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WiFi 240V AC Led Dimmer - Speech Controlled
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# WiFi 240V AC Led Dimmer - Speech Controlled

See also blog post:

## TL;DR

I wanted to build my own WiFi dimmer, to connect to Alexa (Amazon Echo Dot).
The end-result is a combination of DimmerTest_ESP_V3B with AvrDimmerCoprocessor_V3.
The used parts are an ESP8266 (I used a Wemos D1 Mini Clone), an ATTiny45 (or ATTiny85),
some sort of power module to supply 3.3 volt, and a zero-cross-detector/triac dimmer module.

## The Long Story

The story started with a nice offer in a cheap goods shop, of quite big (12,5 cm wide) light
bulbs, with built-in WiFi control. So I bought 4 of them. Three of them I did hang above my
dinner table, and #4 was the spare one.

After all wiring was done, neatly tucked away in plastic tubes, we could start to use them.
And that was when disaster struck... For some reason, the bulbs make a high frequency noise.
I'm old enough not to hear this anymore, but my two daughters could not stand the sound of it.
Very effective teenager repellent. And the weird part was that the sound stays on, even if the
lights are off. As a half measure, I did add a wireless switch, to cut the power to the lights
when they were off. But using them was really a no-go. So they had to go (the lights, not the kids).

So what's next? I did need some lights, and the wiring was done by now. The new plan was to
buy similar light-bulbs, but then the ones without built-in WiFi. As there is no switch in the
wiring, the next step was to "design" and build my own WiFi light dimmer.

After some googling around, I found a nice dimmer module. It has a zero-crossing detector, and a Triac.
You can use it to dim 240V AC lights. It works on 3.3 or 5V, has a digital output for the zero-cross
detection, and a digital input to "start" the Triac to conduct at a given moment until it switches
off again at the next zero crossing.

The plan was to connect this to an ESP8266 WiFi arduino-like processor. It has the ability to look
at interrupts, and trigger the Triac after a configurable delay. Sounds perfect for the use-case!

So I did build my version 1 setup, and hacked together the program as can be found in DimmerTest_ESP_V1.
It did work sort-of. I could brighten or dim the lights by pointing my web-browser to the web form
as served by the ESP module. But... the lights kept flickering like a candle in the wind. Nice as special
effect, but not for regular dinner use.

My guess is that the ESP has too much to handle for keeping the WiFi alive. It seems to interfere with the
needed clean interrupt routines for sine phase triggering at an exact moment in time. Any shift in time
has as result that the brightness changes, causing the candle flame effect. Too bad. Some more googling
showed that more people ran into this issue.

New plan; why not add a dedicated Co-Processor chip to do the actual dimming, and keep the ESP for the
WiFi control functions. There is this nice little chip called an ATTiny45 (or 85), which is an 8 pin
micro-controller with lots of useful building blocks inside. It has timers, interrupt handling,
serial communication capabilities, and more. It is even programmable with the same Arduino Studio GUI
as I do use for programming the ESP chips. Nice!

The whole setup does not even change that much. Just adding the ATTiny between the ESP and the dimmer
module does the trick.

To test if the ATTiny could do phase cut dimming nicely, I used the program in AvrDimmerCoprocessor_V2A.
It was a copy/paste from a forum (why re-invent the wheel), and it worked nicely using a potentiometer
connected to the analog input on the ATTiny. So no WiFi control yet.

Next step was modifying the code to look like AvrDimmerCoprocessor_V2B. I had to free up one of the
pins as used by the original forum copy/paste example. That pin I did need after this new test for I2C
serial communications. That pin has a dedicated interrupt routine connected, so to free it up, I had to
use a different interrupt mechanism. The so called "pin change intterupts". These monitor ALL data pins
for which you enable it, connected to a single interrupt routine. In that routine, you need to check
for which pin (if more than one enabled), and for which edge (falling or rising) the interrupt was.

Happy to see that V2B also worked nice, I could change it further to remove the analog input with the
potentiometer, and change to I2C serial (digital) input. That's in the final version piece of code
as can be seen in AvrDimmerCoprocessor_V3.

Now to check if the ESP was able to talk as I2C master to the Co-Processor ATTiny slave device, I did
create simple program DimmerTest_ESP_V3A. It uses the "Wire" library to talk I2C, using pins D3 (SDA), 
and D4 (SCL). These two pins have an on-board pull-up resistor on the Wemos D1 board, which were nice
to re-use for the necessary I2C termination.

Apart from the Wire library, I also put in a web server, WiFi manager, and OTA-update (over the air
updates). A super simple web form gave the option to change a brightness number between 0 and 100, which
was send over I2C to the Co-Processor.

And again, it works! No flickering candle in the wind anymore. Smooth dimming. Fixed for a bit more than
one Euro, and some nice extra hobby time.

As I did want to control the lights using voice, I looked for a library which works with Alexa (Amazon
Echo Dot). The library I found was the "FauxmoESP" library. I took the standard example code, and added
the I2C Wire code to it. The fauxmo stuff seems a bit outdated, so I did not manage to combine it (yet)
with the WifiManager. WifiManager is a standard library with which you can dynamically configure the
WiFi network (SSID+Password) to use. So for now the settings are hardcoded. Will leave that for later.

The end result can be found in code DimmerTest_ESP_V3B. Which talks to AvrDimmerCoprocessor_V3 in the

For photo's and schematics, see the images folder.

Thijs Kaper, 12 October 2019.

## Software Links:

(1)   - Arduino IDE, used both for ESP and ATTiny

(2) In Arduino IDE, board manager URL's for using ESP and ATTiny (in file -> preferences):,
    Install both ESP8266 and ATTinyCore via Tools -> Board -> Manager.

(3)  - ATTiny Core for Arduino IDE - sources / README's.

(4)   - The Alexa Connector Library

(5)  - needed for fauxmo

(6)  - needed for fauxmo

Note: most other needed libraries can be installed from the Arduino IDE using Sketch -> Include Library -> Manage.

## Search terms for used products (on AliExpress, or eBay):

(1) "AC Light lamp dimming LED lamp and motor Dimmer Module, 1 Channel, 3.3V/5V logic, AC 50/60hz, 220V/110V"
    (approx EUR 3,22 for 1) - brand: "RobotDyn", it has a zero-crossing detector and Triac on board.

(2) "10pcs D1 mini - Mini NodeMcu 4M bytes Lua WIFI Internet of Things development board based ESP8266 WeMos"
    (approx EUR 19,17 per 10).

(3) "2pcs/lot HLK-PM03 AC-DC 220V to 3.3V Step Down Buck Power Supply Module Intelligent Household Switch Converter"
    (approx EUR 4,37 per 2) - brand: "Hi-Link".

(4) "10PCS ATTINY85-20PU DIP-8 ATTINY85 DIP8 85-20PU ATTINY85-20 DIP new and original" (approx EUR 11,69 per 10).

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