Led sensor: Difference between revisions
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According to [http://www.merl.com/reports/docs/TR2003-35.pdf this] | According to [http://www.merl.com/reports/docs/TR2003-35.pdf this paper], a simple LED can be a light sensor if used in reverse mode. In fact if LED is used in invert, it becomes a variable capacitance. | ||
To test this phenomena, I have used a pin of the FPGA, and design a little component/IP that provides the discharging time in a register. | |||
To test this phenomena , I used | |||
= Code = | = Code = | ||
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[http://fabienmarteau.free.fr/images/synthesis.tar.gz here] | [http://fabienmarteau.free.fr/images/synthesis.tar.gz here] | ||
= How | = How does it work ? = | ||
[[Image:ledtouchschema.png|300px|center]] | [[Image:ledtouchschema.png|300px|center]] | ||
= Results = | = Results = | ||
With a green standard led that | With a green standard led, that gives : | ||
[[Image:greenplot.png|300px|center]] | [[Image:greenplot.png|300px|center]] | ||
Revision as of 20:26, 24 August 2008
According to this paper, a simple LED can be a light sensor if used in reverse mode. In fact if LED is used in invert, it becomes a variable capacitance.
To test this phenomena, I have used a pin of the FPGA, and design a little component/IP that provides the discharging time in a register.
Code
How does it work ?
Results
With a green standard led, that gives :
