DigitalWrite example

Projects Programming
1

Hi All,

I tried the digitalwrite example

It says that I should see either 3.3V or 5V but instead I am seeing 500mV on an Arduino Uno. Any ideas where I have gone wrong?

int ledPin = 13; // LED connected to digital pin 13

void setup()
{
pinMode(ledPin, OUTPUT); // sets the digital pin as output
}

void loop()
{
digitalWrite(ledPin, HIGH); // sets the LED on
delay(1000); // waits for a second
digitalWrite(ledPin, LOW); // sets the LED off
delay(1000); // waits for a second
}

thanks, Sean

2

You should see either 0V or 5V (or if its a 3.3V board, 0V or 3.3V).

Most multimeters cannot react fast enough, change the delays to 5000.

3

You should see the pin 13 led blink. It should be bright even through the on-board resistor. Voltage you measure will be affected by that circuit.

4

Voltage you measure will be affected by that circuit.

With Uno Rev 3, D13 is buffered before driving the LED - so D13 output should be close to 0/5V.

5

Hii !

I got exactly the same problem : I made a very simple circuit with a buzzer, a 100ohms resistor and my Arduino Uno connected by USB to my laptop.

I tried first to use the tone() function, a really low sound was produced by the buzzer (almost impossible to ear). I analised the signal and i get a 500mv voltage. So i tried to send a digitalWrite(pin_buzzer,high) to the buzzer, still have a 500mv voltage. What goes wrong ?

void setup() {

pinMode(8, OUTPUT);
}

void loop() {

digitalWrite(8, HIGH);
delay(3000);
digitalWrite(8, LOW);
delay(1000);
}

Thank you.

6

nardinou:
Hii !

I got exactly the same problem : I made a very simple circuit with a buzzer, a 100ohms resistor and my Arduino Uno connected by USB to my laptop.

I tried first to use the tone() function, a really low sound was produced by the buzzer (almost impossible to ear). I analised the signal and i get a 500mv voltage. So i tried to send a digitalWrite(pin_buzzer,high) to the buzzer, still have a 500mv voltage. What goes wrong ?

void setup() {

pinMode(8, OUTPUT);
}

void loop() {

digitalWrite(8, HIGH);
delay(3000);
digitalWrite(8, LOW);
delay(1000);
}

Thank you.

What buzzer are you using? Try measuring the voltage at the pin with the buzzer removed/disconnected.

You can only get so much current out of a port pin If you ask for too much, the voltage at the pin will drop. This is why things like current-limiting resistors are needed for LEDs -- not only to protect the LED but in cases where you're drving it right from a port pin to "protect" the pin too.

If you find the buzzer is drawing too much current and causing the pin voltage to sag, you need to use a different method to drive the buzzer, such as putting a transistor between the port pin and the buzzer.