Simply plug your servo into a VEX microcontroller OR a normal controller and feed it a "centering" signal. (750 ms, is it?)
Then, turn the potentiometer, or trimpot, whatever. The motor should spin in an effort to re- center, but it's actions are futile unless you manually twist the trimpot back to center.
Now since my servo is perfectly good, I'm not actually going to take it apart. (sad music plays)
But I'll help you!
Ok. First de-solder the motor from the circuit board. Then solder some wires to the motor. Re-assemble your servo (but leave out the fried circuitry) and there you have a nice, geared motor! For free! Kind of. And you're going green! YAY!
The solder joints to the motor: (notice they are substantially larger)
You might like the fact that servos have everything built in. So.. You can try these "secret motor driver chips" from Solarbotics and HVW Technologies. I'm surprised nobody really knows about HVW Tech. Sure Solarbotics is good, but they're BEAM oriented. So they don't have the Sharp GPGD12 or whatever infrared ranging system like HVW.
But anyways, the Secret Motor Driver is based around a small surface mounted L293D H-Bridge chip, the one everyone knows about. And better yet, the whole circuit fits right in any standard servo! Of course, if you're like Frits and fried your titchy servo, then you're just going to have to control the motor externally. Like usual. Boring old usual.
Here's a pic:
Well, that's it! Hoped you liked it!