AVR-Chat

with a photo transistor, you simply pull it low and take the output 
from the emitter.  Connection wise, +5 connected to collector. 
emitter connected to pull-down resistor which is in turn connected to 
ground.  output is take from the emitter.  When the PT turns on (i.e. 
light), it will pull the output high, when its off (dark), the output 
is pulled low by the resistor.  You will need to play with the pull-
down resistor value to get the right triggering level.  I'd use a 50K 
or so pot but wouldn't run it down below 1K (or use 1K in series to 
protect it).  Once you get a relialable value for the pull-down you 
can substitute a fixed R.  Make sure your I/O pin doesn't have 
pullups enabled.  



--- In AVR-Chat@yahoogroups.com, jay marante <jaythesis@y...> wrote:
> hi!
> i wanna trigger a low-level interrupt on interrupt 1 using a 
phototransistor. what i wanted is that when there is an insufficinet 
light on the phototransistor or when the light is blocked, interrupt 
1 will trigger on low-level. how will i design this? thanks for the 
help...
> -jay
> 
> 		
> ---------------------------------
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