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Re: [SeattleRobotics] lm324 comparitor

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  • Randy Carter
    The LM324 is not a comparator it is an op-amp. As such it was designed to operate as a linear amplifier. It can be used as a comparator with some limitations
    Message 1 of 8 , Jul 19, 2009
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      The LM324 is not a comparator it is an op-amp. As such it was designed to operate as a linear amplifier. It can be used as a comparator with some limitations like it doesn't do rail to rail inputs or outputs well. You can not connect its output directly to a micro controller input pin especially if the LM324 has a negative power supply. A negative output voltage from the op-amp will damage the micro controller. If the Vee supply is tied to ground it is permissible.

      The LM393 and LM399 will work well at detecting simple highs and lows. It will tolerate rail to rail inputs. Don't forget the pull-up resister. The output of the LM393/339 is open collector. All it can do is pull to ground it has no complimentary output transistor to pull the signal high. This makes it useful when transitioning from a 12v analog section to a 5v logic section.

      ----------------------------------------------------
      "What the detractors and critics of electric vehicles
      have been saying for years, is true. The electric
      vehicle is not for everybody, given the limited range
      it can only meet the needs of 90% of the population."

      Ed Begley Jr.
      ----------------------------------------------------


      ---------- Original Message ----------
      From: "pudumula" <pudumula@...>
      To: SeattleRobotics@yahoogroups.com
      Subject: [SeattleRobotics] lm324 comparitor
      Date: Sun, 19 Jul 2009 15:57:40 -0000



      I am doing a line follower robot.
      and using the LED as a light sensor and deductor.
      I am using a lm324 voltage comparator for a project of mine.
      The output of the comparator is to be connected to a micro controller.
      So the power supply i gave to it was +5v to 4th pin and ground to 11th pin.
      Will the ic work if i give ground to 11th pin instead of -5v?

      The output voltage is +0.5v for black region and +2.00v for white region.
      This voltage is got after i connected it to a transistor(BC107) with +5v.
      So i kept the reference voltage to +1v and connected it to inverting terminal of the lm324.
      Then i connected the sensor output to non-inverting terminal.
      In spite of doing all this i get only +3.9v as output.
      Some sa that lm324 is a slowest opamp and they are suggesting me to use LM393/339.
      My Questions are...
      1. Is it advisable to use LM393/339?
      2. Can i use BC107 as a switch or are there any special transistor for the purpose?
      3. Will the ic work if i give ground to 11th pin instead of -5v?




      ------------------------------------

      Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
    • sunil karki
      Hey!        has anyone thought of the sensor alignment,signal conditioning and ambient lights false switching??? comon guys its robotics not a circus?? a
      Message 2 of 8 , Jul 19, 2009
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        Hey!
               has anyone thought of the sensor alignment,signal conditioning and ambient lights false switching???
        comon guys its robotics not a circus??
        a decent built in ADC will be perfect for a sensor, The recent problems i faced in sensor system is that my comparator just blew up when aligning my robot , later on i found that when the sensors output was fed to the comparator then due to some capacitive or inductive effect the comparator went into a mode of oscillation and thus blew itself up,therefore, all the visible and invisible account must be taken care of when dealing in these matters.
        Hope it helped some one ,and i am feeling great sharing my crazy experience.
         

        --- On Mon, 20/7/09, Randy Carter <rwcarter.wa@...> wrote:

        From: Randy Carter <rwcarter.wa@...>
        Subject: Re: [SeattleRobotics] lm324 comparitor
        To: SeattleRobotics@yahoogroups.com
        Date: Monday, 20 July, 2009, 5:52 AM

         
        The LM324 is not a comparator it is an op-amp. As such it was designed to operate as a linear amplifier. It can be used as a comparator with some limitations like it doesn't do rail to rail inputs or outputs well. You can not connect its output directly to a micro controller input pin especially if the LM324 has a negative power supply. A negative output voltage from the op-amp will damage the micro controller. If the Vee supply is tied to ground it is permissible.

        The LM393 and LM399 will work well at detecting simple highs and lows. It will tolerate rail to rail inputs. Don't forget the pull-up resister. The output of the LM393/339 is open collector. All it can do is pull to ground it has no complimentary output transistor to pull the signal high. This makes it useful when transitioning from a 12v analog section to a 5v logic section.

        ------------ --------- --------- --------- --------- ----
        "What the detractors and critics of electric vehicles
        have been saying for years, is true. The electric
        vehicle is not for everybody, given the limited range
        it can only meet the needs of 90% of the population."

