Make a Simple Bipedal Humanoid Robot (Servo Walking Robot)

Bipeds are really cool because they are by far the most recognizable kind of robot. Companies have spent decades and millions to make these things. I've been wanting to make a bipedal bot for sometime now but most of them need a lot of motors and are pretty expensive to make.
I managed to make a simple bipedal robot at home out of essentially four micro servo motors (which are pretty cheap), an arduino and a breadboard. The bot can walk, kick, dance, navigate slopes etc.
Moreover since it's an arduino you can always add sensors or other body parts pretty easily and experiment with the bot.
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Use your epoxy/Hot-Glue/Sugru to attach two motors perpendicular to each other as shown in the pictures. Make two sets of these. Each set forms a leg. Glue the two legs together. I used a broken piece of plastic to ensure that the legs are glued flat and aren't angled with each other.

Now connect the for motors on the breadboard. The last pin in each motor wire is brown signifying NEGATIVE. On the breadboard connect all the left side pins to one common negative pin. Similarly connect all the middle pins to one common POSITIVE pin. These common pins are now connected to the Gnd (for Negative) and +5V (for positive) respectively. The first pin goes into the PWM pins of the arduino. If you've used servo's with an arduino before you'll find this step awfully simple to understand. If you've never used arduino's and servo's before I recommend you view the following link to better understand how they work.
http://arduino.cc/en/reference/servo

http://arduino.cc/en/Tutorial/sweep

http://playground.arduino.cc/ComponentLib/servo

Now attach a piece of cardboard to the top of the legs and mount the arduino and breadboard on to it. Your robot should begin resembling a body with legs now. Wrap any excess wiring that may be present with tape into the robot. Hanging wires disrupt the robots balance while walking.

Take two square pieces of card and stick them to the bottom of the legs to give the bot bigger feet and better balance. I used clay to make the join look neater.
Structurally your bot is now complete!

Programming is the hardest part of this bot but I have a few programs that I've already managed to get working with this bot. Load them onto the robot and watch it do wonders!
Once you're done loading a program onto the bot you can use a USB-Wall pug (Like those that come with modern smartphones) to run the bot directly off the grid. Although in this configuration the power wire can occasionally disturb the bots balance making with wobble while walking.

Your bot is done. Remember that this isn't the end. The above set up is very simple so you can always add to it.
Two motors on the side can make arms and complete a humanoid. Moreover you can easily add sensors to the bot and make it do different stuff. For example, by adding a tiny LDR and a servo controlled pen refill I made the bot protect a car. It fired a projectile if anything came in the way. Have a look at the video.

(Too see how to add an LDR to an arduino : https://www.instructables.com/id/Laser-maze-Securit... )
Hope you liked the instructable. Feel free to comment below. :)
Enjoy!