Just passing through from a sports newsgroup....

[Tim]

....thought I'd ask a simple question.

What is the name given to a device that detects light - ' A light detecting
diode'???
I want to contact on of these to an outside light.

Thanks

T

 

[John Popelish]

Tim wrote:

...thought I'd ask a simple question.

What is the name given to a device that detects light - ' A light detecting
diode'???
I want to contact on of these to an outside light.

Thanks

T

There are several kinds of light detecting devices. There are photo
resistors (photo conductors, light dependent resistors) that are
essentially variable resistors that have lower resistance (conduct
better) when illuminated than when in the dark. Some key words to
search would be photo resistor, photocell, cadmium selenide, cadmium
sulfide.

Any diode junction will absorb light and produce voltage (photo
voltaic effect) or allow reverse current (photo conduction) is biased
with a reverse voltage. Key words: photo diode, PIN diode.

The photo diode can be part of a transistor, so that the transistor
amplifies the photo current. Key words: photo transistor.

All these need some additional parts to allow them to drive a relay or
other power switch that operates lights or other AC loads based on
light level. But such circuits are already produced as commercial
products.

e.g.
http://www.cedgec.com/Products/Automatic%20Light%20Control%20w%20Dawn.htm

--
John Popelish

 

[Ben Weaver]

Photodiode.

But for that application you could also use a phototransistor or LDR
(Light Dependant Resistor).

Ben
~~~

Tim wrote:

...thought I'd ask a simple question.

What is the name given to a device that detects light - ' A light detecting
diode'???
I want to contact on of these to an outside light.

Thanks

T