spark plugs

On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
<robin_listas@es.invalid> wrote:

>On 2023-12-22 01:03, RichD wrote:
>> I recall working on an arc lamp power supply, which used
>> a spark gap for ignition.
>> 
>> I wondered, and still do, are there any design techniques
>> or formulas, to obtain a specific desired voltage pulse
>> across the gap?  Or is it cut and try, regarding the gap size
>> and current?  (the current break, that is)
>
>That's strange, an arc lamp is low voltage, high current. The ones I 
>have seen needs the points to touch for an instant, then separate, 
>either automatically or manually. During use, the points can be at a 
>distance of about one centimetre.
>
>Using a a high voltage spark to initiate the thing? I don't know if that 
>is possible, I have not seen it.

It's how Xenon flash lamps are triggered.  The big capacitor is
charged less than 1 KVolt, which isn't enough for such a long gap (the
length of the fused quartz flash tube).  The trigger wire is wrapped
around the flash tube and when pulsed with 10 or 20 KV, causes a
conductive path to form in the Xenon gas (about 0.1 Bar) within, and
boom!

Joe Gwinn

On 2023-12-25 16:28, Cursitor Doom wrote:
> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
> <robin_listas@es.invalid> wrote:
> 
>> On 2023-12-22 01:03, RichD wrote:
>>> I recall working on an arc lamp power supply, which used
>>> a spark gap for ignition.
>>>
>>> I wondered, and still do, are there any design techniques
>>> or formulas, to obtain a specific desired voltage pulse
>>> across the gap?  Or is it cut and try, regarding the gap size
>>> and current?  (the current break, that is)
>>
>> That's strange, an arc lamp is low voltage, high current. The ones I
>> have seen needs the points to touch for an instant, then separate,
>> either automatically or manually. During use, the points can be at a
>> distance of about one centimetre.
>>
>> Using a a high voltage spark to initiate the thing? I don't know if that
>> is possible, I have not seen it.
> 
> In the older style transformer-only arc welders, the arc has to be
> struck manually by momentarily shorting out a low voltage/high current
> secondary winding; typically 50 to 80V. This can be a messy and
> frustrating process at times, even for a skilled tradesman. Newer
> style inverter welders use HF AC for a 'soft start' which is much
> cleaner and faster. I've not heard of a high voltage start method
> either.

The arcs I handled were the lantern of cinema projectors, and they used 
DC, of about 30 volts when running. With DC, the positive electrode 
wears significantly faster (electrons hitting it, was the explanation we 
got), so it is thicker and longer than the negative to compensate. The 
positive also develops a cavity on the tip, while the negative sharpens. 
The most light goes back in the direction of the negative, where an 
hyperbolic mirror projected it forward towards the film and the lenses. 
A tick metal plate with a lever was used instead of a switch, to allow 
the light to pass or not.

Unless I got positive and negative reversed, this was a bunch of years 
ago :-)

They used arc lights because not only they were very intense and white, 
but the light came from a tiny spot, which is ideal for focusing. But 
they were temperamental. Ours were adjusted with an electric motor with 
a lot of speed reduction, plus manual adjustments. The projectionist had 
to be watching the thing almost constantly; a bit of arc light was 
projected with a tiny periscope and mirror on a piece of cardboard, so 
we could see the shape of the electrodes, distance, position.

The modern counterpart is a xenon arc lamp. It doesn't wear out, I 
understand, but has to be replaced after a number of hours (10000?).


-- 
Cheers, Carlos.

