What to do with 1,200 Sharp GP2A25J0000F Sensors and Cables? Put your ideas here please!

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Comments

  • Ken Gracey wrote:
    The following e-mail is likely in your inbox:
    Yup. Two copies, in fact.

    -Phil

    We really like you! Probably not the kind of attention you're seeking, is it? Let me know if you received the message at two different e-mail addresses. I'll unsubscribe one (or two) of them.

    On the specs, seems I've lost something in translation. Datasheet says:

    3. Key Parameters:
    • Detecting distance : 1 to 9mm (White paper)
    3 to 7mm (Black paper)
    • Undetecting distance : over 27mm (White paper)

    Ken Gracey
  • dgately wrote:
    In the product description, I see the following: "At the right distance of .03" they'll also detect the difference between black and white" Should that be .3" ? Three hundreds of an inch seems "oh so small"...
    .03" is correct. These sensors were positioned very close to the slots in the ActivityBot wheels.

    -Phil
  • What happened to the 4 pack for $10
  • DigitalBob wrote: »
    What happened to the 4 pack for $10

    I guess the extra components make up for the difference:

    (4) Breakout cable from sensor to 3-pin (#805-28107)
    (4) 220 ohm ¼ resistor (#150-02210)
    (4) 10 k-ohm ¼ resistor (#150-01030)
    (4) 3-pin headers (#451-00303)
    (2) packs jumper wires (#800-00016)

  • ercoerco Posts: 19,697
    dgately wrote: »
    Should that be .3" ? Three hundreds of an inch seems "oh so small"...

    dgately

    Exactly what I thought, dgately!
  • dgately wrote:
    In the product description, I see the following: "At the right distance of .03" they'll also detect the difference between black and white" Should that be .3" ? Three hundreds of an inch seems "oh so small"...
    .03" is correct. These sensors were positioned very close to the slots in the ActivityBot wheels.

    -Phil
    So, in a line-follower application, they would almost touch the surface? Any debris along the path (like, dust) may be larger than .03".

    dgately

  • dgately wrote:
    So, in a line-follower application, they would almost touch the surface?
    Not necessarily. It depends upon the level of detail you want to resolve. .03" is optimum for patterns with high spatial frequency. It's all about the angle between the IRED and the sensor chip, and the lens on said chip. But for line following, which doesn't require a lot of detail, a more distant positioning would probably work fine.

    BTW, one huge advantage of this sensor is that it relies upon modulated IR, so it's immune to interference from fluorescent lights and the like.

    -P{hil
  • Ordered!
  • ercoerco Posts: 19,697
    BTW, one huge advantage of this sensor is that it relies upon modulated IR, so it's immune to interference from fluorescent lights and the like.

    -Phil

    THAT'S HUGE! Did not know that. MUCH mo bettuh. Will order now fo sho.

    And per that .03 debate, I understand that that was necessary for reliably detecting the thin "lines" of a slotted encoder disk. I was thinking in terms of simply following a 1/2" line, and I'll bet that these sensors are up for doing that from considerably further away, at least .150"-.200" if not 0.300".

  • Phil Pilgrim (PhiPi),

    Could these be used to measure fan RPM like in the SIC (Stamps in Class) Industrial and Process Control texts?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 22,624
    edited 2020-02-09 - 21:37:38
    Not sure. You'd have to check the docs for the response time. A fan blade is tilted, so it might not be at the sweet distance long enough to register. You'd be better off sticking a half-black/half-white disk to the fan hub.

    -Phil
  • ercoerco Posts: 19,697
    You'd have to check the docs for the response time.

    Very true. Modulated IR receivers like the TSOP1838 have a delay in response. I always thought it was clever how the BoeBot used that to its advantage for object detection. Even the relatively slow BS2 has time to send out a 38 kHz IR signal, then leisurely check the 1838 afterwards for any reflected low signal. The IR pulse is long gone, but the 1838's delayed response makes it all possible.

    Nothing wrong with a delayed response, as long as you calibrate for it A bit like the scenario where your group is running away from a tiger. You don't need to be the fastest. Just don't be the slowest.

  • Phil Pilgrim (PhiPi),

    PC and IC both used a black/white segmented disk glued to the fan hub.
    IC used an IR LED and IR phototransistor, which PC used an IR module (photo-reflector?)
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