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Brock Craft

Chapter 14

Building a Remote-Controlled Car You can buy remote-controlled car kits in hobby shops, but building your own is much more fun @@md and it’s easy to do with an Arduino and a little ingenuity. In this project, you create a fully drivable remote-controlled (RC) car by using an ordinary household remote control, an Arduino, and servo motors. You use your Arduino to decode the signals coming from any of your remotes and then use the decoded signal to tell your car to move forward,  backwar d, and turn . One cool thing about th is project is that after you figure out how to use any old remote control with your Arduino, you can transfer this capability to just about any other project that you want to add a remote control to!

 Selecting and Preparing Your Parts The parts you need are shown in Figure 14 -1. You should get together the following components to build your car, which will tak e about fewer than five hours from starting gun to finish line: * An Arduino * A remote control * TSOP2438 or TSOP4838 Infrared Receiver Module (Vishay Semiconductor) (Mouser Electronics 782-TSOP2438, and RS Components #708-5070). Alternatively, use a PNA4602 module. * Two continuous-rotation servo motors (such as GoTeck GS-3360BB, Futaba 90000008, Jameco #283039, or the Arduino Servo Module, Rapid #73-4464) * A battery holder for 6 AA batteries and a 9V battery clip * Six AA batteries * Eight header pins * A breadboard For the chassis:  ® 

* Two cylindrical cans of Pringles Brand Potato Chips * Two rubber bands about 8cm (3-4 inches) * A piece of scrap plywood or balsa wood, at least 11x17cm (4x7 inches) * A ball caster kit (Tamiya Brand @@md or Jameco #358336 or Cool Components #000984) * Mounting hardware or hot glue * Self-adhesive hook-and-loop fastener (optional)

Figure 14-1: The parts you need for this project.

You can use any Arduino for this project. An Arduino Uno is shown in the figures. The awesome thing about this project is that you can use pretty much any remote control you have in your house. You don’t h ave to use the Toshiba remote shown in Figure 1 4-1. We have six of them, and we only use two, so I grabbed a spare one. You should select a remote that has arrows in the directions that you want to drive: left, right, forward, reverse, and @@md the all-important @@md stop! I got one of our ol d television remotes because it has a circular input pad, with a button in the center, which is a good place for the “brakes”. It is  possib le that during test ing, y our remo te will not be detectable. You migh t need to try a different one if you can’t detect it during your testing. The key component of this system is the Infrared (IR) Receiver module, a Vishay Electronics TSOP2438, which operates on the 38KHz carrier frequency. Other frequencies are used as well, but you need to detect 38KHz, one that is most common to hou sehold remote controls. The component works by sensing the Infrared light patterns emitted by your remote and translating them into digital output signals your Arduino can read using a special IR library.

Only infrared light can be detected by the sensor @@md its epoxy case acts as a filer on other light frequencies. However, ambient light has infrared signatures, too. For example, a fireplace is a great source of heat and is also in the infrared spectrum. So this component is designed to ignore such stray noise. Servo motors come in two flavors: 180 degree sweeping motion, or continuous rotation. Because you are using these motors for propulsion, you must get continuously rotating servos, such as the ones listed. The servos operate at 5VDC and can be somewhat power hungry. They also come with an accessory kit th at contains mounting plates and armatures and an assortment of screws for mounting them. You need an additional angle bracket if you want to mount the servos using th is hardware. You can also s imply mount them to your car with hot glue. You use a 9V battery pack for the p roject. You could use a single, rectangular 9V cell, b ut it won’t last very long. The servo motors are pretty power hungry. You shou ld get a 9V battery  pack t hat holds six AA cells. They offer a nice balance between lifespan and weig ht. The heavier C or D cells last longer, but they may be too heavy for your car to move easily. Look for a battery holder that has a snap connector like those used for 9V batteries. This makes it

You need eight header pins. The long er ones are easier t o work with. You use two for your  bat tery pack, and the oth er s ix to conn ect your servo s to the breadbo ard. He ader pin s usual ly come in long strips, so just break off a short section of two pins and two short sections of three pins each. For the chassis, you can use any small piece of wood you might h ave lying around. The styling of the chassis is up to you, but the frame itself is carrying the weight of the components and the more weight you have, th e more durable your design needs to be. A  pie ce of s crap plywood shou ld do nicely. Yo u can also use plastic, balsa wood , or ev en cardboard, as long as it’s large enough to support all of your components and the material is not too heavy. Probably the tastiest part of the project is the two cans of Pringles, which you use as the car’s wheels @@md sadly, not the fuel. You can use almost any kind of rigid disc as a wheel, but Pringles (in addition to being edible) are easy to get, cheap, and the cans have a metal base. You need two wheels, so that’s two cans. You can use small or large cans, since you are only using the metal base. I’d recommend large cans (more chips to eat!). You also need two rubber bands that can fit snug ly around the cans without distorting th em. Without them, your wheels won’t get very good tr action.