PL9823 Web Controlled LEDs

Introduction

We thought we would start with something a bit whimsical.

Since we are early in the academic year

This all started when my my wife decided that we should do something with the 60 or so telephone insulators she has been collected for the past 30+ years. Perhaps put a led in them and stick them in the garden she suggested.

So ... I went looking on Ali Express for cheap LEDs. Thinking a bunch of different coloured LEDs would be fun. And I found:

Not only are the LEDs any colour I want, they can be any of 16 million or so colours. And they are individually addressable. Each led in the circuit can be a different colour and the colours can change.
So I bought 100 of them!
Then over the next several days - with much reading of web pages and tutorials and libraries - I managed to get them to work.

Thanks to:

http://fastled.io/
The guy with the Swiss accent: https://www.youtube.com/watch?v=YJQG9JnDemM&t=7s
https://hackaday.com/2017/01/20/cheating-at-5v-ws2812-control-to-use-a-3-3v-data-line/

And I built the following. The real thing is wandering about here somewhere with a battery attached to it.

The NodeMCU ESP8266 micro-controller runs the show
The push button cycles through the various led programs that I wrote
The LEDs, of course, light up
And the prototype board holds it all together and provides electrical connections

I then spent the next month off and on writing led "programs" so that pushing the button does something.

I currently have 8 programs that flash the lights in various ways,
obviously, there are an infinite number of possibilities.
If you changed the layout of the LEDs to say - a grid - you could show pictures ...

It then occurred to me that use a web page could web control the selection of light program.

Thanks to the ESP8266s built in wifi and web server.
So I did

Credentials

URL is: 10.10.45.10

ID: pl9823

PW: neopixelnot (neopixel belongs to adafruit)

If you want to control the lights you need to be connected to the Steele ssid (wifi network).

Details

Code

The code was written in the Arduino IDE and compiled and uploaded to the ESP8266 with the Arduino IDE.

The IDE is running on a Raspberry Pi.

Click her for information on Installing the Arduino IDE on the Raspberry Pi

And there is a problem. We put a password on the request to get the web page to change the lights but look:

Anyone with network packet analyzer like wireshark can see the ID and Password!

And then the web page is displayed

HTTPS vs HTTP

The simple answer to this problem is instead of doing http:// We do https:// ... But we can't because the ESP8266 does not do https.
Then, of course you ask the question - who cares if my lights get change by some hacker. And the answer is probably nobody. But this is an example of Internet of Things (IOT) and the Things are often much more critical that whimsical flashy lights Things like:

Live Billboards - you might not get paid if someone draws a mustache on the local politician
Pond pumps - could flood your yard and kill your goldfish (real story, but probably not a hacker).
Room lights
Greenhouse control
Pacemakers
Predator Drones Just sayin...
...

Our proposed solution is to create a middle man to handle https. So the http is only on a LAN, not the less forgiving WAN.

More on security next time.

Hardware

Block Diagram showing controller chip, LEDs and how they are daisy chained.

Data flow. The way these PL9223 and other addressable led devices work is that 24 bits for each of the led RGB colours are sent down the data wire. So in the case of 5 LEDs, 24 x 5 = 120 bits are sent from the ESP8266.

The first led grabs the first 24 and latches them. The remaining 96 are sent to the second led

The second grabs the next 24 and the remaining 72 are sent on.

Etc. for all the LEDs in the chain.

NodeMCU ESP8266 Development Board

NodeMCU is an open source IoT platform.^[4]^[5] It includes firmware which runs on the ESP8266 Wi-Fi SoC from Espressif Systems, and hardware which is based on the ESP-12 module.^[6]^[7] The term "NodeMCU" by default refers to the firmware rather than the development kits. (Wikipedia)

NodeMCU ESP8266

Schematic

Controlling using a 5V Arduino

3.3 V ESP 3.3V vs 5V PL9823
To control the 5 Volt WS2811 (and others) with an ESP8266 at 3.3 volts you need to shift the level.

The data sheet states that a logic high input will be detected at a minimum voltage of 0.7 * Vcc. If you’re running the LED at 5V, this means 5 V * 0.7 = 3.5 V will be needed for the WS2811 to detect a ‘1’ on the data line. While you might get away with using 3.3 V, after all the specification in the data sheet is meant to be a worst case, it’s possible that you’ll run into reliability issues.

To perform the level shift, a signal diode is placed in series with the power supply of the first LED. This drops the first LED to 4.3 V, which means a 4.3 V * 0.7 = 3.01 V signal can be used to control it. The logic out of this LED will be at 4.3 V, which is enough to power the rest of the LEDs running at 5 V. This information came from hackaday.com.

Controlling using a 3.3V ESP8266

Button

The 50K Ohm resistor is called a pull up resistor. it ensures that the Pi input pin is normally connected to 3.3 Volts. This ensures that the input is not floating. If it were left floating then random environmental electrical noise could cause the input to go from 0 to 1, like, randomly. Because the resistance is so high no significant current is flowing. 0.066 MilliAmps

1K Ohm resistor between the switch and the ground is in case we accidentally set the pin to output rather than input. This will limit the output current in case the pin is set to output and the switch closed.
You may need to debounce the input from a switch with some logic or delays. As the switch closes there is a period when it goes from open to closed a few times before it closes solidly. The easiest way to do this is to delay a few milliseconds before using a switch value. (https://en.wikipedia.org/wiki/Switch#Contact_bounce)

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