The last shot

[Rhys]

Today I went and did some more high-speed photography. It was jolly good fun and I share with you my last shot of the evening. I'm a little perplexed though as to why every time I upload the images from tonight, I get strange lines across them. I compare the image on the computer with the uploaded version and there are no lines on the original but are after it's been uploaded. My only guess is there's some form of corruption going on somewhere. Very strange as data checksums should take care of that!

[Rhys]

Turned out to be a Firefox problem. Firefox isn't rendering the images well. Internet Explorer has no such problem.

Meanwhile, some other of today's photos:
http://farm4.static.flickr.com/3461/3760806690_ef196a2e33_o.jpg
http://farm3.static.flickr.com/2632/3760009851_23f99d8919_o.jpg
http://farm4.static.flickr.com/3487/3760806990_325d8565fa_o.jpg

[seanhoxx]

Awesome stuff, very cool, .22 caliber pellet?

[Spookonthe8ball]

I like the crayon crack :) The 1st two are falling at about the same angle. Looks to be a .177 cal to me.
Spook

[Csae]

They seem blurry, isn't the whole point to freeze things ?

[r3g]

Epic shots. Howd you go about taking them?

[Rhys]

As far as blue goes, the exposure was pretty fast. Around 1/35,000th of a second.

The .177 pellet travelling at 500fps had been slowed by the two crayons to a point where it was sharp in the image. Given that during 1/35,000th it would have travelled 0.17 of an inch with no crayons present and thus been a blurred cylinder, I don't think that's too bad.

Now, if you want to take photos that are really crisp, showing each flying fragment without any blur then you need a microflash. These retail from $3,000 up to $100,000. It is possible to build your own and I'm researching this right now. Bear in mind that just the diodes (and you need 8 at least) are $28 apiece. The transformers are upwards of $18 and you need two and that's the cheap one. The capacitors are going to be $30 plus each. Oh yes - and the little matter of voltage - you're dealing with 25,000 volts at the main supply and 50,000 volts as the ionising pulse. High speed photography is a dangerous pursuit. The pellet gun I'm using is harmless in comparison to the flashes.

Now, with a microflash, you can take images with 1/1,000,000th second and shorter exposures. That's enough to reduce movement on a 2,000 fps bullet down to 1mm.

As far as how I took them - you're just going to have to buy my book. I'm writing a book at the moment and it will include plans for building all sorts of juicy stuff - sound triggers, delay units, light activated triggers, microflashes and possibly radio triggers as well. And you'll see photos showing how to do it all, photos showing common errors etc. I'm hoping to get the book completed sometime in September and on the shelves about then. It might be released as an E-Book and a POD book.

[Mark_48]

A little practice and you're getting good at this. Is the strobing feature on the 580EX fast enough to freeze incremental steps of the motion.

A couple suggestions to consider if you get serious with the high voltage stuff...

First of all I'd recommend not doing it unless you have a really good background with electricity and safety, but as you'll probably forge ahead without regard to that recommendation....

- Have a second person with you, preferably someone with some basic CPR training.

- Keep one hand in your pocket while working on the equipment.

- Do not wear clothing of synthetic fabrics (rayon, nylon...). These can tend to ignite quite rapidly from exposure to the heat and the arc of an electrical flash. Natural fabrics such as cotton and wool are safer and less likely to ignite. Fire retardant shirts can be purchased reasonably at a store that sells work clothes (Typical brands Nomex, Bulwark)

- Design your equipment so it has a deadman switch that the second person can release to denergize the equipment if something happens.

- Design your equipment such that it has some means to indicate when its energized, such as a light or buzzer.

- If you do get a shock don't hesistate to get checked out medically. You can sustain internal tissue and muscle damage as well as surface skin burns. A blood sample can be checked for certain enzymes that will indicate if internal muscle or tissue damage has occurred.

- Provide a means to disable and secure the equipment if you aren't around. In the industry this is commonly refered to as a "Lockout/Tagout" procedure. You don't want kids or nosy neighbors getting into something potentially dangerous. There are safety covers that can be locked in place over an AC plug to prevent its use. This includes ensuring that capacitors are discharged.

In regards to your book... Be clear to readers that may use your book as a guide into high voltage flash devices, that they do so at their own risk and no liability pertaining to injury or death shall be placed upon the author in those regards.

Have fun and be safe.....

[Rhys]

It's all quite a simple circuit, Mark. Essentially it's two circuits - one for charging the main capacitor to 20,000v +/- 5,000v and another for firing the trigger circuit at 45-50kv. Generally, people seem to try to make them both start on 12v DC. Oddly enough I have a spare LCD monitor transformer in my drawer and it's 12v DC.

The 15-25KV power supply is normally a TV flyback transformer. I'm looking at car ignition coils though, wondering whether they can be set to produce a low KV as they're dirt cheap. At the high end, they can produce 100KV.

[Mark_48]

Yup, Creating high voltage isn't difficult. I built the two power supplies shown below back in the 70's. The top one is about 3" in length and put out -10kV at around several microamps. Internally it has an air gapped ferrite core transformer that put out about 2kV and used diodes/caps for voltage multiplication up to the 10kV. A 555 IC and transistor was used to drive the primary of the transformer. The entire circuit was vacuum potted in epoxy to provide internal insulation from HV leakage. The product had been developed for powering Vidicon tubes.
The power supply below was built as a bench test unit for Gen II image intensifiers and had a similiar circuitry with a few extra bells and whistles for regulation and control.

What you want to build is a cake walk for simplicity, but you are getting into power levels that warrant some care in handling and that's what I want to emphasize.

Please excuse the poor quality images. The top one was a scan off a 35mm contact sheet and the one below from a MF contact sheet. Originally done as product shots for the company. Build stuff and take pictures, it was a fun job.

[Rhys]

Yes. It's dead simple. I want to build it with parts that are easily available in any country as there are people that will need to copy it. I'm thinking of future-proofing also which is why I'm thinking more toward ignition coils. Television flyback transformers and television cascades are going to be only slightly more common than Dodos in a couple of years - as everybody buying TVs buys LCD models. On the other hand, that does mean that 12v 6a LCD transformers are going to become much more common and popular - which is what will drive the coils.

[Mark_48]

Neon sign transformer would be the easiest way to go rather than electronic. Plug it in to 120vac, rectify the secondary, and you're good to go. There's a few on ebay presently and likely to be in good supply for a while.

If you have any friends at your local electric utility, see if they can "borrow :rolleyes:" one of these for you......
http://cgi.ebay.com/GE-Type-JVM-5-Voltage-Transformer-16-500-Volts-Hybute60_W0QQitemZ150362703194QQcmdZViewItemQQptZB I_Circuit_Breakers_Transformers?hash=item230250c55 a

We built a Jacobs Ladder using one of those by energizing the low side with a Variac plugged into a wall outlet. It worked fine just once with a real mean and nasty looking blue arc rising up the wires. When the arc broke at the top, the counter EMF of the transformer blasted back into the Variac and smoked the Variac. If you want real power this is the way to go :D.