Step 1: Parts and tools needed
If you find an old printer you can take apart, you can probably get the motor, the wire, a 3 pin connector, and possible the transistor and the diode for really cheap.
I used Radioshack and a site called www.taydaelectronics.com. Radioshack because it had the parts and Tayda because it lets you order in quantities of 1 and the shipping is low. Substitutions are very possible. Any transistor with enough continuous current capacity for the motor should work, in this case 800ma. I encourage scrounging a motor if you’re up for taking stuff apart, they’re in everything. If you're in a hurry to make this before Halloween all of this stuff can be purchased at a radio shack store.
Parallax PIR sensor Module $9.99
1-3/4” Mini perfboard (Comes in pairs) 1.99
If you scrounge a motor, try to get one like this with a gear, it will give the spool and the glue that holds it something to grip on to.
4 “AA” Battery Case
Any case that is in series to provide 6v will work, I like this one because it has a switch already installed on it.
TIP41C POWER TRANSISTOR NPN 100V 6A
If you need to buy this at the store, radioshack stocks the TIP31 and TIP120 either of which would also work.
120 Ohm resistor
1 1N4004 1A 400V Diode
If you don’t have some you can strip it out of an old phone cable, use some speaker wire. If you need to buy some there’s a link below, 2ft each of green, red and black 22awg stranded wire should do it.
If you’re uncomfortable soldering you can use this IC socket for the transistor, cut it down the middle with some clippers and you have two transistor sockets for 2 cents:
Long Rubber Band (as sold to hold file folders shut)
Cardboard, about 2 square feet of it.
Paper Glue or Wood Glue
A Paper clip
A milk cap
A 3" to 4" plastic jar lid wide enough to make the drum of the spool
Thread or fishing line
Paper Towel tube or TP tube
Pin or tack
Pumpkin Pail (Only needed if you want to hang it from the ceiling, not needed for hidden over door mount)
Hobby Knife (such as Xacto)
Hot Glue Gun
Black permanent marker