        Ed Begley Jr.
        ------------ --------- --------- --------- --------- ----

        ---------- Original Message ----------
        From: "pudumula" <pudumula@gmail. com>
        To: SeattleRobotics@ yahoogroups. com
        Subject: [SeattleRobotics] lm324 comparitor
        Date: Sun, 19 Jul 2009 15:57:40 -0000

        I am doing a line follower robot.
        and using the LED as a light sensor and deductor.
        I am using a lm324 voltage comparator for a project of mine.
        The output of the comparator is to be connected to a micro controller.
        So the power supply i gave to it was +5v to 4th pin and ground to 11th pin.
        Will the ic work if i give ground to 11th pin instead of -5v?

        The output voltage is +0.5v for black region and +2.00v for white region.
        This voltage is got after i connected it to a transistor(BC107) with +5v.
        So i kept the reference voltage to +1v and connected it to inverting terminal of the lm324.
        Then i connected the sensor output to non-inverting terminal.
        In spite of doing all this i get only +3.9v as output..
        Some sa that lm324 is a slowest opamp and they are suggesting me to use LM393/339.
        My Questions are...
        1. Is it advisable to use LM393/339?
        2. Can i use BC107 as a switch or are there any special transistor for the purpose?
        3. Will the ic work if i give ground to 11th pin instead of -5v?

        ------------ --------- --------- ------

        Visit the SRS Website at http://www.seattler obotics.orgYahoo! Groups Links



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      • Dennis Clark
        Yes, the LM325 can be used with a single supply. My guess is that you haven t gotten the OpAmp configured properly. Google for a schmitt trigger opamp
        Message 3 of 8 , Jul 20, 2009
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          Yes, the LM325 can be used with a single supply. My guess is that you
          haven't gotten the OpAmp configured properly. Google for a "schmitt
          trigger opamp" circuit to see how to do it well.

          DLC

          >
          > I am doing a line follower robot.
          > and using the LED as a light sensor and deductor.
          > I am using a lm324 voltage compatitor for a project of mine.
          > The output of the comparitor is to be connected to a microcontroller.
          > So the power supply i gave to it was +5v to 4th pin and ground to 11th
          > pin.
          > Will the ic work if i give ground to 11th pin instead of -5v?
          >
          > The output voltage is +0.5v for black region and +2.00v for white region.
          > This voltage is got after i connected it to a transistor(BC107) with +5v.
          > So i kept the reference voltage to +1v and connected it to inverting
          > terminal of the lm324.
          > Then i connected the sensor output to non-inverting terminal.
          > In spite of doing all this i get only +3.9v as output.
          > Some sa that lm324 is a slowest opamp and they are suggesting me to use
          > LM393/339.
          > My Questions are...
          > 1. Is it advisable to use LM393/339?
          > 2. Can i use BC107 as a switch or are there any special transistor for the
          > purpose?
          > 3. Will the ic work if i give ground to 11th pin instead of -5v?
          >
          >
          >
          >
          > ------------------------------------
          >
          > Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
          >
          >
          >
          >


          --
          Dennis Clark
          TTT Enterprises
        • Thomas
          Hi, I seem to remember someone asking me about where they could find a Hero 1 robot. I don t remember who it was. Anyway, I have two on my ebay store for sale
          Message 4 of 8 , Jul 20, 2009
          • 0 Attachment

             Hi,

            I seem to remember someone asking me about where they could find a Hero 1 robot. I don't remember who it was. Anyway, I have two on my ebay store for sale if anyone is interested.



            Thomas Messerschmidt



            Check out my ebaY Store:





          • fred miller
            looking for a good comparator LMC series IS A RAIL TO RAIL op amp and very low current http://www.national.com/ds/LM/LMC6681.pdf it comes in single ,dual and
            Message 5 of 8 , Jul 20, 2009
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              looking for a good comparator LMC series IS A RAIL TO RAIL op amp and very low current

              http://www.national.com/ds/LM/LMC6681.pdf it comes in single ,dual and quad and used them before for a great comparator


              --- In SeattleRobotics@yahoogroups.com, "pudumula" <pudumula@...> wrote:
              >
              >
              > I am doing a line follower robot.
              > and using the LED as a light sensor and deductor.
              > I am using a lm324 voltage compatitor for a project of mine.
              > The output of the comparitor is to be connected to a microcontroller.
              > So the power supply i gave to it was +5v to 4th pin and ground to 11th pin.
              > Will the ic work if i give ground to 11th pin instead of -5v?
              >
              > The output voltage is +0.5v for black region and +2.00v for white region.
              > This voltage is got after i connected it to a transistor(BC107) with +5v.
              > So i kept the reference voltage to +1v and connected it to inverting terminal of the lm324.
              > Then i connected the sensor output to non-inverting terminal.
              > In spite of doing all this i get only +3.9v as output.
              > Some sa that lm324 is a slowest opamp and they are suggesting me to use LM393/339.
              > My Questions are...
              > 1. Is it advisable to use LM393/339?
              > 2. Can i use BC107 as a switch or are there any special transistor for the purpose?
              > 3. Will the ic work if i give ground to 11th pin instead of -5v?
              >
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