35Views7Replies

Author Options:

Photocell dropping resistor size for photocell input to a Arduino UNO Answered

I purchased an Arduino UNO. The plan is to use a photocell

as and input to energize a relay as an output. The photocell I have has a value of 2.3K ohms when it sees light and 30K ohms when dark.

What value dropping resistor should I put in series with this photocell across 5 volts dc to gnd?

7 Replies

user
rickharris (author)2018-02-12

For all microprocessor interfacing issues I strongly recommend
http://www.picaxe.com/docs/picaxe_manual3.pdf

Select as Best AnswerUndo Best Answer

user
omowright (author)2018-02-11

Will it need a series resistor? 2.3K is already large enough when it sees light (2mA current). Maybe the question is not understood ...

Select as Best AnswerUndo Best Answer

user
mskrocke (author)omowright2018-02-11

It looks like https://learn.adafruit.com/photocells/using-a-photocell has the answer.
Thanks for your reply............

Select as Best AnswerUndo Best Answer

user
caitlinsdad (author)2018-02-11

You can put the LDR(Light Dependent Resistor) or photocell in a pulldown circuit to use as an Arduino sensor input. https://learn.adafruit.com/photocells/using-a-photocell Good luck.

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2018-02-11

Cdad's link contains exactly what you need to know.

Select as Best AnswerUndo Best Answer