Introduction: Multi-Color LED Fog Spreader

This Instructable is my entry into the Halloween contest. If you like it, please remember to vote.

Fog machines are common equipment when it comes to Halloween, but they have their drawbacks. They shoot fog in only one stream, and the fog is limited to the color white. Now you will be armed with knowledge about how to create a fog spreader that has colors which you can change with the flip of a switch.

Step 1: Materials

For this you will need:

  • Fog machine.
  • 2 sections of PVC pipe.
  • PVC T fitting that fits your pipe
  • 12 bright red LED's
  • 12 bright blue LED's
  • 1 SPST (single pole, single throw) switch
  • 1 SPDT (single pole, double throw) switch
  • Soldering supplies
  • Wire (several yards)
  • Hot glue and hot glue gun
  • Drill with 1/2 in bit and 5 mm (or close) bit.
  • Epoxy
  • Cable ties
  • X-acto knife
  • Tape measure
  • Piece of scrap wood
  • Some sort of strong tape (Foil tape is recommended. This stuff is amazing)

The best place to find cheap LED's is on eBay. You can get 100 from China for under $10, including shipping.

Step 2: Prepare Pipe

First, remove the nozzle cap from the fog machine. If it does not come off, you will have to epoxy the finished rig to the fog machine once building is complete.

Epoxy the nozzle cap to the base of the T connector and allow to dry. (hint: use 5 min epoxy. it saves time)

Insert the 2 segments of pipe into the unused portions of the T piece. I didn't glue these but you may need to.

Use foil tape (or duct tape) to cover the ends of the pipes so the fog does not escape where we don't want it to.

Step 3: Drilling the Pipe

Start with everything on one side of the T, then move to the other and repeat.

First measure the total length of the pipe. Depending on how long of a pipe you have, the distance between holes and number of holes will vary. I used 3 holes on each side with about 8 inches between each, and a 2 inch offset form the end of the pipe and the T connector. Don't make too many holes because the fog will not spread out as it should. Generally 3 is a good number per side.

Mark the holes and drill them. But remember; measure twice, cut once.

Once the holes are drilled you may have excess plastic around the hole. I believe this is caused by my drill having low power so your results may be different. Use a X-acto knife to remove the excess plastic and make the hole clean.

If, like me, you used a spade drill bit, when drilling the hole was completed, the bit punctured the back side of your pipe, cover that hole with foil tape to prevent fog from escaping.

Step 4: Prepare LED's

For this step, do it once of the blue LED's and repeat it for the red LED's.

Mark and drill two 5 mm holes in the piece of scrap wood. The holes should be about 2 inches apart. This will be used as a LED soldering jig.

Take half of your LED's and separate them from the other half of the LED's. On the first half, bend the negative lead of the LED down to the right. This group of LED's will be called the "positives, because the positive lead is sticking up. For the other group, bend the positive lead down to the left. This group of LED's will be called "negatives," because the negative lead is sticking up.

Place a "positive" in the hole on the left side of your jig and a "negative" in the right hole on the jig.
Solder the bent leads to each other and repeat for the rest of the LED's.


Step 5: Attaching the LED's

Again, this step will need to be repeated for each color of LED. This step may seem inefficient, but I decided to add the second color after the first was complete. If you wish to do this differently, go for it, and let me know how it works.

Cut your wire so the positive and negative wires are staggered like in the first picture. Make sure that you have enough wire so the LED's will sit with one on either side of the hole in the pipe.

The pairs of LED's will be wired in parallel. Solder the two positive wires to the positive lead of the two LED's. Then solder the two negative wires to the negative lead of the LED's.

Tape the completed LED assemblies to the pipe on top of the holes in the pipe. Make sure the LED's are pointing outward, in the same direction of the hole. Then do the same for the rest of the LED assemblies.

Once all the LED's have been soldered to the wire and taped to the pipe, hot glue them to the pipe. I only tacked the LED's to the pipe so I can remove and reuse them later if necessary.

When repeating this step for the other set of LED's, tape them to the other side of the pipe.


After repeating, use cable ties to hold the wires in place.

Step 6: Wiring the Switches

First cut off the head of the AC adapter. Strip the wires and test which is positive using a multimeter or other method, usually it will be marked on the wire.

Wire and solder all the electric components according to the diagram. Note that the LED symbol on the diagram means all LED pairs, wired in parallel, of one color.

Regarding the number of LED's you should use, and what specifications your AC adapter will need, see the photo notes in the 3rd picture. If you have any questions about this step, post a comment or PM me, and I will try to reply quickly.

Step 7: Use

Check your wiring for shorts before testing this for the first time.

Once you are sure that your wiring is not faulty, attach the spreader to the nozzle of the fog machine using the piece that was taken from it in Step 2.

Fill your fog machine with fog fluid and plug it in.

Now plug in the AC adapter and flip the on switch. If things went according to plan, one color of LED's should light up. Flip the color selection switch and watch the other color of LED's turn on.

Wait for the fog machine to warm up and make some fog.

Amaze yourself and your friends with your awesome new toy.

Here is a video of it in action.

On Halloween, all the trick-or-treaters loved this. If you did too, please vote.

DIY Halloween Contest

Third Prize in the
DIY Halloween Contest