Each LED uses up to 20 mA of current, and each
pixel has three LEDs (a red, green, and blue), so
that’s potentially over 15 amps! Of course, this is
the maximum current if you’ve got all your LEDs
on white, at maximum brightness. If you know
that you’re not going to hit this, you may be able to
get away with a lot less. Even with them all on full
brightness of a single colour (red, green, or blue), this
comes down to five amps.
DANGER!
Our screen came with three points to supply power,
which should reduce the amount of current through
each point. All three are connected on the PCB
though, so you shouldn’t connect them to different
power supplies, just three times from the same
one. This will reduce the resistance between the
power supply and the LEDs. We do have some
concerns about the quality of the joints joining the
leads onto the PCB. The wire around the soldered
blobs seemed prone to fraying.
We wouldn’t be comfortable using this display at a
high current because of this fraying, and the potential
fire risk this entails. That’s not to say that there isn’t
a safe way of using these displays (after all, anything
sets on fire if you put enough current through it).
There are plenty of applications where you can use
this sort of display without using the high current
levels that could cause risks – if you don’t need to
illuminate all the LEDs, or don’t need them all bright,
you can run this safely. Make sure you’re familiar with
the issues before going down this route.
If this screen isn’t big enough for you, it does
come with a connector to daisy-chain multiple
ones together (in this case they can be powered
by separate power supplies, as long as you tie the
grounds together).
As well as power, it takes memory to run these as
the microcontroller has to be able to manipulate the
graphics data and send it out. You need three bytes
of RAM per pixel, so our screen will use 768 bytes
of RAM. An Arduino Uno has 2kB of RAM, so there’s
enough to fit our screen in, provided we don’t need
too much additional memory.
Our screen came on a flexible PCB, but had no
specifications attached, so we don’t know how tight
it’s supposed to bend before breaking, or how many
times it’s supposed to withstand bending. It creaks a
little while bending, so we suspect the best answer
to the above questions is not very tight, and not
very often, however ours didn’t actually break during
our testing.Addressable RGB LEDs are a great way of
making your builds stand out. Generic WS2812B
LEDs can be cheap, but come with no support or
documentation, and are of variable quality – for
experienced makers, this may not be a problem but
it might lead to confusion for beginners. It’s best to
start small to make sure you know what’s going on
before diving into a display this big. While it’s great
to get cheap bits, the extra money on a reputable
manufacturer may be worthwhile if you need
support or parts to handle high currents.DIRECT FROM
(^) SHENZHEN
Above
With careful control
of the brightness,
you can run this
off a single USB
connection
Our screen came with three
points to supply power,
which should reduce the
amount of current through
each point
”
”
FIELD TEST