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I have a Raspberry Pi 1 Model A and am trying to control an LED from an app that I will be running on it. The wiring I'm planning on going with is:

enter image description here

Even though thats a RPI 3 in the diagram above, the concept is the same:

  1. Connect the RPi to a suitable power source (via Micro USB)
  2. Connect the 3.3V pin on the RPi to the power rail on the breadboard
  3. Connect the column where the LED (1.2V @ 100mA) will be placed to power through a resistor (47 ohm)
  4. Then just connect the column where the LED's 2nd leg is located back to a GPIO pin that is configured to be an output pin

So I wanted to verify (I'm afraid I'm going to fry my pi!):

  • That the wiring is correct; and
  • That I'm using the correct resistor to do the job (R = V/I = (3.3V - 1.2V)/.1A = 2.1V / .1A = 21 ohms...so I figured 47 ohms is OK); and
  • That I should be configuring my GPIO pin to be on output pin afterall

Thanks!

smeeb
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1 Answers1

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There is some considerations:

  • A maximum of 16mA per GPIO with the total current from all GPIOs not exceeding 50mA.

  • Calculate the resistance, its the limiter for the current.

    Normal data for a red LED: ~1.8 volt, 16mAmpere (0,016A)

    U = 3.3V - 1.8V = 1.5V

    R = U / I

    1.5V/0.016A = 94 ohm

And regarding the schematic, this is working, your a bit turned around. enter image description here

MatsK
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