electronic ignition

lapeer20m · 07-14-2006, 11:33 PM

quick question for you electronic wizards out there.....

i want to find/buy/make a circuit that switches off and on several times per second. What i want to do is connect this switching circuit to an automotive ignition coil to make a spark plug spark.

anyonw have any simple ideas?

eggman · 07-15-2006, 12:43 AM

I am no electronic genius by any means, but would an automotive flasher work?

frank-id · 07-15-2006, 01:35 AM

What is the purpose for the spark device.? Flaming exhaust? Use an old distributor and turn with 12 volt fan motor with a speed control. Frank

lapeer20m · 07-15-2006, 04:39 AM

it is for a flame....propane powered. Size and weight and energy consumption are all issues since it's for a bicycle.

A flasher is an excellent idea, but just isn't fast enough........oh wait....perhaps a flasher that does not have the proper load will flash fast enough......(ya know how it flashes fast when you have a burned out bulb, that just might be the ticket)

I'm gonna go play with that idea!

Thanks

Jason

The distributor powered by a fan motor is good too, but not for the bicycle application (although i dind't mention bicycle in my original post)

We're working on "art" projects for burningman

frank-id · 07-15-2006, 01:33 PM

I'd sure like to go to that event. Costs lots of money.
My suggestion for a vw or similar distributor could work great. The distributor could be driven from chain or tire. The unit would add some artsy
flavor. I wanna build a motorized picnic table. Got any pics to share?
Frank

the_experience03 · 07-15-2006, 08:29 PM

The commercially available kits just use a $5 parts store coil and a spark plug. They just turn the thing on and off with a relay. I'm sure something like that could work.

Griff · 07-16-2006, 12:08 AM

What about those little generators that contact the tire & spin to make a bicycle headlight work? Couldn't you convert the frequency to something usable for your application? That way, as long as the bike is moving, it would have a signal. Of course, signal speed would vary with ground speed without some sort of frequency clip, i.e. headlight brightness is directly proportional to bike speed.

L'il help there, Electrotechies!

the_experience03 · 07-16-2006, 02:46 AM

Correct me if I'm wrong, Jason, but I don't think you want this thing to be working while you're driving so the tire operated gizmos wouldn't work, correct? I still say go with the generic $5 tractor coil.....

Kirbystud · 07-16-2006, 09:28 AM

There is a web site you can buy exhaust flame kits.WWW.eatmyflames.com I think it's only $45 for a single.

lapeer20m · 07-16-2006, 07:31 PM

the coil and a spark plug are not a problem....the problem is how to make it spark.

dewalt 14.4 volt batteries will be used to power the contraption.

When it comes to wireing a 12 volt coil...

Obviously for the high voltage circuit you connect the center of the spark plug with an insulated wire, ground the proper part of the spark plug

the low voltage circuit you connect your ground all the time to the proper terminal, then you connect the hot wire to the proper terminal, and when the hot (+) wire is REMOVED from the terminal the spark plug sparks.

What i'm trying to find, is an electronic device that will connect then disconnect the hot wire going to the coil several times per second.

I think the turn signal flasher will work...the old mechanical type that flashes real fast when you have a burned out bulb in the circuit. I would estimate it to flash at 2 or 3 times per second.

Quote:

Correct me if I'm wrong, Jason, but I don't think you want this thing to be working while you're driving so the tire operated gizmos wouldn't work, correct?

If you had a small propane powerd flame thrower on your bicycle, wouldn't you use it while riding???

I am actually rather amused by the idea of spinning a distributer with the rear tire.......but getting all the geometry correct would be a little difficult..i'm not sure i have the desire to make it bullet proof enough to work everytime. IT is very important to make sure the propane ignites on it's way out of the flame thrower. Unburnt propane floating down toward the operater is less than desirable. Propane is heavier than air. Although it is being used in outside in a well ventilated area, which will certianly help to reduce the danger. I do not remember the LEL and UEL of propane off the top of my head. Natural gas would be a much safer fuel for this setup, but it's difficult to find lng in a bottle. It is used by some city buses and cabs, but not nearly as easy to find as propane.

The propane cylinder (coleman grill size) will be mounted in a safe spot that is easiy accessable to the rider and can be turned off with a quarter turn valve if necessary. The nozzle for the flame will be about 8 feet off of the ground and pointed straight up. The size of the flame should only be about 6 or 8 feet above the nozzle. (as opposed to 30-50 feet for my full size flame thrower)

A super easy and portable electronic ignition would be a tazer, but regular citizens cannot purchase them here in michigan. I think they run off a 9 volt battery or something similar.

lapeer20m · 07-16-2006, 07:40 PM

talk about usless trivia!!!

i went back and found the uel and lel for propane it's 2.1%- 9.5%

first we'll talk real quick about the fire triangle..

