LED doesn't light up

I am currently using Arduino Pro Mini and a 9 Degree sensor stick, SEN-10321.

I came up with an Arduino Shield myself so that I could connect Receiver to my Arduino and to my sensor easily. I have placed two LEDs, with green LED connected to Pin 12 indicating its power, and a red LED to pin 13 so my internal LED would also display it on the red LED.

Instead of seeing the two LED lighting up, only my green lighted. I have checked the connectivity in between and it is connected. I have also grounded them together but it is still not lighting up.

Help needed, please help!

Could you be a little more forthcoming, and post some details that would help us help you?

How you have tried to light the LED would seem to be a basic part of this question.


So sorry I wasn’t clear enough. I am currently working on a Quadcopter Project and I am supposed to be using Ardiono Pro Mini 3.3V with the sensor, SEN-10724. I have to come up with a shield where I can place the Arduino, Sensor, any resistors or LEDs on the board.

I have attached images of my Arduino Planning of how I intend to connect receiver to my Arduino then to my Electronic Speed Control and my Arduino Shield.

I have two LEDs built in. The one connected to Pin 12 indicates if there is power and the one connected to Pin 13 will flash the internal LED on the Arduino on the LED itself. I was expected two LEDs to light up after I’ve uploaded the Arduino Programme in it but instead the LED connected to Pin 13 did not light up.

Could it be due to the two resistors connected to VCC? The reason I’d place the two resistors there because input voltage is 5V and this sensor can only take in 3.3V.

The program would be helpful.


This is the one I’d uploaded on my Arduino

MultiWii_2_1.ino (34.4 KB)

Where's the ten line sketch you wrote to test the LEDs?

Connect your Arduino to the LED in this way:
Pin 13 ----LED ---> Resistor----GND

Try the Blink Example: File>Examples>01.Basics>Blink

See if this works first.

I tried the blink example as well but it just doesn't light up

You may have a damaged pin/LED. Have you tried any/all of the other digital pins using that LED?

Yup I did and it lighted up. I used a multimeter to check if there was connectivity and there is. So does it mean that the pin may still be damaged even if there is connectivity in between them?

If your multimeter has a diode function, try checking the LED with that by touching the meter positive to the anode, negative to cathode. If it lights up, the problem is something else.

It did light up. So I guess it could probably means that my pin is damage right?

I guess it could probably means that my pin is damage right?

Easy enough to check the voltage of the pin with your meter when it's high or low with a digitalWrite().

Perhaps you connected the LED backwards.