Xenon flash tube

I got several of these xenon flash tubes down at Rat Shack on sale for less than 2 bucks each.

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Anyone have a design for a junk box circuit that could be used for experimenting with these, say firing them from a TTL logic output?

Reply to
bitrex
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I guess this works but I don't have anything like that trigger transformer in stock...

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Reply to
bitrex

Well, you apply 300 volts across the end leads, with electrolytic caps to store as many joules as you think it can stand; that's not specified. Wild guess might be 30ish.

Than apply a fast high-voltage spike to the center lead, through a trigger transformer.

Google images, schematic photoflash. TTL could fire a small SCR to pop the trigger transformer.

Reply to
John Larkin

Google is your friend.

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You need a trigger transformer, a 400 volt SCR, a storage cap, and a HV power supply of about 250 volts or so.

Reply to
Tom Miller

On Mon, 7 Sep 2015 20:20:14 -0400, bitrex Gave us:

Look up "SCR strobe light circuit".

It was a lab experiment we did way back in the mid seventies.

Reply to
DecadentLinuxUserNumeroUno

Find a store that processes the disposable film cameras and see if they will give you a few. The ones with the built in flash will have everything but the SCR. Most times they are free for the taking.

Reply to
Tom Miller

They still make those?

Reply to
bitrex

Sure. They're quite common at weddings.

Reply to
krw

or just buy the parts for a kit:

Drivel: My palatial office building has a chronic security problem from the bums and deadbeats camping out behind the building. So, I installed a motion detector, which drives a xenon strobe light. It doesn't do anything useful, except produce enough light for the security cameras to take decent pictures. It's main purpose is to act as a bum repellent. They have no idea what the device might be, and don't particularly want to find out. So, they leave.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

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Everybody's got a little light under the sun.

Matt Roberds

Reply to
mroberds

It's pretty trivial; just grab an automobile's ignition coil, a resistor and 12V supply, tap a pushbutton and it flashes. The primary side will have a few more volts than TTL likes, but a HV transistor (few hundred volts) will suffice.

Reply to
whit3rd

I've done this, and have a lesson-learned: You need an optocoupler between the TTL (or CMOS) logic and the xenon flash circuitry.

When I built the xenon flash for logic control, I used a CMOS logic signal to trigger a small SCR which controlled a capacitor discharging through a trigger transformer. Turns out that enough flash energy came backwards through the SCR gate to completely confuse the CMOS logic.

The CMOS was not damaged, but didn't work either. The solution was to interpose a commodity 4N36 optocoupler: The coupler was driven by the logic, and in turn triggered the C106D SCR.

Joe Gwinn

Reply to
Joe Gwinn

We used to use one in a strobe. Big yellow cap from Sprague.. 5 uF, 400 V.

George H.

Reply to
George Herold

That's only 0.4 joules, which is OK for a stroboscope but wimpy as a photoflash. A stroboscope is limited by average heating of the flashtube, whereas a photoflash is limited by exploding it in one zap.

300 joules is a pretty big flash, typical for a pro flash with a big spiral flashtube.
Reply to
John Larkin

Den tirsdag den 8. september 2015 kl. 18.00.20 UTC+2 skrev John Larkin:

here's a 4800J one:

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-Lasse

Reply to
Lasse Langwadt Christensen

Try this:

Get dark adapted and look down at a scene, some objects and maybe a newspaper, pretty close. Blast that with a couple hundred joules of flash, close up. The afterimages are astonishing.

Reply to
John Larkin

I don't know, is that a good idea? Your pupils are wide open and you hit the eyes with a very bright light. Maybe Dr. Hobbs can comment.

Reply to
Tom Miller

On Tue, 8 Sep 2015 09:32:14 -0700 (PDT), Lasse Langwadt Christensen Gave us:

Here's another... bigger.... WAY bigger...

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Reply to
DecadentLinuxUserNumeroUno

On Tue, 08 Sep 2015 09:44:51 -0700, John Larkin Gave us:

Stare at this one then close your eyes.

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What do you see?

Reply to
DecadentLinuxUserNumeroUno

Oh fun... let's try and guess some numbers. So I think the eye can take 1mW with the blink reflex. (That is, if you look at the sun you get about 1 mW, but then blink and close your eyes..) I'm not sure how long it takes to blink, is 100ms too long? So (maybe) 0.1 Joules into the eye. So you flash 100 Joules onto a piece of paper.. how much goes into your eye? (I'll not worry about reflectivity of the paper... maybe it's 30-50%... but that goes into JL's few hundred Joules.) And then a ratio of the area's say 12" square for the paper (300mm) and 5mm diameter for the eye. A ratio of 60 in length or 3600 in area so ~0.03 Joules into the eye.

(OK a lot of assumptions in just taking the area ratio...)

I guess I might give it a try. Does it hurt your eyes when you do it John?

George H.

Reply to
George Herold

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