Hey, I'm building a small hydrogen-powered rocket for a project.
So far, I've been using one of those push-button piezo sparkers. I'd like to switch to an electronic sparker so I can fire it using a transistor as a switch.
Would Marx generators be the best way to go? They don't seem very reliable. All I need is a small spark, maybe a millimeter long.
No need for diode multipliers, a single inductor driven from an IGBT would probably do, or
a modified flash circuit from a cheap camera? What is the voltage needed for the spark gap?
Not much really, I just need a spark. The ignition chamber is maybe 1mL, and the hydrogen is in the right ratio with oxygen, so just about anything should work
No, you need to know the size of the spark gap and lookup the breakdown voltage of the
gas mixture involved, then scale by a safety factor.
You could use a very thin piece of wire (28 ga) and push an Amp of 5V or 12V through it.
An interesting fact is that some metals suck oxygen from the surrounding air when red hot,
and thus don't reliably ignite explosive mixtures - the metal burns in preference. I noticed this
with steel wool which will burn in an air-butane mix without setting it off!
Vaporizing wire will generally work though!
Spark gaps are reusable, which is much more convenient.
MarkT:
a modified flash circuit from a cheap camera? What is the voltage needed for the spark gap?
3 Kv per mm for air.
A cap discharge through a transformer will work.
The problem will be finding a suitable transformer.
A high power xenon trigger tranformer may work.
But the small ones from maplins , etc will not.
Ignition coils for the likes of gas hobs work but very difficult to find in small quantitiy.
You could try e-matches used for amateur rocketry and pyro which use current not volts.
GoForSmoke:
You could use a very thin piece of wire (28 ga) and push an Amp of 5V or 12V through it.
+1 Tinfoil
3KV per mm is for flat plate gaps. A couple of points takes less. Those piezo spark lighters generate 1500V.
Ahhhh, you can get smoke and flame out of a 1/4 Watt (or less) resistor but it takes a little while.
Contact buttons when the contacts open the beginning spark ionizes air allowing longer spark so .....
cross two wires or pins and run 20mA 5V through and pull them apart in a gas jet.
Who hasn't sparked wires with 12V across them by rubbing them together, even accidental-like?
aarg:
+1 Tinfoil
Used all mine for my hat. :o
What about using one of those piezo-electric igniters, like you see on push-button lighters, and for bar-b-ques? Those are fairly easy to get, and fairly low cost (cheap to free if you find an old lighter somewhere).
OP already suggested that in his first post.
I think he should elaborate more about his hydrogen rocket.
WE should not be offering advice on his experimental fusion propelled vehicle rocket in a public forum.
Not without patent rights anyway.
Every spark plug in every car has a small induction coil above it. It is fed 12 v. D.C., and when the primary circuit is interrupted, they generate a robust spark in the engine cylinder, even under high pressure. This used to be done with a single induction coil, and they can still be bought. Thier whole purpose in life is to make a really high potentail across the secondary when the current flow across the primary is broken. I used one in an electric fence. Raccoons didn't approve of it.
jrdoner:
Every spark plug in every car has a small induction coil above it. It is fed 12 v. D.C., and when the primary
Older ones had one coil only.
They are large.
Small transformers for high voltage are speciality items which are hard to find.
jrdoner:
Raccoons didn't approve of it.
They are not supposed to 
How about using one of these?
DC 3,6 V-6 V Um 400kv-boost Step Up Power Module
DC high voltage generator Inverter Ignitor Coil modul DIY kit
Boardburner2:
OP already suggested that in his first post.
Whoops! Reading comprehension fail...my bad...sigh.
You can buy electronic cigarette lighters for not too much, they run an 12v remote cell.
I wonder if the sparker can be built right into the valve if there is a valve.
I have used one of these for igniting a propane torch: https://www.sparkfun.com/products/retired/11218 no longer available but it looks like similar items are super cheap on eBay: http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&LH_BIN=1&_nkw=high+voltage+generator&_sop=15
I ended up using one of these instead: Silicon Nitride Igniter - 12V - COM-11694 - SparkFun Electronics. It takes a second to heat up so the spark would be better if you want immediate ignition.
Thanks for all the replies!
Someone asked me to elaborate on my rocket. It really won’t take much.
I’m using electrolysis to separate about 1-2mL of water. In my current design, I have the sparking wires right next to the electrodes. The entire setup is enclosed until ignition, separated from air by around 1mL or water.
It’s not very large, but it shoots very well.
And to elaborate on the spark gap, its about 0.8mm between two copper leads in a mixture of H2 and O2 gases