mandag den 25. december 2023 kl. 19.04.07 UTC+1 skrev Carlos E.R.:
> On 2023-12-25 16:28, Cursitor Doom wrote: 
> > On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R." 
> > <robin_...@es.invalid> wrote: 
> > 
> >> On 2023-12-22 01:03, RichD wrote: 
> >>> I recall working on an arc lamp power supply, which used 
> >>> a spark gap for ignition. 
> >>> 
> >>> I wondered, and still do, are there any design techniques 
> >>> or formulas, to obtain a specific desired voltage pulse 
> >>> across the gap? Or is it cut and try, regarding the gap size 
> >>> and current? (the current break, that is) 
> >> 
> >> That's strange, an arc lamp is low voltage, high current. The ones I 
> >> have seen needs the points to touch for an instant, then separate, 
> >> either automatically or manually. During use, the points can be at a 
> >> distance of about one centimetre. 
> >> 
> >> Using a a high voltage spark to initiate the thing? I don't know if that 
> >> is possible, I have not seen it. 
> > 
> > In the older style transformer-only arc welders, the arc has to be 
> > struck manually by momentarily shorting out a low voltage/high current 
> > secondary winding; typically 50 to 80V. This can be a messy and 
> > frustrating process at times, even for a skilled tradesman. Newer 
> > style inverter welders use HF AC for a 'soft start' which is much 
> > cleaner and faster. I've not heard of a high voltage start method 
> > either.
> The arcs I handled were the lantern of cinema projectors, and they used 
> DC, of about 30 volts when running. With DC, the positive electrode 
> wears significantly faster (electrons hitting it, was the explanation we 
> got), so it is thicker and longer than the negative to compensate. The 
> positive also develops a cavity on the tip, while the negative sharpens. 
> The most light goes back in the direction of the negative, where an 
> hyperbolic mirror projected it forward towards the film and the lenses. 
> A tick metal plate with a lever was used instead of a switch, to allow 
> the light to pass or not. 
> 
> Unless I got positive and negative reversed, this was a bunch of years 
> ago :-) 
> 
> They used arc lights because not only they were very intense and white, 
> but the light came from a tiny spot, which is ideal for focusing. But 
> they were temperamental. Ours were adjusted with an electric motor with 
> a lot of speed reduction, plus manual adjustments. The projectionist had 
> to be watching the thing almost constantly; a bit of arc light was 
> projected with a tiny periscope and mirror on a piece of cardboard, so 
> we could see the shape of the electrodes, distance, position. 
> 
> The modern counterpart is a xenon arc lamp. It doesn't wear out, I 
> understand, but has to be replaced after a number of hours (10000?). 

more like 500hours

mandag den 25. december 2023 kl. 01.45.49 UTC+1 skrev Cursitor Doom:
> On Sun, 24 Dec 2023 16:54:06 -0700, Don Y 
> <blocked...@foo.invalid> wrote: 
> 
> >On 12/21/2023 8:07 PM, whit3rd wrote: 
> >> Sure, there's formulas; 
> > 
> >The problem is quantifying the environment. The medium between 
> >the electrodes plays a role -- as do the shapes of the electrodes, 
> >etc. 
> > 
> >> an auto spark coil takes high current from 12V on the primary 
> >> to build up field energy, then when the points open, the stored energy (less a bit for the 
> >> resistivity of the iron) blasts the spark hard. After warmup, the current limit resistor 
> >> (often a PTC type) gives a lower current for the now-hot engine. 
> >> 
> >> Energy is conserved, a little under L times the square of the current, over two, per spark. 
> >> The gap size has to be small enough that the arcing doesn't occur in the 
> >> wrong place... and the conductivity of the gap determines the spark duration (low 
> >> gas denslty, lower resistivity and faster spark). 
> > 
> >We had a VC approach us shortly out of school (70's) asking 
> >us to design an "electronic ignition" -- no rotor, etc. 
> >Back then, 1MHz processors were the norm. And, only 
> >1802's were low enough power to run in an automotive 
> >environment. 
> > 
> >We knocked together a prototype in short order (the code 
> >is trivial -- as is the hardware, if you don't have to 
> >plan for production!) and demonstrated how we could adjust 
> >the advance and dwell based on RPM and "general performance 
> >criteria". 
> > 
> >The VC had hoped we could enhance the value by compensating 
> >for plug degradation, indicating needs for service, etc. 
> > 
> >You can't (cheaply) *look* at the plug voltages but you can 
> >look at "characteristics" of each firing. And, if you ignore 
> >absolutes and, instead, do relative comparisons (this plug 
> >to that, this plug NOW to this plug a month ago, etc.) you 
> >can make some crude inferences. 
> > 
> >But, there are just too many variations to account for! 
> >No two plugs are produced alike. No two coils (we had a coil 
> >per plug). Wires get dirty and rerouted. etc. 
> > 
> >None of us had a desire to make a career out of this -- or 
> >ANYTHING automotive -- so we bowed out when he wanted to 
> >present to the automakers. The only way to do ANYTHING is 
> >in huge quantities -- which means, you do FEW things! 
> >(We'd rather have lots of varied challenges than just a few) 
> > 
> >Amusingly, I now find myself reviewing those (ancient) notes as I 
> >look to design an ECU for "one last *big* ICE" (for myself). 
> >I think it would be cool to be able to dial in operating 
> >constraints, dynamically: performance, fuel economy, emissions 
> >quality, etc. 
> > 
> >[This sparked from a discussion with a colleague over designing 
> >similar controls for race cars... let the controls "learn" 
> >the characteristics of the track so the driver doesn't 
> >have to tell the controls when he's entering a straightaway, 
> >deep curve, etc.]
> Indeed. Could easily be done with a Raspberry Pi or an Arduino even 
> that matter I would imagine.

needs hard real time so raspberry pi is useless  
an Arduino might do to implement something like what manufacturers did 30+ years ago ..

