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beginning BEAM questions

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  • mountainieer2000
    hi, I am trying to build a little BEAM robot that will home on a special light source by using a LM386 and two 38k Hz IR Reciever modules from Radio Shack(part
    Message 1 of 7 , Sep 30, 2005
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      hi,

      I am trying to build a little BEAM robot that will home on a special
      light source by using a LM386 and two 38k Hz IR Reciever modules from
      Radio Shack(part number 276-640). How would I wire them and would they
      work to home in on a 38k Hz source from a 555 timer?


      On a seperate tangent, I am trying to use a little surplus wireless
      phone battery (3.6v) to power the above mentioned robot. It came with
      wires but they apparently lead nowhere(they had no voltage across
      them). The battery has two metal plates on it, one on each side, who
      happen to have 3.6v accross them so I tried soldering new leads onto
      them. The solder did not flow on like it is suppossed to. I even tried
      "painting" on the solder to form a cold solder. That also didn't work.
      The solder does not adhere/stay on. Any suggestions on how to attach
      the leads, either with a different soldering technique or different
      mechanism(zip ties/tape?)?

      Thanks in advance, mountainieer2000
    • wilf_nv
      I just love questions which trigger an idea for an interesting solution as I write the reply. 38kHz IR receivers have digital (on/off) outputs signals and
      Message 2 of 7 , Sep 30, 2005
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        I just love questions which trigger an idea for an interesting
        solution as I write the reply.

        38kHz IR receivers have digital (on/off) outputs signals and cannot
        be interfaced directly with the LM386 inputs. The LM386 "expects" two
        small analog input signals the difference of which is amplified and
        raises or lowers the analog output voltage connected to the midpoint
        of the two series connected motors. When the inputs signals are
        balanced the LM386 output voltage is +V/2.

        So how do we convert the 38KHz RX output from digital to analog?

        To convert the digital output of these IR receivers to an analog
        function that can interface with the LM386, the 38kHz carrier
        frequency must also be frequency or amplitude modulated at a lower
        frequency (ie 100Hz) with a triangle waveform. Since the receivers
        trigger and reset at some minimum light level at the center of the
        carrier frequency, the 0-100ma ramping LED current which controls the
        IR LED light level will cross this threshold at some light level.
        Using a ramping amplitude modulation causes the receiver with the
        higher light level to trigger earlier and reset later than the
        receiver exposed to the lower light level. When the light exposure is
        the same on both receivers, they should trigger and reset at the same
        time.

        Similarly, +/- 1kHz frequency modulation of the 38kHz carrier will
        have the same effect as the receiver sensitivity is a combination of
        both amplitude and LED frequency variation with respect to the center
        frequency.

        FM is more efficient in terms of controlling LED current but AM may
        provide better sensitivity and linearity of the receiver response.

        The resulting IR receiver output waveforms will be 100Hz Pulse Width
        Modulated rectangular waveforms which can be filtered to convert to
        analog and then connected to the two LM386 inputs to generate the
        LM386 analog output signal based on the difference in analog signal
        at the inputs.

        This design should be quite straight forward and I will be happy to
        post a complete circuit of this 38kHz Herbie a little later tonite.

        One more comment: Unlike the differential 38kHz receiver for Herbie
        applications as described, an absolute distance measurement would be
        difficult as these highly integrated 38kHz IR receivers have
        automatic gain control (AGC) to compensate for changes in light level.

        wilf

        --- In beam@yahoogroups.com, "mountainieer2000"
        <mountainieer2000@y...> wrote:
        > hi,
        >
        > I am trying to build a little BEAM robot that will home on a special
        > light source by using a LM386 and two 38k Hz IR Reciever modules
        from
        > Radio Shack(part number 276-640). How would I wire them and would
        they
        > work to home in on a 38k Hz source from a 555 timer?
        >
        >
        > On a seperate tangent, I am trying to use a little surplus wireless
        > phone battery (3.6v) to power the above mentioned robot. It came
        with
        > wires but they apparently lead nowhere(they had no voltage across
        > them). The battery has two metal plates on it, one on each side, who
        > happen to have 3.6v accross them so I tried soldering new leads onto
        > them. The solder did not flow on like it is suppossed to. I even
        tried
        > "painting" on the solder to form a cold solder. That also didn't
        work.
        > The solder does not adhere/stay on. Any suggestions on how to attach
        > the leads, either with a different soldering technique or different
        > mechanism(zip ties/tape?)?
        >
        > Thanks in advance, mountainieer2000
      • Wilf Rigter
        I forgot, It is safer to locate a proper battery holder for your battery. NiCd batteries often have solderable tabs spot welded to the terminals. If you must
        Message 3 of 7 , Sep 30, 2005
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          I forgot,
           
