Simple check of button and led circuit please

Other Hardware General Electronics
1

I have many toggle switches on my 'Flightgear' simpit. Now I wish to activate a led when the switch is actioned without using another pin and without more code.
This works in Wokwi, but in real life do I risk smoking my arduino?

const int buttonPin = 2;

void setup() {
  pinMode(buttonPin, INPUT);
  Serial.begin(115200);
}

void loop() {
Serial.print(digitalRead(buttonPin));
delay(50);
}

Capture du 2023-03-29 21-39-25
Capture du 2023-03-29 21-39-25474×519 27.7 KB

2

A LED will not reliably draw your input low when the button is not pressed.
Add a 10 k resistor in parallel with the LED.

3

No extra parts required if you do this.
Connect the LED/resistor between 5volt and pin.
Connect the switch between pin and ground.
Use pull up on the pin in setup(), like this.
pinMode(buttonPin, INPUT_PULLUP);
Adapt your code, because the pin is normally HIGH, and LOW when the button is pushed.
Leo..

4

What is really going on here? It's impossible to see how it's actually connected:
image

1 Like
5

Thanks for following.
So the resistor should only be in parallel with the LED not in series or I must add a second one?

6

The resistor always goes in series with the LED.
What aarg is confused about is the green line through the resistor body.
Leo..

7

The green line through the resistor a visual Wokwi problem, I could'nt resolve that.

But I should put a resisitor in parallel or series with the led? I've seen both solutions and now show my ignorance.

8

An additional 10k bleed resistor across the LED would be needed in your circuit (post#1)

If you follow the advice in post#3 then you only need a (1k) resistor in series with the LED.
The bleed resistor there is provided in software, with INPUT_PULLUP.
Leo..

9

You should add a second one from the button to gnd to be sure the pin is pulled low by default.
@Wawa's suggestion might be easier.

10

11

That diagram does not show how OP should connect the LED/switch.
Leo..

12

Wawa's solution works perfectly in Wokwi and I understand now.
The digital read will be tuned according to the default property behaviour.

led_switch

Thanks all.

13

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