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There are too many different LEDs on those lists. Here is a 3mm bargain pack of 100 LEDs from TX how is a person suppose to know what they are? So if they are same voltage & current as 5mm they are just as bright. Looks like I need a 2D batteries and a resistor.
It depends.
I have found most 3mm LEDs have max 10 to 20mA current rating and 5mm typically have 25 to 30mA rating. The voltage is a function of the band-gap (chemistry and doping) and therefore independent of diameter.
Other people may have dealt with different 3 and 5mm LEDs so they will have different answers. There are about 3000 3 and 5mm LEDs at my distributor. I'll let you look them up.
Now that I've written all of that, are you willing to tell us why you want to know?
When you buy a bag full of very cheap Chinese LEDs they make them appear bright by focussing the light beam into a narrow angle that you can barely see to one side.
The Kingbright LEDs linked have a very wide angle but seem to be very dim. Luxeon Lumileds and Cree are very bright and have a wide angle.
Two AA alkaline cells will light a red, yellow or old green LED for a long time. But their 3V drops to 2V then a blue, modern green or white LED will not work since they need about 3.3V.
It depends.
I have found most 3mm LEDs have max 10 to 20mA current rating and 5mm typically have 25 to 30mA rating. The voltage is a function of the band-gap (chemistry and doping) and therefore independent of diameter.
Other people may have dealt with different 3 and 5mm LEDs so they will have different answers. There are about 3000 3 and 5mm LEDs at my distributor. I'll let you look them up.
Now that I've written all of that, are you willing to tell us why you want to know?
The 18 LED security lights that I built wires rusted out in the weather with no protection it is easier to start over build new LED flashers with LDR on the same PC board. I ordered new LEDs but did not notice they are 3mm until they came in the mail. Cross sectional area of 3mm is 64% smaller than 5mm that alone makes them harder to see in the dark. I think I will build a circuit with 3mm LED just to see if I can see it in the dark 200 ft away.
If the LEDs are fairly directional (narrow beam) then the diameter of the housing won't make much difference to the light output, so 3mm and 5mm should look much the same at a distance. If the bargain LEDs happened to be out-of-spec manufacturing rejects then there could be brightness variations within the batch.
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