That’s an interesting servo! It could be “strung” with dial cord to a larger pulley to rotate a sensor deck.
Thanks for the URL!
Alan KM6VV
I have one of them, here. They are no good for robotics. It just vibrates when close to the commanded position. I can’t see how they would be good for anything. There must be tension in the rigging to prevent the hunting.
If one needed 360 deg. rotation, one could use sprockets like below to get the 1:2 servo rotation increase. One could also do somewhat the same using plastic jar lids and string (but would look extreamly DIY).
Nice little link chain and sprockets, but the big sprocket would have to be on the servo, and the small one connected to the servo table. Or I’ve missed something.
Nah, jar lids are too tacky! But thanks for the additional URL.
I did dig up a drive train that I removed from a CD ROM drive. I have two, and the one with the worm screw is slower, and would work. I think they use it to open/close the drive door, and the disk tray. It’s just a small DC motor, and a cam operated switch. Some sort of encoder would be needed. More thought needed.
Alan KM6VV
You could use a stepper motor to only go so far. At least that is my impression on how one works.
Yes,
A stepper motor would probably work fine. And I’m quite familiar with them. I looked around this afternoon for some very small steppers that I have. Probably one of the better solutions.
Of course, it’ll need an index sensor to orientate it to “forward” on the 'bot.
Alan KM6VV
I’ve never used stepper motors, but I think they may not work well with loads unless geared down, and can be some what power hungry unless provisions are made for reduced holding voltages. Just don’t see them used much in bots.
That is why I would look into using a geared assembly like what is in a printer or cd tray assembly. It can be geared down quite a bit.
Depends on the load. I run steppers on my CNC’d Sherline mill and lathe. Normally, (real) servos are geared down, but not steppers.
This application wouldn’t need much torque. One can reduce the holding torque when idle.
Stepper motor weight/torque ratio is poor when used for robots. My first robot (a LONG time ago) used a pair of 85 oz/in NEMA #32 steppers. I threw the 'bot together with some very heavy steel pulleys I had on hand. A Small 8085 uP board ran some L/R driver boards. A pair of 12V GelCell batteries powered it.
But steppers are very easy to run! Great for positioning! I’ve always liked them, and collect them from the surplus outlets when I can find them.
Oh! I just remembered where a possible candidate for the sensor deck rotate might be! Airpax M82102, 5v 20 ohms, 7.5 deg/step. Has an attached opto-switch for position.
Alan KM6VV
I took apart a printer just the other day, got 3 or 4 opto sensors, some good connectors, and lots of smt parts 
Yeah, I’ve taken quite a few printers apart! Nice steppers!
I worked right next (next parking lot) to Weird Stuff surplus, I found a lot of stuff!
Alan KM6VV