Palflash 500, nanosecond light source

[dexters_lab]

i picked up this pulse light source a while ago and want to figure out why i get no flash out of it.

its a simple device with two air-gap spark flash devices inside with a capacitor bank.

would like some ideas on getting this working, i think the problem might be more mechanical than electronic but we will see!

[TheBay]

Did you try firing it from the trigger ports, do they require a voltage or just short to trigger. I guess each trigger port is to fire the 2 lights at different times or together?

Probably a sticky relay

[dexters_lab]

no, not tried the trigger inputs. i am (foolishly?) assumung that if the test doesnt work then the trigger inputs wont either

i will check the input circuit closer to see what kind of input it might be

sadly there is no documentation i can find for this 

[TheBay]

Looks a very interesting device, would love to see it fire.

Do you have gas you can feed it too?

[T3sl4co1l]

Beefy!

Gap seems a little wide for 9kV, which should be the case; you don't want that sparking just any time.  And there should be a spark plug or trigger electrode or something like that nearby, which I'm guessing is coming from the black boxes on the board.  So, I'd check those first, see if you can get those to do anything.

I'd want to guess the inputs are TTL level or something like that, but whatever it is, you should probably be able to find out from tracing the circuit?

Tim

[Rufus]

I would say it isn't going to discharge without a low dielectric strength gas feed. Likely a rare gas Argon, Neon, Xenon etc and possibly a mixture with air.

It is a flash tube without the tube.

[Jay_Diddy_B]

Hi,
 I did a little searching. The palflash 501 will work with Argon or Air.

I suspect that you will have to reduce the size of the gap if you are using air. I think if you loosen the big nut, you slide the silver coloured rod up and down to adjust the gap.

This is a triggered spark gap design. The small arc will ionize the gas and cause the main arc to fire.

You may have to feed the unit with air from a compressor to extinguish the arc.

Regards,

Jay_Diddy_B

[SeanB]

You will need to reduce the gap or pump the unit down internally to a low pressure to fire that large gap. Probably 0.2 to 0.5bar suction will do to fire that gap, and if you have some argon to feed into the supply port as well it will do a nice bright flash. Likely the original configuration was that the one nipple was the gas suction, fed to both top ports of the flash gap, and the other tube went down below to the lower posts to provide the gas supply. The suction would also purge the case.

Likely there was the mod done to reduce gas usage, but this contaminates the case. The suction removes the ionised gas so it will not contaminate the gap. You can see from the deposits in the pipe that the top was the suction side, the lower was supply.

[dexters_lab]

thanks guys

I will pickup a argon regulator for a mig welder and rig an argon supply up to it shouldn't cost more than £25 or so to do this, machine mart are only 20 mins away, hmmm!

A friend also commented that the gap looks too big so i will get my spanners out and have a go at adjusting it and see what happens for part 2!

@SeanBZA: i dont think there was ever a piped gas supply to the bottom electrode, there doesn't seem to be any evidence of that and there is no way you could route the pipes to the underside because of the way it fits into the case. I think they just used the gas flow from the top electrode to do all the work. The case is not designed to be pumped down either, nothing is remotely air tight!

I will have a look at it soon and post results!

[miguelvp]

Some random info from the web:

http://www.pulsephotonics.com/palflash.htm

http://www.photonicsonline.com/doc/dynamic-schlieren-imaging-palflash-501-0002
I didn't register so I didn't download the datasheet:
http://www.photonicsonline.com/doc/dynamic-schlieren-imaging-palflash-501-0001

Chinese site translated by google:
https://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Fwww.hrtlaser.com%2Fcn%2Fproduct-detail-52.html

it has the datasheet, it was too big so I made pictures but not too exciting, I attached them

Some uses of the device:
http://hiviz.org/hsi/ss/schlieren/index.htm

http://hiviz.org/hsi/ss/rem222/index.htm


But I wonder if the inner tube in the sparkgap is supposed to move or not, or if it was supposed to have something in the inner part that broke off. But I'm just guessing.

[mikeselectricstuff]

That gap looks way too big to fire at 9Kv in air.
My guess would be that it wants to breathe argon.
Xenon & other inert gases are too expensive for use in an open-flow system.
Maybe Nitrogen?
It looks like it uses a cheap gas, otherwise you'd expect to see a gas control valve to turn the flow on when required.
I wonder if the second tube is simply to allow the main one to be blocked to avoid wasting gas.
Is the unit sufficiently well sealed to allow pressurisation? It probably isn't designed for negative pressure as I see no precautions against outgassing from components.
The 2 gaps are probably to allow measurement of speeds - look at distance moved between 2 images at known intervals.

[mikeselectricstuff]

You may have to feed the unit with air from a compressor to extinguish the arc.

