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Re: [SeattleRobotics] query...

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  • sunil karki
    hi there! parallel ports are good in sinking than sourcing current,so you can use pullup resistors like 10k from standard source(5 v) and it can act as a open
    Message 1 of 11 , Apr 1, 2009
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      hi there!
      parallel ports are good in sinking than sourcing current,so you can use pullup resistors like 10k from standard source(5 v) and it can act as a open collector type i/o port.To be on the safe side do use buffers!
      thats what i know about LPT !

      --- On Wed, 1/4/09, abhi_6929 <abhi_6929@...> wrote:

      From: abhi_6929 <abhi_6929@...>
      Subject: [SeattleRobotics] query...
      To: SeattleRobotics@yahoogroups.com
      Date: Wednesday, 1 April, 2009, 3:22 AM






      what is the voltage high from the parallel port output pin if we use MATLAB???

















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    • abhi_6929
      hello all!!! i have a small query regarding a project tat i m building.I want to use an IR sensor for obstacle detection(IS471F).Now,the sensor is supposed to
      Message 2 of 11 , Apr 26, 2009
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        hello all!!!
        i have a small query regarding a project tat i m building.I want to use an IR sensor for obstacle detection(IS471F).Now,the sensor is supposed to be isolated from the IR LED radiation for detection purposes.I want to know how i can achieve that.What can be used to isolate the sensor from the IR radiation.
        Apart from this i am also not sure what are the types of obstacles that would reflect IR radiation and hence can be detected.
        Any help would be appreciated...
        THANKS!!!
      • Jim McBride
        Black nail polish. ... [Non-text portions of this message have been removed]
        Message 3 of 11 , Apr 26, 2009
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          Black nail polish.

          At 11:28 AM 4/26/2009, you wrote:


          >hello all!!!
          >i have a small query regarding a project tat i m building.I want to
          >use an IR sensor for obstacle detection(IS471F).Now,the sensor is
          >supposed to be isolated from the IR LED radiation for detection
          >purposes.I want to know how i can achieve that.What can be used to
          >isolate the sensor from the IR radiation.
          >Apart from this i am also not sure what are the types of obstacles
          >that would reflect IR radiation and hence can be detected.
          >Any help would be appreciated...
          >THANKS!!!
          >
          >


          [Non-text portions of this message have been removed]
        • Larry Geib
          Here s a start to getting your creative juices flowing... http://www.kronosrobotics.com/an150/AAN150.shtml Not the LED and sensor on opposite sides of a pice
          Message 4 of 11 , Apr 26, 2009
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            Here's a start to getting your creative juices flowing...

            http://www.kronosrobotics.com/an150/AAN150.shtml

            Not the LED and sensor on opposite sides of a pice of proto board and
            a pice of black tape as a shield.

            Larry


            On Apr 26, 2009, at 11:28 AM, abhi_6929 wrote:

            > hello all!!!
            > i have a small query regarding a project tat i m building.I want to
            > use an IR sensor for obstacle detection(IS471F).Now,the sensor is
            > supposed to be isolated from the IR LED radiation for detection
            > purposes.I want to know how i can achieve that.What can be used to
            > isolate the sensor from the IR radiation.
            > Apart from this i am also not sure what are the types of obstacles
            > that would reflect IR radiation and hence can be detected.
            > Any help would be appreciated...
            > THANKS!!!
            >
            >
            >
            > ------------------------------------
            >
            > Visit the SRS Website at http://www.seattlerobotics.orgYahoo!
            > Groups Links
            >
            >
            >
          • David L Buckley
            Or http://www.parallax.com/Portals/0/Downloads/docs/prod/stamps/web-BSM-v2.2.pdf page 250 These can work up to maybe 18 inches. David
            Message 5 of 11 , Apr 27, 2009
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              Or
              http://www.parallax.com/Portals/0/Downloads/docs/prod/stamps/web-BSM-v2.2.pdf
              page 250
              These can work up to maybe 18 inches.

