This page may take a few minutes to load due to all of the diagrams.  Please read this entire page carefully before building - it may help you to figure out any problems beforehand, and help you figure out any additional supplies/tools that you may need.  

You are welcome to print this out for your own use (set your printer to black and white so it doesn't waste colored ink on my crappy MS paint drawings), but do not publish it or sell it.

Materials

- 2' x 4' sheet of ½" plywood
- 12¼" x 22" piece of ¼ of plywood or masonite 
- 21 standard house light switches (be sure they have screw and quick-connect sockets on the back)
- one face plate for switch
- 10 feet of red #12 solid-gauge copper wire
- 10 feet of black #12 solid-gauge copper wire
- 15 feet of white #12 solid-gauge copper wire
- 21 # 8/32 bolts 
- 42 # 8/32 nuts
- 84 # 8/32 cut washers
- spray paint (white)
- spray paint (whatever color you want)
- 22 gauge copper ignition wire or speaker wire ( 500' rolls are available at Skylighter for around $25) 
- about a dozen 1" wood screws or nails
- several ½ pan-head wood screws
- an 8' extension cord (3 conductor, 14 gauge)
- 40 small alligator clips
- 40 solderless eyelet connections for # 18 gauge wire
- 2 spring loaded clips big enough to fit onto 12 volt car battery posts
- 12 volt car/lawn mower/boat/motorcycle battery
- drawer/cabinet handle (optional)

Tools

- drill
- jigsaw

LETS GET STARTED

Start by cutting the ½" plywood to the dimensions shown on the left.  The tan pieces represent the plywood, the gray piece piece is the ¼" plywood/masonite (it will be used for the face of the board).  The front piece is 4" x 22", and the back piece is 8" x 22" (on both front and back pieces cut one of the 22" sides at 20º so it will be flush with the angled pieces - see diagram of assembled box below).  The angle between the 7¾" x 10 5/8" side pieces should be 20º. Plywood can usually be found at construction sites.  Carpenters usually have PLENTY of scraps left over that would be perfect for this firing panel.

On the left side panel, drill a ½" hole at 2" from the bottom and 2" from the end.  This is where the power cord will come in to the box.  On the same side you'll also need to cut a hole to mount one of the switches on the outside of the box (this will be the master switch). OPTIONAL:  if you want a power indicator light, drill a small hole, about 3/8" wide, above the power cord hole.

Before we wire the box, we need to get power into it.  Take the 3 conductor extension cord and cut it in half.  Take the half that is attached to the plug-in end with the prongs.  Strip the outer casing about 8" to expose the 3 wires inside.  Snip off the ground wire (colored green); you won't be needing it.  Thread the remaining wires through the ½" hole you cut in the side of the box.  Do this until the outer casing of the extension cord comes inside of the box.  Once it does, use some high-strength adhesive to fill the hole area around the cord to secure it in place.  Don't use hot glue; it won't work.  For added strength, you could fasten the wires to the inside wall of the box using large hammer-in staples.  Strip the end of the white wire and wrap it around the bolt (between the two washers) in the very middle of the back side of the box.  Tighten the bolt.  This will be the common ground wire.  See the picture below for clarification.  Strip and attach the black wire to one of the lugs of the master control switch (the one mounted on the side).

What you just created is an electrical bus where the switches act as circuit breakers.  All 20 firing switches on the board are hooked up in a parallel sequence, that is, they will all receive electricity at the same time.  The master switch on the side regulates the power that goes to the firing switches.  If the master switch is off, then the circuit is broken and no electricity will reach any of the firing switches. 

Note: It may be easier to cut the wire into 5-6" strips and attach one to each switch before you insert it into the face plate.  Then, you only have to connect that wire to the hole/screw of the adjacent switch once the switches are all mounted.

Run black wire from the remaining quick connect lug of the top row of switches to the the corresponding bolt on the back panel.  Do the same for the bottom row, but use white wire.  Use a black permanent marker to number the switches on the front panel and the corresponding bolt on the back.  The internal wiring of the box is complete. Click Here for an actual photograph of the wiring of my box.   OPTIONAL: if you want, you can add a power indicator light that will turn on when you flip the master switch to let you know that the firing switches are getting power.  You can buy small lamps down at a local Radio Shack.  Put it in the small hole you drilled and glue it.  When it's dry, attach one of the wires to the common ground bolt on the middle of the box's back panel.  Attach the lamp's other wire to the bolt of the VERY FIRST switch you wired (not the master switch).  Click on the link above to see a pic of my box.  The lamp's wire is yellow.

