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I thought of this idea independently of [link], which suggests a result, but not a mechanism for it.
Most descriptions of how to make the brightness of an LED compensate for ambient light have two separate parts -- one part to sense the light levels, and the other to dim down the LED.
This idea
combines the two tasks into a single component, which ought to reduce manufacturing costs.
This idea is to send an electric current through a photocell, use that current to charge a small capacitor.
Whenever the voltage in the capacitor is above some threshold, turn the LEDs off, and also drain the capacitor. Whenever the voltage in the capacitor is below that threshold, turn the LEDs on.
If the switching is done fast enough, the LEDs will appear to be dimmer than their full brightness, instead of looking like a blinking light.
Similar idea
small_20autodimming_20LED
[goldbb, Jul 22 2014]
LED Light Sensor
http://www.thebox.m...op/LED_Sensing.html
Uses a single LED to automatically dim based on ambient light. [ytk, Jul 22 2014]
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Unless you can explain how putting both
components in the (disposable) bulb, rather than
having the sensor mounted on the (permanent)
fixture saves costs, I'm going to say baked, like
crazy. |
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You don't need to do any of this stuff. An ordinary LED
can be used as a light sensor. (link) |
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But I'm pretty sure not one that is actively being
powered, or even set up in a circuit to be powered. |
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It's moot whether it can sense light while it's
powered, because the light that it's emitting would
throw off any measurements anyway. Besides, the
idea being proposed doesn't involve measuring light
while the LED is powered, but rather in the
intervals when it's not powered (by using a pulse-width modulation scheme to
control LED brightness,
such that there are very brief intervals for which
the LED is turned off as a way of controlling the
brightness). That's no different from using the same
LED to both emit and detect light, which you
absolutely *can* do (see the link I provided with my
earlier post for an example of how to do so). |
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