robots.net blog for Jhoffa_

23 Apr 2003

Wed, 23 Apr 2003 19:21:21 GMT

It's been a while since my last update.

The "Big Trak" platform has been discarded in favor of a full size mild steel & fiberglass prototype. EMI problems and weight limitations ultimately did it in, but what I learned from it was helpful in refining the final design.

The new chassis (still incomplete and in the welding jig) is all that's pictured right now. But the electronics were significantly improved over what was previously listed on my page. I hope to have the chassis welded, ground, painted and crawling tentatively around the living room sometime this weekend.

Updates, pictures & diagrams will be sporadic. Added as cash, time and motivation allow.

15 Jan 2003

Wed, 15 Jan 2003 05:19:45 GMT

Updated the project page a little, posted a couple of pictures and a schematic. It's still pretty incomplete and out of order though.. a few errors I noticed. I will straighten it all out when I get time.

Experimenting with ultrasonic ranging and got the stuff for laser & fiber optic "whiskers" recently. Haven't done much with those yet, but I hope to check it out and add that soon.

6 Jan 2003

Mon, 6 Jan 2003 08:57:01 GMT

Quick Update: The Big Trak's superior size, zero turning radius and general aesthetic appeal won out, so it's new test platform.

I posted a few pictures of it as it is currently. Although the original circuitry lends itself to modification, it was all removed (except for the shaft encoder and drive motors) to facilitate testing various sensors and other electronics. Likewise, the finished version will reside within the original plastic body, but for now it's been removed for testing.

Right now it's 16F877 powered (soon to have multiple PIC's from the way things are looking) is equipped with HPWM driven IR detection, an L298 full bridge driver circuit with diode protection and a linear adjustable voltage supply with nicads for power.

At the moment it is programmed for simple obstacle avoidance and pet irritation, but compass and sonar experiments will follow shortly.

BTW, to anyone who's contemplating a small H-Bridge project, IMO, the L298 is the way to go. It's got built in current sensing and it doesn't seem to have the hyper-sensitive, freaky little "noise" issues that plagued the mosfet drivers I tested.

It's cheap too, you can pick them up online from Mouser.com

5 Dec 2002

Thu, 5 Dec 2002 02:59:13 GMT

It's here. My long anticipated Big Track, the toy I always wanted arrived today.

Looks pretty good too. Little dirty. Ripped it completely apart, scrubbed it with soapy water and a paint brush then hosed it off in the shower.

These things have about the absolute lowest quality circuit boards imaginable. Just unbelieveable. There are several places where the component legs caught the traces and peeled them away from the board itself.. then the whole mess was washed over with a wave of solder. It works though! Which is a suprise because it's supposed to be broken. I wiggled components, cleaned the contacts and it fired right up! Maybe I jostled something while taking it apart, but it works. At least for now.

Hey, there's a little optical shaft encoder in there! (And room for another, but the gearbox is moulded over it. Last minute design change maybe?)

I like this allot. It's bigger, zero turning radius and it adds interest. I think it's going to take the truck's place as platform for my sensor/battery experiments.

(My dog hates it.. absolutely loathes it.)

29 Nov 2002

Fri, 29 Nov 2002 20:50:40 GMT

Oh my.. someone is sending me a "Big Trak"

The Big Trak was one of those ultra-cool toys back in about the early eighties. It was a programmable (via keypad) severely styled truck/tank looking thing that stored so many instructions and then carried them out on demand. I never owned one, but like every other kid at the time I absolutely drooled over them. I loved these things, they almost make the awful disco music and "big hair" of the eighties forgivable.

In the pictures I have found it looks pretty big, it may even be a better platform that the 4wd truck because of the turning radius (center axle differential steering) and just the larger size in general.

Of course it had to be broken :(

(some type of problem with the electronics, the rest of it is supposed to be in good shape. So at least I won't have any guilt pangs about opening it up.)

11 Nov 2002

Mon, 11 Nov 2002 04:58:51 GMT

Updated: Pictures & Information

The basics, a general outline of my bot project.

A few pictures..

3 Nov 2002

Sun, 3 Nov 2002 08:42:03 GMT