This repository contains code and related documentation for the Light Pet hardware.
The hardware platform is the NodeMCU obtained from here. The version I have appears to be the 2nd generation / v1.0 / V2 board (comparison of NodeMCU boards) and is pictured below along with a pinout. My board appears to be the 'official' Amica version that complies with the NodeMCU spec, but with Aliexpress it's always a bit difficult to tell.
![Image of NodeMCU v1.0] (docs/images/nodemcuv2.jpg)
![NodeMCU v1.0 pinout] (docs/images/NodeMCUPinout.jpg)
| Quantity | Item | Notes |
|---|---|---|
| 1 | NodeMCU v1.0 | |
| 1 | TSL257 light to voltage converter | I chose this over regular photresistors because this seems to give a greater range of usable results. |
| 1 | KY-037 microphone module | I may swap this out for something else in the future, or some other sort of sound sensor. This isn't quite as sensitive as I'd hoped for, and it's impossible to read a usable sound wave without an external DAC and possibly expanded storage to store the sound samples. |
| 1 | SHT21 I2C temperature and humdity sensor | |
| 1 | 4052 analog multiplexer | This is used to multiplex the TSL257 signal and the KY-037 signal into the NodeMCU's single input. I have the TI version (CD4052B) but NXP make an equivalent unit with the same pinout under the part number 74HCT4052. |
| Assorted resistors | ||
| Assorted capacitors | ||
| Assorted jumper cables for breadboarding |
At the moment everything is constructed on a breadboard (pictured below), however at some point it would be nice to make things more permanent with a home etched circuit board.
![Light pet on breadboard] (docs/images/breadboard.jpg)
Below is a schematic of the circuit you need to get all of the sensors working properly. Also note that I have
included a Fritzing file for your convenience in the docs folder.
Datasheets for the parts that I used can be found in the docs/datasheets folder if more information on the reasons
for particular parts is needed.
Briefly:
- The SHT21 datasheet shows a sample circuit which includes the two resistors and the capacitor.
- We use a voltage divider across the TSL257 to just lower the output voltage a little so that it doesn't clip on the NodeMCU's analog input
![Light pet schematic] (docs/images/schematic.png)
My NodeMCU board came with the Arduino firmware. If yours doesn't (I think some versions come with Lua based firmware) then you'll need to flash the Arduino firmware to use the code I've provided.
My code makes use of a few libraries that you'll need to install using the library manager in the Arduino IDE. These are:
- A library for the SI7021 from Low Power Labs
- The nanopb library for dealing with protobufs
- The TaskScheduler library for making use of protothreading.
The first two libraries should be installed by downloading a zip of the master branch from the linked github pages and then installing them in the Arduino IDE with Sketch->Include Library->Add .ZIP library. The TaskScheduler library should be available via the Sketch->Include Library->Manage Libraries interface.
You'll also need to add the ESP8266 boards to your Arduino IDE by following these instructions. This should also add the ESP8266 specific libraries we will be using.
Currently the code writes the protobuf encoded data to the Serial connection, but the next step will be to send this to a location on the network via UDP.