[0:00] In this episode, we’re looking at dangerous things that come in boxes from China.
[0:05] It’s a holographic LED fan.
[0:08] It’s so exciting my camera fell off its mount!
[0:11] It’s pretty interesting - I wasn’t expecting so many ICs.
[0:15] Let’s get it powered up and see how it works.
[0:19] This thing is terrifying.
[0:21] It’s not that loud, but the sound it makes as it spins up makes you want to keep your
[0:26] distance.
[0:27] That’s why I thought I’d do this demo holding it in my hand..
[0:29] There are a bunch of patterns built into the SD Card on the device that it cycles through
[0:34] and you can use the remote control to skip forward and backwards.
[0:38] There’s also some windows software that will turn movies into files that can be played.
[0:43] This seems like a great opportunity to ask you to subscribe to the channel!
[0:47] Don’t forget to enable notifications so you don’t miss any new content.
[0:51] I’ll also do a quick plug for the channel sponsor PCBWay - they’ve been supporting the
[0:55] channel for a while and we’ve done quite a few projects with them.
[0:59] They’ve produced some really high-quality PCBs for our projects and they are great to
[1:02] work with.
[1:03] Check out the link in the description.
[1:06] You can also connect to the device over WiFi and use an iPhone or Android app to control
[1:10] the device and upload new content this way.
[1:14] The blades are pretty solid, and unsurprisingly if you get whacked by one it really hurts.
[1:20] It’s just a flesh wound
[1:24] Fortunately, no permanent damage was done, but be careful if you are messing around with these.
[1:29] I would recommend eye protection.
[1:32] It’s a pretty fun bit of kit, there are other versions available, some of them have longer
[1:36] blades and you can get some with two blades for even more brightness.
[1:40] Let’s take a look and see how it works.
[1:43] We’ll start off with the base of the unit.
[1:45] This is removed using these four screws.
[1:48] The PCB is attached to the base with these screws and to the motor with these screws.
[1:53] It’s pretty interesting we can see that we are using wireless charging technology to
[1:57] transfer power from the base of the unit to the top of the unit.
[2:01] This chip is an XKT-412 - it’s a wireless power transfer chip - we came across this
[2:07] kind of thing when we were looking at how Wireless LEDs work.
[2:11] The XKT-412 drives this power MOSFET at a high frequency.
[2:15] This in turn drives the static coil at its resonant frequency.
[2:19] This power transmitting coil is coupled to the receiver coil that is attached to the
[2:23] top of the device.
[2:25] There’s no physical connection so the top can rotate freely.
[2:29] It’s pretty clever.
[2:30] There’s an MCU an MC30P6250 - this has a 2K EPROM next to it which I guess contains the
[2:38] program it’s running.
[2:39] This is connected to the two IR receivers and is responsible for starting and stopping
[2:43] the motor.
[2:44] Initially, I wasn’t sure how the remote control commands were being transmitted to the top
[2:49] of the board.
[2:50] I started to think that there was something clever going on with piggybacking a signal
[2:54] on top of the wireless power.
[2:56] But then I noticed this LED on the opposite side of the board.
[2:59] The MCU is retransmitting the remote control signals using this transistor and the LED
[3:04] on the other side of the board.
[3:06] The only other thing of interest on the bottom PCB is the motor driver.
[3:10] It’s a PT2432 which is a brushless DC motor driver.
[3:16] Moving to the top of the device we have these four screws - once you’ve undone them you
[3:21] can just lift up the PCB.
[3:23] This is a single PCB that holds the brains and all the LEDs along with their driver chips.
[3:29] It’s pretty amazing that all this is spinning around really quickly - why don’t all the
[3:32] electrons just fly off?
[3:34] There are only two wires coming into this board, these come from the receiver coil that
[3:39] is picking up the wireless power.
[3:41] This is fed into a T3168 which is a wireless charging receiver IC.
[3:47] This outputs the 5v that is used to power the top board.
[3:50] There’s also what looks like a 3.3-volt low drop out regulator for the MCU and the WiFi
[3:55] module.
[3:57] The WiFi module is an ESP8285 module.
[4:00] And the MCU or brains of the operation is an ARMv7 32bit Cortex-M4 CPU.
[4:06] There are 224 RGB LEDs on my version, these are driven by these 16-bit shift registers
[4:14] that have constant current LED drivers built-in.
[4:17] There are 42 of these chips in total, giving us the 3 channels for each of the 224 LEDs.
[4:24] I believe it’s using PWM to show different levels of brightness and there are a limited
[4:29] number of shades that can be displayed.
[4:31] There is quite a sharp cut off from lit pixels to unlit pixels and I’ve seen this with other
[4:36] LED displays.
[4:38] To display a pattern the MCU shifts out data really quickly and then latches it on the
[4:43] outputs of the shift registers.
[4:45] Provided it does this fast enough and in sync with the rotating motor you get a stable image.
[4:50] There are no obvious means for the MCU to know where the blades are so I’m assuming
[4:55] that the blades are turning at a constant known rate and the MCU just needs to make
[4:59] sure it clocks the data out at the correct rate to keep in sync.
[5:02] But there may be something more clever going on - the images do seem to appear to always
[5:07] come out with the same orientation.
[5:09] Maybe the same route that is used for the remote communication is also used for this
[5:14] synchronisation.
[5:15] It’s a pretty amazing bit of kit.
[5:17] And it looks really cool. It’s good fun to play with.
[5:20] Let me know what you think in the comments.