Help identifying piece from printer. What is that?

Hello. Yesterday I disassembled a HP deskjet 3420 printer that was no longer working properly. Amongst the 2 working DC motors, I found this little piece of hardware:

After googling a bit, I found out that this might be a paper sensor. Close to it there was a small piece of plastic that would fit right in the middle of the "U" shape. I thought this could be some kind of trigger that would interrupt a signal or something.

My question is: How can I use this with my Arduino? Also, is there any other interesting piece of hardware, besides the 2 DC motors, inside a inkjet printer that I should pay attention to? As you can probably guess, I'm a total newbie regarding electronics :)

Thanks a lot for your time, Cassiano

This sensor is composed of an infrared emitter on one upright and a shielded infrared detector on the other. By emitting a beam of infrared light from one upright to the other, the sensor can detect when an object passes between the uprights, breaking the beam. Used for many applications including optical limit switches, pellet dispensing, general object detection, etc.

you have 3 wire the ground, the led and the ir photo transistor but for finding them i cant help... sorry... but once you got it sorted out try plugging it this way... (i have some of these and work good that way...)

Thanks a lot, Madrang! I'll try to figure out the wirings. Do you know if it might damage if I wire it the wrong way?

If someone could please take a look at the following image: www.cassianorabelo.com/_posted_images/2009-07-06-hp-printer/hp.jpg

You can see that there is a diode sign close to the wires.

Also I took a picture of the other side of the board which I put here: www.cassianorabelo.com/_posted_images/2009-07-06-hp-printer/hp2.jpg

It shows how the wiring goes. I know this is a lot to ask for, but any help is greatly appreciated.

Kind regards, Cassiano

The line on the second picture, that connects both sides is the ground on the schematics. You have identified the diode and the not connected line of the diode is the anode, which has to be connected in series with the 200 ohm resistor to +5v. What is left is the collector of the transistor which is connected in series with 5.6KOhm resistor to +5v.

Hi Mircho. The line that connects both sides is the green one. The blue goes to the catode and the black only goes to the diode.
I’m kind of new to electronics and could never guess that the green could be the ground and not the black. Thanks for pointing it out! It worked like a charm!

Best regards,
Cassiano