Holy Smokes! A Small, Portable, Controllable, Cost-Effective, Battery-Operated DIY Fog Machine.
When searching for a controllable mini fog machine for a simulated trashcan fire for PlayMakers Repertory Theatre's production of My Fair Lady, it quickly became apparent that there is no readily available, cost-efficient product that one can purchase for live entertainment fog generation on a small scale. Additionally, our trash can needed to reside on stage through several scenes before it had to wisp out convincing smoke for an entire scene.
The few existing hand-held foggers were decidedly out of our budget, and the need for remote control of the fog meant that a traditional dry ice method would need some serious re-tooling before being an option. Going back to the drawing board, we researched other ways in which smoke could be generated. Housing inspectors often use hand-held smoke generators, but those mechanisms require a squeezing action to activate a pump that generates the smoke. This is not really something that could be easily recreated or sustained on stage. In the food industry, there are smoking "guns" that are loaded with a small bit of hard wood and are lit to smolder, and are usually used in smoking things like cheeses. These create a good bit of smoke but would also require a remote ignition on stage, which is impractical.
Most vaporizer pens can be easily disassembled. At most, a few screws must be removed to gain access to the battery and electronic components. Vaporizer pens and electronic cigarettes operate by taking a low amount of voltage from a battery pack in order to heat up a small heating coil within a metal housing. It also includes a wick soaked in a propylene glycol solution. In normal operation, one would power on the device and hold a heating button. Inhaling on the mouthpiece draws air through a vent below the heating chamber, causing the solution to be vaporized by the heating coil and resulting in smoke being expelled through the mouthpiece.
For our setup, we dismantled the device to isolate the heating mechanism and to bypass the electronic control board. Most vape pens have a limit on how long the heating coil will run, thus limiting the duration and amount of smoke the device can expel. This is a safety precaution that keeps the device from overheating. As with every electrical device, by bypassing a safety feature, one must accept responsibility for the possibility of overheating and the dangers that are inherent with low voltage devices. Be aware that the heating coils can heat up to 350 to 375 degrees F. However, these coils are also located within a metal chamber surrounded by a glass chamber. This tends to disperse the heat and allow for a manageable, safe installation. Vape pens also use a circuit to regulate the voltage supplied by the included 12V-24V battery, although you would not want to run that much voltage directly through your heating coil. Usually, between 3V and 6V is needed to heat up the coils to produce smoke, but the ultimate voltage is dependent upon the heating coil included in the specific device. We found that 4.5V, or three AA batteries, in our system, produced an adequate amount of smoke.
Voltage needed depends on resistance of Vaporizer Coil. The relationship between Voltage and Resistance determines the amount of smoke produced, as well as what the safe rating should be for cables and connectors. OHMs law allows us to determine the Wattage and Amperage of our device based on variable Voltage and Resistance. The formulas are: Current = Voltage/Resistance and Wattage = (Voltage)^2/Resistance. Most Vaporizers have heating coils between .5 and 2 Ohms of resistance. We are aiming for between 20 and 40 Watts worth of smoke output. For our .5 Ohm coil with a 4.5V battery, we are able to generate 40.5 Watts of smoke at 9 Amps. With the continual air circulation over our coil from the fan, we were able to run a much hotter coil without burning it out. Always turn on fan before applying power to heating coil.
We also found a trade-off between voltage and longevity of the heating coils and wicks. We found that the lower the voltage, the longer the heating coils and wicks were able to last before needing replacement. At 4.5V, our device was able to last through the entirely of tech before needing a coil replaced and around three days before needing a new wick. We ran the device approximately one to two hours a day total, with the longest time being left on constantly at 20 minutes. We had to refill the fluid in the device once before afternoon rehearsal, once before evening rehearsal during tech, and once every three shows during performance run. We were able to get through a week of shows before needing to replace the wick. The second heating coil lasted the entire two-week run.
The heating coil and glycol chamber of our device was attached to the housing of the vape pen unit. We disassembled the rest of the device from the housing and detached the positive and negative leads from the battery and the circuit board. Then we soldered wire extensions to the leads and connected them to a small radio-controlled wireless DMX dimming unit. For the input voltage of 4.5V, three AA batteries in a small pack were wired into the dimming unit. A small 6V brushless fan was placed at the air intake of the vape pen to push air backwards through the system. It ran remarkably well underpowered, at 4.5V.
When using the remote dimmer as a switch, be sure to proportion the maximum output for the channel with the Vaporizer to match what would be needed for optimal smoke. For our .5 Ohm coil, we needed 4.5V so we profiled maximum output of our Dim B channel to 37.5% of the 12V battery.
Within moments of being powered on, we were able to get reliable and consistent smoke from the device. We then secured the whole setup into the trash can and controlled everything from the lighting console. For our theatrical purposes, a 0% nicotine propylene glycol solution was used. We also selected a neutral, vanilla scent to minimize the distraction to the actors and audience.
Overall, the project was a success. Though there are dangers in working with low-voltage in electronics, with proper soldiering and by using the correctly rated cable, hardware, and installation and electrical insulation techniques, one can minimize the risk of electrical shock and fire.
By Dominic Abbenante
Lighting Director & Resident Designer, PlayMakers Repertory Company
Item Total Cost Electronic Vape Pen (2 coils $30 and 3 wicks included) Electronic Vape Fluid $13 (120 mL, more than needed for the run) Tiny Brushless Fan $5 4.5 V Battery pack $2 TOTAL $50 Note: The wireless remote-controlled DMX dimmer was taken from stock, but could be replaced by a few toggle switches for actor/technician.
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|Title Annotation:||17TH BIENNIAL TECH EXPO DISPLAY AND CATALOG|
|Publication:||TD&T (Theatre Design & Technology)|
|Date:||Jun 22, 2019|
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