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I hardly ever get a crack at later version's. You do the best you can...
and then,
There's the next thing that has to be done.
Redesign is expensive. I keep trying to push modular designs, But it's much more expensive compared to putting everything 'under one roof'.
George H.
It's for measuring a photographic strobe light as the strobe happens.
It was chosen by my customer, in whom I am in awe because of the amount that he manages to get done with the little bit of technical knowledge that he has. Which, since I don't know much about photometry either, means that I don't know if it's necessary or not.
It just needs to respond to the strobe, not ambient -- so I'm not sure if it needs to be blue enhanced or not, even if blue enhanced photodiodes are the right thing to use for photometry.
-- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Tinted glass perhaps?
With a strobe, it's not like you are overloading the sensor for a long time, so I think damage isn't an issue.
Meditating on my navel, can you devise a servo/feedback circuit such that the circuit acts to limit the current, and the servo is also a measurement of the light output.
On a sunny day (Fri, 02 Dec 2011 19:21:50 -0700) it happened Jim Thompson wrote in :
How does this work out with Obummer as your boss?
-- Then that statement is perfectly true. :-)
-- Down here we say: "When momma's happy, everybody's happy."
Ambient rejection is easy: highpass filter. Strobes make a lot of light for a short time.
10 joules of light dumped in 1 millisecond is 10 kilowatts of light.John
The tube efficiency varies on a bazillion different factors, so you can't count on light output being linear with current (or, I believe, even power input).
Alas.
-- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
I saw it written out this way "If momma ain't happy, ain't nobody gonna be happy!"
[...]-- Regards, Joerg http://www.analogconsultants.com/
It is still linear with time of course, given fairly constant current input. This is what digital cameras do -- photosensor (PD or phototransistor?) integrates light in the overall scene, then a big fat (actually very small, SO-8 or less) IGBT turns it off. The ESR and ESL of the photoflash cap limit current to a safe value (usually something like
150A), then a diode and cap clamp the turn-off spike.Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
I had one client whom I really admired as well. Unfortunately the (non-EE) president passed away. He had a drive I've hardly ever seen in anyone else, and all the way into his 80's. Once when he was bouncing ideas off of me to check them out there was a situation where Kirchhoff's law simply didn't allow one method. "Hmm, yeah, I remember Kirchoff. Is there no way to get around that law?"
That would probably require some sort of shutter. Maybe LCD?
You could test linearity. If you have another light source that is lit all the time and then strobe you get two different current values. One at rest with just the small light, and the other during the strobe. Now place an optically attenuating material in between so that both light sources must go through it. Strobe again. If the ratios are the same you should still be in the linear range.
-- Regards, Joerg http://www.analogconsultants.com/
He's deeply suspicious of using parts outside of their specifications, having been burned before.
I can't entirely disagree with him, but OTOH it would be nice to just pipe 10 times as much light to the thing -- I'm sure there's plenty to be had.
-- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Back in the '90s, when I was working toll road electronics, we were trying to get a camera to sync to a strobe so that it would have a short shutter (this was early electronic frame CCDs) and would eliminate the ambient. The strobe was to be IR, so it was to be bright and quick. Unfortunately, they broke up the R&D group before we could get this to work... :-(
Charlie
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