Go Down

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


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!


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


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


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

Go Up