              David



              --- In SeattleRobotics@yahoogroups.com, Larry Geib <LJGeib@...> wrote:
              >
              > Here's a start to getting your creative juices flowing...
              >
              > http://www.kronosrobotics.com/an150/AAN150.shtml
              >
              > Not the LED and sensor on opposite sides of a pice of proto board and
              > a pice of black tape as a shield.
              >
              > Larry
              >
              >
              > On Apr 26, 2009, at 11:28 AM, abhi_6929 wrote:
              >
              > > hello all!!!
              > > i have a small query regarding a project tat i m building.I want to
              > > use an IR sensor for obstacle detection(IS471F).Now,the sensor is
              > > supposed to be isolated from the IR LED radiation for detection
              > > purposes.I want to know how i can achieve that.What can be used to
              > > isolate the sensor from the IR radiation.
              > > Apart from this i am also not sure what are the types of obstacles
              > > that would reflect IR radiation and hence can be detected.
              > > Any help would be appreciated...
              > > THANKS!!!
              > >
              > >
              > >
              > > ------------------------------------
              > >
              > > Visit the SRS Website at http://www.seattlerobotics.orgYahoo!
              > > Groups Links
              > >
              > >
              > >
              >
            • abhi_6929
              ... the thing is...i hav to isolate the sensor from direct IR radiation but not from the reflected radiation which is the basis for detection i.e i hav to keep
              Message 6 of 11 , Apr 27, 2009
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                --- In SeattleRobotics@yahoogroups.com, "David L Buckley" <david@...> wrote:
                >
                > Or
                > http://www.parallax.com/Portals/0/Downloads/docs/prod/stamps/web-BSM-v2.2.pdf
                > page 250
                > These can work up to maybe 18 inches.
                >
                > David
                >
                >
                >
                > --- In SeattleRobotics@yahoogroups.com, Larry Geib <LJGeib@> wrote:
                > >
                > > Here's a start to getting your creative juices flowing...
                > >
                > > http://www.kronosrobotics.com/an150/AAN150.shtml
                > >
                > > Not the LED and sensor on opposite sides of a pice of proto board and
                > > a pice of black tape as a shield.
                > >
                > > Larry
                > >
                > >
                > > On Apr 26, 2009, at 11:28 AM, abhi_6929 wrote:
                > >
                > > > hello all!!!
                > > > i have a small query regarding a project tat i m building.I want to
                > > > use an IR sensor for obstacle detection(IS471F).Now,the sensor is
                > > > supposed to be isolated from the IR LED radiation for detection
                > > > purposes.I want to know how i can achieve that.What can be used to
                > > > isolate the sensor from the IR radiation.
                > > > Apart from this i am also not sure what are the types of obstacles
                > > > that would reflect IR radiation and hence can be detected.
                > > > Any help would be appreciated...
                > > > THANKS!!!
                > > >
                > > >
                > > >
                > > > ------------------------------------
                > > >
                > > > Visit the SRS Website at http://www.seattlerobotics.orgYahoo!
                > > > Groups Links
                > > >
                > > >
                > > >
                > >
                >
                the thing is...i hav to isolate the sensor from direct IR radiation but not from the reflected radiation which is the basis for detection i.e i hav to keep sumthin between the LED and the sensor...i want to know wat cud serve the purpose...
              • David L Buckley
                Look in the link I gave you, it is quite clear the IR LEDs are in tubes to block the light. That is what you are trying to block - LIGHT - it is just that some
                Message 7 of 11 , Apr 27, 2009
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                  Look in the link I gave you, it is quite clear the IR LEDs are in tubes to block the light. That is what you are trying to block - LIGHT - it is just that some things are transparent to IR light and opaque to visible light. Metal foil (kitchen foil) blocks both. Experiment with other materials, if it works, then it works and if it doesn't then it doesn't.
                  David

