For this Instructable we will be utilizing a mousetrap to build a simple robotic claw! This design focuses on gripping power and the finished claw is capable of picking up most anything that can fit into its jaws, including cell phones and a large roll of duct tape!

Step 1: Mousetrap Robot Claw

The basic design of the Mousetrap Claw is very simple. Using a servo and some Lego-assisted leverage you are able to open the jaws of the mousetrap, and upon the release of the servo the jaws of the mousetrap will naturally shut. Build a grippy attachment onto the jaws, and it becomes useful as a homemade claw since one of the main issues with DIY claws is gripping power.

This Instructable details mainly the mechanical side of the build, however this design is intended to be used with a servo and microcontroller. I will detail how to hook it up to a servo in the final step. I chose to separate this so that people have the option to attach it to whatever they please (such as a small robot arm, or mobile rover).

Step 2: Materials

For the mechanical side of the build you will need:

A mousetrap
Popsicle Sticks
Legos or wood blocks
Duct tape
Hot Glue
Small Zip-ties

To operate electronically you will need:

A servo
A microcontroller, I am using the chipKIT uC32

Step 3: The Pulley System

The assembly of this project is relatively simple, and open to interpretation. For mine, I cut the mousetraps top off so that I could stagger the non-moving side of the claw back, ideally giving it a bit bigger "bite".

First, I took my Lego blocks (small wood blocks would work as well) and stacked them about an inch and a half tall. Then I hot glued them into the middle of the section of the mousetrap behind the hinge. Then I hot glued another Lego block behind the stack to reinforce the system. I duct taped everything to ensure it would hold.

Finally I took my Zip-ties and zipped one around the mousetrap bar. I then strung them together until they reached over the lego-stack and to the popsicle sticks behind the mousetrap. Careful when you do that that you don't position the head of the Zip-ties in such a way that they will snag on the top Lego.

Step 4: The Claw!

Once you have assemble the pulleys system it is time to build the claw! I did this by cutting my Popsicle sticks in half, then hot gluing them to the sides of small Lego blocks. I did this in three segments each at about a 20 degree angle from the last so as to create a curved "hook". Then of course, duct tape reinforcement! Finally I Zip-tied the bottom of the claw to the front bar of the mousetrap as shown in the last picture.

Step 5: Operation and Adding Electronics

To open or close the jaws of the mousetrap, simply pull back on the Zip-ties.

I hot glued two Popsicle sticks to the bottom of the mousetrap to extend off the back so that I had room to mount the servo.

To operate with a servo, just attach the last Zip-tie to the arm of the servo. Then hot glue the servo to the Popsicle sticks. I would recommend using duct tape to reinforce this connection as well, in addition to taking a small Lego or wood block and placing it next to the servo (on the side closest to the mousetrap) and hot gluing it to both the servo and the Popsicle stick. I then glued a Popsicle stick to the top of my small Lego and the top of the servo. Servos tend to be notoriously difficult to keep in place with just hot glue or duct tape, especially when there is any degree of tension on them, so reinforcement is always recommended.

Note: This design will require a servo with a decent degree of torque to operate, I tried it using a very small servo and it had a hard time pulling the claw open, so if that is your issue you may need a stronger servo. Or try making the Lego tower taller to increase leverage.

In order to operate this electronically, wire your servo to the uC32 as shown in the diagram (the board shown is actually from Sparkfun, but the wiring is the same). Then open the chipKIT development platform MPIDE and go to File->Examples->Servo->Sweep and run it to see your claw in action!

Step 6: Applications for a Mousetrap Claw

This Instructable only details how to build and program your claw with what is basically demo code. However, this design is intended to be used with any homemade robots, as a wearable "robot claw-hand" prop, or even as part of a stand alone robot arm!

If you are interested in the homemade robots application, Instructables user JayWeeks does an excellent series on making the rest of your robot with household materials, feel free to check it out!

Another expansion idea would be to take this design and rotate it 90 degrees, then build it onto an animatronic head! Since the human jaw functions in a (loosely) similar way to a mousetrap, one could make something pretty realistic, or at least interesting looking!