So, long ago I had read about propane fire poofers. They're pretty cool... I mean, who doesn't love fire?! But, no matter how awesome, they could get pretty boring after a while of seeing the same large fireball. I never built one because I wanted something that would be exciting and thrilling every time I fired it up. So, I put the project on hold until I could come up with an awesome idea.
Back in December 2010, I was daydreaming in class about who knows what, when I thought of my fire poofer project. I thought back to this project I had read about a while back on Mikey Sklar's website where he uses an ultrasonic sensor mounted underneath a trampoline to shoot off a fireball every time someone jumps. This is pretty sweet, but it has the potential to get pretty repetitive. After a few hundred jumps, I would imagine I would get tired of seeing the same small fireball and crave something more. (besides, I don't own a trampoline!) I tried to think of ways I could apply a fireball shooter to things in ways that would be pretty awesome. I thought of using a microcontroller to sync the fire to the beat of music - now that would be pretty cool, and the patterns would always be different, so it wouldn't get as boring as fast. Then I thought of the game Guitar Hero, which uses five frets, and I had my idea! Simply interface a Guitar Hero controller to a microcontroller that would power some relays which would in turn fire off solenoid valves on five individual fire poofers! Now this could be cool; a large fire "sculpture" that is playable by anybody. Read on to see how I turned this idea into reality in a week's time!
I figure this is as good a place as any to place a disclaimer about my project. FireHero uses controlled blasts of propane gas to create pyrotechnic flame effects. DO NOT EVEN THINK OF ATTEMPTING THIS PROJECT UNLESS YOU ARE FULLY QUALIFIED AND FEEL COMFORTABLE WORKING WITH EXPLOSIVE GASSES, HIGH PRESSURES, ELECTRICITY, AND OTHER THINGS THAT CAN KILL YOU IF YOU DO NOT KNOW WHAT YOU ARE DOING.
Step 1: Acquire necessary parts and materials
Much of the project uses common steel or brass NPT pipe and fittings. You may already have many of the parts you'll need lying around, and the rest can be found at your local Home Depot. To duplicate this project exactly you'll need to get the parts listed below:
- POL x 1/4" male NPT full-bore adapter (3)
- 1/4" FNPTx1/4" flare fitting (3)
- 1/4" MNPTx1/4" flare fitting (3)
- 1/4" flare nut (3)
- 1/4" copper refrigeration tubing
- 1/4" NPT ball balve (4)
- 1/4" NPT tee (5)
- 1/4" NPT close nipple (9)
- 1/4"x6" nipple (3)
- 1/4" FNPT quick disconnect coupling
- Fisher 67C high flow 55-135psi regulator
- 1/4" NPT 150psi pressure guage (2)
- 1/4" NPT 90 degree elbow
Propane Distribution and Flame Effects
- 1/4" ball valve (2)
- 1/4" quick disconnect coupling
- 1/4" NPT tee (5)
- 1/4" NPT 90 degree elbow
- 1/4" needle valve
- 1/4" MNPTx1/4" flare fitting (5)
- 1/4" close nipple (8)
- 1/4" x2" nipple (6)
- 3/4"x1/4" bushing
- 3/4" ball valve (2)
- 3/4" NPT tee
- 3/4" NPT close nipple
- 3/4"x2" nipple (2)
- 3/4"x3/8" reducing bushing
- 3/8" tee (4)
- 3/8" NPT 90 degree elbow (2)
- 3/8"x6" nipple (3)
- 3/8"x4" nipple
- 3/8"x1/4" reducing bushing
- 1/4" NPT 150psi 12v solenoid valve (5) (the valve's diaphragm material should be propane-compatible, such as Nitrile or Viton)
- 1/4"x6" nipple (5)
- 1/4" flare nut (5)
- 1/4" copper refrigeration tubing
- 25'+ high pressure propane-rated hose w/ male quick disconnect fittings at each end
- Arduino microcontroller (Uno or Duemilanove will work)
- 5v relay (5)
- 2N222 transistor (5)
- 1A blocking diode (5)
- breadboard and jumper wires
- Playstation 1 or 2 controller breakout (I ripped one out of an old PS1)
- Guitar hero controller
- Terminal blocks
- 12v battery
- computer with monitor and speakers
- Propane-rated Teflon tape (you'll probably need several rolls)
- 18AWG or higher wire (at least enough for 6x the distance you plan to be from the flame device while it's operating)
**Note that depending on how you plan on supplying propane, this parts list may change slightly. This will be explained in more detail in the next few steps.**
Step 2: Purge the tanks
As far as working with propane tanks goes, it's really not that dangerous as long as you follow some basic safety precautions. Remember to perform the following procedures in an open, well-ventilated area away from any source of ignition (also be aware that brushed motors from fans are a source of ignition). If you buy a new tank, they already come purged completely with inert gas (some are even under a slight vacuum) and you can work with it safely.