                  --- In SeattleRobotics@yahoogroups.com, "abhi_6929" <abhi_6929@...> wrote:
                  >
                  > --- In SeattleRobotics@yahoogroups.com, "David L Buckley" <david@> wrote:
                  > >
                  > > Or
                  > > http://www.parallax.com/Portals/0/Downloads/docs/prod/stamps/web-BSM-v2.2.pdf
                  > > page 250
                  > > These can work up to maybe 18 inches.
                  > >
                  > > David
                  > >
                  > >
                  > >
                  > > --- In SeattleRobotics@yahoogroups.com, Larry Geib <LJGeib@> wrote:
                  > > >
                  > > > Here's a start to getting your creative juices flowing...
                  > > >
                  > > > http://www.kronosrobotics.com/an150/AAN150.shtml
                  > > >
                  > > > Not the LED and sensor on opposite sides of a pice of proto board and
                  > > > a pice of black tape as a shield.
                  > > >
                  > > > Larry
                  > > >
                  > > >
                  > > > On Apr 26, 2009, at 11:28 AM, abhi_6929 wrote:
                  > > >
                  > > > > hello all!!!
                  > > > > i have a small query regarding a project tat i m building.I want to
                  > > > > use an IR sensor for obstacle detection(IS471F).Now,the sensor is
                  > > > > supposed to be isolated from the IR LED radiation for detection
                  > > > > purposes.I want to know how i can achieve that.What can be used to
                  > > > > isolate the sensor from the IR radiation.
                  > > > > Apart from this i am also not sure what are the types of obstacles
                  > > > > that would reflect IR radiation and hence can be detected.
                  > > > > Any help would be appreciated...
                  > > > > THANKS!!!
                  > > > >
                  > > > >
                  > > > >
                  > > > > ------------------------------------
                  > > > >
                  > > > > Visit the SRS Website at http://www.seattlerobotics.orgYahoo!
                  > > > > Groups Links
                  > > > >
                  > > > >
                  > > > >
                  > > >
                  > >
                  > the thing is...i hav to isolate the sensor from direct IR radiation but not from the reflected radiation which is the basis for detection i.e i hav to keep sumthin between the LED and the sensor...i want to know wat cud serve the purpose...
                  >
                • Francesco De Comité
                  Message 8 of 11 , Apr 27, 2009
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                  • Peter Balch
                    There are four effects that you have to worry about. You are trying to measure the IR light emitted by the LED and reflected off the obstacle. Effect 1: the
                    Message 9 of 11 , Apr 27, 2009
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                      There are four effects that you have to worry about.

                      You are trying to measure the IR light emitted by the LED and reflected off
                      the obstacle.

                      Effect 1: the obstacle may not reflect much IR. I don't find that's a big
                      problem. Most stuff you find in a living room reflect IRs pretty well. Even
                      black objects. Not all reflect to the same degree so you can't measure the
                      strength of the reflection to determine distance.

                      Effect 2: light falling sideways onto the IR receiver can overload it.
                      Hence, the receiver should be in a tube and the tube should be matt black
                      inside (and appear black in IR). I generally use some sleeve off a coax
                      cable which is probably not ideal. Be careful with light coming in the back
                      of the tube - that's caught me out in the past. You should mount the
                      receiver slightly forward of the LED because the LED will scatter some light
                      backwards.

                      You can buy receivers with different angles of acceptance. The front of the
                      plastic casing acts as a lens. The angle is generally stated in the
                      receiver's spec sheet. For obstacle detection, you probably want a narrow
                      angle for both the receiver and LED. (But then you have to be careful that
                      the emitter and receiver are both pointing exactly the same way.) Remote
                      control IR receivers are good because the contain a 38kHz filter but they're
                      really bad because the have an extremely wide acceptance angle.

                      Effect 3: the wavelength of the IR matters. Obviously, the emitter and
                      receiver wavelengths must match. Some receivers have quite narrow
                      bandwidths. Is longer or shorter wavelength better? Shorter wavelengths mean
                      that the receiver is more sensitive to daylight which may swamp the IR
                      signal. Some IR receivers are "water clear" - they let in daylight. Some
                      have built-in IR filters - the plastic looks black. You probably want a
                      filter. You can also get sheets of filter by disassembling old VCRs, etc.

                      Effect 4: the background level of IR matters. If sunlight is falling on a
                      wall, then the wall will be emitting a lot of IR. The obstacle detector is
                      looking for the difference between the receiver's voltage when the LED is ON
                      vs OFF. It may not be able to see a sunlit wall. IR receivers aren't linear
                      so the extra IR from the LED may add 20mV to the receiver's signal in a dark
                      room but only 1mV in direct sunlight. The sensor should compensate for this
                      but many don't.


                      What do I do? I've designed by own, very cheap, sensor which I'm very
                      pleased with. I use short wavelength IR receivers in a water-clear case and
                      very bright red LEDs. The sensor responds to the bright red LED about as
                      well as it responds to it's recommended IR emitter - the LED is not the
                      right wavelength but it's much brighter. It's useful having visible red
                      light as you can see where the sensor is pointing. And any robot looks
                      better with glowing red eyes.

                      The detector measures the background light level (including daylight) then
                      turns on the LED and measures the light level again. By measuring the
                      background light level, I can compensate for the receiver's non-linear
                      response. I can get the same "answer" for the same distance/reflectance in
                      both darkness and a normal room. Direct sunlight is still a problem though.
                      As a bonus, I get a reading of the background light level which I can use
                      for "navigation". I get a light-level and obstacle detector for around
                      $0.60. It only requires 2 PIC pins. (In fact, I often power the LEDs off the
                      same pin as a motor's H-bridge so that's just one pin per sensor.)

                      Peter
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