Go Down

Topic: Blink Program. External LED not working (Read 248 times) previous topic - next topic


Oct 22, 2019, 06:36 am Last Edit: Oct 22, 2019, 06:58 am by ballscrewbob

Falling at the first hurdle question.  So apologies in advance.  This is likely a question you get all the time.
I've searched the forums, and have not found the solution to this problem.

I can't get the external LED to flash.
I'm using a DUINOTECH kit from Jaycar (Australia).  It has supplied all the parts, for Ardiuno UNO, Breadboard, Wiring, LEDs, and resistors.   So it's my assumption the resistors are the correct ones.

The onboard LED is flashing, I'm able to vary the delays in the sketch, to which the LED flash cycle responds appropriately.  

I've tried adjusting the sketch to a different port, and re-wiring appropriately, with no effect
I've tried wiring directly to the 5v port, with no effect.  
I've tried using different GND ports, with no effect.

It's like there's no power to the ports.  Or I'm making an obvious newbie error.

I don't have a multimeter to test directly in the ports, this might be my next purchase.

Thanks in advance

Here's my sketch

void setup()          // Runs once when sketch starts

 pinMode(13, OUTPUT);        // Setting the LED pin as an output

void loop()         // Runs repeatedly
 digitalWrite(13, HIGH);     // Turning the LED on
 delay(1000);                    // Waiting 1 second
 digitalWrite(13, LOW);          // Turning the LED off
 delay(1000);                  // Waiting 1 second



PS.  I'm using a MAC.  I'm usually windows guy, but I'm using my wife's MAC laptop



is the LED connected the right way around? It's a diode so will only work one way.

It's difficult to judge from your photo but counting the empty port 'holes' it looks like your wire is plugged in into port 12 rather than port 13.



Hi Peter,
thanks for your response.

 reconfigured to double-check

1.  I counted out from port 8,9,10 etc up to 13 and made sure the jumper was plugged in there.
I also tried one on each side just .. because I'm starting to doubt my vision and counting.

2.  I tried the LED in both orientations.   I also researched LED polarity.
I'm assuming connecting a LED backwards just results in no action, and it doesn't actually damage the LED

3.  I also tried re-programming the pin number in the sketch to 8, and connected there.  With both orientations of the LED again. And Pin 7. 
4.  I also tried connecting to different GND pins for the negative, and direct to the 5v pin for the positive.  I've also tried different configurations of the breadboard, and jiggling the connectors.

All yielding the same non-flashing led result.

I'm unclear if I am making a basic mistake, or if the board is broken (the chip is clearly working), I still have the receipt for the kit, but if I get another, I'd hate for it also to not work because I'm doing something wrong.

Right now I'm out of ideas and going to sleep on it.
I'll also try in a different computer with a clear head tomorrow.



Oct 22, 2019, 03:17 pm Last Edit: Oct 22, 2019, 03:19 pm by sterretje
Not 100% sure if you tried.

Connect the led/resistor to the GND and 5V of the Arduino. Does it light up?

Which value resistor did you use?
If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.


Also try another LED, they can be bad from the factory, or might be damaged from previous use.


Thanks for your advice.

Yep, tried a new LED and resistor amongst the sets of tests I performed earlier.  Just didn't include it in my write-up. 

I kinda tried to connect the LED and resistor to the 5v/GND circuit, but I'm not convinced I did a good job.  I'll try again when I get a chance

The resistors are 470K. 
They came with the starter kit, so I assumed they were the correct ones.

I'm at work now, I might get a chance to test this in my lunch break.



Oct 23, 2019, 01:30 am Last Edit: Oct 23, 2019, 01:33 am by ballscrewbob
It may be that the resistor value is too high.

Most of the common Arduino circuits use 10K or more frequently less than that.

Some of the value can change depending on the LED specifications.


It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.


That's interesting, and would explain the problem in a consistent manner.  I'll need to head out to buy some more resistors and LEDs, which will likely be on the weekend.

I'll get a multimeter too.

Thanks for your advice


Oct 23, 2019, 05:17 am Last Edit: Oct 23, 2019, 05:20 am by Iansymonds
Hey  Thanks! 
I think you've helped me identify the problem.

This page also helped identify the problem


It's telling me I need (amongst other things) a 470-ohm resistor.

In the beginner kit they have given me, there are 470K ohm resistors.  The K is kinda important.

Imagine having 1000 times the resistance I need.  No wonder.

I have since run the petentiometer test and the fan controller test, both with success, so I can assume the board is working and I am NOT going insane.

I haven't yet purchased more realistic resistors, but do hold confidence in the outcome.

Sheesh, makes it hard when you buy a beginner kit with the WRONG PARTS!.  But then you always learn more from fixing things that don't work rather than following instructions by rote.

Thanks for your help, and I will post back the results of my flashing light test and an operating traffic light.

I feel a 1-star review coming on.


Starter kits should contain the resistors required for the leds. Their value will be below 1k (e.g. 220 Ohm); check your kit ;)
If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.


I feel a 1-star review coming on.
Why even that many? For an electronics supplier to list components like this:

1 x Duinotech UNO Arduino-Compatible Board
1 x USB Cable
1 x Breadboard
5 x 5mm Red LED
5 x 5mm Yellow LED
5 x 5mm Green LED
4 x Tactile Switches
1 x Buzzer Module
1 x 16mm Potentiometer
10 x Resistors
1 x DC Motor with Fan
1 x Pack of Jumper Leads
... is pathetic. No electrical details at all.

(As if the physical dimensions of the pot are more important than its resistance and that it's linear or log, for example?)


I was going to post wordlessly in here, but they need words. 
I have now re-learned how to read resistor bands.

I agree, the packaging is pretty crap and leaves a lot to be desired.

I've sent a complaint to Jaycar and also thanked them for making me work it out for myself.

Go Up