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Picture of Cheshire Cat Pumpkin animated with LEDs
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How to carve a Cheshire cat pumpkin with LEDs animated by an Arduino.

The smile of the cat first lights up white, then the eyes green, followed by the body lighting up blue starting at the tail and moving up to the ears.

 
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Step 1: Materials and Tools

Picture of Materials and Tools
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Tools:
- X-Acto knife
- Paring knife
- Various small drill bits
- Soldering Iron
- Large pin

Materials:
- Pumpkin (I hope you picked this one out on your own)
- newspaper (for putting under the pumpkin while carving)
- heavy paper (card stock)
- LEDs
- solder
- wire
- Arduino
- scotch tape
- 1 paper clip

Step 2: Build the LED frame

Picture of Build the LED frame
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For this part, you should first print out a copy of the stencil at the same scale you will carve the pumpkin.

Next, Take a thick sheet of paper (I used 65 lb paper) and cut a shape out that will cover all of the openings in the cat pattern, but is not too close to the edge of the design (See a comparison in the second picture). Then cut a strip of thick paper about 5cm wide and attach it around the edge of the shape you just cut out.

When the edge is finished flip it over so you can see the inside.
The inside of the frame needs baffles to stop (most) of the light from bleeding between the sections. To achieve this, cut a slightly thinner strip of paper and tape or hot glue it to give definition around the tail, mouth and eyes as seen in the third and fourth pictures below.

To secure it to the pumpkin, take the paper clip (or a thumb tack) and a small strip of paper and attach them to the frame as seen in the last picture below. This allows the frame to stick to the pumpkin carving.

The final step is to coat anything that will touch the pumpkin in scotch tape, so it won't get soggy and tear half way through the night.

Step 3: Solder and program the electronics

Picture of Solder and program the electronics
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I set up the electronics so there are 6 separate LED sets to control.

Section 1 - White Mouth        - Arduino pin 3
Section 2 - Green Eyes          - Arduino pin 5
Section 3 - Blue Tail               - Arduino pin 6
Section 4 - Blue Lower body - Arduino pin 9
Section 5 - Blue Mid Body     - Arduino pin 10
Section 6 - Blue Ears             - Arduino pin 11

To insert a LED into the frame, make a slit with a knife and feed the leads through from the front. Secure it in place with a dab of hot glue on the back.

When soldering all of the LEDs, connect all of the anodes (positive) together and connect this to the arduino +5V.

I used 2 LEDs for each of the 6 sections listed above, so I connected together the cathodes (negative, with the flat side) for each section and connect it to the Arduino pin specified above. The arduino pins may seem strange if you have the newer UNO, but they are the only pins that are PWM of the older boards (I am using a NG in this case).

I then strapped the Arduino to the back of the frame and held it in place with tape and an elastic band.

Then program the Arduino using the .pde file attached to this step. If you need more help in this area there are other good instructables that can explain it better than I could.

Step 4: Carve the pumpkin

Picture of Carve the pumpkin
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Since the design is detailed, the main thing needed for this step is patience. It took me about 3-4 hours to carve the pumpkin.

I made the stencil by tracing an image found online and designing the pieces to cut out based on the lighter parts of the image. If you would like to see the original file, it is in the .psd file attached to this step.

Start the carving by taping the design to the front of the pumpkin. Now take a pin or other small pointy thing (I used a hat pin) and poke along the black lines. You want to poke enough holes so that when you remove the paper, it is still obvious where the lines are, otherwise it is a pain to cut.

When you remove the paper be sure to keep it for reference later. When you carve, start in the middle and work out. If you don't, the parts will lose structural support and could break off.

When carving, I find it easiest to use the smallest knife that will puncture the whole way through the pumpkin, but when this won't work, I use the x-acto knife to cut what I can and poke the rest of the way through by using a drill bit (not in a drill) and using a up/down sawing motion while pushing sideways to cut it out.

Once the pattern is cut out, you will need to shave the inside of the pumpkin so the back of the design in flat for the electronics. See the final image below for more detail
CheshireCatStencil.psd(1767x1295) 6 MB

Step 5: Assemble the pumpkin

Picture of Assemble the pumpkin
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The final step is to stick the electronics inside the pumpkin and turn it on. To give power to the Arduino cut a hole in the back of the pumpkin for a USB cable to pass through and plug it in.

If the frame is having trouble sticking to the pumpkin, you can use extra paper clip anchors to stick it. For better sticking power bend the end of the paper clip you are jamming in the pumpkin about 30 degrees 6mm from the end and stick it in the pumpkin 90 degrees from the final angle. Push it all the way in and twist it to the final position, this will lock it in place.

There are a few pictures below and a movie in the intro to show the final design.

If you have any comments or any pictures of one you made please leave a comment below.

REALLY COOL!