No - the cap will discharge until the arc extinguishes.

[Yago]

Nice light Dexter, looking forward to see the results of your work.

This mean you are moving to stills work now?
Do you mind if I ask how much you paid for this unit? (I am a bit of a photog too).

[mikeselectricstuff]

Reminds me I have an ancient  1000fps flash unit gathering dust somewhere - must dig it out sometime.
I have a suspicion that it may not be much brighter  than a modern white power LED...

[dexters_lab]

thanks for the tips guys,

i just had it open on the bench while i mused over the comments and noticed the gap is very easily adjustable and in fact i have made it fire after adjusting the gap  Didn't half make me jump when it flashed though! I just need to redo it on camera so you can see. 

@mikeselectricstuff
will be trying some argon as it's easy to get hold of and cheap. There is no sealing whatsoever on the enclosure so i'm sure it's not meant to be under anything other than atmospheric pressure. 1000fps flash? sounds interesting maybe you should make a video on it, isn't it about time we saw some of your glassware 

@yago
no, i'm far more interested in high speed video, but it might be fun to so something with it if i can rig up the right trigger based on light or sound. I paid £30 for it including postage, i could have saved a tenner and picked it up as the seller was local to me but i CBA. 

@miguelvp
thanks for the links, i had found them already but i still appreciate your effort! I did wonder about the inner part of the ground electrode being adjustable but i dont think it is. It seems to be set into the plastic insulation that surrounds the trigger electrode.

more to come...

[TheBay]

Wow! glad you are making progress. Looks bright! hope you don't get arc eye or put your finger in there lol!

[mikeselectricstuff]

Might be hard to find something fast enough for a 500nS flash to be useful.
The only thing that comes immediately to mind is an exploding glass prince Rupert's drop.
I wonder if a DSLR has any significant sensitivity to exposures this short?


 

[dentaku]

Might be hard to find something fast enough for a 500nS flash to be useful.
The only thing that comes immediately to mind is an exploding glass prince Rupert's drop.
I wonder if a DSLR has any significant sensitivity to exposures this short?

I didn't heard of Prince Rupert's Drops before Steven Fry shattered one on QI this week.

[dexters_lab]

Smarter every day did a great video on them a while back...

[dexters_lab]

Might be hard to find something fast enough for a 500nS flash to be useful.
The only thing that comes immediately to mind is an exploding glass prince Rupert's drop.
I wonder if a DSLR has any significant sensitivity to exposures this short?

should be fine i think, long exposure in darkness then fire the flash

will try it when i do a an update on it in a few days

[T3sl4co1l]

Reminds me I have an ancient  1000fps flash unit gathering dust somewhere - must dig it out sometime.
I have a suspicion that it may not be much brighter  than a modern white power LED...

I have a military RPM stroboscope, using a xenon filled vacuum tube for the flash.  GenRad 1531, tube is 1538-P1.  Interesting tube, if simple; a shame there's no data on it.

Tim

[dexters_lab]

quick update with some video of it firing and some test shots

the last picture looks good which is shown at the end. I will need to experiment with the setup some more. Of course you have no control over the exposure time so you have to control exposure with the aperture. I was typically around F8 to get a better DOF. I will look next time at upping my ISO to get a higher F and trying different camera angles.

i just need to sort out some triggering mechanism and some things to try with it

It's a bit of a crap thing to work on though, as in they didn't think about how it went together, screw heads hidden under things etc, so i will have to set aside some time to get the control board out and figure the trigger circuit.

[miguelvp]

photodiode triggering of a water droplet, or you could use it for a time of flight distance measurement with a camera but you will have to synch it with the camera refresh rate to get an accurate measurement, 2nd delay trigger might help if the camera sensor has persistance.

Get a bicycle wheel or anything that rotates and freeze it in time, 2nd flash to determine the angular velocity. I bet there are a million uses for that equipment.
 

[dexters_lab]

i was thinking about it last night and i think the best setup would be a simple beam break trigger.

I am thinking that having a tube that i can drop a big ball bearing though with the break sensor at the bottom. This should be usable for dropping other things like water as well.

So i can drop it onto things like glass objects might prove practical, interesting and reusable for various objects.

this guy has some amazing photos using a airgap flash
https://www.flickr.com/photos/mauriceribble/sets/

[Yago]

It's alive!

The shot with the blot and solder reel was a really good indicator of scale.
Close up or even macro only.

It is going to be difficult (impossible?) without being able to sync the light to the event.

Wonder if you could capture ripples across the surface of something oscillating (a membrane?), or a travelling wave on a wire (mechanical).

Cyclic stuff might help zone-in on the event until the trigger is sorted.

Looking forward to more Dexter, cheers