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photo transistor

How do I connect a 5V sensor to a 3.3V input

Hi

I am using a IR sensor (photo transistor) that was ripped out of a ball mouse and I am running it at 5V, but I need to connect it to a Raspberry Pi which runs at 3.3V (at least the IO-pins are). 

I can place a 3.3V regulator before the sensor and adjust the pull down resistors, or use a zener diode to limit the output, but I was wondering wheter my currecnt setup will be safe to use.

Sorry for the poor quality drawing by the way.

Making a fire sensor (question)

With a bit of circuitry can this IR phototransistor replace the following sensor? 

IR phototransistor:http://arduino-direct.com/sunshop/index.php?l=product_detail&p=209

Sensor:http://www.robotshop.com/ca/dfrobot-flame-sensor.html

I plan to interface it with an Arduino