[EE]: Building a PIC-based Robot

   Dan, I changed the topic to separate it from the mower bots.

At 00:53 31-08-01 -0400, Dan Michaels wrote:
>Tom Handley wrote:
>>   Dan, it must be that time of year! My robot has been in a box
>>all summer and I'm ready to get back to work on it.

>Hi Tom,
>
>well it's been 7-8 months since we had the robot follies on piclist,
>so maybe time to come round again :).
>
>My interest is not so much in the mechanical end of things, but
>in the programming/behavioral stuff. What I am really itching
>to do is play with subsumption techniques. Apparently you can
>get some really cool emergent behavior out of this. "Mobile
>Robots" by Jones & Flynn has a really good description - you
>should take a look if you havena seen the book.

   I haven't heard of this but I'll definitely check it out. I'm anxious to
get to work on behaviors beyond it's current `feel and avoid' mode with
bumper switches and IR proximity detectors.

>>   One new thing I want to add is a low cost camera. I have a
>>wireless XCAM2 camera and I found a site with antenna hacks
>>for the camera. The main thing is replacing the directional
>>`paddle' antenna with a dipole or 1/4 wave ground plane. One
>>version uses 5 3cm stubs to make a 1/4 wave ground plane.
>>These were tested in R/C helicopters.
>
>If your bot is large enuf, 12" or so, you might consider
>getting one of those off-the-shelf 900 mhz A-V transmitter-
>receiver pairs - can probably be found for $70-80 at Ckt
>City/etc, and will be FCC approved. And your bot will look
>like a low-flying saucer.
>
>I expect you are going to write some nice robust machine vision
>code and not simply send the pics - yes ???? ;-)

   My bot uses two 6"x9" aluminum panels with 6 3" spacers holding the upper
deck which has nothing on it right now but... I plan on using an R/C servo
to scan an ultrasonic sensor and the compass will be mounted on top via a
wooden dowel with nylon mounting hardware.

   There is still room for the camera though. This is the X10 XCam2 2.4GHz
wireless camera system with a built-in mic. It includes their standard
stereo A/V receiver. The camera, antenna, and base occupies around 3 square
inches. The battery pack adds 3.5"x4"x1.5"h to the above. If you really want
to save space, the camera head is only 1.75"x1.5"x1.75"d and you can take
the PCB out of the base. The hack simply involves replacing the directional
`paddle' antenna with an omnidirectional version. At 2.4GHz, the 1/4
wavelength is around 3cm.

[Just checked X10s site... The A/V receiver is now tiny video-only version]

   X10 is constantly running sales but the system normally sells for $79 and
they usually throw in other things like the battery pack that attaches to
the base, extra X10 stuff, etc... Another approach, though more expensive,
is to buy their 2.4GHz A/V transmitter and receiver separately for around
$50 each and remove the PCBs. The guy hacking these for his R/C helicopter
ended up going this route with a more expensive CCD camera. For more info on
the antenna hack and X10's 2.4GHz wireless cameras:

      http://yb2normal.rcplanet.com/aerialvideo2.html
      http://www.x10.com/products/cameras.htm

>Maybe we'll get to hear from a few others about their bot F&G
>too. I've discovered there are very few PIC-botters around,
>most use 68HCxx.

   Frankly, I would have rather used a 68HC11... I use a CPLD to generate a
20-bit SRAM address and auxillary chip-selects for I/O. There's a parallel
version for bus-based systems using 40-pin PICs and a serial version with
an SPI-style interface for smaller PICs. It fits in a 44-pin PLCC or TQFP
package.

   - Tom

>best regards,
>- dan michaels
>www.oricomtech.com


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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