2 Replies Latest reply on Mar 12, 2017 11:28 AM by ianinini

    GPIO to OpAmp

    ianinini

      Hi,

         

      I've developed a project using a cy8ckit-042-ble: I can send data via bluetooth from my phone, and get an LED to flash the way I want. The LED is wired between pin3.5 and ground, and I drive pin3.5 from high to low as I want.

         

      Now I know I can't safely draw more than 25mA through a GPIO, but for my next step I want to put more current through my LED.

         

      I know I could buy a transistor to create an OpAmp, but I'd like to avoid this if possible. I thought of two options. Can anyone tell me, are either of them sane?

         

      Option 1:

         

      I read that the PSOC4 has 4 OpAmps. I make use of these.

         

      But are these of any use to me? If I'm reading the datasheet correctly, these are low power only. Are they just intended for amplifying low powered input signals? Or can I drive them with my digital logic, and somehow drive my LED directly at a higher current?

         

      Option 2:

         

      My current wiring is simply this:

         

      Pin3.5 ----- Resistor ----- LED -------- Ground

         

      The resistor was chosen to keep the current below 25mA.

         

      Can I replace my wiring with this:

         

      Pin3.5 ----- Resistor -----   | 

         

                                                   |----------- LED -------- Ground

         

      Pin3.x ----- Resistor -----   |

         

      And then drive Pin3.5 and Pin3.x to the same state in software? (I read somewhere I can draw up to 100mA per side of the chip.)

         

       

         

      Or can anyone suggest another option?

         


      Thanks,

         

      Ian.

         

      (Please excuse my ignorance around electronics: I'm a software guy really. Getting the soldering iron out was really quite novel.)

        • 1. Re: GPIO to OpAmp
          user_1377889

          Welcome in the forum!

             

          Well, and how will you limit the current? When there is a limit of 100 mA per side you ought to limit the current.

             

          And: Use bredboards, no solder, easy changing!

             

           

             

          Bob

          • 2. Re: GPIO to OpAmp
            ianinini

            Hi Bob,

               

            Thanks for the welcome. (Good idea to use breadboards. I'll get some.)

               

            The resistors are chosen to limit the current. I know the voltage, so I just choose the resistors such that I = V/R < 25mA per pin. And connect up at most 4 pins of course.

               

            Ian.