Posts tagged: robot cameraman

Dec 24 2010

Robot eye tinkering II

Okay, so I’ve spent a little on the eye. I grabbed a £10 PS3 Eye while grabbing some other casting supplies for the business. And since whether the robot it’ll be attached to works out, I can still use it for webcasting from the workshop.

Also grabbed some M3 nuts; for some reason I have hundreds of M3 screws but no nuts.

Oh, and four flanged bearings. I don’t know the exact strength of these old servos, so didn’t want to make their job harder. For once I found prices cheaper than ebay. Most of the ebay flanged bearings were as pairs, so about £2.50 each for ones with a 3mm ID. Fast Lad Performance did a set of four for £4.08 (£6.45 inc signed postage).

The bearings arrived the other day along with some of the plain (not nyloc) nuts.

While I was waiting for them, I managed to do some repair-soldering on three of the servos with cut-short wires.

This is the sort of thing. Wires under an inch long from the PCB. I cannibalised the cables from some PC case-fans since they already had 3-wire cables with connectors on them at a standard 0.1″ pin spacing. Handily the wires are also the same colours as the servo ones!

Had to trim back the rubber gland a bit on one so the wire could bend sharply enough to clear the mechanism.

Why are the wires always at the end with the mechanical output too? It seems to mean robotics using standard servos end up using oversized brackets to clear the cables.

I also cut up the small servo with broken gearbox and got the potentiometer hooked up to a gear after a lot of trial, error and fusing gear & hubs together with the soldering iron.

When the cross-piece was cut down a bit I also drilled holes and bolted the pot-end to it, and then added the other half of the servo carcass to the conveniently identical-sized focus motor. Means I’ve been able to hide the servo’s PCB in that half for safe-keeping. Nice & tidy.

With the new bearings I drilled out some slices of the old shower cabinet frame and used them as brackets to mount one of the servos. The join is a bit loose because I over-filed the square hole, but it’ll do for the rough version.

I pressed the cowling on and loaded some nuts into it for weight. Weighing them after it drooped, I’ve got another 80grams before the servo gears won’t hold it locked in position it seems. I might be able to get away with that just fine, but it may mean bigger servos if I add an auto-focus mechanism later.

I then grabbed the tin-snips and made up a small mount for one of the small speakers from an old laptop. It looked okay, but I quickly realised it would foul the pan-tilt mechanism. I’ll have to go inside the cowling somewhere.

Need to fab up the pan mount next. Trying to get some weight away from the arms end I’m going to try and run it from a servo near the elbow using some old printer toothed-belt if I can find a matched set of belt gears.

I can probably clear up some of the tinier parts now and make some space again now the basics are together. It should get bigger & cruder as it goes down toward the base. Got some old printer flanged-bearings for the elbox & shoulder (8mm ID).

It’s enjoyable so far. But I really want that cheap camera to arrive. I know xmas post slows things down a lot, but I am a little concerned.

Please excuse the photo quality. These ones were grabbed quickly with the mobile phone. There’s enough loose glass-fibre in the workshop at the moment I’m loathed to take the good camera down there.

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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