Building a robot seems like a lot of fun – until you see how much even the smallest of robots may cost to build. We are talking of two hundred to four hundred dollars for just a tiny (but functional) robot. But what if you do not have that kind of money to spend? Well, with this tutorial you can build your own car-like robot for well under fifty dollars. This robot can drive in all different directions, respond to light, and will surely impress your friends.
Electronics
You will need lots of parts for your robot, including these necessary parts: Two Hitec HS-311 servos, a 5 volt linear regulator, an ATmega8 AVR, a 28 pin DIP socket, a 220uF+ electrolytic capacitor, two 0.1uF ceramic capacitors, two 36 position breakaway male headers, five 340 ohm resistors, five 1.62K ohm resistors, an LED, five CdS Photoresistors, and a grid type PC board with 356 holes. Furthermore, you may also need a 4 AA battery holder, an on and off switch, a 9 volt battery, a 6v 1400 mAh nickel metal hydride battery, an AVR STK serial port dongle programmer, and an AVR ISP2 programmer. Note that the latter parts are not necessary required, simply optional.
Other Materials
As for non-electronic materials, you will need many wires and screws, four 1.5 volt batteries, cardboard, a water bottle, popsicle sticks, duct tape, a computer (with a serial port or a USB to serial port adaptor), scissors, a soldering iron, solder, and safety goggles for protection from flying debris.
Building the Chassis
Once you have all of your materials together you can begin to build the chassis of your robot. Start by making some wheels out of your cardboard. They should be roughly six inches in diameter, but the size does not totally matter. Cut them out with a sharp knife and remove any burrs that may have been left on.
Modifying the Servos
Now you must modify your servos so that your robot can drive. Unscrew the long screws mounted on the corners of the servo and open up the servo to reveal its inner workings. Pull off the largest gear to find the pot, a small screw like object. Plug in your servo’s controller and set it to zero degrees. Rotate the pot to make the gears stop rotating. Glue the pot so that it remains in place. Next, find the stop on the main gear. Remove it. Finally remove the slot from the inside of the gear that was attached to the pot and reassemble everything just as you found it.
Building the Chassis, Part 2
After you have modified your servo, remove the screw that connects the motor to the small wheel. Cut a small hole in the center of your wheel and stick the freshly removed screw through it. Now attach your servo mounts to the underside of your servos and take a firm piece of plastic or cardboard (size 3 inches by 6 inches) and mount the servos to it via the screws that came with the servos. Make sure that the wheel section will overhang on the short side of the platform. Then place some tape on your servo wheels, stick your cardboard wheels to the servo, and tighten the screw.
Creating the Castor
To make the front of your robot, take a small water bottle and cut the top part off of it so that the bottle is roughly the same width all the way down. Place the bottle on top of your robot between the servos and use rubber bands to secure it to the robot’s chassis.
Electronics
Now for the difficult part – the electronics. Take your NiMH battery pack and mount it on your robot’s chassis with tape or Velcro. You can also use a battery pack with AA batteries for the same amount of power. Use the schematic located here:http://www.societyofrobots.com/images/sbs_avr_schematic.png to properly solder and connect all of your components to your PC board in a working fashion. If you do not know how to properly solder, you should find someone who does. Those with a working knowledge of electrical components will greatly be able to help you get the electronics right on your robot. Finally plug in the battery, servos, photoresistor, and serial cable into the PC board and stick the board into the bottle at the front of the robot. Tape down any loose wires that may get in your robot’s way.
Programming
You will need to download some software if you want to program your robot. Don’t worry – the software is totally free of charge, but you will need a Windows computer in order to run the programs. You need WinAVR, PonyProg2000 and AVR Studio. Read the manuals for both programs so that you can familiarize yourself with how they work. If you have no idea how to program your robot, simply download this file that the guys at Society of Robots worked so hard to create:http://www.societyofrobots.com/downloads/sbs_source_photovore_v1.zip, as it is necessary to program your robot. You can use this code with the AVR Studio program. Now connect your robot to your computer and fire up PonyProg2000. Locate which port your robot is connected to, select it in PonyProg2000 and select Write All from the Command menu to write the program to your robot. It should take somewhere between thirty minutes and an hour. And that’s that – your robot should be fully functional.
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