[SOLVED] Arduino Starter Kit Project 15: Hacking Buttons

Hardware The Arduino Starter Kit
1

Hi everyone!

I've been trying to get the last project in the official Projects Book working, to no avail. I dismantled an old pocket calculator and made sure I know how to trigger a button press on the membrane underlying the buttons but the circuit wasn't working. My suspicion landed on the optocoupler being faulty, so I built a circuit with two LEDs to keep it simple and test the component - still nothing.

Please see the video: https://www.youtube.com/shorts/k31_U7Y1-H8
The LED before the optocoupler is obstructing a 220Ohm resistor hooked up to digital pin 2 via the red wire. The LED past the optocoupler has the anode connected to pin 5 and the cathode to pin 4 of the optocoupler. The component should be switched on roughly every 4 seconds, as the pre-optocoupler LED indicates. I tried with multiple LEDs and both optocouplers that came with my Kit.

Is it possible that the optocoupler is dead? Or have I misunderstood something completely and the circuit is built wrong?

For completion, the code is as follows:

const int optoPin = 2;

void setup() {
  pinMode(optoPin, OUTPUT);
}

void loop() {
  digitalWrite(optoPin, HIGH);
  delay(500);
  digitalWrite(optoPin, LOW);
  delay(4000);
}

Any tips much appreciated - thanks!

2

Actually, I've just realised I indeed built the circuit wrong. the second LED was closing it, completely bypassing the optocoupler! And I do need power on the other side, obviously :slight_smile:

3

Hi there!
If you solved your issue, please edit the title of your post to include "Solved" or "Closed".

Thanks!

4

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