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Reflective Optical Detection — Parallax Forums

Reflective Optical Detection

JomsJoms Posts: 279
edited 2010-05-08 02:50 in General Discussion
I am working with the lab in the Prop Education kit that is IR Object Detection.· This seems to work great but I am attempting to use a different IR sensor, I believe it is a photo diode.

I have 4 of these units and can't seem to figure out how they work at all.· I have searched and searched google, and everything just shows the principle of them, but not how to wire one.

Does anyone have any ideas or help here?

Comments

  • hover1hover1 Posts: 1,929
    edited 2010-05-07 20:10
    Do you have a part number or data sheet on the devices?
    Jim
  • JomsJoms Posts: 279
    edited 2010-05-07 20:34
    http://media.digikey.com/pdf/Data Sheets/Avago PDFs/APDS-9102.pdf

    This is one of them that I am trying. I actually have 4-5 different units, so I don't think I have a bad one. I have been looking at it on a scope and having probably figuring out the output.

    My end goal is to detect RPM of a shaft with a reflective light sensor. Basically a white dot on the shaft every time it goes around. When searching both google and the obex everything I find is related to the split beam style.
  • hover1hover1 Posts: 1,929
    edited 2010-05-07 21:16
    It's a IR transmitter and a phototranistor detector. There is no need to modulate the IR. The Chapter you cite is for reading distances and will not help with reading RPM. You just need to read input pulses for a certain time period and translate that to RPM.

    I saw an object recently to measure RPM using Hall Effect sensors (same principle), but I can't find it right now. (Parallax, PLEASE new Forum software).

    I'll post if I can find it.
    Jim
  • JomsJoms Posts: 279
    edited 2010-05-07 21:25
    I found that one in the OBEX earlier and downloaded it. The problem with the sensor, is I am having problems getting an output. Is there a good drawing somewhere that shows resistor values, etc.

    Thanks for the help, and second the new forum software. I can never make the search work right...
  • LeonLeon Posts: 7,620
    edited 2010-05-08 02:50
    Connect pin 3 (emitter) to ground and connect pin 4 (collector) to Vcc through a 2k2 resistor. You need a suitable resistor for the LED, of course, 220R should do. You should see the collector switching if you put something in the gap to interrupt the beam. I've used similar parts without any problems for measuring motor speed.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Leon Heller
    Amateur radio callsign: G1HSM
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