photoflash circuit

Something to check out -- seems to me that is somewhere around the frequency that can trigger epileptic seizures in people who are susceptible. Not sure the exact frequency, but it seems it is around

8 or 10 Hz.

mikey

I should imagine you could make one much easier (and more adaptable) using some superbright white LEDs instead. Alternatively you could just look at this dude's website which makes your monitor function as a "dreamachine".

It doesn't seem too particularly work for me. All it succeeds in doing is making a pesky/annoying flickering sensation.

If you still want to make one using a Xenon strobe, then surely Don Klipstein's website will be of interest if you haven't read all of it already.

The tube you linked to doesn't seem very generous with the technical specifications. But based on it's apparent size and just pulling rough numbers from thin air I should think somewhere around 350V at an energy of around 200mJ per flash would probably not be too outrageous. This would suggest a capacitance of around 3.3uF. At 200mJ the flash will probably be very wimpy (maybe even wimpier than what can be achieved with a few good LEDs), but if you go too far above this at 10Hz, the lamp will probably get rather hot. A quartz flashtube would be better suited.

You may want to look at modifying the guts of a disposable flash camera. I've found info on mods using google.

"kell" wrote in news: snipped-for-privacy@f14g2000cwb.googlegroups.com:

Doesn't Radio Shack sell something that does this? You hook it to your stereo and it flashes the strobe with the music. Probably can get one at Spencer Gifts,too.

--
Jim Yanik
jyanik
at
kua.net

Perkin Elmer bought Heimann Opto thirteen years ago. The AllElectronics part *looks* similar to this- these tubes are not designed for 10Hz:

Yes, pilots have been know to experience this when the strobes flash back from the rotating propellers. Some people may have a latent susceptability to it. The frequency has to match the alpha wave of a susceptable person.

Al

The spec on these is 40% output reduction in 5000 hours @ 4 Hz with nominally 20 joule flashes, so IIRC you should get about the same life at 10 Hz with 8 joule flashes, maintaining the same average power.

Well... Something doesn't quite compute. The Perkin Elmer device claims a nominal maximum operating power of only(!) 30W. Considering it's size 30W is still very impressive in my mind. I guess at high flash energies almost all of the energy gets lost as radiation (visible and mostly infrared I guess) so it doesn't directly heat up the glass. I would imagine at much lower flash energies xenon is a less efficient radiator (and perhaps a higher percentage of the energy would be wasted heating the electrodes), so more heat would have to be convected away rather than radiated. So perhaps some further derating is justifiable.

Suppose 15W average power, 350V flashes, 10Hz. Then each flash is 1.5Joules for a capacitance of around 25uF. 1.5J flashes would be quite decently bright. At 10Hz an aluminum electrolytic capacitor would be less than ideal given their high ESR and low ripple current rating. Ideally one would use a Mylar or oil filled, or similar type of low ESR high ripple current rated capacitor.

Right you are, I was a bit hasty reading that data sheet.

The constant avarage power for the same tube life at different flash rates is only approximately true and only over a limited range, the additional derating is a good idea. But I think the limiting factor near rated power levels is less likely to be heating than electrode erosion; the evaporated bits of electrode will deposit on the inside of the tube both darkening it and trapping Xenon gas in the deposits, reducing the tube pressure. Both of these effects gradually reduce light output with constant electrical power input. Lower power flashes will evaporate less electrode material per flash, in a very roughly linear manner over some limited range of power near the tube data sheet ratings.

This is per my recollection of data on high power laser pump flash tubes (where feedback is often used to maintain constant light output as the tube ages, up to a limit of course). I see no reason why the little photo flash tubes should be different in this regard, although that does not mean that some good reason does not exist :-).

Is that really a selling feature? Something tells me that the OP doesn't want to be blinded...

Generally speaking though aircraft stuff easily costs ten times what it seems it aught to cost due to special reliability requirements and the FAA and whatnot.

You want strobes? Try small airplane strobes. You can get blinded by these.

Al

In message , Al writes

Another thing to check out is the level of UV produced. A lot of Xenon lamps produce wavelengths down to around 200 nm and come with a warning not to view them with the naked eye.

--
Graham

If you want power, why screw around.

And the cost was not bad, $160 or so. And it will be reliable.

Al

I bought this:

It comes with a circuit diagram. Shows a voltage doubler off the 120 volt ac power line, with 22 uF caps. There is another .47 uF cap that charges up through a pot (for timing) until it fires a neon bulb that turns on an SCR connected to the triggering coil; and the 22 uF dumps into the strobe. I have to get a neon bulb and an SCR before I can build the circuit. I have some hi-com (three quadrant) triacs if I can figure out how to use one of them in place of the SCR. In that case it's just a trip to Radio Shack for the neon bulb and I can build my circuit. Funny thing, the parts list specs the 22 uF caps as 315 volts, when they should be seeing 340 volts from the doubled peak line voltage. Fortunately I have some 450 volt 22 uF caps.