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ynwia Guest
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Posted: Fri May 09, 2008 3:45 am Post subject: Help For Optical To Electrical Converter Design |
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The project is to detect the onset/offset of pictures on a computer monitor (CRT or LCD). Monitor starts with a totally dark background, then a 300x300 picture appears for a few hundred milliseconds then switches to darkness, then another 300x300 picture, then dark background again...
Once the circuit detects optical change(darkness to pic, pic to darkness), it either immediately outputs a TTL pulse or changes it current status like a flipflop. The response time should be as small as possible and 1 millisecond is definitely the upper limit. (microseconds or even nanoseconds would be ideal)
I already made a simple circuit with TAOS TSL230R. It kind of works except its output is frequency (not a single pulse or constant voltage) and I have no idea of its response time.
The options in my mind Idea are
1.Arrow Go analog. For example, Idea Photodiode->op amps->voltage regulator (7805 ).
2.Arrow Digital. For example, Idea Photodiode->op amps->microcontroller (pic 12f675 )
Which one do you suggest?
Any specific parts/circuit solutions to recommend ?
Any info is highly appreciated. |
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vtech
Joined: 08 May 2006 Posts: 1264 Location: USA
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Posted: Fri May 09, 2008 5:48 am Post subject: |
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When you say it is a frequency, it IS a TTL pulse that can be used as a trigger to control another device such as a micro controller.
You are already looking at the right place.
Instead of going the discrete way, why not experimenting with any of the TSL12.13,14 etc. You have a photodiode & op-amp/driver already packaged & they are in the microsecond region. Depending on the video & it's luma(brightness) content, you just may have to tweak the TSLxx sensor's position or use some sort of tiny magnifier lense.
http://www.taosinc.com/category.asp?cateid=20 |
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