Author Topic: newb photo cell quetion  (Read 587 times)

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Offline harpoTopic starter

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newb photo cell quetion
« on: April 11, 2011, 08:24:24 PM »
i have seen photo cells (own a few) resist in the dark but let power flow in the light
are there photo cells that do the opposite?
if so can you send me a link to a shop for them?

Offline MikeK

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Re: newb photo cell quetion
« Reply #1 on: April 11, 2011, 09:13:51 PM »

Offline vinniewryan

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Re: newb photo cell quetion
« Reply #2 on: April 11, 2011, 09:40:22 PM »
Though if you connect the output of a photocell to the base of a PNP transistor with a pulldown resistor, you've just basically reversed the photocell's output through the transistor to output high when there's no light, and low when there is.

Offline Soeren

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Re: newb photo cell quetion
« Reply #3 on: April 15, 2011, 10:12:15 PM »
Hi,

i have seen photo cells (own a few) resist in the dark but let power flow in the light
are there photo cells that do the opposite?
LDR's (if that's what you're referring to have more resistance in darkness than in light and there are none that are opposite that.
How you use that function is up to you however and an inverting circuit will get you the opposite function.

Which circuit is the best depends on what you need, binary action (i.e. light/dark) or a linear varying output.
Regards,
SÝren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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