Indoor Air-Quality Monitor / Sensor Playground Project
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INTRODUCTION
The Sensor Playground was designed to be a fun, easy-to-build platform for you to experiment with software, sensors, displays, the IoT, etc. It grew out of a project I started after my wife suggested that some of the reasons for how we had been feeling might be related to our indoor air-quality.
It has been intentionally structured to make is straightforward for anyone with modest soldering skills and a bit of experience with tools like Arduino, to be able to construct a project that suits their ideas.
See: https://hackaday.io/project/182619-sensor-playground for more information.
It takes a kind-of "landing pad" approach, where you can build up the board and plug-in different kinds of processor modules, sensor sub-modules, displays, etc. without the need to solder them directly to the board. The number and variety of things you can plug in is virtually entirely up to you.
BUILDING YOUR OWN
There aren't a lot of "required" components, short of perhaps the power supply section & the processor module and even that has been designed to give you a wide range of choices.
For example if you don't have a need for an encoder you don't need to install it or its supporting pull-up resistors. Same holds for the PCB-mount buttons. As for the sensors, I designed the PCB so that the processor I2C bus, SPI bus and a UART are available via sockets or pins at a number of locations across the board. This lets you connect the devices you choose at the points that make sense to your particular application. While there are outlines for some of the sensors that I chose to use, these are by no means the ones you have to select.
3.3V, 5.0V & GND are made available on most connectors, so that it's easy to find a nearby power connection.
The component mounting types are all through-hole, making it pretty simple to solder in what you want and there is a fair amount of space to get your soldering iron into the places you need it to go.
SURFACE MOUNT COMPONENTS...! (relax, they're optional!)
I did add one (optional) surface-mount component: A processor reset controller.
If the processor module you choose doesn't already provide a power-on reset, or perhaps its unreliable, then you can elect to install this component. It's only three pins and should be relatively easy for those with basic soldering skills and a reasonably steady hand to install. The only other component needed for the reset circuit is a 100K, through-hole resistor. See? Not so hard after all!
PROCESSORS
I mentioned that you have flexibility in terms of your choice of processors. This is due to fact that the board has been designed to take one of two common processor module types:
- The ESP32 "DevKit"-style modules, from Esprssif, Inc.
- A host of "Feather" form-factor modules.
The ESP32 modules are dual-core powerhouses, with WiFi, Bluetooth, large memory, etc. If you have a processor-intensive application, the ESP32 is a great choice.
The "Feather" modules are a form-factor and pin-functionality specification created by AdaFruit. These modules are available with a wide range of processors, memory, IO, etc. and the pin-out is nearly identical across them all. To date, I've used ESP8266 Feather modules, ESP32 modules (same processor as the ESP32 DevKit, different form-factor), & ARM Cortex M0. Given the circuit design I've chosen, all of these work on the Sensor Playground board.
I chose to focus on I2C, SPI and UART as the primary mechanism for connecting with the sensors, displays, and other IO. This allows for a wide range of devices to be connected, while limiting the amount of digital IO that would otherwise need to be provided across the PCB. There are a few GPIO pins available on one of the headers (the same pins I use for the encoder and its button, along with the PCB- mount push buttons).
What if I want other IO than just SPI, I2C or UART?
Glad you asked! If you elect to use a Feather form-factor processor module, you could be in luck! That specification also allows for the addition of "Feather Wing" expansion modules to be plugged onto the top of Feather processor modules. You can find a pretty wide range of IO option boards that should satisfy a pretty wide range of requirements.
Alternatively, you could build something that uses SPI or I2C to drive an ADC or DAC. That would provide a nice means for gaining analog I/O and would allow the addition of non bus-based sensors. I'm considering designing an add-on to do just that.
How do I build this thing?
I'll be adding some construction guides soon. These will give you hints about how to go about building the version of the Sensor Playground that best suits your application needs.
To find the construction guides, along with tips, etc., look in the "doc" folder at the top level of this project.