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Which arduino borad to buy? Answered

http://arduinoteacher.appspot.com/matrix_8.html

Hello! And i am interested in starting arduino! But i am not familiar with the hardware spec of arduino boards. I have some electronics and programming bg as an physics student. I read the above tutorial, the led matrix looks like a easy/cool starter project.

However, i have a question, For 4 by 4 matrix, it need 4 outputs and 4 grounds. With 14 i/o pins on an arduino uno (0to13), is 7 by 7 the maximum for upscaling this design without multiplexing? Or if i can get a "shield" that add more pins to the uno? Should i just get a arduino mega with 54 I/O pins? Since it is not that expensive, Is the tutorial compatible with a mega?

Actually my target build is two 15 by 15 matrix displaying identical image. Can i rig up two identical led matrix, connect both in parallel to the same board?

Thank you in advance! for your replies!!

Discussions

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2 years ago

I personally like the MEGA because not only you have more pins, but also more programming space, and I want to say it's faster too. It enables complex designs requiring many UART ports, interrupts, PWM and analog pins, etc.

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The arduino Due is also nice, ARM based, but has 'quirks' that differentiate it from the rest. It's faster due to 32 bit arm microprocessor. It's 3v3 logic, so be careful. It's more sensitive to stuff like that. It also offers some real DACs if I recall right.

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If you get an UNO, avoid the ones without replaceable chips. Those are IMHO garbage. Get the ones with the full DIP package on them, because if you fry it, then no worries, a $4 replacement chip will almost certainly fix it. And it allows you to program any chip you want and then install it into a final project easily.

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If you are really clumsy, get the ruggeduino. Every input has protection, and the board is (almost) bulletproof.

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Lastly, I like the tiny breadboard arduino pro's. They are just a jellybean arduino with the typical standard ATmega328, no thrills. But they are small and great for smaller projects where price and size are a concern. I bought 5 clone boards for $15.

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Downunder35m-max-

Reply 2 years ago

The Mega has it's purpose and glory when it comes to a large amount of extras, like display, SD, encoders, motors, sensors and so on.
As you already pointed out using "standard" code from some website almost always means you have to do some modifications to the code.
Mostly the pins but when it comes to timers and interrupts even more.

I have to say that for every purpose and skill level there is an Arduino to fit.
That makes getting into microprocessors very easy - if you take your time ;)
The one thing I really don't like about Arduino is the compiling part.
Even if you know the code you found is for the Arduino in question and you have collected all required libraries it does not mean you can compile it with success.
Only too often a specific version of the IDE is required, same for certain libraries, especially if the author made changes to them.
From my starting experience I know it can be a real pain if you think your code is correct but won't compile and the error messages make no real sense.
I have spend days finding errors that disappeared after using a different IDE version ROFL

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2 years ago

You don't necessarily need a lot of pins. Shift registers allow converting a serial data stream into several outputs. Of course you are literally trading speed for pins, but if you are just running LEDs as indicators, there is no problem.

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One thing I have to point out against the MEGA and non-ATmega328 boards is that some of the code you find is written to work on the most common arduino UNO, or 328 chip. Things like using PORTX commands instead of digitalWrite, which complicates the more advanced projects, as you need to be aware of the MEGA pinout.

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Downunder35m

3 years ago

Only real difference between 8bit Arduino is the pinout, so for example sketches you might need to adjust those to what is available.
Unless size matters I alsways go for the Mega as it offers so much more for just a few bucks more.
And you can expand the matrix till you run out of pins, only issue could be the speed for the refresh but I doubt you will notice it with your bare eyes.

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mchau2Downunder35m

Reply 3 years ago

thanks for the reply! The lower refresh rate you point stems purely from more rows to load right? You are right that shouldnt matter, we are talking milliseconds...

And may i ask again on whether i can connect 2 identical led matrix in parallel ? How does the current split on an arduino? Should i use a <220 ohm resister?

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Downunder35mmchau2

Reply 3 years ago

For higher loads it is recommended to use a transistor on the output.
In case of an LED basically any will do.
So instead of sending the signal directly to the resistor you send it to a transistor that does the switching.
Gives a bit protection for your outputs as well.

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mchau2mchau2

Reply 3 years ago

http://playground.arduino.cc/Main/ArduinoPinCurren...

I only know the analog method of using value sin the link, (40ma or 200ma) ohms law to determine the resistance, voltage across/ current.... but i read somewhere and i quote, "unlike analog electronics, micro controller like arduino is not picky on the resistors as long as it can differenciate high and low"... how many ohm should i use?