Building a simple walking robot is really easy. Don't let the number of steps fool you into believing otherwise. This robot is basically made with a handful of household items and some simple electronics that you can easily pick up at Radioshack. In fact, this robot is entirely zip tied together, which makes building it and modding it extremely easy. If at any point you are unhappy with how its built, cut the zip ties away and zip tie it together differently.
The "brains" of this robot are also easily modifiable since it is based on an Arduino development board. Programming it and changing the code is extremely straight-forward. Even people with no programming experience can usually get up to speed pretty quickly and start coding their own robotic routines.
For me, this robot was mainly an experiment to see what would happen if I built a full-on robot that was like one of the many Simple Bots that I have built. It was interesting to see how much more robust one of these creatures become when you give it some computer logic.
Step 1: Go Get Stuff
(x4) Rubber spatulas
(x2) 6" turnbuckles
(x1) 2" x 48" aluminum ruler
(x1) Ballpoint pen
(x1) 4-40 x 1/4" nut and bolt
(x1) Arduino Uno REV 3 (Radioshack #276-128)
(x2) Parallax 4-6VDC Standard Servo (Radioshack #273-441)
(x2) 3x1 male header pins (strips of 40 available in Radioshack #277-077)
(x1) Parallax Ping Sensor (Radioshack #276-136)
(x1) Heavy-Duty 9V Snap Connectors (Radioshack #270-324)
(x1) 9-Volt Battery Holder (Radioshack #270-326)
(x1) Size M Coaxial DC Power Plug (Radioshack #274-1569)
(x1) Multipurpose PC Board with 417 Holes (Radioshack #276-150)
(x1) 90-Ft. UL-Recognized Hookup Wire (Radioshack #278-1221)
(x1) Enercell® Alkaline 9 Volt Battery (Radioshack #25-853)
(x1) 5-1/2" Zip Ties (Radioshack #278-1631)
Step 2: Saw
Cut a 10" section off one end using a hacksaw.
Step 3: Bend
Bend the aluminum slightly (to about 30 degrees) using a rubber mallet or hammer.
If you don't have a bench vise, hang the ruler halfway off the edge of your workbench, place a block of wood atop the ruler and clamp it firmly in place. You have now made an impromptu bending rig.
Simply hammer down on the ruler until it bends down over the edge of the workbench.
Step 4: Take Apart
Set them aside for some other project.
Step 5: Drill
Repeat this for the second servo.
Step 6: Mark and Drill
Place the servo horn at the 3" center point on the turnbuckle.
Position the horn such that it is making a "V" perpendicular to the length of the turnbuckle. This should, by default, position two more "V" shapes pointing to each side of the turnbuckle. Make marks in the valley of each of these "V" shapes.
Finally, drill these two marks with a 1/8" drill bit.
Repeat on the second turnbuckle.
Step 7: Mark
Step 8: Drill
Step 9: Remove
Step 10: Mark Again
Rotate the servo 180 degrees and repeat on the opposite side.
Step 11: Drill Again
Step 12: Zip Tie
Trim away the excess zip tie tails.
Step 13: Reattach the Horn
Put the first servo horn back on such that all of the "V" shapes are parallel to each of the edges.
Fasten it in place with the mounting screw.
Repeat for the second servo motor.
Step 14: Mark and Drill a Bit More
On the other side of the same servo, place the Arduino board and make marks in each of its mounting hole. Try to fit the whole thing to one side of the ruler's bend.
On the opposite side of the ruler's bend, place the battery mount and make a mark.
Drill all of the marks that you have just made with a 1/8" drill bit.
Step 15: Insert
Step 16: Attach
Repeat this process for the second turnbuckle.
Step 17: Mounting Holes
Make multiple marks on the spatula's handle on all sides of the turnbuckle to indicate drill holes for zip tying it to the turnbuckle.
Drill the marks that you have just made with a 1/8" drill bit.
Flip the spatula upside down, and place the other spatula on top of it right-side-up. Align them so they are of matching height.
Use the first set of drill holes as guides to drill another set of holes in the other spatula. This should end up as a mirror image of the first (i.e. inverted, but otherwise identical).
Step 18: Front Legs
For the best results, make sure they roughly mirror each other in position and height.
These two spatulas will serve as the front legs.
Step 19: Hind Legs
Note that the rear legs of this bot were slightly shorter than the front legs. However, this is not a hard rule. Experiment and see what works for you.
Step 20: Spacers
Cut the pen's tube into 1/4" sections using a razor blade.
These will be used as spacers for mounting components
Step 21: Trim
Step 22: 9V Adapter
Solder the red wire to the central terminal and the black wire to the plug's outer terminal.
Screw back on the plug's cover.
Step 23: Sensor Board
Solder the Ping sensor in place at a slight angle such that if you hold the board parallel to the ground, it would appear to be rotated about 45 degrees clockwise. This should counter-balance the fact that the PCB will get mounted to the board at about a 45 degree angle.
One the opposite side of the PCB that the Ping was soldered to, nstall two 3-pin male headers such that each one has a pin that is soldered to the ground rail, and a pin the is soldered to the power rail.
Step 24: Wires
Solder a 6" black wire to the ground rail.
Solder a 6" green wire to the terminal that the Ping's signal pin is connected to.
Solder a 6" green wire to each of the remaining header pins that are not connected to a power or ground connection. These two wires will correspond to the signal pins for each of the servos.
Step 25: Program
This code could definitely be more robust, but I will leave it up to you to expand upon it.
Step 26: Sensor
Zip tie it firmly in place.
If the sensor is not level to the ground, gently bend its pins until it is.
Step 27: Arduino
Zip tie it firmly in place.
Step 28: Attach
Step 29: Plug
Step 30: Wire It Up
Plug the black wire from the PCB into the Arduino Ground socket.
Plug the green wire from the Ping sensor into the socket for digital pin 7.
Plug the green wire from the front servo into the socket for digital pin 9.
Plug the green wire from the rear servo into the socket for digital pin 10.