led is not working when I am using with a button and an alarm.

Projects Programming
1

Hi, I am using an Arduino Uno. I tried to turn on the led when I pressed the button.
In my code, the button and the alarm were working fine, but the led is not turning on.

when I tried to turn on the led itself without the button and the alarm, it was working fine. So, I do not think led itself is a problem.

Can you help me find out why the led is not on? I attached my Arduino and the code below for the reference.
Thanks!

#include <SimpleTimer.h>
#define button 2
#define LED 13
#define alarm 8

SimpleTimer timer;
int pState = LOW;
boolean booked = false;

void setup(){
  pinMode(button, INPUT);
  pinMode(LED, OUTPUT);
  }

void loop(){
  int state=digitalRead(button);

  if(pState==LOW && state==HIGH){
    if(booked==false){
      booked= true;
      digitalWrite(LED,HIGH);
      timer.setTimeout(5000,beep);
      }
    }
  pState=state;
  timer.run();
  }

void beep(){
  booked=false;
  digitalWrite(LED,LOW);
  tone(alarm,1000,20);
  delay(100);
  tone(alarm, 1000, 20);
  delay(100);
  tone(alarm, 1000, 20);
  }

IMG_4614.jpg
IMG_4614.jpg4032×3024 564 KB

2

You need to use a pullup on the button pin:

pinMode(button, INPUT_PULLUP);

then connect to button to GND and check for LOW

Otherwise the state of the button pin is not defined and might just stick to HIGH or LOW.

3

Thanks for the reply, but the button is working fine with my original code. My problem is the led light that is not turning on. :frowning:

4

Image from Original Post so we don't have to download it. See this Simple Image Posting Guide

IMG_4614.jpg
IMG_4614.jpg4032×3024 564 KB

...R

5

Photos of the hardware don't give a reliable indication of connections. Please make a simple pencil drawing showing the connections and post a photo of the drawing.

I'm not familiar with the SimpleTimer library. I do all my timing with millis() as illustrated in Several Things at a Time.

Have a look at Using millis() for timing. A beginners guide if you need more explanation.

...R

6

yejincolor:
Thanks for the reply, but the button is working fine with my original code. My problem is the led light that is not turning on. :frowning:

What does the serial debug output tell you?

i.e. is...
a) the code doing the right thing, but the led just not illuminating
b) the debug output is also doing the wrong thing, so the led is consistent with what the code says it is doing (just not illuminating as you want it)

You seem to have a pull-down Resistor on your button? That is good, but It looks to me that the button is also connecting to ground when pressed? I could be wrong. This is why we need a circuit diagram.
Personally I would scrap the external resistor and use the internal pull-up. It is much easier and eliminates an external component.

7

This is the image of my circuit. My code does not have any error messages, but the led does not light on.

Screen Shot 2020-06-19 at 6.25.35 PM.png
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Screen Shot 2020-06-19 at 6.25.35 PM.png
Screen Shot 2020-06-19 at 6.25.35 PM.png2170×1416 417 KB

8

This not your real circuit. It is just a fritzing image. So it might be that there are still differencies between your real breadboard and the image.

Usually on these long breadboards the contactlines that run along the long outsides (horizontal in your picture) are divided in the middle. This means your connection to ground of the arduino (the black wire) ends in the middle.
The connection towards the LED trough the resistor has no connection to ground. That might be the reason why the LED does not light up.

In the fritzing diagram a 150 Ohm-resistor is used
For 5V this value is a bit low. The current will be (5V -1.8V) / 150 Ohm = 21 mA.

Arduino-IO-pins are rated for 20 mA. The LED will surely light up with 5 mA. Of course not with maximum brightness. But you will clearly see it.

5mA requieres a resistor of (5V -1.8V) / 0.005A = 640 Ohms.

From the real picture I cannot see the colors of the rings on the resistors. Do you have a digital multimeter
with which you can measure resistors?
If not: If you want to do more than serial-output to your computers screen = add some hardware a digital multimeter is a must. You will encounter dozens of situations where you have to check electrical things with a digital multimeter.
best regards Stefan

9

Thanks.

Pin #13 is also the onboard LED on most Arduino boards. Is the onboard LED working?

Can you answer the questions in my post #5 please?
What are you seeing on the serial debug window when you press the button?

This should be printing a 1 every time the button is pressed and the LED is turned on...

if(digitalRead(LED)==HIGH){Serial.print(digitalRead(LED));}

This should be printing a 0 every time the timer pops and the LED is turned off...

if(digitalRead(LED)==LOW){Serial.print(digitalRead(LED));}

We need to establish if it is the button that isn't working or the LED.

Edit: Stefan has a very good point about the break in the breadboard "busbar" lines.
This is as indicated by the break in the blue and red lines in the picture (post #3).

10

Thank you StefanL38 and pcbbc! My problem was solved!
I did not know the + and - horizontal line on my breadboard was divided into two!

11

Hi,

From the real picture I cannot see the colors of the rings on the resistors. Do you have a digital multimeter
with which you can measure resistors?
If not: If you want to do more than serial-output to your computers screen = add some hardware a digital multimeter is a must. You will encounter dozens of situations where you have to check electrical things with a digital multimeter.
I would recommend this one:

price $25. Of course there are cheaper ones but his one offers measuring of frequency, dutycycle, diodes and capacity

If the shipping-costs are not too high I would recommend this one
This has even a build in flashlight and bluetooth. So you can display the measurings on your smartphone. And you can use it as a slow-speed oscilloscope or long-term-datalogger.

best regards Stefan

12

yejincolor:
Thank you StefanL38 and pcbbc! My problem was solved!
I did not know the + and - horizontal line on my breadboard was divided into two!

Yes, I'm fairly the manufacturers started doing this a while back. I'm also fairly sure I never had this issue at school, but that was about 35 years ago...

I'm sure it's useful if you require different rails for different parts of your circuit.

But it's caught a few people out over the years, so no shame in it. Usually people just wire in jumpers to "bridge the gap". I've also seem people remove the back of the breadboard and permanently solder across to to bars. Would recommend removing the break in the lines with a Sharpie if doing that though, so you don't forget.

Edit: Again Stefan has excellent advice with regards to a meter.

Also it is worth pointing out that a meter cannot measure the difference between 0v and a floating pin. So if you want to test if a pin is 0v (and not floating) the way to do that is test from 5v to the pin. If the pin is indeed 0v you will see +/-5v on the meter, otherwise you will still see 0v if it is floating.