I am toying around with using my Arduino as a tester for my antique camera shutters. I'm very new to arduino but understand the basics.
I have at my disposal a couple photocells and resistors.
How I think it could work:
setup the photocell on one side of the shutter (its a focal place curtain shutter so i can remove the lens), using set up a low powered laser pointer on the other side, positioning it so it projects onto the cell.
I dont need to measure values, just open and closed, but I do need to measure time, as accurately as possible (1000/sec if possible).
I imagine I'd need to specify what the closed value would be, since ambient light would have an effect, as well as what the open value would be, so it knows when the curtain is open.
Ive seen some projects doing something similar but using an ir diode and sensor, and I have played around using a photocell to send a reading to the serial monitor.
Essentially what i need it to output is a millisecond value of how long the sensor reads that the curtain is open.
If anybody has anywhere for me to start looking, or other projects with similarities I'd be greatly appreciative. I could probably get my hands on a ir led and sensor, but that would take time and like the challenge of making this work.
The arduino would be able to cope with this easily. The photocell is another story. Do you have a datasheet for the exact photocell you have? If not, you could always just suck it and see.
What you want is a photo transistor.
Common ones have glass dome tops and you can easily build a shade with a short length of heatshrink. Ambident light no longer an issue.
Just measure pulse width... Several good techniques are found with forum search..
Hi, use an IR LED as source and IR phototransistor and you won't have an ambient light problem.
The transistor could sit in the focal plane without any shading or light proofing.
It's not if you can measure 1 millisecond. It's how many times you can measure per millisecond, 100x is not the most but is it less than a practical difference? But then you can always round off.
It's possible to measure intervals down sub-microsecond. 1-pin cap sense does that. You probably don't need that many decimal places, do you?
Use the laser for interference patterns, IR led detector won't false on room light. It's near-IR, a color we don't see from a special led.
BTW, most digital cameras see IR as white. Red leds put out IR enough to show white on them too.
Try signalling IR detectors with red leds. Now you can see the signal without a camera. It's just colors.
