$50 Robot Challenge!
The idea is to have a common robot for a bunch of simple little quick robot contests.
OK, here's the skinny on the sub-$50 (actually, sub-$40!) design we
came up with about a year ago. To simplify ordering (and because the
products and prices are good), big pieces come from Pololu, and
general electronics come from Digikey.
The chassis is one of Pololu's: <http://www.pololu.com/catalog/category/26
>
These come in a variety of colors, which could be a fun way for us to
easily tell our bots apart. They're $5.95, or $5.40 in quantities of
10.
Then add the "chassis completion kit" -- actually, you'd buy one of
these for every two bots: <http://www.pololu.com/catalog/product/
762>. That's a twin motor gearbox (with motors), ball caster, and
wheels. It's $29.95 ($15 per bot), or $27 ($13.50 per bot) in
quantities of 10. This is by far the most expensive part of the bot,
but it's some pretty decent hardware.
That takes care of the mechanics. Now for electronics: we use a 400-
point breadboard like this one: <http://www.pololu.com/catalog/product/351
>. It's $3.75 ($3.38 in quantity), and means that this would pretty
well be a no-soldering kit (except perhaps for some adapters or
connectors that you might need depending on what accessories you add
to it). Of course you could replace this with a PC board or perf
board if you prefer. (See <http://www.pololu.com/catalog/product/330>
if you're into that sort of thing; it's a prototyping PCB that fits
neatly over the chassis.)
Into the breadboard we stuff an ATMega48 chip, which is $1.69 and is a
great little chip. It's a mid-range member of a family that includes
smaller (ATMega16) and bigger (ATMega168) members for those who want
more (or less!) horsepower. We add an 8MHz resonator to control the
clock speed, a 754410 motor driver chip, and a hodge-podge of support
parts (resistors, caps, etc.), all through-hole for use on broadboard
or PC board. Kit also includes breadboard wires, of course.
Sensors may need some additional discussion (Pololu has some neat new
ones we should consider, like both analog and digital reflectance
sensors at a good price; see <http://www.pololu.com/catalog/category/
7>). Would probably include a couple of buttons and some form of
reflective sensor. Also, though it's not in the current design, I'm
going to push for some LEDs -- a robot can't have too many blinky
lights.
So that's the bot itself, which comes to about $38 in quantities of
10. To program it, you'd also need an Atmel programmer, and a RS232-
to-breadboard adapter (which isn't too hard to make for o few bucks,
or you can buy a nice one from Pololu for $10). We were originally
planning to put a bootloader on the chips, which would eliminate the
need for a programmer, but at this point I think we should just get
the bot out there and roving around the table the old-fashioned way,
and worry about bootloaders later.
Rather than us all placing our own separate orders and paying full
price, I'd hope that we could get together 10 or more orders in our
local area and place them together, to get the price break. So please
don't rush over to Pololu and Digikey just yet! But this gives you an
idea of what we've been working on.
Best,
- Joe