I’m about to start a project wherein i want to create a big sheet (4 x 2 meters) filled with 5V (WS2812) addressable LED strips.
The main difficulty is that it all needs to be battery powered. Since my main knowledge is programming rather than electronics i am having a hard time figuring out how this would work, and if its even possible at all. By searching the internet i find myself confused in different approaches, volts, amperes and watts.
I want to control all this from a box with the batteries, an Arduino and some sensors.
Any general advice on how to do this battery-wise would be greatly appreciated.
You need to give out one more spec to get a good estimate … how many LEDs / meter ? I’ve seen anywhere from 30 LEDs/m to 144/m in the commercially available strips. I’d assume that whatever linear spacing you have will be good for both (horizontal and vertical) directions.
At 30/m that’s 120 x 60 = 7200 LEDs !!! Using 33% of full power as an average (my SWAG) that’s 20 mA x 5 V x 7200 = 720 W, 144 A. At full power that would be a peak draw of 430 A !!! A single deep cycle lead acid battery, and multiple DC/DC converters, might provide that level of current for 10’s of secs at a time but the wiring would be thick. Realistically count on having multiple batteries.
In general terms, you need to know the total energy needed.
So you will need to know how much current (amps) each strip consumes X number of strips
Multiply that by the voltage a strip needs, and you have the power (watts) needed to run all the strips. Multiply that by time it has to run and you have Energy (watt-hours).
Now find a battery that can supply at least that much energy (watt-hours) and you’re set.
This is oversimplified, and there are ways to optimize the numbers, but in the end it’s all just an energy calculation.
Thats 60 LEDs per meter and 5V. I would like to have 10 of those, so that’s 50m total, but will be cut into different sizes.
Since i want to control it with an arduino i think i can attach multiple wires to it so it won’t be one long strand, but rather 5(at least for the code and power) wires from the Arduino.
Quatro:
Thats 60 LEDs per meter and 5V. I would like to have 10 of those, so that’s 50m total, but will be cut into different sizes.
That's 3000 LEDs, ~ 42% of my number above. But, since the strips are a fixed 60 LEDs/m, the vertical and horizontal spacings (LEDs/m) are unequal. Is that what you want ?
There might be some combination of 2 LiPo’s in series, “N” LiPo’s in parallel, that could work but my guess is that it would be more $$s than a “car battery” solution and both would require multiple DC/DC converters to get the 5V needed.
A single group 24 marine battery should work, providing 30+A @ "12"V (= 60+A @ 5V) for 2 hours while still having enough CA to handle short duration spikes at max current. A normal car battery might work too but suffer a shorter overall lifetime (number of charge/discharge cycles).
I might look very closely at using a single “golf cart” 6V battery (T105), which would be more than sufficient current and runtime -wise. And with some tricky wiring, avoid the DC/DC converters. The added cost of the special battery would more than offset the cost of the DC/DC converters. The trick would be to drop the proper amount of voltage in the wiring and connections so as to keep the voltage at the strip between 4.5 - 5.5 V despite the variations in current draw and battery state of charge (voltage).
Of course this all depends on my SWAG of typical use vs max brightness. Perhaps it would be smart to power a subset of your display w/a benchtop supply and get some typical current draw numbers.
