Controlling a LED matrix display - schematic for connecting an Uno

Using Arduino Project Guidance
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I wish to make a project based on a LED matrix display (specifically the Red LED Dot Matrix Display for Arduino - datasheet attached) wherein the array is controlled LED by LED, in an animated way. But I'm really confused as to what hardware is needed and how to wire it up.

Currently I have Arduino Uno R3s aplenty (as in, 9 of them). Is that a suitable board to control the LED display? There are wires, breadboards, power supplies etc. on-hand. Are there any other Arduino boards or chips required for this project?

If anyone has a schematic and Sketch for a similar project, that would be much appreciated. I think that once I get the wiring done and a single LED blinking, I can work it out from there.

Please let me know if I'm thinking about this all wrong. Especially if you can suggest the right way to approach it.

TL;DR I am truly a newbie at this. Previously I've only completed a single project, and that was a close adaptation of one I got off the Jaycar site (where I got the LED array) which included both a schematic and the initial Sketch (which was then adapted to get the effect required).

XC4621-dataSheetMain.pdf (765 KB)

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Check out this tutorial. You can also download the library and example code

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drewthommo:
Currently I have Arduino Uno R3s aplenty (as in, 9 of them).

Just a mention. The inexpensive boards you have are fraudulently labelled. They are not UNOs, but a variant of the earlier Arduino Duemilanove. :roll_eyes:

The UNO is defined by the 16U2 USB interface chip which has the capability of being programmed for HID and other functionality - but that is rarely used.

The boards you have are programmed with the UNO bootloader so they will - mostly - behave as a UNO with the CH340 driver installed on your Windoze PC so you should have no further troubles but I do think it is important to understand what is a real UNO and what is not. :grinning:

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Paul__B:
Just a mention. The inexpensive boards you have are fraudulently labelled. They are not UNOs, but a variant of the earlier Arduino Duemilanove. :roll_eyes:

I visited Jaycar the other day & grabbed two more of the Uno boards they sell (one of the original 9 was from them). I'll keep the others aside for 'junk projects', but this one is important to me, so thought it was worth the expense to stick to the genuine (& correctly labelled) article.

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Well the Duinotech is certainly a genuine UNO design even if not produced by Arduino.cc. Whether it is in any way more reliable with its huge expense, than any other clone manufacturer is moot. We here generally recommend purchasing one or two from Arduino.cc purely in order to support the development project.

The description on the Jaycar page that "Input voltage: 7-14VDC via Vin pin" however annoys me. That is not the proper way to power a "real world" project such as you describe; you power it with regulated 5 V via the "5V" pin (but may need to disconnnect that when programming it).

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Paul__B:
The description on the Jaycar page that "Input voltage: 7-14VDC via Vin pin" however annoys me. That is not the proper way to power a "real world" project such as you describe; you power it with regulated 5 V via the "5V" pin (but may need to disconnnect that when programming it).

OK .. I'm not sure I understand the full implications of that, but I'll come back and read it again after first coffee of day.

Paul__B:
The description on the Jaycar page that "Input voltage: 7-14VDC via Vin pin" however annoys me. That is not the proper way to power a "real world" project such as you describe; you power it with regulated 5 V via the "5V" pin (but may need to disconnnect that when programming it).

The power requirements are something that confused me. I was trying to figure out which power supply to use for running 1 x Arduino and (/controlling) 2 x LED arrays (rated as 5V with max 3 Amp). I got a 30W 5V 6A Mini Power Supply, having assumed the Arduino could run on 5V, given it can be powered by USB.

It was only then that I noticed the stated voltage requirements of 7-14VDC! What the..?

In any case, and getting back to my query in relation to the power supply, it states under the Specifications tab.. Regulation Type SMPS. Will that power supply be suitable for this project? Each display can use up to 15 watts and it will have the Uno to power on top of that (which itself won't be used to power anything else, so I'm thinking it won't need much current). At no time will all the LEDs be at maximum brightness, so I'm hoping the remainder of the 30W will be ample for the Uno.

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And that is indeed my concern about the long-standing and persistent advice that the Arduino should be operated from a voltage other than 5 V.

The power supply you cite should fulfil the job perfectly, operating your displays and powering the Arduino via the "5V" pin (and of course, ground). The only concern in this respect is that when the USB port is plugged into a PC, it might if the external 5 V supply is higher than the PC's USB supply, "back-feed" power into the PC's USB interface and cause trouble, so it is advisable to disconnect the 5 V from the UNO or Mega 2560 when connecting to the PC.

My "potted" explanation concerning the on-board regulator of the older Arduinox:

[Inserted later :astonished: ]

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Paul__B:
The power supply you cite should fulfil the job perfectly, operating your displays and powering the Arduino via the "5V" pin (and of course, ground).

Thanks for confirming! :slight_smile:

Paul__B:
The only concern in this respect is that when the USB port is plugged into a PC, it might if the external 5 V supply is higher than the PC's USB supply, "back-feed" power into the PC's USB interface and cause trouble, so it is advisable to disconnect the 5 V from the UNO or Mega 2560 when connecting to the PC.

Yep. While that 'back feed' did not occur to me, I never intend to have both USB and any other power sources connected at the same time. ATM during development I have only one LED array running, powered solely by the Arduino, which is itself being powered via USB. I'm limiting max brightness (to 10 of 255 levels) in order to limit the current load on the Arduino (not sure if that's necessary, but better safe than sorry). Besides, 10 seems plenty bright enough to see how the program is working (or in most cases, failing to work as expected!).

Once I have the program sorted, I'll change the max brightness, upload the compiled sketch and unplug the USB before (connecting the 2nd array &) going to the 240V power supply.

When that happens, I'm hoping it will be bright enough to .. be seen from the ISS. :wink:

Oh, in case it's not obvious, my original question is now answered. I have one unit wired up, mounted on a base, and sketches (both the examples of others and my home rolled ones) running.

Thanks to all who contributed. If it wasn't for your help, I'd still be staring forlornly at all the parts, while weeping softly.

I'll likely start a new question on 'API documentation for libraries'. While it cropped up due to this project it seems a significantly different topic, better suited to a dedicated question.