Details of the Wifi Car

Mechanical
  • Chevy Avalanche from RadioShack (can't find it online, I think it's $30 new, i got just the car (no remote no box) for $10)
  • Removed internal radio
  • Figured out drive (black/white from back) and steering (black/yellow from front) wires

    Driver Board
  • SN754410 from Acroname (link)
  • 5V regulator 7805 from Radioshack (link)
  • Four inputs go to telephone cable which plugs into router (read below)
  • OK, here's a schematic

    Router
  • WRT54g with OpenWRT
  • RC Car Server is a merge of a sample TCP server and [mbm]'s GPIO tool mentioned here.
  • Added /etc/init.d/S70rcServ which runs the rcServ program. Make sure it's executable! (chmod +x S70rcServ)
  • Soldered wires to the four points mentioned in the SD Card Mod, no ground or power
  • Those go to a telephone socket in the front of the router
  • When I was building this, just like NASA, I forgot about ground. In some of the pictures, you'll see a thin blue wire that goes to the outside of the antenna connector. That's the driver board's ground.
  • Source and compiled

    Power
  • Initially I wanted to put an SLA on there. like a 4Ah that's 3.5 lb or so. But even that's too much for the shocks of the car... and besides, a 9.6v pack will overvolt to 11V when fully charged... the router will only shut down at around 7.8 volts, so it's fine. Oh and it only takes 400mA or so so the 1600mAh pack should last it for hours.
  • The drive motors take about 2 amps at stall, which sometimes overheats the chip. In the video, towards the end you can see the car being kinda sluggish... that's because the chip overheated and thermal shutdown kicked in. It takes a few seconds to cool off, then it's back in action. I am working on a new driverboard with a better chip. I realize I could build an h-bridge, but it's kinda a hassle. Chips are easier.
  • I haven't changed the default 18mW transmit power. When I add a cooling fan to the driver chip and the router, then I'll bost that up to get some more range. But without a camera, it'll go as far as you can see it, so range isn't an issue like it is with the 27MHz radio.
  • Oh and a second 9.6v battery powers the drive motors. That way they're separate and stalling the motors doesn't reset the router.

    More Stuff
  • Add a serial camera like this one, but that'll take about three seconds per frame. I just saw a USB Webcam hack that I'm definatly going to have to check out.
  • I made a PDA driver, but it doesn't use the touch screen yet. Soon, though, "just drag your finger gently across the pad and ..." -Q, "Tomorrow never Dies"
  • Any ideas?

    Page Created by Yasha Okshtein