          It is safer to locate a proper battery holder for your battery. NiCd batteries often have solderable tabs spot welded to the terminals. If you must solder directly to the battery,terminals you can improve your chances by roughing the surface with emery cloth or a file. You also need a high wattage soldering iron in order to heat the surface up quickly while avoiding overheating the bulk of the battery, possibly destroying it in a violent explosion.
           
          wilf
           
          ----- Original Message -----
          Sent: Friday, September 30, 2005 12:09 PM
          Subject: [beam] beginning BEAM questions

          hi,

          I am trying to build a little BEAM robot that will home on a special
          light source by using a LM386 and two 38k Hz IR Reciever modules from
          Radio Shack(part number 276-640). How would I wire them and would they
          work to home in on a 38k Hz source from a 555 timer?


          On a seperate tangent, I am trying to use a little surplus wireless
          phone battery (3.6v) to power the above mentioned robot. It came with
          wires but they apparently lead nowhere(they had no voltage across
          them). The battery has two metal plates on it, one on each side, who
          happen to have 3.6v accross them so I tried soldering new leads onto
          them. The solder did not flow on like it is suppossed to. I even tried
          "painting" on the solder to form a cold solder. That also didn't work.
          The solder does not adhere/stay on. Any suggestions on how to attach
          the leads, either with a different soldering technique or different
          mechanism(zip ties/tape?)?

          Thanks in advance, mountainieer2000


        • Wilf Rigter
          Here are two circuits that provide the double modulated IR beam. I used 40kHz but this is a nominal value that can be adjusted to suit. The 40kHzHerbie1
          Message 4 of 7 , Sep 30, 2005
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            Here are two circuits that provide the double modulated IR beam. I used 40kHz but this is a nominal value that can be adjusted to suit. The 40kHzHerbie1 circuit uses two 555 (or a single 556) timers for excelent stability. The 40kHzHerbie2 circuit uses two 74HC14 Schmitt triggers, is simpler but may drift more. The component values of the 40kHz oscillator will require fine tuning for the right frequency.
            This is a general purpose solution that may be used in other designs.
             
            wilf
             
             
             
            ----- Original Message -----
            From: wilf_nv
            Sent: Friday, September 30, 2005 3:02 PM
            Subject: [beam] Re: beginning BEAM questions


            I just love questions which trigger an idea for an interesting
            solution as I write the reply.

            38kHz IR receivers have digital (on/off) outputs signals and cannot
            be interfaced directly with the LM386 inputs. The LM386 "expects" two
            small analog input signals the difference of which is amplified and
            raises or lowers the analog output voltage  connected to the midpoint
            of the two series connected motors. When the inputs signals are
            balanced the LM386 output voltage is +V/2.

            So how do we convert the 38KHz RX output from digital to analog?

            To convert the digital output of these IR receivers to an analog
            function that can interface with the LM386, the 38kHz carrier
            frequency must also be frequency or amplitude modulated at a lower
            frequency (ie 100Hz) with a triangle waveform.  Since the receivers
            trigger and reset at some minimum light level at the center of the
            carrier frequency, the 0-100ma ramping LED current which controls the
            IR LED light level will cross this threshold at some light level.
            Using a ramping amplitude modulation  causes the receiver with the
            higher light level to trigger earlier and reset later than the
            receiver exposed to the lower light level. When the light exposure is
            the same on both receivers, they should trigger and reset at the same
            time.

            Similarly, +/- 1kHz frequency modulation of the 38kHz carrier will
            have the same effect as the receiver sensitivity is a combination of
            both amplitude and LED frequency variation with respect to the center
            frequency.

            FM is more efficient in terms of controlling LED current but AM may
            provide better sensitivity and linearity of the receiver response. 
             
            The resulting IR receiver output waveforms will be 100Hz Pulse Width
            Modulated rectangular waveforms which can be filtered to convert to
            analog and then connected to the two LM386 inputs to generate the
            LM386 analog output signal based on the difference in analog signal
            at the inputs.     

            This design should be quite straight forward and I will be happy to
            post a complete circuit of this 38kHz Herbie a little later tonite.

