11x10 adressable LED Grid

The cheaper option - as you apparently discovered with just a little research - is eBay or Aliexpress. Generally much cheaper than Amazon. The penalty? Very slow delivery. :astonished:

That is indeed how you use them, chained and sharing the same three controlling pins like the MAX7219s.

Advantage? May be a trifle cheaper, but requires a higher voltage supply to operate LEDs in series.

You can, noting that with individual LEDs, not all of the 110 positions in the Word Clock need to be populated.

Disadvantage: Only one LED at any time can be lit by an Arduino Nano at 30 mA brightness. Generally much inferior to using MAX7219s.

Safe? Perfectly good and safe given that you have an adequate power supply. 110 LEDs would be 6.5 Amps at full brightness white but as long as the code never commands that (or the LEDs do not default to that on switch-on which they should not), a couple of Amps should be adequate.

OK, well at 30 LEDs per metre, 11 LEDs is 33 cm width between the outer LEDs, so that is a fairly large clock. :+1:

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If the design is indeed like the pic @Paul_B posted, it seems to me there are perhaps 22 words or groups of letters, each group containing between 2 and 8 letters. Around 80 LEDs in total. Each word or group needs to be switched on or off individually. 5 Arduino pins could drive 5 PNP transistors like bc327 to power the rows and 5 more Arduino pins could drive 5 NPN transistors like bc337 to drive the columns of a 5x5 matrix with a word at each position in the matrix. So that's around 80 LEDs + series resistors, 10 transistors and 10 resistors for the transistor bases. Just a thought.

Thanks for the explanation. I think I will go with the strips anyway. Seems to me that the single LED option will be one that requires a lot of maintenance. Especially considering that my soldering skills are very bad :smiley:

I got one last question for you guys:
I read a couple of times about RGBW LEDs. Is there actually such a thing or is it just a different acronym for the same thing? I mean all RGB LEDs can shine white, right? So what would be the difference between an RGB and an RGBW LED?

The RGBW LEDs can generate a "true" white by incorporating an actual white (fluorescent) LED. Also RGBWW LEDs which have both "Warm" and "Cool" white. :grin:

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I'm currently searching a suitable PSU for the project. Since I need at least 6.6A I was searching for 5V and 10A ones.

I noticed, that all the ones that have "only" up to like 5A are rather compact (i.e. the trafo is directly at the power plug and there is just one cable) and all the ones with more than 5A are rather clunky (i.e. there is a cable to the trafo unit which lays on the floor and then another cable to the device). Can you maybe recommend me to a powersupply, that is compact and has sufficient power or does that not exist?

For example DC 5V 12V 24V Adapter Netzteil AC 100 V 240V 1A 2A 3A 5A 6A 8A 10A ladegerät Konverter Adapter Für LED Streifen Licht CCTV Lampe|AC/DC Adapters| - AliExpress here you can choose the V_out and I_out and the ones with 1,2 and 3A come with small shapes and 6, 8 and 12A come with the bigger shapes. (BTW: Thanks again to @Paul_B for recommending aliexpress, I fucking love it. It's not just cheaper than amazon, but also has way more choices for electronics)

6.6A? Really? When are you going to light all the LEDs in the entire display at full brightness? This was mentioned in reply #21.

I figured better save than sorry... What would you consider sufficient?

It's best to calculate your worst case scenario and add a small "fudge factor". I can't do it for you because I don't have all the details. But, if you know the individual LED current, and how many LEDs at maximum you will have on simultaneously, you can just multiply and get the answer.

If you are near the beginning of your project, you can dictate what the typical LED current will be. You can also use the most efficient LEDs you can find, to lower the current requirement.

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The thing is that the "plug pack" (American: "Wall Wart") designs necessarily have an output cable. This is a problem because that cable has resistance so that by the time you get to the end of the cable - and a connector which may not be adequately rated for the current - you lose voltage and regulation at higher current levels.

The "open frame " or "cage" supplies for heavier currents are based on you providing a sufficiently heavy (and short) output cable to minimise voltage drop and allow adequate regulation. Some have multiple output terminals so you can share the load over multiple cables.

Now if you are set on using the WS2812 arrays with potential visibility from across the street, there is some possibility of accidentally activating all LEDs at full power and the maximum current draw. As long as this does not accidentally happen at turn-on and your code behaves itself, lighting only about one fifth of the LEDs at any one time, a lesser current rating will be OK.

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Yes, I know I might calculate it. The thing is just, that I have never worked with such LEDs and I don't know how bright this maximum brightness actually is. I could of course wait for the LEDs to arrive (which takes like a month) then experiment with one LED and then order a PSU, but then I will lose another month :smiley: But from the way you guys are talking about these LEDs, I'm getting the impression, that for a word clock application I will probably never need a more than like 75% brightness if I don't want to blind people that are looking at it.

I think this is not what I was talking about. What you refer to as "plug pack" is something like this, right? I was more talking about this in contrast to this. Both of which seem to be plug packs.

I would like to be able to use half the LEDs at the same time, because I'm considering to create some pattern that appears at every full hour or smth. I'm thinking about a diagonal fading bar running from top left corner to bottom right corner. But as mentioned before, I can't estimate what level of birghtness I will need. I'm assuming it's never gonna be more than 75%, but I can't test. in that case my highest current draw would be something like 2.5A and a 3A PSU would be perfectly fine.

Also those LEDs are likely to draw closer to 32 mA when wide open than 60 mA

OK, picking on your examples, this is a plug pack" or "Wall Wart":


Now this is generally referred to as a "brick" or similar (and absurdly overpriced!):

Both of these have an output cable and connector which substantially impair their output regulation.
This is an "open frame" supply, with an enclosing housing I would call it a "cage" supply:

Whatever do you mean?

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https://www.pjrc.com/how-much-current-do-ws2812-neopixel-leds-really-use/

I measured the current on the strip I have behind my monitor for decoration. It did come close to 60mA per pixel... problem is, there are so many flavours of NeoPixels out there...

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So rather than "likely to draw closer to 32 mA", you really meant to say: "You may find counterfeit WS2812 chips that do not work to specification". :angry:

@Paul_B Thanks for the clarification!

No, I said what I meant to and I've seen that myself, but it as it deviates from the norm and you've personally observed it I see the importance of you correcting the fact.

If I get one of those open frame PSUs, how do I provide input to it? Would it be "standard practice" to use a cable, cut it open and just connect the 3 conductors to the 3 input clamps of the PSU? Isn't that somewhat unsafe? Or is there a cleaner solution involving shrinking tubes or some kind of connectors?

Can you please tell me, what those are called? A foto alone doesn't help me much. And also: I would need a crimping tool to use those, right?