3 things are needed to make things burn: Oxygen, fuel, Ignition

Not all fuel is dangerous all the time, that's where the UEL and LEL come into play

for those not familair with LEL (lower explosive limit) and UEL (upper explosive limit...aka ufl Upper/Lower flamable limit) this is the range at which a fuel will ignite

the range for propane is 2.1%- 9.5%

In theory, if there is more than 10% propane mixed with air, it will not ignite. In an enviroment with say 30% propane (you would need a respirator to breath) you could light a match, and the propane would not ignite.

Same goes for concentrations below 2%

wtd · 07-16-2006, 08:44 PM

Curious, are you going to somehow control the propane as well?

It would seem, with a constant flow of propane, every spark after the first one is superfluous, no? I guess that you've figgerd all this stuff out, how to extinguish the flame between sparks and such, but, if the propane discharge is being controlled, whatever controls the propane would control the spark as well.
Don't think I'd worry too much about the unburnt propane floating down around the operator, the bicycle (hopefully) will be moving and the flume will just trail along like smoke from a train stack. Even being heavier than air it still isn't like a rock, takes a while to settle.

I think the auto flasher is the ticket, as you say and don't know but as with all car stuff, would imagine they'd be pretty big power hogs.

Bitchin' project, can't wait to see the photos

lapeer20m · 07-16-2006, 10:21 PM

gonna have an electric solenoid valve to allow the propane to flow.

i should draw a diagram,...perhaps i'll update this post later

the propane is a liquid in the cylinder and only changes to a gas at a certian rate.....in the casae of a 20# BBQ cylinder, the flame is about 4 or 5 feet high as it comes out of a 3/4" pipe, depending on a few factors.

propane always leaves the cylinder as a gas (i'm pretty sure the new opd valves do not allow propane to leave as a liquid, even if you turn the tank up side down)

for the flame thrower application, the gas leaves the cylinder and is allowed to collect in an "expansion chamber" (really this is an old propane cylinder with a non-opd valve...they can be had for nearly free)

The valve is left open on the lpg cylinder connected without a regulator to the expansion tank. This allows propane GAS to build up pressure inside the expansion tank. When a suitable amount of pressure is presumed to have built up, a 3/4" solenoid valve is opened and allows propane gas to shoot out of the 3/4" pipe past the ignition sorce, and a large fireball escapes.

A 1/4 turn valve on the LPG tank allows for quick shut down in case of emergency. Having the pipe that comes out of the expansion tank be over 8 feet tall also adds a good measure of safety (can't burn people if they are below the flame)

Keeping the lpg cylinder at least 20 feet from the expansion tank is another measure of safety. Safety has to be an important priority when dealing with something with as much kinetic energy as a 50 foot flame thrower.

all in all, it's quite safe. There are hundreds of them at burningman, and as far as i know, nobody's ever been killed by a flame during the event.

the_experience03 · 07-17-2006, 12:22 AM

Have you considered a regulator that allows more than the 11 inches of water column a standard one does? Wait....is there even a regulator in this system? It might be a good idea as it will help with the expansion of the gas.

wtd · 07-17-2006, 01:06 AM

Wow, this is going to be quite a device to see on a bicycle ..
So you're looking for a device to control both the spark and the solenoid? Since you say when "a suitable amout of pressure is presumed to ..", I'm guessing that a human makes this presumption and opens the valve and you wish to automate this?
If the varying wheel speed is not a problem, Radio Shack has an IR photo emitter and detector (individual components) - one on each side of the wheel and cards or something else in the spokes to block the beam ... runs on 1.5V and the switch part handles 20V and about 25 mA or so, enough to toggle a relay that would handle the load. Cost is about 3 bucks if I remember right. Wiring is simple, battery to the emitter and two leads out of the detector that switch your load. Don't know how much they cost, but one of those ding-dong things on the 7-11 door would work with something in the spokes to break the beam and replace the gong with the load. Actually those things are just the Radio Shack thing noted above with a gong connected and packaged up.

lapeer20m · 07-17-2006, 08:42 AM

you are a genious! (even if i can't spell it) I love the emiter/detector idea with the spokes from the wheel. That'll take care of the spark on the spark plug...

as far as a regulator goes, it regulates pressure in the system. I want MORE pressure! More pressure = bigger flame.

i don't want to automate the opening of the solenoid. It takes about 5 minutes for pressure to build up in the expansion tank, and this only allows for 1 or 2 blasts of the flame thrower before you have to stop and wait for pressure to build up again. The solenoid is connected to a standard doorbell or other momentary on switch.

Another big problem, that is too difficult to address on the bicycle is the LPG tank icing up. The liquid propane is leaving the cylinder at such a rapid rate that the cylinder literally forms a layer of ice around it. cold propane doesn't build nearly as much pressure as room temperature propane. To combat the ice problem with my bus, i wait till a tank begins to ice up, then disconnect it and set it in the jacuzzi for a while (when nobody's in it) 105* is no where near too hot for propane, and it does a super fast job of heating things back up.

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