View Full Version : High-speed photography
As you know I'm building a setup for high-speed photography and am awaiting parts from Thailand.
Meanwhile I discovered a very interesting site with details of how to build your own high-speed flashgun. I can honestly say it looks a little dangerous but I'm going to have to have a go at this sometime!
http://users.abo.fi/joheriks/hispeed/howto.html
mattdm
05-21-2009, 07:32 PM
Wow.
Well, we'll miss your postings. :)
Anthony
05-22-2009, 02:37 PM
Make sure you wear boots with thick rubber soles and you SHOULD be OK :D
Mark_48
05-22-2009, 02:56 PM
Make sure you wear boots with thick rubber soles and you SHOULD be OK :D
And keep one hand in your pocket.....
...or just keep your distance as shown below.
Making up a 115kV live tap (Northampton, MA)
Since then I have looked for and found some ultra-high speed flashes. There're apparently some very high speed magnesium flashbulbs. Now those look like they might be the most economic route - I just hope the company responds to me. There are a couple of companies selling arc flash and Quartz flash units too. Everybody is POA though.
Dread Pirate Roberts
05-23-2009, 07:12 AM
Wow a large home made capacitor.
Good luck with the project.
Anthony
05-23-2009, 07:16 AM
POA always sounds expensive to me :eek:
Interesting. From what I've seen and read so far, it appears that some people claim that Xenon tubes have an afterglow. I have not read this so far in my book on High-Speed Photography and Photonics though and have noted also that some specialist ballistic photography flashes use Quartz-Xenon flash tubes which does indicate that those that claim Xenon tubes have an afterglow are really mistaking a longer flash for "afterglow". At 1/35,000th the fastest flash on a 580EX2 is really quite long.
Anyway, I'm on hold until I get some more bits and bobs. I'm heading out today to get a 1/4" nut to attach to my Schmidt trigger so that I can get started with water droplets etc.
seanhoxx
05-24-2009, 11:29 AM
Rhys you get that all built and set up it might be time to get a few 'interns' who want to learn by doing as you satnd back......WAY back, and watch! it all sounds really neat though. Just a thought, and keep in mind I have NOT researched it but the Xenon tubes are the a pressurized gas tube? if so i would have ti think there would have to be some degree of afterglow from the stimulation of the gas molecules, they couldn't 'settle down' instantly?
I was reading more of Edgerton's work and it seems he gets 1/100,000th exposures from xenon which suggests to me - since it's an inert gas - that (and one of the guys I work with is a retired physics professor) the "afterglow" is more to do with trying to pass too much current over time through the xenon. Discussing with him, we decided that it was highly likely that the capacitor used was too large in capacity. Thus, a series of Xenon tubes wired in parallel would burn up the current faster with a shorter flash. Of course each tube might need a separate driver which means that we might end up with a series of micro flashes or we could well end up with a single synchronised flash pulse of high brightness and short duration. The main problem with multiple drivers is that each would have a certain current overhead which means that the flash output would be reduced. It's a series of interesting issues to consider.
Mark_48
05-24-2009, 05:29 PM
The Vivitar 283 and others similar use an SCR to quench the flash arc. This shortens the duration and serves to reduce the output, dependent on the light the sensor sees.
If you're still considering about 20kV for flash, it'll likely be difficult to quench that magnitude of voltage easily. From 300v to 450v might be an easier target and considerably safer.....
http://www.mouser.com/Search/Refine.aspx?Keyword=flashtube
That's a very interesting page Mark. Any ideas where I can look for a planned, buildable flashgun circuit?
I had a crazy idea... If I can build a small flashgun, that concept could be applied to bigger flashguns too... and even to ring flashes.
Mark_48
05-24-2009, 07:06 PM
You might be able to extract some ideas from here....... :)
http://www.repairfaq.org/REPAIR/F_strbfaq.html
and...
http://members.misty.com/don/donflash.html
Hmm... THis looks interesting.... http://www.goldmine-elec-products.com/prodinfo.asp?number=G13603
It needs the circuit behind it but it's definitely interesting!
Mark_48
05-27-2009, 03:22 PM
I dragged this relic out of my barn. Somewhere back in the 70's I put this together with mostly junkbox parts. I can't recall for sure where I got the flash head, reflector, and capacitors, I think it may have been from a local electronics surplus parts store.
It's basically a power pack with 2 levels of power which is toggle switch selected. The switches either put one 850uf capacitor in or two 850uf in parallel. The resistors limit the charge current so as not to smoke the selenium rectifier stack or the power transformer. Fully charged it's close to 400vdc :eek:. The lamps on top are neon that indicate which caps a charged and when AC power is on. In the flash head is the trigger transformer which fires the flashtube. I used to have a hand drawn schematic, but thats been long lost.
Really not hard to put together something basic like this. The more difficult part would be controlling flash duration and power, which the documents I previously linked should give an idea how.
Out of curiosity today I tested my setup with my flash. It triggered nicely. I'm going to have to fine tune as when I fired an airsoft pellet through teh beam, nothing happened. Maybe I missed. Maybe I just need to turn the dial a bit more. I'll have to check tomorrow. Part of the problem is that I designed my Schmidt trigger with a wide gap with the intention of catching ice cubes, fruit etc descending into beverages.
seanhoxx
05-27-2009, 09:49 PM
the small size of the pellet you said .177mm right? and the velocity it may be small enough and going fast enough not to fully break the beam? mark 48 nice piece of DIY work, man I bet that could 'bite' the hell out of you!
No. Airsoft is 6mm. That's plenty big enough. I just need to adjust the sensitivity.
.177 is .177 of an inch or in metric 4.4958mm. Again - plenty big enough.
Mark, that looks very interesting : o
Portable power supplys are so expensive, DIY is pretty wow for something like that.
Mark's kit is pretty awe-inspiring.
I don't know why portable power supplies are so expensive. All they are is a battery and an inverter!
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