On 12/25/2023 11:39 AM, Lasse Langwadt Christensen wrote:
> needs hard real time so raspberry pi is useless

Can't you discard the slushware that comes with the rPi and
just use the *hardware*?

> an Arduino might do to implement something like what manufacturers did 30+ years ago ..

The innovation is to *learn* what the race circuit looks like
(to the engine+driver) and use that knowledge to anticipate
calls for power, calls for fuel efficiency, etc. -- because
you have been watching the driver's actions to determine
what he will want from the vehicle.

Apparently, different racing organizations have different
"rules" for the types of kit that the vehicle can sport
as well as *controls* that the driver can access (e.g.,
one only allows a "Push to Talk" button).

Any device that you had to explicitly train would be a loser;
it needs to *watch*, at racetime, and assume that (track)
pattern will be repeated until powered off.

mandag den 25. december 2023 kl. 20.20.46 UTC+1 skrev Don Y:
> On 12/25/2023 11:39 AM, Lasse Langwadt Christensen wrote: 
> > needs hard real time so raspberry pi is useless
> Can't you discard the slushware that comes with the rPi and 
> just use the *hardware*?
> > an Arduino might do to implement something like what manufacturers did 30+ years ago ..
> The innovation is to *learn* what the race circuit looks like 
> (to the engine+driver) and use that knowledge to anticipate 
> calls for power, calls for fuel efficiency, etc. -- because 
> you have been watching the driver's actions to determine 
> what he will want from the vehicle. 
> 
> Apparently, different racing organizations have different 
> "rules" for the types of kit that the vehicle can sport 
> as well as *controls* that the driver can access (e.g., 
> one only allows a "Push to Talk" button). 
> 
> Any device that you had to explicitly train would be a loser; 
> it needs to *watch*, at racetime, and assume that (track) 
> pattern will be repeated until powered off.

i.e. you have no experience on the matter

On 26/12/2023 12:06 am, Carlos E.R. wrote:
> On 2023-12-22 01:03, RichD wrote:
>> I recall working on an arc lamp power supply, which used
>> a spark gap for ignition.
>>
>> I wondered, and still do, are there any design techniques
>> or formulas, to obtain a specific desired voltage pulse
>> across the gap?  Or is it cut and try, regarding the gap size
>> and current?  (the current break, that is)
> 
> That's strange, an arc lamp is low voltage, high current. The ones I 
> have seen needs the points to touch for an instant, then separate, 
> either automatically or manually. During use, the points can be at a 
> distance of about one centimetre.
> 
> Using a a high voltage spark to initiate the thing? I don't know if that 
> is possible, I have not seen it.

The high pressure xenon arc lamps I built my power supply to drive were 
being used as UV light sources in the Photochemistry group at 
Southampton University.

It took about 20kV to drive a spark between the electrodes, which dumped 
enough xenon ions and electrons into the gap to sustain a glow discharge 
for the few microsceconds it took for the tungsten electrode surface to 
warm up enough to sustain an 24A arc  at about 20v or so.

They ran hot and were filled with a couple of atmospheres of xenon gas, 
and relied on silica glass to keep the gas inside and the tungsten 
electrodes spaced apart. Moving the electrodes wasn't an option. 
Providing a third - trigger - electrode to allow easier starting was 
possible, but not popular.

I set up a stable constant current so the lamp provided a more or less 
stable output - turbulent convection currents in the xenon gas meant 
that it wasn't all that stable in the short term.


-- 
Bill Sloman, Sydney

The same kind of lamp was used to illuminate sports fields and airports 
at the time. Specialist applications, but there were quite a few of them 
around.

