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In order to build a basic robot, you'll need several simple components. You can find most, if not all, of these components at your local electronics hobby shop, or at a number of online retailers. Some basic kits may include all of these components as well. This robot does not require any soldering:  Arduino Uno (or other microcontroller)  2 continuous rotation servos 2 wheels that fit the servos 1 caster roller 1 small solderless breadboard (look for a breadboard that has two positive and negative lines on each side) 1 distance sensor (with four-pin connector cable) 1 mini push button switch 1 10kΩ resistor 1 USB A to B cable 1 set of breakaway headers 1 6 x AA battery holder with 9V DC power jack 1 pack of jumper wires or 22-gauge hook-up wire Strong double-sided tape or hot glue You'll be building the robot's body using the battery pack as a base. This should be the end that the battery pack's wire is coming out of The servos should be touching bottoms, and the rotating mechanisms of each should be facing out the sides of the battery pack. It's important that the servos are properly aligned so that the wheels go straight. The wires for the servos should be coming off the back of the battery pack. Make sure that they are solidly attached to the battery pack. The backs of the servos should be aligned flush with the back of the battery pack. The servos should now be taking up the back half of the battery pack. It should hang over the front of the battery pack just a little bit, and will extend beyond each side. Make sure that it is securely fastened before proceeding. The "A" row should be closest to the servos. If you attached the servos properly, there should be a flat space made by them touching. Stick the Arduino board onto this flat space so that the Arduino's USB and Power connectors are facing the back (away from the breadboard). The front of the Arduino should be just barely overlapping the breadboard. Firmly press the wheels onto the rotating mechanism of the servo. This may require a significant amount of force, as the wheels are designed to fit as tightly as possible for the best traction. If you flip the chassis over, you should see a bit of breadboard extending past the battery pack. Attach the caster to this extended piece, using risers if necessary. The caster acts as the front wheel, allowing the robot to easily turn in any direction. If you bought a kit, the caster may have come with a few risers that you can use to ensure the caster reaches the ground. i

Summary:
Gather your components. Flip the battery pack over so that the flat back is facing up. Align the two servos on the end of the battery pack. Affix the servos with your tape or glue. Affix the breadboard perpendicularly on the open space on the battery pack. Attach the Arduino microcontroller to the tops of the servos. Put the wheels on the servos. Attach the caster to the bottom of the breadboard.