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Topic: Help with a OPB704W object sensor (Read 670 times) previous topic - next topic

Bean35

I would like to build an optical tachometer with this sensor. Not sure if I need to have any resistors between it and my arduino. I have included a copy of the datasheet. I am a noobie and would appreciate any assistance. Thanks!

RIDDICK

the input diode cant take more than 40mA...
so u should limit it to 20mA...
u can use a resistor for that: (Vcc-1.7V)/(20mA)
e. g: Vcc=5V: (5V-1.7V)/(20mA) = appr. 165R

the output current should be far below 25mA...
u could use an internal arduino IO pin pull-up resistor for that (it is somewhere between 18kR and 50kR):
pinMode(inputPin, INPUT); digitalWrite(inputPin, HIGH);
http://arduino.cc/en/Reference/DigitalWrite

take care to get the polarities right... :)
A and C is +... IIRC
-Arne

Bean35

RIDDICK, Thanks for your response! A + C stands for anode and collector I think?  That means there is a resistor on the anode that is hooked up to 5V . So the cathode and emitter are hooked up to ground? Sorry for newbie questions I am learning alittle more everyday. Thanks again for your time!!!

RIDDICK

yes, i think cathode and emitter can go directly to ground...
that would make sense...
but to b sure u should take a look in the datasheet... they often show example circuits...
-Arne

Bean35

RIDDICK, Thanks again for your response! I was able to find an example and the cathode and emitter do go to ground. My only other question is I think this sensor is analog therefore I will be using one of the analog in pins. Is this correct? Again sorry for the newbie questions and Thank You for your time!!

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