I have made a circuit on a breadboard that powers to LEDs from the same pin(pin 3), only 1 lights up and its always the last one in the circuit.
Why does it happen and can I light both from the same pin?
LEDs should not be placed in parallel with each other.
Each LED ‘must’ have a series dropping resistor of its own, try 220Ω.
Continuing to ‘not’ using a resistor well result in Arduino damage.
Thanks I will try, but why does it not split but it goes directly to the last LED in the circuit?
Can't tell with no component details but my guess is that the two LEDs have different specifications, perhaps they're different colours. If you had a resistor each it might have done something.
Steve
Connecting electronic components improperly will damage your Arduino.
I repeat:
LEDs should not be placed in parallel with each other.
Each LED 'must' have a series dropping resistor of its own, try 220Ω.
Continuing to 'not' using a resistor well result in Arduino damage.
i5-4670k:
but why does it not split but it goes directly to the last LED in the circuit?
Because each LED has a specific colour, the colour and to a lesser extent the internal construction of the LED both affect the forward voltage drop. With no resistor or only one, then the LED with the lowest forward voltage drop takes all the current and the other LED has not got enough voltage to even light. As you photograph shows you have two different colours that is why only one LED is turning on.
If you had two identical colours then maybe you would get two on at once but they would be unlikely to have the same brightness.
Note that the LEDs are wired in parallel so there is NO last LED in the circuit. It is only last because that is the way you have physically wired them. From the electrical point of view this physical arrangement in entirely irrelevant. Swap them over and see.
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One of the LEDs may be 'backwards in which case it won't light up.
I once received a batch of LEDs from Lafayette Radio (which would pin down my age without looking at the avatar photo) where the flat part was on the side rather than on the cathode end. I would put a pair of them in a breadboard, in parallel but reversed from one another, and then remove the one that didn't light up.
Don
i5-4670k:
but why does it not split but it goes directly to the last LED in the circuit?
Assuming both LEDs are oriented the same way, the one with the lower forward voltage will hog current.