Is this LED Matrix damaged ?

[afesheir]

Dear Everybody ..
I've bought 10 pieces of 8*8 Led matrix (Part Number: gnm-23881AS). When I tried to test them (trying to light up each led of the 64) by applying 5V on column and 0 on the row, I have been depressed as some leds lighted up and some didn't light. So, I returned to the shop from where I bought them and got new other 6 pieces. When testing them, I've got the same problem. So, It's hard for me to think that 16 pieces are damaged (and it is also hard to persuase the shop of that to get money back ).

Do anybody suggest other connection diagram or other stuff or you think that REALLY 16 pieces are DAMAGED and have to be returned to the shop ???

This link may be useful: GNM-23881 (- )
Regards

 

[alexan_e]

The leds have to be used with a resistor in series to limit the currant or they can be damaged.
Your link says that these are 1.8v Vf leds so when you apply 5v to them you will have problems, you have to use a resistor about 220-270ohm, this will limit the current to about 10-15mA.
To calculate the resistor for a given power supply you use R= (Vpsu-Vf)/I
Vpsu is the power supply voltage, Vf if the led forward voltage drop (1.8v in your case) and I is the current in Amperes (for example 0.01 for 10mA)

Alex

 

[afesheir]

I've already attached a resistor. Note that some leds light up and some don't.
The surprising stuff is that the link above states 1.8 Vf. This link: **broken link removed** states 10-20 Vf. !!!!!!!!!!

 

[alexan_e]

Did you use a resistor from the start or just now because If the leds are damaged there is no way to make them work again.
Did you see them light the first time because I don't think they burn instantly , I think they turn on very strong and then they change the color because they overheat and then burn.

Alex

 

[afesheir]

No not just now. I know that a resistor must be added from the start

 

[alexan_e]

Did you connect each row and column combination?
like 1-1, 1-2, 1-3....2-1, 2-2, 2-3.....3-1, 3-2, 3-3....

Alex

---------- Post added at 17:40 ---------- Previous post was at 17:34 ----------

Also check if you connect the correct pins because the row and column pin numbers are mixed, they are not in order 1,2,3,4...

Alex

 

[dayanpad]

Dear This is impossible.
I just checked my 8*8 led matrix, supplying power using Nokia phone chager
all LED light up same bright, way I applied power
visit near your seller with power supply and check near seller

 

[afesheir]

Pins are not in order ?? OK, I'll check this and back to you again. Thanks Alex

 

[alexan_e]

The pin numbers are shown in your link

Rows(1,2,3,4,5,6,7) = pins 9, 14 ,8 ,12 ,1, 7, 2, 5
columns(1,2,3,4,5,6,7) = pins 13, 3, 4, 10, 6 ,11 ,15 ,16

Edit: now they are correct

Alex

 

[afesheir]

Nice note, I'll check this combination

 

[alexan_e]

I have edited my post two times , now it is finally correct but you can use the pin numbers directly from the picture, the circled numbers show the pin number

GNM-23881Ax

Alex

 

[afesheir]

It seems that this was my problem. I've tested some leds and they follow the expected sequence. Thanks alot Alex

---------- Post added at 17:18 ---------- Previous post was at 16:18 ----------

Done Successfully, 64 LED are all OK. Thanks Alex