In this episode, we're looking at dangerous things that come in boxes from China.
It's a holographic LED fan.
It's so exciting my camera fell off its mount!
It's pretty interesting - I wasn't expecting so many ICs.
Let's get it powered up and see how it works.
This thing is terrifying.
It's not that loud, but the sound it makes as it spins up makes you want to keep your
distance.
That's why I thought I'd do this demo holding it in my hand..
There are a bunch of patterns built into the SD Card on the device that it cycles through
and you can use the remote control to skip forward and backwards.
There's also some windows software that will turn movies into files that can be played.
This seems like a great opportunity to ask you to subscribe to the channel!
Don't forget to enable notifications so you don't miss any new content.
I'll also do a quick plug for the channel sponsor PCBWay - they've been supporting the
channel for a while and we've done quite a few projects with them.
They've produced some really high-quality PCBs for our projects and they are great to
work with.
Check out the link in the description.
You can also connect to the device over WiFi and use an iPhone or Android app to control
the device and upload new content this way.
The blades are pretty solid, and unsurprisingly if you get whacked by one it really hurts.
It's just a flesh wound
Fortunately, no permanent damage was done, but be careful if you are messing around with these.
I would recommend eye protection.
It's a pretty fun bit of kit, there are other versions available, some of them have longer
blades and you can get some with two blades for even more brightness.
Let's take a look and see how it works.
We'll start off with the base of the unit.
This is removed using these four screws.
The PCB is attached to the base with these screws and to the motor with these screws.
It's pretty interesting we can see that we are using wireless charging technology to
transfer power from the base of the unit to the top of the unit.
This chip is an XKT-412 - it's a wireless power transfer chip - we came across this
kind of thing when we were looking at how Wireless LEDs work.
The XKT-412 drives this power MOSFET at a high frequency.
This in turn drives the static coil at its resonant frequency.
This power transmitting coil is coupled to the receiver coil that is attached to the
top of the device.
There's no physical connection so the top can rotate freely.
It's pretty clever.
There's an MCU an MC30P6250 - this has a 2K EPROM next to it which I guess contains the
program it's running.
This is connected to the two IR receivers and is responsible for starting and stopping
the motor.
Initially, I wasn't sure how the remote control commands were being transmitted to the top
of the board.
I started to think that there was something clever going on with piggybacking a signal
on top of the wireless power.
But then I noticed this LED on the opposite side of the board.
The MCU is retransmitting the remote control signals using this transistor and the LED
on the other side of the board.
The only other thing of interest on the bottom PCB is the motor driver.
It's a PT2432 which is a brushless DC motor driver.
Moving to the top of the device we have these four screws - once you've undone them you
can just lift up the PCB.
This is a single PCB that holds the brains and all the LEDs along with their driver chips.
It's pretty amazing that all this is spinning around really quickly - why don't all the
electrons just fly off?
There are only two wires coming into this board, these come from the receiver coil that
is picking up the wireless power.
This is fed into a T3168 which is a wireless charging receiver IC.
This outputs the 5v that is used to power the top board.
There's also what looks like a 3.3-volt low drop out regulator for the MCU and the WiFi
module.
The WiFi module is an ESP8285 module.
And the MCU or brains of the operation is an ARMv7 32bit Cortex-M4 CPU.
There are 224 RGB LEDs on my version, these are driven by these 16-bit shift registers
that have constant current LED drivers built-in.
There are 42 of these chips in total, giving us the 3 channels for each of the 224 LEDs.
I believe it's using PWM to show different levels of brightness and there are a limited
number of shades that can be displayed.
There is quite a sharp cut off from lit pixels to unlit pixels and I've seen this with other
LED displays.
To display a pattern the MCU shifts out data really quickly and then latches it on the
outputs of the shift registers.
Provided it does this fast enough and in sync with the rotating motor you get a stable image.
There are no obvious means for the MCU to know where the blades are so I'm assuming
that the blades are turning at a constant known rate and the MCU just needs to make
sure it clocks the data out at the correct rate to keep in sync.
But there may be something more clever going on - the images do seem to appear to always
come out with the same orientation.
Maybe the same route that is used for the remote communication is also used for this
synchronisation.
It's a pretty amazing bit of kit.
And it looks really cool. It's good fun to play with.
Let me know what you think in the comments.