If you use a tank that previously held propane, you have to make sure that there is no high pressure propane left - make sure that the tank is at or very close to atmospheric pressure. The best way to do this is to hook up a propane attachment such as a blowtorch or similar and let it burn until it goes out from lack of propane. Remember, there will be propane vapor left in the tank, but as long as it does not mix with air it is not explosive.
Once the tank is purged you need to remove the valve, which is most of the time easier said than done. I've had tanks where the valve comes right off after a few hits on the monkey wrench with a hammer, and others where I've needed three people helping me to hold the tank down and pull on a cheater bar. Your best bet is to strap the tank to something big using ratchet straps, like the side of a workbench or a steel support column, whatever you have around. Then use a monkey wrench wrench to grab the valve and either throw a cheater bar onto it or hit the crap out of it with a mallet until it starts to budge. The valves unscrew counter-clockwise (NOT reverse-threaded, unlike POL fittings); they screw into the tank with a standard 3/4" NPT fitting. Don't worry about mauling the valve with the monkey wrench; you're not going to use it anyway.
If the monkey wrench idea isn't working for you, I've successfully welded a tool made out of pipe that fits in and around the POL valve to grab it. If you're using a 20# tank, you may have to get rid of the collar around the valve to make it easier to unscrew. I've done this easily with an angle grinder; just double check that you're not cutting into the metal of the tank, only the collar. Once the valve is loose, unscrew it by hand. *Note: I once had a close call where the POL valve did not completely vent all the propane to the atmosphere (probably due to the excess flow valve), and there was still 30psi or so of propane inside the tank as I started unscrewing the valve. Fortunately, I heard the hissing of propane through the threads before I unscrewed it all the way. Moral of the story: be ABSOLUTELY sure that your tank does not contain any high pressure gas. The best way to completely ensure that your tank is empty is to connect it to a propane appliance such as a grill or torch and let it run until it goes out.
At this point you're going to want to either purge the tank completely of any residual propane vapor with an inert gas such as CO2 or Nitrogen, or use a 3/4" plug to cap the tank until you can. Some people say to purge the tank by filling it with water, but I would strongly advise against it. Propane tanks have special oils inside that coat the steel to prevent corrosion, and adding water washes these away and allows for the tank to begin rusting from the inside out.. not something you want on your hands when storing large quantities of high pressure, flammable/explosive gasses. I personally use CO2 to purge my propane tanks.
You can see the apparatus I used to purge the 100# tank below. I have a 20# CO2 cylinder and regulator which I use whenever I'm working with propane systems to purge and check for leaks.
The method for purging involves using a 3/4"x1/4" bushing attached to a 1/4" pipe tee with two ball valves on either side. One ball valve is the discharge, and the other is connected to the CO2 supply. close the exhaust valve and open the supply valve to fill the tank with CO2 (I like to bring it up to at least 30-40psi) so that it contains a mixture of CO2 and the residual propane. Then close the supply and once the tank is in an open area (I only purge outside) open the exhaust valve to purge. Repeat this process 2-3 more times until you're comfortable that there's no more propane.
Don't be freaked out when the tank still smells like propane afterwards - the propane gas is long gone but the Mercaptans that propane companies use to give the gas its odor will linger for a long time. My garage smelled like "propane" the whole time I was building FireHero and working on the tanks, but it's not a cause for alarm. You can even take a blow torch and pass it over the opening of the tank, nothing will happen.
Step 3: Build the supply system
In this step, we'll assemble the propane supply system, which is responsible for taking high pressure propane from our supply tanks, regulating it down to a lower pressure, and storing it to be used by our flame effects.
When doing any plumbing with a flammable gas, it is especially important to make sure that each joint is sealed with properly-applied hydrocarbon-rated Teflon tape and that your system has zero leaks in it.
I used three 20# tanks with individual shutoffs chained to manifold with a pressure gauge. The gas then passes through an adjustable 50-135psi propane regulator and into the buffer tank, which has a second pressure gauge attached to it. The gas is fed through a ball valve and into a quick-disconnect coupler to make its way to the main accumulator tank.
A commonly-asked question: why did I use three 20# tanks instead of one big one? The reason for this is simply that it's all I had on hand - of course, a single 100# tank for the supply would have been optimal, but at the time all I had on hand were three 20# tanks. Using a single 100# tank would also cut down on the number of fittings required for the supply system, as you wouldn't need to run individual lines to each tank.
A note about using copper tubing to connect each tank: the copper refrigeration tubing is rated for pressures well above what you'll ever see in a propane system. However, copper tubing is very sensitive to repeated flexing of the line. Flexed enough, the copper will be weakened significantly and can and will break, releasing high pressure propane everywhere until the excess flow-limiting valve on the 20# tank kicks in. If you're using a 100# tank, you won't have this luxury. Ideally, you'd use high pressure propane-rated hose to connect each tank, although the ideal system wouldn't be using little propane tanks like this. Just be sure to limit motion of the copper tubing during use.
