IN A NUTSHELL

Brink rover is remote control toy truck bought from Wal-Mart. It's remote control is connected with my PC. When you are driving it using those controls above, you are basically communicating with my PC and my PC is communicating with the remote which in turn controls the truck. We also mounted a cordless webcam on the truck so you can see where you are going :) There is small image server that sits on my PC, and when you press connect, it starts streaming video to you, 1 frame per second.

DETAILS

To start this project, first hurdle was to connect the remote with PC. Once you put your head around it, it's kind of simple.

Let me start by explaining how the remote works. All the regular remotes have 4 buttons, their shape or size of implementation might be different, but essentially 1 button for each direction. When a button is pressed, the circuit for that particular direction is completed and that signal is sent to the car.

I'd to replace each button with some button which can be controlled electronically (works with electric signals rather than have to press physically). I used a "transistor" for this (for those interested, I used a NPN transistor - 2N3904 available at RadioShack). A transistor is a small electronic component which has 3 legs. If you attach one leg to the positive end of circuit, one end to negative, and apply a small current to third leg, it switches the transistor "ON" and it lets the current flow in the circuit.

With transistors in place, the next step was to control the transistor from PC. The simplest way to interface any electronic device with a PC is using the parallel (Printer) port. I got an old printer cable from the thrift store, chopped one end, and connected 4 data cables to 4 transistors and the ground to common ground of remote.

Once the hardware portion was complete. I used a freeware utility to send data to printer port. I was now officially able to control the remote from my PC. The next objective was to interface that utility with internet.

For that, I wrote a server in PHP which accepts connection on a specific port from internet and passes the data on to that utility. To interface with this server, the front-end client was made in Flash. Flash has best of both worlds, one can make graphic rich user interface and it's real easy way to talk to sockets.

Since, flash does not talk to any scripts that are not hosted in the same domain as itself, I'd to serve the flash file from my system. So, now I needed an HTTP server. It seemed an overkill to use apache to serve just one file, so I just wrote a very basic HTTP server in PHP (NOTE: I'm just using PHP executable and running it standalone).

Last and least of the problems was to serve the images from webcam. I used another free utility for that. It takes the pictures from the USB reciever of the cordless cam mounted on the truck and sends it to flash whenever a user is connected to the rover.

UPDATE - 07/05/2005

Initially, our webcam was always ON, whether or not somebody was driving the rover. So, the battery drained out in 2-3 hours. Finally, I got around to making a remote switch for the webcam. I'd to hack the webcam and replace the manual push button switch with a RWS-434 434MHz RF Receiver Module & Holtek HT-648L 8-Bit Decoder IC combo. A TWS-434A 434MHz RF Transmitter Module & Holtek HT-640 8-Bit Encoder IC combo was added to the another data pin on the printer cable.The PHP server was modified to send an ON signal whenever anybody connects and an OFF signal whenever somebody disconnects, essentially saving us a lot of battery power. Another small modification was to replace the existing battery chamber of the webcam with an external custom one where we can plug 2 batteries now.