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IR object detection — Parallax Forums

IR object detection

nelson1000nelson1000 Posts: 25
edited 2006-09-19 19:50 in Robotics
Hello,

I was wondering if anyone could help me? I am using this and am having no luck. I was wondering if it is similar to the ones that came with my BOE-BOT? and if not how can I use it?

Thanks for the help,

Nelson

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-21 23:30
    At first glance it would appear to fully compatible with the one included with the BOE-Bot.· Are you able to swap it with one from the BOE-Bot and get different results?


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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • nelson1000nelson1000 Posts: 25
    edited 2006-05-22 03:41
    The only results that I get are that it does not work! I even have it hooked up the same way. The one thing that I thought that could be wrong was that the 3 leads would be in a different order, but that was not even the problem.

    Nelson
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-22 04:09
    You didn't answer my question though, if you swap it with one from the BOE-Bot does that one suddenly work?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • nelson1000nelson1000 Posts: 25
    edited 2006-05-22 04:13
    ya sorry about that I am just a little frustrated! Yes that is exactly what happens, as soon as the one that came with the BOT it works....


    Nelson
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-22 05:18
    Sounds like the units you got may be damaged or bad.· You might want to return them.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • nelson1000nelson1000 Posts: 25
    edited 2006-05-22 17:28
    After reading what is on the HVW's site

    "The PNA4602M, like all IR decoders of this nature, does NOT measure distances, detect objects or sense color changes. This device takes an incoming IR signal, modulated at 38 KHz, strips-off the carrier and provides the user with a clean, stable data stream that represents the originally encoded data. It is intended for IR data transfer only."

    I guess that this can not be used for object detection.

    Thanks all for your help,

    Nelson
  • allanlane5allanlane5 Posts: 3,815
    edited 2006-05-22 18:01
    Well, sometimes you have to take vendor claims with a grain of salt. It turns out that the BOE-Bot DOES in fact use "IR decoders of this nature", and uses a reflected IR-signal at 38 Khz to trigger the IR decoder.

    Meaning, by ITSELF all it provides is a reciever and decoder of 38 Khz IR light. Through programming your BOE-Bot, you can use that facility to detect objects. Measuring distances is harder, and measuring color changes is not possible.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-22 19:12
    Nelson,

    ·· Essentially that's how all of those decoders work...Why this one isn't doing what's expected I don't know.· But it should in theory be useable for object detection.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • nelson1000nelson1000 Posts: 25
    edited 2006-06-04 02:16
    I thought that I should post an up-date, I ordered new IR detectors from parallax. I finally received them, and am still having no luck getting them to work. I have been through 3 pairs so far and the only ones that have worked have been the original 2 that came with my BOE-BOT kit. The last 4 that I have received have been an updated model of the same IR detector (not having a metal cage type thing) I was wondering if anyone else has had these and if so, please tell me how you got them to work.

    Basically, I was wondering if all three leads coming off of it were in the same order?

    Thanks,

    Nelson

    Post Edited (nelson1000) : 6/4/2006 9:15:02 PM GMT
  • A.C. fishingA.C. fishing Posts: 262
    edited 2006-06-05 01:13
    I bought some without cages, and with them my boe-bot will refuse to turn. Is this what happens?

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  • nelson1000nelson1000 Posts: 25
    edited 2006-06-05 22:47
    Not exactly, I can't even get the indicator LED to flash when I use the ones with out cages. I wire it up exactly as it is in the Robotics with the BOE book, then change from the caged type to the new type and nothing happens.

    Nelson
  • Andy Lindsay (Parallax)Andy Lindsay (Parallax) Posts: 1,919
    edited 2006-06-06 16:50
    Make sure there are no commands between FREQOUT 8, 1, 38500 and irDetectLeft = IN9. It has to be like this:

    FREQOUT 8, 1, 38500
    irDetectLeft = IN9

    Try a 220 ohm resistor in series with the IR LED when you use the PNA4602. Point the IRLED in a direction where there are no objects for a long ways, then try putting your hand in front of the IR LED (to reflect IR at the receiver). If you have fluorescent lights around, turn them off while you are testing this. Direct sunlight can cause problems sometimes too.

    If you have a voltmeter, try reading the voltage at the PNA4602's output (the pin connected to the I/O pin). Use a really long FREQOUT command, like FREQOUT 8, 60000, 38500. This will give you a minutes worth of measuring time with the voltmeter. During this time, your BASIC Stamp will not be able to report any signals because it will be busy sending the FREQOUT signal to the IR LED. As you reflect the beam from the IRLED at the receiver, its output should send a low signal (0 V). When the IR beam is going off into space, the IR receiver should send a high signal (5 V).
  • RicoRico Posts: 2
    edited 2006-09-16 19:30
    Has anyone figured this out? I'm having the same trouble. My old sensor which came with the kit (metal case) works fine. I got 10 pna4602 receivers from digikey and they don't.

    Help?
    -Rico
  • Andy Lindsay (Parallax)Andy Lindsay (Parallax) Posts: 1,919
    edited 2006-09-18 17:05
    Is this the part number? PNA4602M-ND

    It should work. With the IR detection circuit on the Boe-Bot, I can swap the two parts (no changes to circuit, same pinout), and it works fine either way. We've been doing it for years.
  • RicoRico Posts: 2
    edited 2006-09-19 19:50
    The devil is the details... Let me explain. I'm actually building my own sensor module for another robot but wanted to base it off what I had worked with from the Boe-Bot. I have an osc scope and function generator to prototype with and can definitely see a difference in behavior that affects my design.

    The PNA 4602 tends to chatter more when tranisitioning form detection/no-detection. Also, when I step through frequencies towards the center frequency (freq at detection should be proportional to distance), I find a very narrow range of frequencies, <1 khz over ~20cm.

    The 2 parts from my old kit have less chatter (almost none) and detection frequencies vary over ~5 khz over ~20cm.

    I've tried burtsing the output as suggested in other forums (<= 16 pulses). Didn't help. I'd I've played with different LED intensities. No luck either.

    So I'm hoping to find the original part as a first option, or I'll have to modify my design a bit. Probably something along the lines of:
    http://www.oricomtech.com/projects/irpd-an.htm
    Cheers,
    Rico
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