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Author Topic: Burned an 8x8 dot matrix  (Read 2117 times)
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Hello,

I bought an 8x8 LED Matrix from eBay. I don't have the schematic so I used the diode testing functionality of my voltmeter. Once I saw how the connection were working, I tried to light one of them with the Arduino Uno.

I connected of the pin (+) of the matrix to a resistor (220 Ohm) and then to the 3.3V output of the Arduino, and the other pin (-) to the GND pin of the Arduino. It burned the LED.

I then tried something else: I connected another pin (+) to a 27K resistor and another pin (-) also to a 27K resistor and then to the GND. It nonetheless burned the second LED.

So before I destroy all the matrix, could somebody tell me what's i'm doing wrong?
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Sounds like you need a datasheet for that part.
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+3.3 --- 220 Ohm --- (+)LED(-) --- GND

That should put AT MOST 15 mA (3.3/220) through that LED.  I'm surprised that burned it out.

+3.3 --- 27000 Ohm --- (+)LED(-) ---  27000 Ohm --- GND

That should put AT MOST 0.06 mA (3.3/54000) through the LED.  I'm surprised that would light the LED, let alone burn it out.
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Quote
So before I destroy all the matrix, could somebody tell me what's i'm doing wrong?
Basically no, because what you are doing sounds sort of OK.
The bit that is not is that 3V3 from the arduino is limited to 50mA on many models of arduino.

So you are either not doing what you think you are doing, doing something else you are not telling us or have a very low current capable matrix.

I did get some RGB LEDs from ebay and I found that about three of the batch of 50 burnt out with only a few mA going through them. I also found that the red was rather dim on all but one of the LEDs. I think that some LEDs you get on ebay are actually from the reject bin.
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I did get some RGB LEDs from ebay and I found that about three of the batch of 50 burnt out with only a few mA going through them. I also found that the red was rather dim on all but one of the LEDs. I think that some LEDs you get on ebay are actually from the reject bin.

Sure...but two 27K resistors? Nothing you could possibly do to a LED with 5V and a 27K resistor should kill it.

I'm going with your "not doing what you think you are doing" theory.

For starters: How does he know the LEDs are dead?

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I know I burned the LEDs because when I tested after with the diode testing feature of the voltmeter, they didn't work anymore ; also with the 3.3V voltage they didn't work anymore.

Strangely enough, one of them worked, while the others burned out.

The LED in the LED matrix don't look light normal LED, they look like "flat LEDs". Is it normal or is it the sign of "low voltage matrix", what current should I put through the LED then and how can I know if the matrix is of this type?
« Last Edit: November 12, 2012, 03:07:22 am by 8rmfyj5U3Qk » Logged

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Isn't there a part number you can share?
Some marking on the side of the chip, or on the bottom on the "artwork" for lack of a better name?
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Ok looking at the facture gives me the exact product: Rot 5mm 6*6cm "Display 2088AB-6 JC-H3 64"
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It might help if you told us what you bought - a link to the ebay page?

'Low voltage' or not, LEDs don't vary enough for what you're saying to make any sense.
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It's this product: http://www.ebay.de/itm/320979627939?nma=true&si=weX7sq8%2B4qZaLduHlMc4ggbduGI%3D&rt=nc&_trksid=p4340.l2557&orig_cvip=true

Sorry for not having providing this information before!
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Did the LED light up at all when you 'killed' it? Just for a second?

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"Artikeleln are new and unused and will be delivered and invoiced. The individual LED lights are very sensitive and even at 1.5 volts. Total area of ​​120x120cm and 256 LED!

Each module has the following specifications:
Color: Red
Style: 8 x 8 (64 LED)
Voltage: 1.5 - 2.3 V / LED
Power: about 10 - 20 mA / LED
LED diameter 5 mm
Product Number: 2088AB-6 JC H3
Dimensions: 60 x 60 x 6 mm"

I'm not finding anything with that part number.
You should be able to safely use a 5V supply and a 1K resistor and be able to figure out the pinout for this part.
(5-1.5)/1000 = 3.5mA
That shouldn't damage anything no matter what 2 pins you test to.
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> Did the LED light up at all when you 'killed' it? Just for a second?

Yes, just very brightly for a semi-second and then just a mini point of the LED and then nothings.

I'll retry with a 1K resistor and keep you informed but basically that's what I did with the 27K so I'm a bit confused.
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It's a perfectly standard LED display, the only mystery is whether it's common anode or common cathode. I think the problem is in your diagnosis of 'burned'.

Get a 5V supply and a 1K resistor.

Connect a pin to 5V with the resistor and try connecting pins on the opposite side of the matrix to ground.

If nothing lights up, turn the matrix around and repeat.

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I'll retry with a 1K resistor and keep you informed but basically that's what I did with the 27K so I'm a bit confused.

An LED only has two legs so there's only two ways to connect it - forwards or backwards.

Neither way would do what you describe with Arduino voltages and a resistor (220 or 27k).
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