*small* spark generator

I need to generate sparks between two pieces of brass, about a half
inch apart or slightly more. I want each spark to be triggered by a
logic line going high (going low would work, too.) The voltage supply
is 6v or 12v from a battery. The problem is that I need the circuit to
fit inside a 1.5" inside diameter PVC pipe, and not take up more than,
say, 3" of the pipe length, discounting battery. I was looking at
autotransformers, but I'm not finding anything that will fit in that
space. I don't need more than 1-2 sparks a second, but I want the
circuit to be reliable. Can anyone suggest a circuit design that fits
in a small space like this?

I'm aware of the safety risks in generating a voltage high enough to
cross 1/2" of air, and the spark won't be anywhere that a finger can
get into it. If it wasn't for the voltages involved, I'd tinker
something up by trial and error, but in this case I don't like the
possible consequences of "error", so I'd rather get expert advice. I'm
willing to wind my own transformer if that's needed. Thanks!

"ScottM" <scott.a.mayo@gmail.com> wrote in message 
news:af0c7308-1e62-48c5-bde0-e414fe061927@p16g2000yqc.googlegroups.com...
>I need to generate sparks between two pieces of brass, about a half
> inch apart or slightly more. I want each spark to be triggered by a
> logic line going high (going low would work, too.) The voltage supply
> is 6v or 12v from a battery. The problem is that I need the circuit to
> fit inside a 1.5" inside diameter PVC pipe, and not take up more than,
> say, 3" of the pipe length, discounting battery. I was looking at
> autotransformers, but I'm not finding anything that will fit in that
> space. I don't need more than 1-2 sparks a second, but I want the
> circuit to be reliable. Can anyone suggest a circuit design that fits
> in a small space like this?
>
> I'm aware of the safety risks in generating a voltage high enough to
> cross 1/2" of air, and the spark won't be anywhere that a finger can
> get into it. If it wasn't for the voltages involved, I'd tinker
> something up by trial and error, but in this case I don't like the
> possible consequences of "error", so I'd rather get expert advice. I'm
> willing to wind my own transformer if that's needed. Thanks!
>

May I suggest an electronic gas stove igniter?

The most common type runs fro a i.5V cell using a single transistor blocking 
oscillator to generate about 250V - that charges a capacitor which is dumped 
into a HV pulse transformer a few times a second by aa gas discharge tube - 
replace the tube with a thyristor and you can control it.

If you're lucky, you might find a handheld igniter, alternatively go to 
recycling and look on the backs of scrap gas stoves.

Alternatively; look for a tiny SMPSU (DVB-T tet top box type thing)  with a 
little re-arrangement of the blocking oscillator wiring you can make a 5V or 
12V inverter - you should be able to produce a continuous ark between the 
pins that were the primary at about 20kHz or more. 

On 2012-05-19, ScottM <scott.a.mayo@gmail.com> wrote:
> I need to generate sparks between two pieces of brass, about a half
> inch apart or slightly more. I want each spark to be triggered by a
> logic line going high (going low would work, too.) The voltage supply
> is 6v or 12v from a battery. The problem is that I need the circuit to
> fit inside a 1.5" inside diameter PVC pipe, and not take up more than,
> say, 3" of the pipe length, discounting battery. I was looking at
> autotransformers, but I'm not finding anything that will fit in that
> space. I don't need more than 1-2 sparks a second, but I want the
> circuit to be reliable. Can anyone suggest a circuit design that fits
> in a small space like this?

Have you looked at a Tazer?



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--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

On Saturday, May 19, 2012 11:36:21 PM UTC+2, ScottM wrote:
>  The problem is that I need the circuit to
> fit inside a 1.5" inside diameter PVC pipe

Potato gun?

On Sat, 19 May 2012 14:36:21 -0700 (PDT), ScottM <scott.a.mayo@gmail.com> wrote:
> I need to generate sparks between two pieces of brass, about a half
> inch apart or slightly more. I want each spark to be triggered by a
> logic line going high (going low would work, too.) The voltage supply
> is 6v or 12v from a battery. The problem is that I need the circuit to
> fit inside a 1.5" inside diameter PVC pipe, and not take up more than,
> say, 3" of the pipe length, discounting battery.

  [...]

ScottM,

You might take a look at this item and its associated video:

  Spark Gap Igniter - 4.8V -- $15
  http://www.sparkfun.com/products/11218

It's not completely clear whether their "gap <0.5inch" is compatible
with your "about a half an inch or more".  Also, it looks like a close
fit (see the photo with a quarter-dollar for size comparison).

