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Electronics => Electronics => Topic started by: Blood-man on August 09, 2009, 09:50:06 AM

Title: Photoresistor tutorial
Post by: Blood-man on August 09, 2009, 09:50:06 AM

I'm really confused by the photoresistor tutorial. I used analog multimeter and biggest photoresistors from Radioshack set. I get 6.703 KOhm. Is it OK? And can you explain me why I need to solder the end of photoresistor to the ground? I thought that it got to be analog output, because microcontroller not gonna read the ground, so it don't make any sense.

Title: Re: Photoresistor tutorial
Post by: sonictj on August 09, 2009, 10:06:10 AM

a photoresistor is a variable resistor.  It changes its value with different amounts of light.  You are simply creating a voltage divider circuit where you ADC channel connects between the two resistors.

gnd-------Photoresistor--- to ADC ----normal resitor---+5V

or

+5V-------Photoresistor--- to ADC ----normal resitor---gnd

the only difference is whether the voltage will increase or decrease which more light