# 8*8 blue dot matrix led display's specifications

1. Aug 8, 2017

### judy_tab

Hey,

I want to ask you about the array led component: 1.9mm(0.8’’)8*8 blue dot matrix led displays

(model no:KWM-20882XBA).

I saw the technical data sheet but I couldn’t find the specifications related to the radiant intensity with its coefficients that should be included in technical sheet related to it.

In fact, the coefficients I want to know about them are g1(i),g2(i),g3(i),g4(i) in the intensity formula:

I(teta(i),phi(i))=g1(i)*exp(-(log2(2))*((abs(teta(i))-g2(i)).^2)*((((cos(phi(i))).^2)/(g3(i))^2)+(((sin(phi(i))).^2)/(g4(i))^2)))

(where i is the led index in the matrix)

I’m in hurry and I really want to know these coefficient to use it.

Thanks

http://planck.reduaz.mx/~imoreno/Publicaciones/OptExpress2008.pdf.

Last edited by a moderator: Aug 8, 2017
2. Aug 8, 2017

### Staff: Mentor

Welcome to the PF, Judy.

I don't think I've seen that kind of spatial distribution information for LEDs in the past on their datasheets. Can you post a link of an LED datasheet that does include those coefficients?

You may just need to end up measuring the distribution of that module if it's important in your application. Do you have the equipment in your lab to do that kind of measurement?

3. Aug 8, 2017

### judy_tab

Actually I haven't found a datasheet that includes these total informations, however I found some that includes the intensity vs radiation angle.

This is a simple exemple of a datasheet that includes only the radiation pattern(intensity vs radiation angle):
http://www.mouser.com/ds/2/678/V02-0133EN0-908697.pdf

and if the radiation pattern is available, do you have any idea if we can get those parameters(g1i,g2i,g3i,g4i) like in the link pdf that I have attached before?

But, from this statement in the link I have attached and from the pictures posted at the end of the pdf link, I though there are informations about those specifications which must be provided by the manufacturer.

The statement is:
""Most manufacturers use θ1/2 (the view angle when radiant intensity is half of the value at 0°) to characterize the angular distribution of LEDs with a single intensity peak. This parameter is simply g31 if Eq. (1) has only one simple Gaussian, e.g. I(θ)=g11exp[-ln2(θ/g31) 2 ]; and this is related to c31 (i.e., c31=−ln2/ln(cosθ1/2)) if Eq. (2) has only one simple cosine power, e.g. I(θ)=c11[cos(θ)]c31 . Another attribute used is the total included angle, or θ90, which describes the cone angle within which 90% of the total flux is radiated. However, additional parameters are needed to render the shape of the radiation pattern. Therefore, we propose that the manufacturer should include a simple formula (like those reported here) with its coefficients in their technical data sheets.""

Unfortunately, I don't have the ability in equipment to do such measurement.
I also contact the manufacturer ADAFRUIT responsible of this led array component but they didn't answer yet.

Can you help me?

4. Aug 9, 2017

### Staff: Mentor

So it sounds like the paper is just proposing that datasheets include more of this type of information. I'm guessing you will just have to measure it for now.

What is the reason you need this information? Is it important for some reason in your design that includes this display?

5. Aug 9, 2017

### judy_tab

Actually, I want to optimize the light-emitted from this led array on a target image.
So, the algorithm that I work with includes calculating the appropriate intensity of the leds which includes these parameters.