To make the power supply, use the remaining half of the extension cord with the socket end.  Strip the end where it's cut about 8" or so.  Get rid of the ground wire.  Attach the positive and negative wires to the large spring-loaded clips, and hook these clips to the battery posts.  Use only a fully charged, 12 volt 100+ amp  battery.  When you want to connect your control panel to power, plug the pronged end of the extension cord into the socket end - but don't connect the power yet.

Now you're ready to start wiring your fireworks.  For each device (or series of devices) that you wish to ignite, you will need one set of wires to run from the panel to that firework.  Cut two lengths of 22 gauge wire however long the distance is between where the firing panel is and where the fireworks will be.  It should be no less than 40 feet.  If you're using professional firing wire, then just cut one piece (since there's two wires in each piece).  Tape the wires together.  It may be cheaper and easier just to buy multi-conductor wire of the same gauge  (many readers have told me that speaker wire works fine, too)  Multi-conductor wire is several insulated wires all bound together in one casing, like the extension cord.  On one end of the wires, strip them and attach them to the eyelets.  On the other ends, attach alligator clips.  Here's what each end of the wire should look like. 

Remember, if you're using all twenty switches in your display, you will twenty of these wires.  Since this box may be somewhat heavy, it's a good idea to buy a drawer handle or two and attach them to the sides/back of the unit to make it easier to carry.

WIRING THE FUSES

CAUTION: Never wire fireworks while the panel is attached to the battery!!  To ignite a single fuse, you'll need a 1.5-2 inch piece of ignition wire (a wire that will heat up and burn through when a current is passed through it).  There are several different types of wire that can be used, as long as they are between about 31-38 gauge.  You can use a few strands of steel wool, or cut the insulation off of a larger, stranded wire and use one of the strands.  Never use copper - copper is an excellent conductor, which will pass current from the + wire to the - one without heating up much.  The very best thing to use, however, is specially made ignition wires, which are usually alloys of copper and nickel (copel), or nickel and chromium (nichrome).  Both of these are available 10 foot lengths of different gauges from Firefox.  Some of my readers have found it at other places as well, such as VWR International and www.resistancewire.com (click here for some information before going to the latter site).

When current is passed through the wire, it may only glow for a second before it burns through, so you want to be sure that it will ignite the fuse.  Using a small knife, strip away the outer layers of the fuse until the black powder core is exposed.  Wrap the piece of ignition wire around the fuse several times, being sure that it touches the power core at least twice.  Make sure the wire doesn't touch back on itself, which would cause a short circuit.  Now, take the long firing wire described above, and attach the alligator clips to either end of the ignition wire wrapped around the fuse.  Once again, make sure the alligator clips don't touch each other.

Now you need to attach the other end of the firing wire - the one with the eyelet connectors - to the firing panel.  Attach one of the eyelet wires to the # 1 switch by detaching the first nut and washer from the corresponding bolt.  Put the eyelet over the bolt, and put the nut and washer back on.  Take one end of the bare copper wire (the common ground) out of the little hole, slide the other eyelet wire over it, and push it back in.  The entire setup should look like this:

To fire the device, plug in the control panel to the end of the extension cord going to the battery.  Turn on the main switch on the side, and hit switch # 1 on the control box.  Once the fuse lights, turn it off. Wa-la!  Better than lighting the fuse and running away, isn't it?

Warning: DO NOT plug the box into a 120V wall outlet.  Although it can plug in like an appliance, it's extremely dangerous and it violates electrical code regulations (would you feel safe plugging in some thing that you built yourself anyways??).  The ignition wire only needs about 12 volts at (at most) .5 amps to burn through, anyways - not 120 volts.

APPROXIMATE COST OF PROJECT: Anywhere from $40 to $60, depending on whether or not you can get free wood and the cost of the supplies in your area.

Troubleshooting and Problems   

*If the fuse doesn't light, you'll have to go back and check all of your wiring.  Make sure that the bolt you've hooked the wire up to corresponds with the right switch you're flipping.

If you have any other questions, feel free to email me.