LED is dim on digital output

Other Hardware LEDs and Multiplexing
1

Hi

My board is a DccEle - DCcduino Mega 2560

When i test my LED's on the assigned +5V, the LED's light up very brightly and receive +5V.
When i tested my LED on a digital output pin that was assigned the value of output, it only lights up the LED very dimly even with no resistors. When testing with a multimeter, the pin only gave out +2.5V ish.

I purchased a clone board as the board will be permanently encased in my product design product so I so no reason to purchase the official version.

Thanks in advance :slight_smile:

2

even with no resistors

Never do this.

Show us your wiring, a schematic, and your sketch.

3

Sorry (newbie)!

Wiring:
Standard led: + = pin 30

  • = Gnd

Sketch:

void setup() {
pinMode(13, OUTPUT);
}

void loop() {
digitalWrite(13, HIGH);
}

4

I don't have a 2560, but:

Why are you use pin 30 when the code is for 13?
Use a 220 ohm resistor with the LED

D13-----Anode of LED------cathode of LED----220 resistor----GND

Then try:
digitalWrite(13, HIGH);
delay(500);
digitalWrite(13, LOW);
delay(500);

5

See this for LED information:

1 Like
6

Thanks for the help.

Possible stupid question :Don't LEDs reduce the current, so would a 220ohm resistor cause there to be less current and therefore less brightness?

7

Possible stupid question

Yep.

Current is the same in all parts of a serial circuit. It is the resistor that controls the current flowing through the LED. Miss out the resistor and you blow something up or at least damage it.
See
http://www.thebox.myzen.co.uk/Tutorial/LEDs.html

8

I tried the LED with no resistor using the digital output and it was still only dimly lit, so I don't know how to make it brighter :confused:

9

Use a resistor!
Are you connected to D13?

If you are indeed physically connected to the right pin, looks like you may have damaged the output.
What happens if you use D12 etc. ?

10

I have tried using a resistor on a different output and i still experience the same problem. The problem is not the led nor the board being at it's max current. So does this mean that the board is the problem?

Is there a way to externally power the LEDs but still control them using the Arduino?

11

I have tried using a resistor on a different output and i still experience the same problem.

Then you are doing something else wrong that you are unable to tell us about, probably because you don't realise it . It is very unlikely it is the whole board.

Get your meter and measure the output voltage of the pin when it is high and not connected to anything and when it is connected to the LED and resistor to ground.

If you haven't got a meter then get one, a cheap one is less that $10. If you don't want to get a meter then change hobbies.

12

Grumpy_Mike:
Then you are doing something else wrong that you are unable to tell us about, probably because you don't realise it . It is very unlikely it is the whole board.

Get your meter and measure the output voltage of the pin when it is high and not connected to anything and when it is connected to the LED and resistor to ground.

If you haven't got a meter then get one, a cheap one is less that $10. If you don't want to get a meter then change hobbies.

lol'd

:grinning:

13

When testing with a multimeter the pin only gives out 2.5V (with nothing connected to the board except the power supply and the USB).
The circuit is simply one led leg in the digital pin and the other in ground.
I know that the max current is not being reached as when i connect the led to +5V, it is bright.
As mentioned earlier "My board is a DccEle - DCcduino Mega 2560" so could this be the cause of the problem?

14

When testing with a multimeter the pin only gives out 2.5V (with nothing connected to the board except the power supply and the USB).

So in that state do you see 5V at the 5V pin? And have you set the pins you are testing to be outputs?

My board is a DccEle - DCcduino Mega 2560" so could this be the cause of the problem

My understanding is that it is a low quality Russian clone, but it is likely that the processor chip is the same.

The circuit is simply one led leg in the digital pin and the other in ground.

You have been told about that before. Do not do it.
If you continue to ignore our advice you will be ignored in turn.

15

Sorry, I had put resistors, but i forgot to mention it :confused:

Using my multimeter, I tested the 5V pin and it was 5V

I think the writing on the processors says (it's difficult to read):
ATMEGA2560
16AU 1434

16

Well if the 5V is stable then it is looking like a poor qualtiy processor., maybe from the reject bin.