            One more comment:  Unlike the differential 38kHz receiver for Herbie
            applications as described, an absolute distance measurement would be
            difficult as these highly integrated 38kHz IR receivers have
            automatic gain control (AGC) to compensate for changes in light level.

            wilf

            --- In beam@yahoogroups.com, "mountainieer2000"
            <mountainieer2000@y...> wrote:
            > hi,
            >
            > I am trying to build a little BEAM robot that will home on a special
            > light source by using a LM386 and two 38k Hz IR Reciever modules
            from
            > Radio Shack(part number 276-640). How would I wire them and would
            they
            > work to home in on a 38k Hz source from a 555 timer?
            >
            >
            > On a seperate tangent, I am trying to use a little surplus wireless
            > phone battery (3.6v) to power the above mentioned robot. It came
            with
            > wires but they apparently lead nowhere(they had no voltage across
            > them). The battery has two metal plates on it, one on each side, who
            > happen to have 3.6v accross them so I tried soldering new leads onto
            > them. The solder did not flow on like it is suppossed to. I even
            tried
            > "painting" on the solder to form a cold solder. That also didn't
            work.
            > The solder does not adhere/stay on. Any suggestions on how to attach
            > the leads, either with a different soldering technique or different
            > mechanism(zip ties/tape?)?
            >
            > Thanks in advance, mountainieer2000


          • Wilf Rigter
            oops! Oh well, Here are two circuits that provide the double modulated IR beam. I used 40kHz but this is a nominal value that can be adjusted to suit. The
            Message 5 of 7 , Sep 30, 2005
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              oops!
               
              Oh well,
               
              Here are two circuits that provide the double modulated IR beam. I used 40kHz but this is a nominal value that can be adjusted to suit. The 40kHzHerbie1 circuit uses two 555 (or a single 556) timers for excelent stability. The 40kHzHerbie2 circuit uses two 74HC14 Schmitt triggers, is simpler but may drift more. The component values of the 40kHz oscillator will require fine tuning for the right frequency.This is a general purpose solution that may be used in other designs
               
              wilf
            • Joseph Charles
              Hi Wilf, what an interesting idea. I can see how the circuits are amplitude modulating the IR beam (via the ramping triangle wave), but how are they frequency
              Message 6 of 7 , Oct 3, 2005
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                Hi Wilf, what an interesting idea. I can see how the
                circuits are amplitude modulating the IR beam (via the
                ramping triangle wave), but how are they frequency
                modulating it?

                I know I'm a pedant (sorry!), but should the cap value
                of the lower 555 be more like 0.001uF, not 1uF? What
                would you suggest for the value of the cap in the
                receiver circuit?

                I can see I'll be up one night this week measuring
                things again! :)

                Jo


                --- Wilf Rigter <wrigter@...> wrote:

                > Here are two circuits that provide the double
                > modulated IR beam. I used 40kHz but this is a
                > nominal value that can be adjusted to suit. The
                > 40kHzHerbie1 circuit uses two 555 (or a single 556)
                > timers for excelent stability. The 40kHzHerbie2
                > circuit uses two 74HC14 Schmitt triggers, is simpler
                > but may drift more. The component values of the
                > 40kHz oscillator will require fine tuning for the
                > right frequency.
                > This is a general purpose solution that may be used
                > in other designs.
                >
                > wilf




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              • Wilf Rigter
                Hi Jo, I should have pointed out that this idea uses either AM modulation OR FM modulation but not both. Cut, paste and MODIFY darn it! You are absolutely
                Message 7 of 7 , Oct 3, 2005
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                  Hi Jo,
                   
                  I should have pointed out that this idea uses either AM modulation OR FM modulation but not both.
                  Cut, paste and MODIFY darn it! You are absolutely right about the cap of the lower 555:  it should be 0.001uF.   The filter cap on the output should be about 0.33 -1uF. The 100K pull up resistors are probably not required. Good luck with testing it.
                   
                  wilf
                   
                      
                  ----- Original Message -----
                  Sent: Monday, October 03, 2005 5:51 AM
                  Subject: [beam] Re: beginning BEAM questions

                  Hi Wilf, what an interesting idea. I can see how the
                  circuits are amplitude modulating the IR beam (via the
                  ramping triangle wave), but how are they frequency
                  modulating it?

                  I know I'm a pedant (sorry!), but should the cap value
                  of the lower 555 be more like 0.001uF, not 1uF? What
                  would you suggest for the value of the cap in the
                  receiver circuit?

                  I can see I'll be up one night this week measuring
                  things again! :)

                  Jo


                  --- Wilf Rigter <wrigter@...> wrote:

                  > Here are two circuits that provide the double
                  > modulated IR beam. I used 40kHz but this is a
                  > nominal value that can be adjusted to suit. The
                  > 40kHzHerbie1 circuit uses two 555 (or a single 556)
                  > timers for excelent stability. The 40kHzHerbie2
                  > circuit uses two 74HC14 Schmitt triggers, is simpler
                  > but may drift more. The component values of the
                  > 40kHz oscillator will require fine tuning for the
                  > right frequency.
                  > This is a general purpose solution that may be used
                  > in other designs.
                  >
                  > wilf



                             
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