WARNING!: This pumpkin is extremely dangerous and you definitely should not make one of these. The instructions were posted here are for entertainment purposes only. I do not condone the manufacture or use of flamethrowing jack-o'-lanterns. Seriously, nothing good will come of making one of these. Don't do it.
Step 1: Go Get Stuff
For carving the jack-o'-lantern, you will need:
- A large pumpkin (mine was probably about 18" in diameter)
- An assortment of cutting knives. Serrated seemed to work the best.
- A marker
- Paper and pencil
- A spoon
- Other scraping implements. I found a chisel worked very well.
For the remote controlled flamethrower:
- Door lock actuator
- SquidBee transmitter and receiver. I had these lying around from a previous project. Any Arduino/Xbee combination should do.
- An extra ATMEGA168 or ATMEGA28 (only if using the Squidbee setup above as the receiver has no chip)
- Small can of WD-40
- 12" x 12" x 1/8" sheet of black acrylic
- SPST 5V relay
- 5" x 2.5" x 2" project box.
- SPST momentary pushbutton switch
- 10K resistor
- (x2) 9V battery snap
- (x2) M-type plug adapters
- Misc. long zip ties
- 16" x 2" x 1/4" aluminum extrusion
- 3-1/2" x 1/4 bolts
- (x6) 1/4 nuts
- Tea light
Step 2: Cut a Cap
Cut around the stem of the pumpkin at an angle (with the knife slanted in towards the stem of the pumpkin)
After you are done cutting all the way around, remove the stem. This will serve as your lid later on.
Step 3: Gut It
Remove the guts from the pumpkin. To start it should be easy simple to pull them out by hand, but this is going to quickly become too difficult.
Using a metal spoon or other scraping tool (I found a chisel works best) scrape the sides of the pumpkin and remove all of the slimy innards. The inside should be reasonably smooth and clean when it is done.
Step 4: Design a Face
Draw a face on a piece of paper and then cut it out and tape it to the pumpkin.
One thing to keep in mind is that the mouth needs to be large and about halfway up the pumpkin or the flames aren't going to be able to shoot out.
Step 5: Trace
With a marker, trace the outline of the face onto the pumpkin and remove the paper.
Step 6: Cut
Cut out the pumpkin's face. For the larger and more complicated shapes like the mouth, it help to cut it out in smaller pieces instead of trying to remove one large chunk from the pumpkin.
Step 7: Bend
Make a mark about 6" from one of the edges of the aluminum extrusion.
Line up this mark with the edge of the workbench and clamp it between the workbench and something stiff and flat like a 2x4 or metal bar.
Grab the protruding edge firmly and push down until it is bent to 90 degrees. In doing so, you may want to push it slightly past 90 degrees as the aluminum tends to spring back a little when done.
Step 8: Brackets
Download the following files for the motor mount and candle holder.
Use these files as cutting guides to cut the pieces out of 1/8" acrylic.
At times like these, having a laser cutter or using a laser cutter service comes in handy.
Step 9: Drill Holes
Use the two mounts that you just cut out as drilling guides on the aluminum extrusion.
The motor mount should line up with the long edge of the extrusion and you should use a marker to mark all 4 corner holes.
The candle mount should be slightly backed off from the short edge. Make two marks for those holes as well.
When you are done, drill 1/4" holes through the aluminum using a drill press.
Step 10: Attach Things
Stack the two motor mounts and align the motor atop it. Zip tie it all to the aluminum bracket.
Below it zip tie the small WD-40 can. The actuator from the motor should be aligned and touching the top of the can, but not yet pressing down firmly onto it.
Step 11: Candle Mount
Insert the two bolts upwards through the bottom of the aluminum bracket. Fasten them in place with bolts.
Thread on another bolts onto each. Twist this about 3/4" down.
Place the bottom of the candle holder (the side without the large hole) onto the bolts. Then place the top candle holder bracket.
Fasten the whole thing in place by threading on another nut onto each.
Step 12: Battery Adapter
Solder the 9V battery snap to the M-type plug such that the red wire is connected to the tip and the black wire is connected to the barrel.
Don't forget to slip the plug's cover onto the wire before you solder.
Step 13: Program the Receiver
Open the SquidBee transmitter node and remove the Arduino from the XBee shield.
Change the power jumper on the Arduino to select USB power (if necessary).
Program the Arduino with the following code:
When done, disconnect the USB power, change the power selection jumper, and plug the XBee shield back in.
Step 14: Program the Transmitter
The transmitter is a little bit trickier if you are using a SquidBee setup because it is lacking an ATMEGA chip.
First unplug the XBee shield.
If necessary, add and bootload and the chip.
Then, like the other board, change the power selection jumper to USB, and then upload the following code:
Lastly, change both of the TX/RX jumpers on the XBee shield from USB to XBee.
Step 15: Switch
Drill a 3/8" hole (or whatever is appropriate for your switch) in the side of your project enclosure.
Install the pushbutton switch.
Step 16: Antenna
Install the antenna into the side of the enclosure opposite the switch. Be careful not to break the wire connecting the antenna to the XBee.
Step 17: Wire the Transmitter
Solder a wire to one leg of a 10K resistor. Solder the opposite end of this wire to one of the switch terminals.
Plug in the side of the resistor with the wire soldered to it into pin 2 of the Arduino. Connect the other end of the resistor to ground.
Solder a wire to the other terminal on the switch and connect this wire with 5V on the Arduino board.
Lastly, plug your 9V battery connector into the power socket on the Arduino board.
Step 18: Power
Plug in a 9V battery to power up the transmitter.
Step 19: Case Closed
Fasten shut the transmitter's case.
Step 20: Wire the Reciever
Affix the relay to a small piece of perfboard.
Connect one of the relay's coils to ground on the Arduino board and the other to pin 3.
Attach 9V to one of the relay's load pins and a long red wire to the other. To get easy access to the 9V power source, I broke off the top of the 9V battery snap and soldered a wire directly to the +9V battery connector tab (notice the extra red wire coming from the 9V battery snap).
Attach an extra long black wire to ground.
Step 21: Put It Together
I lost the case for my SquidBee transmitter node (the pumpkin receiver) a long time ago. I find that a piece of black gaffers tape typically gets the job done.
I plugged in the 9V battery and passed the red and black wires through the hole in the side of the case neat-like.
Then, I slapped a piece of black tape on top and called it a day. This will be inside the pumpkin, so aesthetics don't matter quite as much.
Step 22: Wire the Motor
Wire the motor to the relay wires such that when the relay closes, the motor's actuator pushes down. In this case, red went to blue and black to green. It may be different for another motor.
Step 23: Put It in the Pumpkin
Place the whole contraption inside of the pumpkin.
Make sure that the battery is plugged in.
Also, make sure that the lid fits. If the lid does not lay flat, trim it appropriately to work.
Finally, it is a good idea to test to see if the the WD-40 sprays when the button on the transmitter is pressed down. It is easier and exponentially safer to debug this when there is no flame present.
Step 24: Candle
Once it is certain that everything is working as it should, it is time to add fire.
First off, find the transmitter. Make sure no one or nothing is pressing down on the button and it is somewhere safe.
Light a tea light and place it in the candle holder.
Step 25: Fire!
Take a number of steps way back from the pumpkin and press the trigger on the transmitter. If all is well with the world, the jack-o'-lantern will blast a burst of hellfire out of its mouth.
Shock and awe all innocent bystanders. This is the stuff nightmares are made of.
All of that said... SERIOUSLY, DON'T MAKE THIS.