Step 4: Build the distribution system and the flame effects
The propane enters the main accumulator tank through a second quick disconnect fitting. In the pictures below, there is a tee where gas can be routed to the left to fire up a Ruben's tube, a separate flame device from another experiment. You can ignore those fittings when replicating this build. The line also splits up into the pilot light manifold which has a ball valve so it can be shut off completely and needle valve for fine adjustment of the pilot light size. The pilot lights can be adjusted anywhere from candle size to a 5 foot flame.
The gas then splits off again, making its way into the 100# storage tank via a 3/4 ball valve where it is stored to be released by the solenoid valves. This is also connected through a second 3/4" ball valve to the large "menorah" assembly which serves to route gasses to each individual solenoid valve. The "menorah" is only switched on right before the show starts. The pictures are very self-explanatory.
Note that many of the plumbing systems shown are overly complicated and use more fittings than necessary, such as a 3/8"x1/2" bushing combined with a 1/2"x1/4" reducer to accomplish the same thing as a 3/8"x1/4" bushing. This is because I actually completely stripped the shelves of my local Home Depot of most of the fittings in the sizes I needed, so this was my quick last-ditch solution. An easy way around this is to drive to other Home Depot stores to plunder them all of their fittings, or to order all your fittings online from a place such as Grainger or McMaster-Carr.
Step 5: Build the control electronics
The pictures above show my setup: the guitar is plugged into a header I salvaged from a PlayStation 1, which is connected to my Arduino Uno. The Arduino decodes the serial data from the controller, looks for button presses, and cycles power to the relays accordingly.
The relays are then connected to the solenoid valves on the main assembly via a nice long wiring harness using a common ground setup.
To play FireHero, the player simply watches a video of the guitar hero chart and plays on the guitar accordingly. Every time he presses a button while strumming on the guitar, the Arduino will fire the appropriate relay and thus the flame effect corresponding to that note.
You'll have to wire the five digital outputs of the Arduino (the default is pins 1,2,3,4,5) to relays which will then control the solenoid valves. Of course, this requires the use of a transistor and a blocking diode (a quick Google search on Arduino relay circuits will clear this up). I then used six 25' lengths of single-conductor wire (I used 14AWG because that's what I had lying around, but the wires only have to carry a few amps in the worst case scenario, so 18AWG or 22AWG will work fine too) to hook the relays up to the solenoid valves. A common-ground wiring harness is simple to make, and everything is powered by a small 17Ahr 12v battery.
To use the provided Arduino firmware, you'll need to download the PlayStation 2 Controller Library here. V1.5 is the latest and is required for the provided code. Follow the instructions for the library on how to hook up your controller - Bill Porter has put up some great resources and has spent a huge amount of time making this library accessible to everyone and helping people troubleshoot. (If you're reading this, thanks Bill!)
Step 6: Finishing up: hooking everything up and start playing!
Use a propane-rated hose to connect to supply and accumulation quick disconnect fittings. I used a polypropylene hose, which is compatible with propane vapor. Any other type of air hose will melt and degrade when exposed to the propane vapor! THIS IS EXTREMELY IMPORTANT! Nobody wants a hose carrying propane to suddenly split open and start whipping around, spraying propane vapor everywhere. Be SURE to use propane-rated materials. The ideal hose is a rated nitrile rubber, braided hose.
Once everything is hooked up, I like to pressurize the entire system with CO2 to the full working pressure (about 90psi for me) and do a thorough leak test. Use a spray bottle containing soapy water and look for bubbles to appear after spraying on fittings. Wipe off the excess water afterwards to prevent corrosion. A side benefit of purging with CO2 first is that I can be sure that there's no air in the system and therefore zero chance of flashbacks occurring. If there is enough air in the system to provide a mixture of 2-10% propane, when ignited the system WILL flash back until it reaches the supply tanks, at which point it will stop. Obviously, this is bad! Just purge completely with CO2, and then fill completely with propane and nothing bad will happen :)
I use a blowtorch to light the pilot lights. A quick wave of the torch over the pilots will light them beautifully. Adjust the needle valve to the desired height of your pilot lights, and then you can start testing.
While using pilot lights is one of the cheapest and easiest methods of ignition, it is also one of the least reliable. A strong gust of wind can easily blow these pilots out (there are other ways to build them so that they are less susceptible to wind). You shouldn't really be shooting off balls of fire on a windy night anyways, but you'll definitely have to really choose a calm night if you build the system to spec as it is here (as in <1mph winds).
To start testing, fire off the solenoids individually - most of the pilots lights will probably get blown out. One really tricky thing with these pilot lights is positioning them so that they are close enough to light the blast of propane reliably, but not so close that they get blown out by the huge blast of cold, high pressure propane. You'll have to experiment and adjust each individually. Note that this is also sensitive to changing wind directions. Keep the blowtorch lit and close by to re-light them quickly if the need arises.
Step 7: Conclusion
This was version one of my FireHero device - be sure to check out the teaser of version 2 below!
You can also check out FireHero 2 on my website, www.chrismarion.net.
Have a great day!