photoflash circuit

[kell]

I'm going to build a circuit that flashes a strobe rapidly. If anybody
would like to know why, look up "dreamachine." There was an article in
the New York Times recently about it. The classic dreamachine uses a
motor and rotating cylinder with a light bulb in it to flash at 10 Hz,
but it will be much easier just to use a strobe.
I just need to know the voltage and the joules for each flash of the
strobe so I can build a circuit. I may use this bulb:
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=FLT-8&type=store
Open to suggestions for better strobe bulbs in terms of durability,
because the device I build may go through hundreds of thousands of
flashes in its life, perhaps millions. But mostly I need to know
required voltage and energy per flash for the example flash tube, or
flash tubes in general.

 

[Si Ballenger]

I'm going to build a circuit that flashes a strobe rapidly. If anybody
would like to know why, look up "dreamachine." There was an article in
the New York Times recently about it. The classic dreamachine uses a
motor and rotating cylinder with a light bulb in it to flash at 10 Hz,
but it will be much easier just to use a strobe.
I just need to know the voltage and the joules for each flash of the
strobe so I can build a circuit. I may use this bulb:
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=FLT-8&type=store
Open to suggestions for better strobe bulbs in terms of durability,
because the device I build may go through hundreds of thousands of
flashes in its life, perhaps millions. But mostly I need to know
required voltage and energy per flash for the example flash tube, or
flash tubes in general.

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

 

[Mike Fields]

I'm going to build a circuit that flashes a strobe rapidly. If anybody
would like to know why, look up "dreamachine." There was an article in
the New York Times recently about it. The classic dreamachine uses a
motor and rotating cylinder with a light bulb in it to flash at 10 Hz,
but it will be much easier just to use a strobe.
I just need to know the voltage and the joules for each flash of the
strobe so I can build a circuit. I may use this bulb:
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=FLT-8&type=store
Open to suggestions for better strobe bulbs in terms of durability,
because the device I build may go through hundreds of thousands of
flashes in its life, perhaps millions. But mostly I need to know
required voltage and energy per flash for the example flash tube, or
flash tubes in general.

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

 

[Jim Yanik]

I'm going to build a circuit that flashes a strobe rapidly. If
anybody would like to know why, look up "dreamachine." There was an
article in the New York Times recently about it. The classic
dreamachine uses a motor and rotating cylinder with a light bulb in it
to flash at 10 Hz, but it will be much easier just to use a strobe.
I just need to know the voltage and the joules for each flash of the
strobe so I can build a circuit. I may use this bulb:
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item
=FLT-8&type=store Open to suggestions for better strobe bulbs in terms
of durability, because the device I build may go through hundreds of
thousands of flashes in its life, perhaps millions. But mostly I need
to know required voltage and energy per flash for the example flash
tube, or flash tubes in general.

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.

 

[Fritz Schlunder]

I'm going to build a circuit that flashes a strobe rapidly. If anybody
would like to know why, look up "dreamachine." There was an article in
the New York Times recently about it. The classic dreamachine uses a
motor and rotating cylinder with a light bulb in it to flash at 10 Hz,
but it will be much easier just to use a strobe.
I just need to know the voltage and the joules for each flash of the
strobe so I can build a circuit. I may use this bulb:
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=FLT-8&type=store
Open to suggestions for better strobe bulbs in terms of durability,
because the device I build may go through hundreds of thousands of
flashes in its life, perhaps millions. But mostly I need to know
required voltage and energy per flash for the example flash tube, or
flash tubes in general.

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".

http://callmeburroughs.tripod.com/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.

http://members.misty.com/don/

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.

 

[Fred Bloggs]

I'm going to build a circuit that flashes a strobe rapidly. If anybody
would like to know why, look up "dreamachine." There was an article in
the New York Times recently about it. The classic dreamachine uses a
motor and rotating cylinder with a light bulb in it to flash at 10 Hz,
but it will be much easier just to use a strobe.
I just need to know the voltage and the joules for each flash of the
strobe so I can build a circuit. I may use this bulb:
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=FLT-8&type=store
Open to suggestions for better strobe bulbs in terms of durability,
because the device I build may go through hundreds of thousands of
flashes in its life, perhaps millions. But mostly I need to know
required voltage and energy per flash for the example flash tube, or
flash tubes in general.

Perkin Elmer bought Heimann Opto thirteen years ago. The AllElectronics
part *looks* similar to this- these tubes are not designed for 10Hz:
http://optoelectronics.perkinelmer.com/content/Datasheets/AHPF 2640.pdf

 

[Al]

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

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

 

[Glen Walpert]

Perkin Elmer bought Heimann Opto thirteen years ago. The AllElectronics
part *looks* similar to this- these tubes are not designed for 10Hz:
http://optoelectronics.perkinelmer.com/content/Datasheets/AHPF 2640.pdf

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.

 

[Fritz Schlunder]

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.

 

[Glen Walpert]

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 .

 

[Rich Grise]

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.

What about those strobes from the psychedelic '70s? They maintained at
least a 10 Hz flash rate, and lasted for quite some time.

I seriously doubt if they put a whole joule through the thing for one
flash!

Good Luck!
Rich

 

[Al]

What about those strobes from the psychedelic '70s? They maintained at
least a 10 Hz flash rate, and lasted for quite some time.

I seriously doubt if they put a whole joule through the thing for one
flash!

Good Luck!
Rich

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

http://www.ultralightnews.com/lilhustler/strobes.htm

Al

 

[Fritz Schlunder]

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

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.

 

[Graham Orme]

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

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.

 

[Al]

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.

If you want power, why screw around.

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

Al

 

[kell]

I bought this:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G13923&variation=&aitem=1&mitem=1
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.