orders.The sensors are now back in stock but
it caused Guido to start designing for different
sensors in case he had to find replacements.
HARDWARE
At the core of a CO
2
monitor is a microcontroller
that connects to the sensor and a display.The
basic microcontroller in our examples is the
ESP8266. Powering the board and logging data
are additional considerations; Options 1–3 listed
here are powered by USB, Option 4 by battery.
The individual components are not expensive
but generally add up to $100–$200. You can find
the complete parts lists for all these options at
makezine.com/go/co2-monitor.
One reason to look at these different options
is that some of the components may not be
available, which is true not just of the sensors but
microcontrollers as well due to chip shortages.
OPTION 1: IoT Octopus Board
Guido is the developer of the IoT Octopus board
Carter Nelson, Stephan and Odessa Schulz, Guido Burger
5
4
8
2
3
6
7
9
1
M
The red DIY Octopus bare boardhas locations for adding different CO
2
sensors (1)(2), microcontrollers
(3)(4), and displays (4)(5)(6), plus VOC sensor (7), discrete LEDs (8), and NeoPixel LEDs (9).
31
meke.co
J K
Students building CO
2
devices. The Octopus board with SCD30
Grove sensor.
Octopus with SCD30
Feather sensor.
L
and he recommends using it with the Grove
SCD30 sensor (Figure
K
). “You can build the
device without soldering,” he said.“Only two
parts are needed because RGB LEDs and
ESP8266 are already on the IoT Octopus. And it
has the BME680 environment sensor on board
as well.”Or you can solder the SCD30 Feather
sensor instead if you like (Figure
L
).
A separate display is not required because you
can use the Octopus onboard LEDs as “traffic
lights.”If you do want to add a display, consider
the Grove 16×2 White on Blue; you can use Grove
branch (Y) cables to connect both the sensor and
display to the Octopus.
OPTION 2:DIY Bare Board Kit
This version is the same form-factor as the
IoT Octopus and comes as a kit that requires
assembly.The red PCB is compatible with several
different options for microcontroller, CO
2
sensor,
and display (Figure
M
). As a kit, it comes with
a NodeMCU, Grove connectors, resistors, and
M78_024-35_CO2Monitor_F1.indd 31M78_024-35_CO2Monitor_F1.indd 31 7/13/21 9:49 AM7/13/21 9:49 AM
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