LED replacement

[Rajinder]

Hi,
I am looking for a secondary source for LEDs in a project. I am looking at the following specifications to make a comparison, have missed anything out?
Dimensions
Pitch
Colour
VF forward voltage
If forward current
Reverse current
Min and Max current
Lumens output in MC milli candela
Viewing angle
Operating temp
Storage temp
Life expectancy


Have I missed anything out? Would I test the output using a light meter?

Best regards,
Rajinder

 

[shrtrnd]

If you have the data sheet on the primary source LED, I'd use that for identifying a secondary source equivalent.
Do you have the data sheet on the LED you want to replace?

 

[Rajinder]

Hi,
I only have the printed sheets not in electronic format.
This is the information. The primary LED (used at the moment) has the following parameters:

Luminous Intensity(mcd) = 3500 (min) 4500 (max)
IF (forward current) = 30mA
VF (Forward Voltage) = Min (2.7V) Typ (3.0V) Max (3.6V)
Reverse Voltage = 5V
Reverse Current 10uA

We are using it at 20mA current rather than 30mA
It is powered from 5V, so Resistor calculation is 5- 3.0V/ 20mA = 100R, so we have a 120R in circuit

The secondary source LED i.e. the replacement has the following parameters

Luminous Intensity (mcd) = 5000 (min) 8500 (max)
IF (forward current) = 25mA
VF (Forward Voltage) = Min (2.6V) Typ (3.2V) Max (3.6V)
Reverse Voltage = 5V
Reverse Current IR = 5uA

So as before the resistor calculation is 5-3.2/20mA = 90R
However this has a greater Luminous Intensity (mcd) than the one that is used. Which I think means it is more brighter.
My question is that we need the same light output or comparable to the first LED. How can i achieve this?
I though with LED's, that the more current you suppky the brighter they are, so not sure of how to relate this to the Lumnious Intensity figure.

Ideally we need this to be a drop in replacement, the physical dimensions, the dominant wavelength are the same.
Any help would be appreciated.

I look forward to hearing from you.
Best regards,
Raj
PS If you need anymore information from the datasheet then please let me know.