[SML] Advancing development of a new flash for antique cameras

[Jerry Durand]

If you only need 1 flash, then just way overpower the LED.  You may need 
to clear coat it with RTV to contain any explosion.

Could even mount them in sockets so the reporter can change them.

But, LEDs can be way overpowered in a controlled short pulse.  It's not 
hard to get 10 Watt LEDs now, if only used for a moment they don't need 
the giant heat sink.  10 Watt without overpowering it may be all the 
light you need.

On 10/22/2016 07:52 PM, Joe D via Stagecraft wrote:
> I seem to recently recall a discussion on this list, in regards to converting an old-style camera, so that it didn’t consume flash bulbs, which have not been manufactured in many years.  Though, I can’t seem to find it in either my personal archives, or the  http://lists.dreampossible.ca/pipermail/stagecraft/ site.
>
> Anyway, I think the final solution involved using theatrical strobes for the main flashes coming from the reporters.  Then, to simulate the light of the flash bulb itself, if it were visible to the audience, involved connecting a LED to a battery and capacitor, which permitted a light that quickly faded.
> I should add that I am modifying two of the flashes for a Polaroid Land Rover, plus a couple of others that we haven’t obtained yet. They are expensive enough, that we want to resell them after the show, and thus don’t want to introduce any permanent changes to them.
> There was another idea I had myself, which was to use a series of 9v batteries, and attempt to blow a 12v automotive lamp.  They are cheap , and look like a real flash bulb. Perhaps they would blow with sufficient flash to look real, yet not blind the audience.  But, alas, I could not get one  to quickly blow, even by using 9 of my 9v batteries (81 Volts).  My batteries were used, so their current ratings may be reduced a fair amount.  I can increase the current by using a capacitor, but can only perhaps fit two of the 9v batteries into the Polaroid flash.
>
> But, back to the LED idea.
>
> I did a little more research, and saw a number of articles from around 10 years ago, from designers seeking to create LED flashes for our phones.  They used a similar approach, but what surprised me was that they were stating they needed to supply 1 to 2 amps of current to the LED.  I have never seen LEDs, in a small form factor, perhaps a 5mm through-hole style, which had anywhere near that for a peak current rating.  2x the Max constant current seems to be the norm.
>
> I imagine that the fact that the high current is applied only briefly does permit you to push the envelope, in terms of max current. But, rather than taking a trial-and-error approach, I would prefer to use a LED that gives me the data to support my design.
> Of course, I can put multiples of them in parallel. But, with their resistors, this can start to get bulky fairly quickly.
>
> Any suggestions for a source of LEDs, with leads or wires, that don’t have internal resistors, and can accept a brief spike to 1 amp?
>
> -Joe
>
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-- 
Jerry Durand, Durand Interstellar, Inc.
www.interstellar.com
tel: +1 408 356-3886
@DurandInterstel