Hardware Hacking Projects for Geeks

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Part II: Advanced Hacks, Tools, and Techniques

Project Demo

Now it’s time to plug everything in and have some fun!

1. Plug the controller board into the RC vehicle power supply.

2. Connect the IR cannon and the IR sensor to the control board.

3. Switch on the board.

4. Drive towards your other, similarly equipped vehicle and let the duel-

ing begin!

Extensions

There are many additional ways to hack a radio-controlled car. Among the

more fun hacks are modifying the microprocessor software, or adding a

small wireless camera, a sound effects chip, another power supply to power

your own hardware from the car’s battery, or additional sensors.

Software

The version of the software included with this chapter has a few limitations.

For example, when you fire your IR LED at the other car, the software does

not scan the sensors at the same time, which keeps your car from being hit

when firing. This can, of course, be changed. I will leave it to you to dis-

cover this and other optimizations and make your own enhancements.

As mentioned previously, you can change how the cars behave when they’re

hit by modifying this hack’s hardware and software yourself. For example,

you could make one car less susceptible to damage than the other, which

is ideal for rivalries between an older and younger sibling, or between child

and parent.

Figure 13-19: Program the chip

Project Demo

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Chapter 13, How to Make RC Cars Play Laser Tag

Wireless video camera

An inexpensive wireless camera can be mounted on the car to allow you to

sit “in the driver’s seat” as you control the vehicle.

You will need two items for this extension: an inexpensive X-10 wireless

camera kit and a small LCD television set.

The X-10 camera and 2.4 GHz wireless transmitter can be used as is, but you may

find that the camera does not provide very good image quality and is sensitive

to light-level changes. You may want to add a higher-quality camera, such as the

one used in Chapter 6.

Buy the Xcam2 system from http://www.x10.com. You’ll have to make mod-

ifications to its transmitter, including adding an omnidirectional antenna

and a power supply converter.

The antenna that comes with the camera is highly directional, and should

be replaced with an omnidirectional one. A simple 2.4 GHz antenna can be

built from a short length of RG-174 coaxial cable. Take an 8-inch length of

cable and strip away 2 inches of the outer coating, being careful not to cut

the metal shield. Roll it back onto the cable so that a 2-inch length of the

center conductor is exposed. Add solder to the exposed shield. Now, trim

the length of shield and exposed center conductor to 1.17 inches. Cover

the peeled-back shield and exposed center conductor with a length of heat

shrink to protect everything. Remove the directional antenna from the

X-10 transmitter and attach the new antenna so that the 1.17-inch center

conductor section is pointing up. You may need to attach a small plastic or

wooden stick to keep it upright. Do not use metal; it will interfere with the

new antenna.

The X-10 camera expects a 12V power input. Check the voltage output from

your radio-controlled car; it will likely be either 4.8V or 9.6V. If your bat-

tery supplies 4.8V, you will need to connect a 5V to 12V DC/DC converter.

This part can be purchased at http://www.mouser.com. If your battery sup-

plies 9.6V, you will need a step-up switching regulator. The MAX 771 can

be used to convert the battery voltage to the required 12V for the camera

transmitter. Look on the Maxim web site (http://www.maxim-ic.com) for

details. They even offer an evaluation kit to make construction easy.

The X-10 receiver can be used almost as is. You will need to locate a small

LCD TV set with a video-in jack to connect to the X-10 receiver. Simply

plug the video cable from the X-10 receiver into the video input on the

Extensions

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