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Small Embedded Computer with 802.11 for RC Car?
Milo_Mindbender asks: "For
some time now I've been wanting to build an RC car with an on-board
computer and an 802.11 link back to the PC in my office for
telepresence experiments (and just plain fun). As I'm planning on
doing this on my own dime, the big problem has been finding a
reasonablly cheap and low power embedded system board with 802.11 and
the right 'ins' and 'outs' to handle controling the motors (a
parallel port at minimum)." Many seriously cool devices could come
from an embedded 802.11 system, and I'm sure computer controlled RC cars
are just the beginning. Has the Embedded Computing camp hopped on the
wireless networking bandwagon? If not, what's the delay?
"I'm interested in doing two versions of the gadget, one using a system with a less powerful CPU that could do simple preprogramed moves and a second one that would have a CPU with enough power to do low-res video and two-way audio. I figure it would be a riot to remote drive one of these things anyplace in the office complex that has 802.11, stick a high-gain antenna on it and you could probably send it down the elevators and out into the parking lot! Has anyone seen an embedded system with 802.11 of either power level that might fit the bill?"
This product looks to be about what you want, http://www.linux-wlan.com/products/dk80211b.html I don't think it says anything about the price though.
"when the going get's wierd the wierd turn pro." -hst
See Ampltd for their Tiny886ULP PC-104 board with a crusoe processor. Add 802.11 to that using CompactFlash or USB and you've got a low wattage high performance x86 system.
(other pc-104 boards with much slower cpus are available for a bit less money)
I built one while working at OGI a few years ago. I've got a copy of the pages on my current server, at http://www.temple-baptist.com/~omega/ogimabot2/, with a little info on it. I should see if the prof. I was working with still has the slides to convert to HTML...
They're supposedly going to be building a new one soon, and so my research into a next-gen robot may be put to use. I was looking very closely at the Cell Computing parts (http://www.cellcomputing.com/), which aren't cheap ($1k-$1.5k depending), but are the right size and somewhat designed for that kind of stuff. Put that in (instead of on top of, like the current bot) the car (thinking of using a monster-truck chassis) and you can do pretty good. Email me if you have other questions, because I spent a huge amount of time on this project and its related issues.... nospam_omega@temple-nospambaptist. com
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You need something like a palm pilot is size and power. 802.11b is also too much, standard VHF, some sort of wireless serial scheme or Bluetooth is probally a better way to control things.
If you think about what a car needs to do, 802.11b becomes more complicated than the actual application.
Conformity is the jailer of freedom and enemy of growth. -JFK
Good idea, but I don't think you will be able to get everything down to the small size I am assuming you are planning on, and still have enough power to run everything (ie, the car, the computer, etc).
Honestly, if you wanted to do such a thing, I would look into using a 1/4 scale R/C car (read: big, noisy, and expensive), or possibly a go-cart (ie: network enabled Yerf-Dog). Either way, it won't be cheap, but you will gain the power needed to keep everything running for a while.
If you don't need to keep things running for a long time, or you don't need the range, then why do the 802.11?
Grab an FM or PCM radio control box, hook it up to the computer, and control the car. Use VHF/UHF for the camera feedback loop - if you want data feedback, you might try dropping a line of LEDs in the video frame (ie, 8 bits with a read out, digitize using a frame grabber at the remote PC), or look into dropping data into the VBI (potentially that would be more power consuming - ie, to find a VBI insertion module small enough that uses R/C car voltage levels). Or, use telemetry radio modules (Parallax sells them for the basic stamp series).
You would have all the telepresence experimentation room, but could keep the package small and relatively low cost...
Reason is the Path to God - Anon
I used a RC car, and put a X10 camera on it. I wired the car's remote control to the parallel port, and fed the video in - so I could wander around the office with it on my screen, controlled via keyboard.
Pretty fun. The range on the remote wasn't amazing though - could fix that by going to a better car.
-
Let's not stir that bag of worms...
...stick a high-gain antenna on it and you could probably send it down the elevators and out into the parking lot!
Just to clarify, in case it helps... (not nitpicking here). High gain antennas are, like the name says, antennas that transmit stronger signals than 'usual' ones. However, they don't use any kind of magic to do this; there is a price. They are more directional, meaning that they exhibit high gain in one direction and very low gain in others.
An example of this is a flashlight (after all, light is just another form of electromagentic waves). If you take the reflector off of a mag light, you get a bulb that glows equally in all directions (omnidirectional). If you put the reflector on, you can light something much brighter, but you have to point the flashlight directly at it. Also, the area behind the flashlight is completely in the dark.
So, a high gain antenna for your car would probably do best at the transmitting end, where you can point it at the car as at moves. An ordinary whip antenna (not quite omnidirectional - it's ineffective when you view the antenna end-on) on the car should be fine.
If you want to get really fancy, then go ahead and get a high gain antenna for the car. The problem is that you'll need some sort of tracking device to aim this antenna back at the base station. And when you detect that you've lost the signal due to misaiming (hit a bump, jumped off the curb, etc.), you need an algorithm to autonomously find the base station before you get run over by a big truck. Now you know one reason why nasa missions are complicated.
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We did try the thing with X10-wireless cam which is what got us started on this whole thing. It was TONS of fun but the problem was the X10 cam gets a pretty poor quality picture when the car is moving and bouncing around.
Milo from Kangaroo Koncepts
A useful link would be here over at LinuxDevices.com. The board I might suggest to you in the Bitsy with its PCMCIA slot on board. With 16MB of RAm and 32MB of Flash ROM you'd have plenty of space to stick some software to run your car. Grab an off the shelf 802.11 PCMCIA card you can find drivers for and you've got it networked. The board also has USB which works for a camera and total of 21 digital IOs that you can use to control the components of the RC car. A bonus is the card also has audio in and out so you can turn your little car into a little talking robotic badass.
I'm a loner Dottie, a Rebel.