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Re: [OM] circuit to measure shutter speed

Subject: Re: [OM] circuit to measure shutter speed
From: Christopher Biggs <chris@xxxxxxxxxxxxxx>
Date: 10 Feb 2000 11:27:26 +1000
Wayne Shumaker wrote:
> 
> At 12:04 PM 2/9/2000 -0500, Dirk wrote:
> >
> >I looked around locally and no one has this magazine. Without a printed
> >circuit board, it would be very hard to build this project.
> 
> We build stuff all the time without PC board, we just cut blank copper
> circuit boards with exacto knife and route wires where needed. The
> circuit is straight forward, 1MHz oscillator into some counters that
> are gated by the photo diodes with amplifiers and comparators.
> Basically the two PDs gate a counter. You select different combinations
> to get shutter speed or curtain travel time. I will probably modify the
> circuit to use parts I have readily available. All the photo diodes I
> can find seem to be for infrared sensors.
> 

I built a shutter tester for leaf shutters (only one photodiode) on
breadboard.

I used a hi-brightness red LED and a 3mm high speed photodiode.  The
reading goes haywire if you use it under flourescent light because it
picks up the 50Hz mains frequency...

I feed the sensor output into a computer, which works if you're
running a (near) real-time OS.

-- 
| Christopher Biggs --- Stallion Technolgoies  | One of the founding membata,|
| Evil Genius Division, Brisbane, Q, Australia | Society for Creative Pluri. |
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