-- 
Bill Sloman, Sydney

On Monday 25 December 2023 at 18:04:07 UTC, Carlos E.R. wrote:
> On 2023-12-25 16:28, Cursitor Doom wrote: 
> > On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R." 
> > <robin_...@es.invalid> wrote: 
> > 
> >> On 2023-12-22 01:03, RichD wrote: 
> >>> I recall working on an arc lamp power supply, which used 
> >>> a spark gap for ignition. 
> >>> 
> >>> I wondered, and still do, are there any design techniques 
> >>> or formulas, to obtain a specific desired voltage pulse 
> >>> across the gap? Or is it cut and try, regarding the gap size 
> >>> and current? (the current break, that is) 
> >> 
> >> That's strange, an arc lamp is low voltage, high current. The ones I 
> >> have seen needs the points to touch for an instant, then separate, 
> >> either automatically or manually. During use, the points can be at a 
> >> distance of about one centimetre. 
> >> 
> >> Using a a high voltage spark to initiate the thing? I don't know if that 
> >> is possible, I have not seen it. 
> > 
> > In the older style transformer-only arc welders, the arc has to be 
> > struck manually by momentarily shorting out a low voltage/high current 
> > secondary winding; typically 50 to 80V. This can be a messy and 
> > frustrating process at times, even for a skilled tradesman. Newer 
> > style inverter welders use HF AC for a 'soft start' which is much 
> > cleaner and faster. I've not heard of a high voltage start method 
> > either.
> The arcs I handled were the lantern of cinema projectors, and they used 
> DC, of about 30 volts when running. With DC, the positive electrode 
> wears significantly faster (electrons hitting it, was the explanation we 
> got), so it is thicker and longer than the negative to compensate. The 
> positive also develops a cavity on the tip, while the negative sharpens. 
> The most light goes back in the direction of the negative, where an 
> hyperbolic mirror projected it forward towards the film and the lenses. 
> A tick metal plate with a lever was used instead of a switch, to allow 
> the light to pass or not. 
> 
> Unless I got positive and negative reversed, this was a bunch of years 
> ago :-) 
> 
> They used arc lights because not only they were very intense and white, 
> but the light came from a tiny spot, which is ideal for focusing. But 
> they were temperamental. Ours were adjusted with an electric motor with 
> a lot of speed reduction, plus manual adjustments. The projectionist had 
> to be watching the thing almost constantly; a bit of arc light was 
> projected with a tiny periscope and mirror on a piece of cardboard, so 
> we could see the shape of the electrodes, distance, position. 
> 
> The modern counterpart is a xenon arc lamp. It doesn't wear out, I 
> understand, but has to be replaced after a number of hours (10000?). 

I found carbon arc lights to be reliable, as long as they were readjusted every however many minutes. The motorised feed almost matched the burn rate, but there was always variation. I gather earlier arc lights used simple closed cycle gap adjustment, but it caused the light spot to move.

On 2023-12-25 17:58, Joe Gwinn wrote:
> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
> <robin_listas@es.invalid> wrote:
> 
>> On 2023-12-22 01:03, RichD wrote:
>>> I recall working on an arc lamp power supply, which used
>>> a spark gap for ignition.
>>>
>>> I wondered, and still do, are there any design techniques
>>> or formulas, to obtain a specific desired voltage pulse
>>> across the gap?  Or is it cut and try, regarding the gap size
>>> and current?  (the current break, that is)
>>
>> That's strange, an arc lamp is low voltage, high current. The ones I
>> have seen needs the points to touch for an instant, then separate,
>> either automatically or manually. During use, the points can be at a
>> distance of about one centimetre.
>>
>> Using a a high voltage spark to initiate the thing? I don't know if that
>> is possible, I have not seen it.
> 
> It's how Xenon flash lamps are triggered.  The big capacitor is
> charged less than 1 KVolt, which isn't enough for such a long gap (the
> length of the fused quartz flash tube).  The trigger wire is wrapped
> around the flash tube and when pulsed with 10 or 20 KV, causes a
> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
> boom!
Ah, ok, yes.

But there is no conductivity between the high voltage and low voltage parts.

-- 
Cheers, Carlos.

Carlos E.R. <robin_listas@es.invalid> wrote:
> On 2023-12-25 17:58, Joe Gwinn wrote:
>> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
>> <robin_listas@es.invalid> wrote:
>> 
>>> On 2023-12-22 01:03, RichD wrote:
>>>> I recall working on an arc lamp power supply, which used
>>>> a spark gap for ignition.
>>>> 
>>>> I wondered, and still do, are there any design techniques
>>>> or formulas, to obtain a specific desired voltage pulse
>>>> across the gap?  Or is it cut and try, regarding the gap size
>>>> and current?  (the current break, that is)
>>> 
>>> That's strange, an arc lamp is low voltage, high current. The ones I
>>> have seen needs the points to touch for an instant, then separate,
>>> either automatically or manually. During use, the points can be at a
>>> distance of about one centimetre.
>>> 
>>> Using a a high voltage spark to initiate the thing? I don't know if that
>>> is possible, I have not seen it.
>> 
>> It's how Xenon flash lamps are triggered.  The big capacitor is
>> charged less than 1 KVolt, which isn't enough for such a long gap (the
>> length of the fused quartz flash tube).  The trigger wire is wrapped
>> around the flash tube and when pulsed with 10 or 20 KV, causes a
>> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>> boom!
> Ah, ok, yes.
> 
> But there is no conductivity between the high voltage and low voltage parts.
> 

Gas lasers and CFLs are started by a HV transient on the terminals. 

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  
ElectroOptical Innovations LLC / Hobbs ElectroOptics  Optics,
Electro-optics, Photonics, Analog Electronics