Connecting Arduino via a sensor that uses a transistor to switch output?

Using Arduino Sensors
1

Hi all,

I have an IRDOT-1 sensor, which uses an infrared beam to detect when a model train is passing overhead. I'm planning to connect this to the input pin of an Arduino Duemilanove, to indicate to the Arduino when a train has been detected.

Thing is, the IRDOT output is controlled via a transistor - the base goes high when the train is detected, and the current flows through the transistor, from one of the screw contacts to another of the screw contacts.

I've tried googling, and all pages I've been able to find about Arduinos and transistors show how to use the Arduino to control the transistor - not how to connect up an input controlled by another transistor. So I have a few questions:

  • Do the IRDOT and Arduino need to be operating at the same voltage?
  • Will they need to have some sort of common ground connection?

Thanks,
Tbdanny

2

I'd take the collector screw contact to an Arduino pin with pullups enabled, and the other screw to ground. The Arduino pin will be high normally and go low when the transistor closes and takes the pin to ground.