I am trying out a LED+microcontroller project for the first time. I have read articles on the forum to get a basic idea of the implementation but need help on certain points.
The idea is to put up 5 A3 size wall posters on the wall behind my desk and use WS2812B strips as backlights. I am planning on connecting 5 separate strips to an Arduino Nano as follows:
Drawing power directly from the Arduino seems like a bad idea. Will a single 5V power supply be able to power all the strips and the board? How many Amps are required?
How long can I make the wires connecting the breadboard and the strip?
Will I be able to control each strip separately using software?
If I want to control the strips using an IR remote or an app? What is the way to go?
How many leds will there be ?
For a backlight, 60 leds per meter is enough, maybe 30 per meter is okay.
Let's say 60 leds per meter. That makes: 5 panels * 2 sides * (0.42 + 0.297 meter) * 60 leds * 60mA per led = 25.8 A
There will be 430 leds, that is too many for the Arduino Nano, it does not have enough SRAM (dynamic memory).
A single power supply is okay.
2.
Pretty long, a few meters. Add a protection resistor and a capacitor.
3.
Yes. You need some programming skills to have a moving effect simultaneously on multiple panels. The more leds you have, the slower the update of the leds.
Can you tell why you think it might be good to have separate strips to the Arduino ?
4.
I have doubts about the IR remote. With so many leds, the library needs the full Arduino board. The library turns off interrupts while sending the pulses to the ledstrips.
A IR remote receiver does the decoding in software, it uses a interrupt to read the pulses and the interrupt should not be disabled.
With a faster Arduino board, a serial port and a Bluetooth module with an app on a smartphone, that is better but not an easy project. Maybe you can find a good example for that.
There is a way around that, and actually you may be able to just fit the 430 leds in, but it will be tight. Every pixel needs 3 bytes, so that would make the buffer 3 X 430 bytes = 1290 bytes of the full 2KB available. The option is to use 1 buffer which is only as big as needed for 1 A3, and reuse that, filling it with the animation. It will be more tricky to program, but it will fit really easily in SRAM.
It does depend a bit on the thickness of the cable. For the VCC & GND, bigger is better, for the data line thinner is (much) better.
It does not make a big difference. You can split the ledstrips into 5 separate ledstrips, or use a single ledstrip and split them in software. Each led can be programmed for a certain color, assuming that you are going to buy ledstrips with individual programmeble leds.
For example a ESP32. It has Bluetooth and enough memory.
You need to amplify the signal, because it outputs a signal of 3.3V and the ledstrip wants a signal of 5V.
If you think that RGB is ugly, then there are also RGBW and RGBWW ledstrips. I really don't like RGB but I have a RGB + WarmWhite ledstrip which is beautiful I made sure that all the colors are combined in every led, for a smooth result.
Yes, in theory. But that's every LED full blast, which is often avoidable, and TBH hard to be in the same room with. I find the kinda stuff I do, not every LED on at once, never mind full blast, to require way less capacity.
Ideally, you would make your circuit and program, then measure what the current is looking like, then get the dedicated power supply.
If you don't have a bench power supply, you could measure the current with many fewer pixels doing what they will end up doing, measure and figure out what the full project might need.
This article
will put some details to the various recommendations made above and other best practices.
I think the ESP8266 should be okay.
There are new and cheaper versions of the ESP32. If the libraries are updated for those, then there is no longer need for the ESP8266.
I went ahead and got myself an esp8266, an esp32, and a 5v20amp power supply. Now I am facing the following challenges:
My house has no outlet that officially supports more than 16 amps. I can reduce the led length to make sure it never actually draws more than that, however, the power supply is still rated for 20 amp, is plugging it into the 16 amp socket safe?
@Paul_B mentioned that I would need a logic level shifter, is it necessary even though I am using a separate power supply and only the data is flowing from the esp32.
How would I split the live wire and ground wire into separate wires for each panel? I get the concept schematically but what are the best practices to do it IRL?
It's 20A at 5V so 5*20 = 100W. I don't know what your mains voltage is, let's say 110V. So you divide your 100W by 110V and you get 0.9A.
I've never looked at the efficiency of power supplies so I let's assume it's 10% for this calculation. So the maximum needed from the 110V mains is 0.9 * 1.1 is about 1A.
Linear supplies (heavy, have transformers) are about 67% efficient but you can run at max even a burst over max and the transformer field will deliver w/o damage.
Switching supplies have power transistors, not transformers. They tend to be about 95% efficient but don't even take them to full rating, the fail path makes spiky power if a FET doesn't burn up first. It's best to get twice as much switcher as you'll ever need, it'll last extra long just loafing along.
I made sure that all the colors are combined in every led, for a smooth result.