Hope this helps...


Frank McKenney
-- 
  The prohibition of dodgeball represents the overshooting of yet
  another successful campaign against violence, the century-long
  movement to prevent the abuse and neglect of children.  It reminds
  us of how a civilizing offensive can leave a culture with a legacy
  of puzzling customs, peccadilloes, and taboos.  The code of
  etiquette bequeathed by this and other Rights Revolutions is
  pervasive enough to have acquired a name.  We call it political
  correctness.
              -- Steven Pinker / The Better Angels of Our Nature
-- 
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney aatt mindspring ddoott com

On 2012-05-20, Frnak McKenney <frnak@far.from.the.madding.crowd.com> wrote:

> You might take a look at this item and its associated video:
>
>   Spark Gap Igniter - 4.8V -- $15
>   http://www.sparkfun.com/products/11218

The text say 3A draw, the vid says 20A draw.  ?????

Also, be aware Sparkfun, being a small company, doesn't have the
financial/legal horsepower to fight for yer privacy.  They recently
got into trouble cuz some dirtbags used one of their items to make
illegal credit card readers and the govt came down on them, demanding
lists of all their customers.  A deal was worked out and sparkfun
released only the customers that had recently purchased the offending
device, not the entire customer list.  Not saying you shouldn't deal
with sparkfun, jes that you should know what's what.

http://tinyurl.com/7co6lnp

nb



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Support labeling GMOs
<http://www.labelgmos.org/>

On 5/20/2012 9:06 AM, fungus wrote:
> On Saturday, May 19, 2012 11:36:21 PM UTC+2, ScottM wrote:
>>   The problem is that I need the circuit to
>> fit inside a 1.5" inside diameter PVC pipe
> Potato gun?
It's usually a good if the OP states the objective. For a potato gun 
most use a BBQ igniter.

> It's usually a good if the OP states the objective.

Fair enough. It's to make a prop for a play involving mad science. The
spark will be created inside a small brass funnel, and I'd like it to
be bright enough and loud enough to be noticeable at a distance, which
is why I want a longish spark. I'm not igniting anything with it. I'd
prefer not to use a tazer circuit, on the grounds that those are meant
to knock people over; I want something less likely to cause lawsuits
if there's an accidental shocking.

I hadn't considered a continuous arc, on the grounds that I figured
that would eat a lot of energy, but I have to admit that would look
impressive, if possible...

On 5/20/2012 1:37 PM, ScottM wrote:
>> It's usually a good if the OP states the objective.
> Fair enough. It's to make a prop for a play involving mad science. The
> spark will be created inside a small brass funnel, and I'd like it to
> be bright enough and loud enough to be noticeable at a distance, which
> is why I want a longish spark. I'm not igniting anything with it. I'd
> prefer not to use a tazer circuit, on the grounds that those are meant
> to knock people over; I want something less likely to cause lawsuits
> if there's an accidental shocking.
>
> I hadn't considered a continuous arc, on the grounds that I figured
> that would eat a lot of energy, but I have to admit that would look
> impressive, if possible...
I don't think the arc will be heard any distance in the magnitudes that 
you are describing.
If it's for "Mad Science" why not incorporate a Jacob's ladder, much 
more impressive?

Tom

"ScottM" <scott.a.mayo@gmail.com> wrote in message 
news:26c43376-f034-48e1-8337-ac17671469f4@h41g2000yqm.googlegroups.com...
>
>> It's usually a good if the OP states the objective.
>
> Fair enough. It's to make a prop for a play involving mad science. The
> spark will be created inside a small brass funnel, and I'd like it to
> be bright enough and loud enough to be noticeable at a distance, which
> is why I want a longish spark. I'm not igniting anything with it. I'd
> prefer not to use a tazer circuit, on the grounds that those are meant
> to knock people over; I want something less likely to cause lawsuits
> if there's an accidental shocking.
>
> I hadn't considered a continuous arc, on the grounds that I figured
> that would eat a lot of energy, but I have to admit that would look
> impressive, if possible...
>

With a motorcycle ign coil (twin HT lead "wasted spark" type is best) and a 
555 driving a reasonably "fat" MOSFET its pretty easy to get fast enough 
sparks for persistence of vision make it seem continuous.

After playing with the experiment for a while, my ears were left ringing!