Hi
Sorry to break in on this, but being the dimwit that I am I see that some say put the resistor in the negative side , so is this only when you run the LED's in series? (never could understand parallel and series even at school)
If you are only running one LED would you have to put it in the positive side?
Again sorry for putting in on this
Fred
It does not matter which, as long as it is there. If you felt the urge, you could have one each side, as long as the values add up to the needed value. The current starts from the positive pole of the battery, goes through the resistor, then the LED, whatever is doing the switching, and completes by getting to the neg pole. The resistor, LED and switching device can be in any order given that the switching device might need to be at one end or the other of the circuit.
Series means you go through each component in the chain (or series) one after the other. Parallel means that you go through all of them at the same time.
If for example I take one of the blue ones and put for example 5v in to the +leg then I attach my multimeter to the other leg and the ground from the battery the meter displays 2.5v am I correct in that this is the forward voltage of the led.
No.
From the description, your meter is acting as the resistor, and is displaying the voltage across itself at a very low current because voltage meters are generally very high resistance. Because 2.5 volts is coincidentally half of 5 volts, the voltage shown happens to be, at that very low current, the same as the volts across the LED. The way to test is to hook up the LED and the resistor, check that the LED is glowing as expected, then connect the voltmeter ACROSS the LED to read the actual voltage.