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.
-- goldbb, Jul 22 2014

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]

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.
-- MechE, Jul 22 2014


You don't need to do any of this stuff. An ordinary LED can be used as a light sensor. (link)
-- ytk, Jul 22 2014


But I'm pretty sure not one that is actively being powered, or even set up in a circuit to be powered.
-- MechE, Jul 22 2014


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).
-- ytk, Jul 23 2014



random, halfbakery