In this Instructable, we will be detailing how to go about making your very own Tentacle Launchpad! This project was designed as an extension of my Animatronic Tentacle Project, as it seemed a natural second step once you have built a tentacle to send it flying through the air at unsuspecting passerby.

The Launchpad makes use of a mousetrap, ping sensor, and chipKIT uC32 to detect motion and within a few seconds, fire at aforementioned motion.

Unfortunately I soon discovered that the mousetrap was not quite powerful enough to satisfactorily launch the full sized Tentacle, so I ended up using smaller zip-ties to make a mini version which ended up being the perfect size!

It can also be used as a basic desktop catapult if disembodied sea creature arms are not your projectile of choice.

See it in action below:

FDBTBYJIK75CHDL.mp4
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Step 1: Gather Materials

For this project you will need:

Some sort of sturdy circular cardboard (I used a old paper towel holder I found around the office)
A V8 Juice can for weight
Small servo
Mousetrap
chipKIT uC32
Ping Sensor or Ultrasonic rangefinder
Wires
Copper Tape
zUNO clips (2)
Popsicle stick
Two zip-ties (one larger one smaller)

Step 2: Assemble Launchpad

The Build:

The basic assembly includes first attaching the V8 Juice can to the interior of your cardboard roll to make a strong, heavy base. Then hot glue a zUNO clip to the side of the cylinder you want to be approximately the "front". Now clip in the uC32. Take the mousetrap and hot glue the other zUNO clip onto the back about in the middle (of the back). Hot glue the mousetrap to the top of the base keeping in mind which direction it will fire.

I taped a Popsicle stick to the side of the base to use as a "guide" to keep the zip-ties from slipping up the servo arm (toward the gearbox) and not firing when directed.

Using needle nose pliers, bend the tip of the metal bar on the mousetrap so that you can securely affix the large zip-tie to it. Then put the smaller zip-tie around the larger one. Make sure it can still reach the arm of the servo, which you basically have to glue to the side of the base so that it can hold the trap taut.

Wiring of the circuit is explained in the next step and I would recommend waiting until you have assembled the base to do so. I just am resting the rangefinder atop the uC32.

Step 3: Electronics and Code

The circuit is simple. Tape the two positive leads from the servo and the rangefinder to the side of the base with copper tape, then tape a third wire in connecting to the positive "5 Volt" header on the uC32. Then attach the servo and rangefinders grounds to the two ground headers. As for signal wire the servo signal wire is attached to pin 8 and the rangefinder is attached to pin 7.

The code is below! If you have not already make sure you download MPIDE to upload the code to the board.

I currently have the range set to 6 inches but feel free to change that to increase likelihood of triggering the launch.

Lunging.zip
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Step 4: Create Projectiles

In addition to the tentacle, the Launchpad can also be used to catapult a wide variety of small objects. My personal favorites include pens, ping pong balls (I cut out the bottom of a coffee cup to use as a vessel to hold them until liftoff) and "Kamikaze Kisses" (in the spirit of Valentines day). To make the Kisses I simply slit halfway across a ping pong ball and glued lip shaped foam onto the top and bottom of the "mouth". Then I added googly eyes.

Step 5: Aim....FIRE!!

To fire, pull the mousetrap back and instead of placing the metal bar directly across (as you would if you were using it to catch a mouse) pull it over the corner and off the the side so it holds the trap taut. Then loop the smaller zip-tie around the arm of the servo, making sure it is holding the zip-ties (and subsequently the bar) down. When you are ready, wave hand in front of rangefinder to fire. Or set it up in an area where passerby can set it off.

Optional Extension: If you are launching the tentacle, feel free to add a motor with adequate torque to the base of the tentacle, attach a 1/2 inch or so arm to the motor and connect about 3-5 volts of battery power. This way when the tentacle is on the ground it is contracting and un-contracting, to really up the creepiness.