Adafruit Industries

ASK AN ENGINEER 10/15/2025 LIVE

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SHOW and TELL 10/15/2025

This week's EYE ON NPI will help you breathe easier, with the smallest CO2 sensor we've ever seen: it's the Sensirion STCC4 Miniature CO2 Sensor (https://www.digikey.com/en/product-highlight/s/sensirion/stcc4-miniature-co2-sensor) Sensirion has always been our top choice for air quality sensing, and now they've got the tiniest sensor yet with ambient-air CO2 measurements.

We've covered many Sensirion CO2 sensors before, and made breakouts for the most popular like the SCD-30 (https://www.digikey.com/en/products/detail/sensirion-ag/SCD30/8445334) and SCD-40 (https://www.digikey.com/en/products/detail/sensirion-ag/SCD40-D-R2/13684003). Sensirion has also made fully-integrated sensors like the SEN-66 which have an SCD sensor inside (https://www.digikey.com/en/products/detail/sensirion-ag/SEN66-SIN-T/25700945). There's also older eCO2 sensors like the SGP30 (https://www.digikey.com/en/products/detail/sensirion-ag/SGP30-2-5K/7400966) which did 'effective' CO2 measurements by estimating based on organic gas concentrations. While CO2 measurements have always been important for keeping humans and animals happy (https://en.wikipedia.org/wiki/Carbon_dioxide#Human_physiology) - our bodies and brains don't like it when the CO2 concentration goes over ~2000 ppm - it was fairly uncommon to see CO2 monitors in homes or offices. That changed with Covid, because CO2 became a good stand-in for air circulation / clearance: outside air is around 400 ppm, so the closer the indoor air is to 400 ppm the better the circulation.

For folks who need the most accurate CO2 sensing, we'd still point them to the SCD-30 NDIR as a gold-standard (https://www.digikey.com/en/products/detail/sensirion-ag/SCD30/8445334) but it has the side effect of requiring a lot of space and is not particularly low power. The SCD-40 improved on the size/power requirements, using acoustic sensing instead of infrared light. However, if you want something really small, for wearables or phones or portable sensing, we now have a new sensor! The Sensirion STCC4 Miniature CO2 Sensor (https://www.digikey.com/short/nn982w9w) is only 3mm x 4mm x 1.2mm and uses thermal conductivity of the ambient air to calculate CO2 concentration. This means it works only for 'natural ambient air' measurements that have a similar profile to outdoor/indoor air, it's not good for scientific measurement or extreme/outlier locations and situations.

Like the SCD30 and '40 series, the STCC4 will auto-calibrate (https://www.digikey.com/short/nn982w9w) to account for drift. To do that, it must be exposed to outdoor air, with approximate 400 ppm CO2 concentration once a week. Once it has completed its initial startup calibration, it will give measurements with +-100ppm accuracy. Note that this is not as good as the SCD30's +-30ppm or the SCD40's +-50ppm as the tradeoff for the smaller size and price. It also works best with separate temperature + humidity calibration - they suggest the SHT4x series such as SHT40 (https://www.digikey.com/en/products/detail/sensirion-ag/SHT40-AD1B-R3/14322709) or SHT41 (https://www.digikey.com/en/products/detail/sensirion-ag/SHT41-AD1B-R3/15296592) which you can wire up to the peripheral I2C pins for automatic readings. We noted that although the specifications for the STCC4 imply you can use 5V power/logic, that doesn't apply to the SHT4x series so its better to just have everything run at 3.3V.

Sensor readings happen over I2C, and if you've used other Sensirion products you're probably familiar with their 'Command / Response / CRC' style of messaging. Thankfully no clock stretching is used, although it will NAK if the message isn't handled during a read. Two I2C addresses are available thanks to an ADDR pin. And if you want to get started fast, there's a ready-written Arduino compatible library available on GitHub (https://github.com/Sensirion/arduino-i2c-stcc4) as well as Python and embedded C (https://github.com/Sensirion?q=stcc&type=all&language=&sort=). For fast plug-and-play integration, Sensirion has also released an eval board (https://www.digikey.com/short/qwn75j80) and we really like that they went with a simple low-cost Qwiic/Stemma QT design (https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma) with integrated SHT4x that you can use immediately with dev board that has a JST-SH compatible connector.

