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Topic: Read voltage drop from photoresister without a second resistor? (Read 790 times) previous topic - next topic

awawda

I am  starting to play with my Arduino Uno and have a question about hooking a photoresistor to my Uno. Most tutorials connect the photoresistor like this using a second resistor:

Code: [Select]

+5V --> PhotoResistor --> . --> 10K --> Ground
                          |
                        Pin X


I think this technique is called a "voltage divider" and I understand how it can be used to read the variable voltage drop that occurs from the PhotoResistor.

My question is why can't I just measure the drop without the 10K resistor? In other words, would the following work (where we read the voltage drop from Pin X)?

Code: [Select]

+5V --> PhotoResistor --> . --> Ground
                          |
                        Pin X


Thanks a lot!

JimboZA

Because if the photoresistor goes to 0 ohms, you'll have a dead short across your 5v to 0v....
Roy from ITCrowd: Have you tried turning it off an on again?
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza


Erni

Also pin x is connected to ground, so your reading will allways be zero

arbutus

Remember the path to the answer is always the path of least resistance!
Don't breath in the magic smoke!

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