17 years ago
set and limited budget can build. The idea is that this can be built by a
highschool student or class with basic understanding of electronics and
computers and a little supervision from a teacher.
The price is *VERY* important as schools have *NO* money these days.
Overall complexity must be minimal. There should be a very easy to
understand build and operation process. At any point in time, the state of
the system should be "knowable." The whole system's operation should be
able to be debugged and "viewed" using a single debugging session.
The above requirement is why I do not want any programmable
micro-controllers on the system. While we may disagree as to whether or not
this is a reasonable requirement, please understand that this is an
Each component in the system should be easily testable independent of the
system. I.e. the wheels will use a mouse for encoders, so any program what
display mouse movement can test the motors.
I am using a POSIX style OS (Linux) because it is free and IMHO is better
suited for the task. While it is not a RTOS, it does have much better
response time characteristics and the various delays on a system that is
running a set of well define programs is manageable.
I am not using FreeBSD (or any other BSD) for a couple reasons. Device
drivers in linux are both easier to construct and load (IMHO) and more
plentiful. Linux also has better support for video and other I/O.
I am not using Windows for a few reasons. Product activation, each time you
materially change a Windows XP system you need to ask for microsoft's
permission to use it again. In a robot I will likely be reinstalling the OS
multiple times and is just not worth it. Response time, Windows is not as
responsive as a UNIX type system. Bloat, Windows is very large, a UNIX
system can be trimmed down as needed. Stability, Windows is not stable
enough to run for long periods of time.
I am using a mini-ATX or mini-ITX motherboard because it will be familiar to
almost anyone attepting this.
I am still considering the final I/O system. Right now I am using a Velleman
K8000 I2C board, and am not too happy with it. I am looking for a cheap
8255/8253 I/O board, but while I suspect there are vendors that can supply
it for less than $60, I haven't been able to find one. I may end up
building the I/O system off the parallel port.
I am using 3 separate power supplies. One 70W ATX power supply which costs
$35 at mini-box.com, one 12V 1.25A DC/DC converter, and one 5V 3A DC/DC
converter. I'm sure I can get a dual output supply for less.
Any cost cutting ideas and comments would be very welcome.
Robot Parts List $587.00
Motherboard $100.00 Mini-ITX with built in video, network
RAM $35.00 256M DIMM
12V ATX Power supply $35.00 12V 70W ATX
5V DC to DC Converter $35.00 For electronics
12V DC to DC Converter $35.00 For electronics
12V Battery $35.00
12V Charger $10.00
Ride around toy $40.00 Steel shaft w/2 motor wheels
(find at discount, surplus warehouses,
I/O Card $65.00
Electronic parts $50.00 ICs, wire, protoboards,
Wireless Router/WAP 802.11g $30.00 Belken or Linksys on sale with rebate
PS/2 Ball Mouse $3.00
Refurb 40G Hard Disk $29.00
USB Camera $35.00