Dec 14 2010

Robot eye tinkering

Not much tinkering today, but I grabbed a few pics.

This is the rotation section of the “head”. I suppose it would be the wrist if it were a grabber-arm. Little motor’s from the autofocus of an old camcorder, main gear is from a printer paper-feed. It already had a bore of 10mm so I pressed a couple of miniature bearings into it to provide ample support. It’s drilled to 8mm on the other side of the face-plate to the bearings are retained but so the M3 screw remains a static axle. The gear is mounted by drilling through three of the six handy injection-moulding marks on the gear, then tapping the plate. Finding screws that would fit in the recess was tricky.

Mind you it’s all tricky. It’s all built from junk I have knocking about. It’s just handy that human civilisation works on a few different standards and measurements, so if you have enough parts to throw at it sooner or later something will stick together. Trial and error’s what’s taking the longest here, rather than outright manufacture.

Another thing that took time was finally assesing a bunch of used servos I picked up ages ago. About half had broken gear teeth, so while I managed to put together about 5 working ones the rest are just partials unless cheap gearsets are still available for them. (some seem to have all-metal gearsets still available in old-stock form, but since I’m not really spending money on this..)

Actually I am spending a little money. About £20 on ebay for a PS3 Eye webcam for the vision and a couple of ultra-tiny servos from China (1.5g each!) to try and make some moving ears.

The small servo on the right there is one of those with a lot of broken gears. But it’s motor is about the same size as the autofocus motor, so I’m going to try and attatch the servo’s position-pot to that loose middle-sized gear. I’m eyeballing everything on this, but I think that will work and give the head about a 60-degree range of rotation from about 190 on the servo. It should be handy to be able to run it as a servo rather than directly.

How those servo parts attach will depend greatly on how I end up rigging the pan-tilt mechanism with some old Futaba FD30M’s (re-branded S20’s). Presuming they still work anyway; I still need to solder new wires to them and hook them up to the Arduino for testing. Mechanically they’re fine though and should be easy enough to connect to even without servo horns, due to the square spindle style.

That’s the plastic cowling that press-fits to the aluminium plate. I have no idea what it’s from, other than that I found it back when I lived in Hastings and it’s been knocking around my parts bins since. I think it may have come from a motorbike, as I did find some odd bits of faring down the main road at times. Else it came from the old stockroom skip at the factory, in which case there’s no clue at all. It’s a nice tapered shape and not too heavy, so will make a nice cowling here.

I cut up some old difuser plastic to see how the final thing might look. I’m thinking of surrounding the cam inside with a few RGB LEDs to convey things visually. I’d like to fit a speaker too, but nothing’s sprung up at me yet in an appealing way. Time will tell.

This is all evolving from this:

It’s a decade-old Logitec Quickcam with no casing attached to an angle-poise lamp (technically 2 , since I combined them to make a more heavy-duty angle-poise frame) via a block of wood. It’s worked quite nicely as a workshop webcam since it’s been pretty stable and allowed me to move the cam rapidly around, but the attachment leaves something to be desired because the image ends up tilted because of the order of axis. At very least it needed a new mounting arrangement which wouldn’t have been hard.. but running a computer-controlled arm into some machine-vision software with off-the-shelf face-tracking scripts to make a motion-tracking robot cameraman? THAT would be fun.

It may also let me toy around with enhanced and more intuitive computer avatar feedback for video-calls or general computer control. And avoid creepy computer avatars like Dreamer or Pintsize.

I might call it Max.

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