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Topic: 8x8 LED matrix usage? (Read 1 time) previous topic - next topic

Rob3rt

The datasheet for it...
http://www.noodlehed.com/ebay/datasheets/GTM2088ARGB-21.pdf

I had ordered some arduino stuff like a month ago (for playing around). the last thing to arrive was the matrix. Somehow I missed the parameters and imagined it will be tiny... while now it's as wide as whole breadboard.

Any suggestions how to use it until another breadboard arrives (will take around a month, I can't wait!)? The problem is it simply doesn't fit on the breadboard (830pin, 2 lines, has + and - each (these are on the sides) and the main part of 64x5+64x5 pins... I thought of having one end just plugged into arduino's (mine is mega2560 r3) digital pins, but the problem is that there only 8 anodes and 24 cathodes (one line of pins - cathodes only, one - anodes only. And if I plugged the anodes+cathodes one into digital pins, I could put resistors ONLY on the other line, (the output of arduino digital (V) is too high), so lot of leds wouldn't work.

Isn't it possible somehow to adjust the voltage from digital out so it gives lower? Also, a stupid question, what about the current? does the board just take what it needs or what? Any help will be appreciated!!
Thanks in advance!

fungus

Can't you just solder some wires to the pins of the matrix?
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Rob3rt

No, because I'm modelling everything without soldering (solderless breadboard, wires for it)   :(

I don't even have a soldering-iron (I had two, both fried somehow)

AlxDroidDev

Your best bet is to get a driver to interface with the LED Matrix. One excellent option - and the one I use -  is the MAX7219 (get the MAX7219CNG+, which comes in a PDIP package).  You can daisy-chain up to 10 MAX7219. The MAX7221 also works.

Both chips use only 3 pins in the Arduino and there are several libraries written for them (they are a basic SPI device).

Another option is to use 2  x 74HC595: one to drive the anodes and another to drive the cathodes.

Keep in mind that the pinouts for these LED matrices are crazy: nothing is what it seems. Don't assume they are in a certain order or that the anodes is one row and cathodes are another row. They are totally random and you have to map them beforehand, in order to plug them correctly to the driver.
Learn to live: Live to learn.
Showing off my work: http://arduino.cc/forum/index.php/topic,126197.0.html

CrossRoads

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

fungus


I don't even have a soldering-iron (I had two, both fried somehow)


:smiley-eek:

Maybe a new soldering iron would have been better than a big breadboard...
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Rob3rt

The reason I don't want to solder is that I screw it up (idk, maybe I was doing it wrong) and I can't reuse the parts. Thanks crossroads, but the problem that the space between matrix pin lines is as wide as the whole breadboard. I guess I'll just wait for my breadboard... What about power? I know, it's a stupid basic question, but anyway; does a led/matrix/buzzer/any device connected to arduino take whatever current it needs or what?

AlxDroidDev


The reason I don't want to solder is that I screw it up (idk, maybe I was doing it wrong) and I can't reuse the parts. Thanks crossroads, but the problem that the space between matrix pin lines is as wide as the whole breadboard. I guess I'll just wait for my breadboard... What about power? I know, it's a stupid basic question, but anyway; does a led/matrix/buzzer/any device connected to arduino take whatever current it needs or what?


A LED matrix usually needs a lot more current than the Arduino can provide.

For example: depending on the color, a LED can take from 20mA to 40mA. Lets average that to 30mA.

If you decide to light up all the leds in your matrix, you'll need 64 x 30mA = 1,92A That is right: almost 2 amperes. that is more than enough to fry the voltage regulator in the Arduino board. That would be 10W of power the little voltage regulator of the arduino would have to dissipate.

What LED drivers (like the MAX7219) do is to PWM the rows or columns of LEDs to keep the current low. That is pretty clever of them. For us, it seems that all LEDs are lit, but the driver is PWMing them really quick.

One Arduino can power a LED matrix and the MAX7219 and still light up all the LEDs. That can't be done without the driver.

Learn to live: Live to learn.
Showing off my work: http://arduino.cc/forum/index.php/topic,126197.0.html

CrossRoads

I don't think you understand - you connect the matrix to the header pins, plug the header into the breadboard, and the matrix floats above the header with the 16 wires sort of acting like springs.
When you're ready to make it a real project, undo the wires and install the matrix.

Here's the back of a board that is wirewrapped - your matrix would connect to pins, the pins go into breadboard, the wires let you change the spacing from wider to narrower.

All matrices need multiplexing, no more than 8 LEDs are ever on.
Arduino can multiplex 1 LED on at a time, if you have a buffer like ULN2803 than 8 can be multiplexed at a time, take care that the 8 pins do not exceed the current limit of the selected port (see section 29 of the data sheet).
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

fungus

#9
Apr 03, 2013, 04:38 pm Last Edit: Apr 03, 2013, 04:44 pm by fungus Reason: 1

The reason I don't want to solder is that I screw it up and I can't reuse the parts.


Use a couple of these?

http://www.ebay.com/itm/181108690201

Solder the wires to those then connect them to the matrix. No danger of melting the matrix.


(idk, maybe I was doing it wrong)


Maybe your soldering iron wasn't suited to electronic parts. Some cheap ones (aka "firesticks") are for soldering big pieces of metal, they get far too hot for delicate little electronic parts. For electronics you need about 20W.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Rob3rt

My breadboard is that white solderless one, as i remember, mb-102... Whatever, ill wait for the second one. Off topic: any detailed help to connect bluetooth module (I already posted in networking about that)?

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