Category: Robots

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.

Dec 10 2010


I should be clearing up.

I should be doing exercises.

I should be learning more database theory, writing adverts, making moulds, doing accounts, doing innumerable small odd-jobs to get in a smidge of extra cash.

But I’m not.

I’ve indulged myself this last couple of days and it’s felt good. I’ve been tinkering in the workshop.

Long story short, I’ve been trying to motorise the angle-poise lamp I have the webcam attached to, with a view to getting it hooked up to some machine-vision software for motion-tracking and having it run as cameraman. At least it started there, and now I’m looking at adding microphones, a speaker and tri-colour LEDs to turn it into a sort of intuitive feedback device.

It’s essentially a robot arm though, with 6 degrees of freedom. I’ve never made a robot arm before. I also have no spare money to throw at it, so I’ve been running through my various parts bins.

Collecting “useful” things, and/or taking them apart to see how they’re assembled is something of a compulsion. However actually recombining them feels like something I’ve let atrophy. It’s been frustrating at points, but it’s an enjoyable indulgence. And it feels like it’s starting to get back into gear a bit.

It’s also helpfully letting me see what parts are actually still any use to me.

Jun 11 2010

Buster: Chapter 1 in essense

From page one, the book is memory filled. I’m glad to have it because there’s no other way I could remember the details.
Published 1976, Buster the robot is described as “one of the most unusual machines possible in the context of modern technology” and that he “Represents the highest-order machine that technology can produce today”. And I believe it.

It’s a strong contrast to the book itself, as the glue holding the pages in is cracking and the first 14 of them are threatening to come away entirely.

Buster is set out in a three-stage project (accordingly titled Buster I, II and III), in which the same machine is further added to and modified, increasing it’s abilities.

The Buster I phase warns that it will be the most expensive, dealing mostly with converting/building the driveframe, power supply, control systems and so on. Basically building Buster up as a tethered remote control vehicle, going up through the stages of; going from brute-force power switching to logic-level control, adding speed variation control, self-centring steering, and finally converting the controls over to binary.

The Buster II stage starts working on the autonomic reflex system and “brain”.
I’m rather excited that it talks of them separately, indicating lifelike concious and autonomic motivators.
The section also adds sensors and reflexes, as well as low-battery self-monitoring and an alarm to alert the owner of this, which is also used if Buster gets stuck somewhere.
After this comes the cutting of the umbilical controls, and making some form of audio control system (though it mentions the transmission format being compatible with then-current regs for data links between telephones and CB radio systems. This seems rather esoteric now! I had no idea CB radios were often hooked up to telephones.).

Buster III starts by adding the impressive-sounding “tracking function” which ties in with giving him goal-seeking abilities. This then ties in with the hunger alarm, and allowing Buster to seek out his charging station to plug himself in.
I seem to recall from the first time I read the book that this had some sort of contacts on sprung arms. Guess we’ll see when we get there.

Yes, I’m not re-reading the book up front, I’m taking it as it comes (well, chapter by chapter).

By this point Buster should be able to run around by himself, bumping into things, hurtling into empty spaces, and charging himself up when needed.
Beyond this point it talks of the icing on the cake; optional extras and so on. Things like line-following and other variations.

There’s also mention of a theoretical Buster IV, adding microprocessor control on top of the reflexes and goal-seeking. Perhaps these would be analogous to reflexes, instincts and concious learning?

The staged construction and review layout of the book sounds perfectly manageable.

And ultimately it points out that you need to choose some of the design choices at each stage yourself. It’s a recipe, not a design.

It also notes that “despiking” capacitors are omitted on all schematics. Will have to remember that.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into to re-purpose DW blog account.]

May 27 2010

Buster: Car and batteries examination

So here’s the lil fella I picked up for £3..

This little mock quad-bike is pretty lightweight. There’s some metal framework for the axles, but the rest is all a moulded plastic body. I’d be worried about it taking the weight of extra parts if it wasn’t designed to cart around reasonably large children.
The rear drive wheels are pretty worn, and all are the cheap hollow plastic variety.
They’re a lot wider and with less grip than the ones on the original Buster’s frame as best I can judge from the few photos. I’ll keep it in mind as it may have issues with drive and steering.

The rear wheels have separate drive motors, driven together on a static axle. Cheapest design, but running the motors together should be fine.

Controls are pretty simple. Two sealed 6v lead-acid batteries, a two-button toggle for forward and reverse, another for fast and slow (seems to switch the batteries from serial to parallel connection, so 6v to 12v) and a foot pedal switch to make it go.
The controls on the handlebars are purely for show. There’s nothing in them beside a horn powered by a separate set of AA batteries.

I should be able to strip off a few odds and ends, but as it’s a monocoque they’ll be a limit. And since I’m running out of space here, my Buster will need to be able to be stored outside.
I suspect the control electronics may be a bit smaller, even using as close to 1970s parts as I can. Maybe if I upturn a plastic bin on them that’ll be sufficient rainproof housing.

I was quite excited to find it used two 6v batteries, as that’s what Buster was designed to run on. However when I measured them they only read 2.27v each.
Lead-acid batteries are also not meant to be concave.

My charger wouldn’t read it as needing the charge. Rather wish the charger gave out more information on battery status. Charging complete has the same indication as being unable to charge.

As a last-ditch effort I pried the sealed cover off one of the batteries and found three rubber caps. On pulling one off there was a characteristic sucking noise. All the cells were under vacuum. So I suspect the car may have been left out in hot sun for a long time, and literally boiled the batteries dry. So when they cooled the covers were sucked on.
With nothing to loose I grabbed a bottle of demin water and proceeded to refill the cells with a syringe through the tiny vent holes.

Sadly, that didn’t work. Even after a few days for the plates to re-wet, the readings didn’t change at all. Due to construction there’s no way of getting electrolyte back out again to check the gravity. At this point though it’ll just be simpler to spend the £20 buying a new set of more powerful batts.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into to re-purpose DW blog account.]

May 18 2010

Buster: A lucky find

Currently got a bunch of things on order, and a nicely full order book. Hurrah.

Yesterday though I spotted something outside a local charity shop. A Fisher Price ride-on electric car.

When I was a child, I used to get a book out from the library over and over again. “Build your own working robot” by David L. Heiserman, published 1976 (ISBN 0-8306-6841-1). The hardback, it was bright orange and missing it’s dust cover. I read and re-read it, fascinated by the diagrams that were inexplicable yet tangibly logical. I must have been 8 at the time.
I wanted my parents to get me a pair of those electric kids cars just so I could make the robot in it; Buster.
At £100 each though, that never happened. And one day some git took the book out and never returned it. I was gutted for a long time.

Last year though, I found a paperback copy on Amazon. And now, for £3 I have the perfect electric car to do it.

After 21 years, I can finally build my own Buster. I have the chance to fulfil a childhood ambition.

I, of course, will blog it. :)

The tech involved is pretty crude by modern standards, being started in the mid 70s. I’m sure it’d be easier to redesign it with modern parts. But I’m going to see how closely I can do it to the original book. Wooden PCB racks, reed-switches and all.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into to re-purpose DW blog account.]

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