Low voltage 0.2V

Other Hardware LEDs and Multiplexing
1

Hi guys i have progressed with my project and its time to ADD SOME LED's, after wiring some up i noticed they were not working so i just uploaded the basic blink project and the LED's were not lighten up.

But then i noticed that they were lit but very very dim, i then used a voltmeter over the pins and the out put is about 0.2V or lower.

Any idea why this would be?

2

Hi, is that 0.2V with the LED connected or just the bare Arduino pin?

How is the led connected, what series resistor used and are they connected to ground or 5V?

Have you used the blink sketch completely unaltered?

If the 0.2V is the bare Arduno pin with nothing else connected, it could be damaged.

Paul

3

Classic mistake is that you forget to set the pins to be outputs in the setup function.

4

Grumpy_Mike:
Classic mistake is that you forget to set the pins to be outputs in the setup function.

Yeah, but if blink sketch has been used unaltered that can't be the problem.

5

Thanks for the reply guys, the code i'm using is.

#define LED  13
void setup()
{
    pinMode(LED, OUTPUT);
}
void loop()
{
    digitalWrite(LED, HIGH);
    delay(3000);
    digitalWrite(LED, LOW);
    delay(3000);
}

I have the ground from the UNO to the ground on the breadboard, then a jumper from the i/o pin to the breadboard then to the resistor, then the led from the resistor to the ground.

6

LOL, i had may volt meter set on AC.

I now have it on DC but voltage is only 1.8 volts.

7

I now have it on DC but voltage is only 1.8 volts.

Let me do some mind reading:-

  1. The LEDs are red.

  2. You have no current limiting resistors in series with the LEDs

8

Grumpy_Mike:
Let me do some mind reading:-

  1. The LEDs are red.

  2. You have no current limiting resistors in series with the LEDs

I hoped you were going to have the answer but unfortunately wrong on both assumptions.
The LED’s I have tried red and green, I do have a series resistor – but I’m measuring the voltage straight from the ground and the pin output.

9

but I'm measuring the voltage straight from the ground and the pin output.

Without any load?

In which case is the on board LED flashing?

10

Yes without load, and yes the on board led is blinking.

11

OK so it is looking like your board is screwed.

Just try changing the #define LED 13 to another few pins and try that. Avoid pins 0 & 1 but the other should be fine. Note if this is a Uno then you can also use the analog pins using pin number 14 for analog 0, 15 for analog 1 and so on.

12

So, you have a DVM, you are reading 0v and 1.8 volts on a o/p pin and your DVM is set to DC voltage.
What voltage do you get when measure at the 5 volt pin?

13

LarryD:
So, you have a DVM, you are reading 0v and 1.8 volts on a o/p pin and your DVM is set to DC voltage.
What voltage do you get when measure at the 5 volt pin?

All above correct, i get 4.94v on the 5v pin and 3.3v on the 3.3v pin

14

Try another pin other than the one you are using, if it's 1.8, like Mike says screwed.

15

LarryD:
Try another pin other than the one you are using, if it's 1.8, like Mike says screwed.

Yip, i think it's capoot - i tried another board, everything else the same and it worked on the other board.

16

Can't see where you have specified what resistor you are using and I can't see the perfectly focused photo of your setup. Hmmm. OK, another board (what sort are they?) worked. Why do you refer to LEDs as plural?

Given you had the voltmeter on AC, I must be suspicious that was not the only problem.

Pin 13 has a LED on it anyway - is that flashing?