An Inexpensive Smoke / Fog Generator

I have used any number of different methods of animation when building model railroads including movement, sound and light. I have not, however, used smoke... that is until now. The fairly recent advent of smokeless cigarettes, also called e-cigarettes, e-cigs or vapor cigarettes, has provided an opportunity for us to make small, inexpensive and quite impressive smoke machines.

I have been doing some experiments and have come up with a fairly simple method to create a good bit of smoke that can be turned on or off at will.

The smoke maker shown here is appropriate for creating smoking pumpkins on Halloween, getting a chimney to smoke on a Christmas diorama or to provide realistic smoke stack smoke from a factory on a model railroad. It could also be used to have smoke emanate from a burning building, car or airplane crash or a campfire. To turn an e-cigarette into a stand-alone smoke maker you need to identify and purchase a number of items including an e-cigarette (or its heating element) a non-offensive smoke liquid, a small air pump to move the smoke from the heating element to the animation site and an appropriate power supply.

While you can use standard vapor liquid that is designed for e-cigarettes for this project it is not recommended as most of it contains two things that we don't need: nicotine and flavoring. Most vape shops either have or can mix up the liquid without flavoring or nicotine. It can also be purchased in this form from eBay. Better yet, you can use pure food-grade glycerin which is used as the base for most e-cigarette liquid. It is available from eBay and other sources at a very reasonable cost.

The vapor emitted from e-cigarettes, including the one shown here, can set off smoke detectors. While such occurrences seem to be infrequent please use care when using the smoke generator in public buildings.The e-cigarette has a heating element that vaporizes the liquid. These are designed to be heated by 3.7 volt lithium batteries and this voltage should not be exceeded. Don't be tempted to use 5 or more volts as you are likely to destroy the heating element and/or start a fire.

I started out using a very inexpensive e-cigarette that I purchased on eBay. The unit shown here included two cigarettes, batteries and a charger.

The only part of the unit that I used was the vaporizer (the top of the cigarette) and the battery connector. If you solder two wires onto the vaporizer you don't even need the battery connector.

Since I have been disassembling the e-cigarettes to harvest the heating element I spent some time searching eBay for a seller that might be offering just that component. Luckily I found such a vendor and purchased 5 heating elements (shown here) for less than $8 delivered. They are available in several types with varying resistance. I chose 1.8 ohms but the others should work well, too.

The heating elements come nicely packaged in individual compartments.

In addition to the heating element you will need the following parts:

• a small, DC powered air pump (see step below)
• a short piece of brass tubing (3/16" in diameter and about 1" long)
• a 6" piece of flexible tubing to go between the brass tubing and the pump nozzle (from a hardware or pet supply store)
• thin stranded wire
• JST or similar connectors
• pure vegetable glycerin
• assorted tubing (plastic and rubber) to direct the smoke to your project
• a DC to DC power converter (see section below) or batteries
• a small, empty pill bottle with cap + an extra cap (I used one from the local pharmacy that is made of translucent plastic - it is about 2.75" x 1.25" in diameter. The cap pushes on and off as it is not child-resistant) - others should work, too.

Two wires need to be soldered to the end of the heating element. I used thin (26 or 28 gauge or so) stranded wire. One wire goes to the body of the unit and the other to the central portion of it. Make sure the soldered wires don't extend beyond the diameter of the threaded part of the base or you may not be able to get the unit installed in the smoke maker. Also take note that there is a small white O ring just above the threads. Make sure it doesn't get lost.

Be very careful not to plug up the hole that is in the middle of the central shaft. That hole is how air gets to the heating element. The hole is shown by the arrow in the photos below.

I used a hot soldering iron (set to about 525 degrees F) and good quality solder. Fortunately the white insulating material seems to be quite heat resistant and I did not see any damage to it after soldering.

First cut the pill bottle in half being careful to keep the cut even and parallel to the top of the bottle. I used a piece of wire wrapped around the bottle to help mark the cut line.

Cut the pill bottle in half using a fine tooth saw.

Once it is cut drill a 17/64" hole in the bottom of the bottom piece of the bottle (#1). Drill a 3/16" hole in the white cap (#2). Drill another 3/16" hole in the side of the top piece (#4) and a 1/8" hole in the top piece opposite the 3/16" hole (#3).

Hole #1 is for the base of the heating element, #2 is where the smoke comes out, #3 is for the wires that supply power to the heating element and #4 is where the air pump connects. In this photo hole #2 is in the center of the cap. I found that putting it off center helps to return any condensed smoke fluid to the reservoir while having it in the center can put too much fluid back on the heating element.

The heating element goes into the 17/64" hole.

Press and twist the heating element into the hole being careful to keep it vertical and to evenly compress the white O ring.

If the O ring is not tightly pressed against the bottom of the pill bottle some fluid will leak from the top compartment to the bottom one. This is not a big issue as such leaks are usually minimal and the fluid can easily be poured from the bottom chamber back into the top one.

The bottle goes back together like this with the part cut from the bottom at the left and the top, with the second, undrilled cap, to the right.

All that remains is to seal the white wire and brass tube. I used hot glue but other adhesives will work, too.

I joined the two parts of the bottle with electrical tape.

The fluid goes into top chamber. You need to add enough to cover the base of the heating unit. I generally put in about 1/4" of the glycerine. Just make sure that it is deep enough to get to the wick or holes in the side of the heater.

There are a number of small, DC powered motors available on eBay and through Amazon. The one that I have had the most success with is shown here. It works with voltages that are the same as those used with the heating element, simplifying supplying power. The dramatic difference in price is due to one coming from China.

I have also tested another readily available pump. It works well but has a smaller air output nozzle and is quite noisy. It is shown here from Amazon.

Beware of vendors selling used pumps - most of these are 12 volts and many leak. I have had the best luck with those from eBay that are billed as being New and running on 3 to 6 volts.

The heating element expects to be powered by a 3.7 volt lithium battery. You can power you unit from such a battery or you can use a higher voltage that you run through a DC to DC converter (sometimes called a buck converter) The device that I used is inexpensive and has a graphical display showing the output voltage and the current being delivered. I set mine to 3.7 volts and found that my test unit drew a bit more than 1 amp. I have purchased them from Banggood.com for a very attractive price.

They are also available from eBay.

I would suggest not running the smoke unit continuously but at intervals. I have run a test having the power applied for 30 seconds then off for 60 seconds. The unit worked flawlessly for 6 hours.I would be interested in hearing if you have had success with the smoke unit presented here and any modifications / improvements you have made.

dave@davebodnar.com

Visit my web page for updates and modifications that I plan on making:

http://trainelectronics.com/Animation_Smoke/