If you want to integrate the smallest, lowest-cost CO2 sensor we've seen, from the experts at Sensirion, check out the Sensirion STCC4 Miniature CO2 Sensor (https://www.digikey.com/short/nn982w9w) - it's in stock right now for immediate shipment from DigiKey! Order the STCC4 sensor today and by tomorrow morning you'll be taking measurements of indoor CO2 with ready-to-go eval board and firmware example code.

#newproducts

JP’s Product Pick of the Week 10/14/25

AS5600 Magnetic Angle Sensor

https://www.adafruit.com/product/6357

Visit the Adafruit shop online - http://www.adafruit.com

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LIVE CHAT IS HERE! http://adafru.it/discord

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New tutorials on the Adafruit Learning System: http://learn.adafruit.com/

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This week @adafruit we have new works in progress. Pedro is working on a new Raspberry Pi project featuring an eInk Bonnet. Noe is working on a Mac Classic inspired enclosure for the Fruit Jam. Catching up on makes from the community and this week’s time lapse features an articulating elder bone dragon from Minecraft.

E-Ink Bonet

https://www.adafruit.com/product/6418

Fruit Jam

https://www.adafruit.com/product/6200

7.5in eInk Display

https://www.adafruit.com/product/6418

Raspberry Pi 5 2GB RAM

https://www.adafruit.com/product/6007

MagTag 2025 Edition

https://www.adafruit.com/product/4800

Timelapse Tuesday

Elder Bone Dragon By Biocraftlab

https://www.printables.com/refresh?redirectUrl=%2Fmodel%2F1433864-elder-bone-dragon-flexi-toy-figure

https://youtu.be/PDNBE8v1li0

Community Makes

https://www.printables.com/model/1444916-rumi-sword-kpop-demon-hunters

https://www.printables.com/make/2906529

https://www.printables.com/make/2903182

https://www.printables.com/make/2903154

https://www.printables.com/make/2903116

https://www.printables.com/model/1442035-silo-house-with-open-windows

https://www.printables.com/make/2902700

https://www.printables.com/model/1439980-rumi-sword-kpop-demon-hunters-smaller-parts-and-wi

interactive wireless ESP-NOW juggling balls trigger MIDI notes on tap detection. John Park Learn Guide coming soon.

Visit the Adafruit shop online - http://www.adafruit.com

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LIVE CHAT IS HERE! http://adafru.it/discord

Subscribe to Adafruit on YouTube: http://adafru.it/subscribe

New tutorials on the Adafruit Learning System: http://learn.adafruit.com/

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#newproducts

JP’s Product Pick of the Week 10/14/25

AS5600 Magnetic Angle Sensor

https://www.adafruit.com/product/6357

Deep discount during livestream

Visit the Adafruit shop online - http://www.adafruit.com

-----------------------------------------

LIVE CHAT IS HERE! http://adafru.it/discord

Adafruit on Instagram: https://www.instagram.com/adafruit

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New tutorials on the Adafruit Learning System: http://learn.adafruit.com/

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Every week we'll 3D print designs from the community and showcase slicer settings, use cases and of course, Time-lapses! This Week:

Elder Bone Dragon

By Biocraftlab

printables.com/model/1433864-elder-bone-dragon-flexi-toy-figure

Bambu X1C

Polymaker PLA

011hr 57mins

X:202 Y:202 Z:39mm

.2mm layer / .4mm Nozzle

10% Infill / 1mm Retraction

200C / 60C

100g

230mm/s

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LIVE CHAT IS HERE! http://adafru.it/discord

Adafruit on Instagram: https://www.instagram.com/adafruit

Shop for parts to build your own DIY projects http://adafru.it/3dprinting

3D Printing Projects Playlist:

https://www.youtube.com/playlist?list=PLjF7R1fz_OOWD2dJNRIN46uhMCWvNOlbG

3D Hangout Show Playlist:

https://www.youtube.com/playlist?list=PLjF7R1fz_OOVgpmWevin2slopw_A3-A8Y

Layer by Layer CAD Tutorials Playlist:

https://www.youtube.com/playlist?list=PLjF7R1fz_OOVsMp6nKnpjsXSQ45nxfORb

Timelapse Tuesday Playlist:

https://www.youtube.com/playlist?list=PLjF7R1fz_OOVagy3CktXsAAs4b153xpp_

Connect with Noe and Pedro on Social Media:

Noe's Twitter / Instagram: @ecken

Pedro's Twitter / Instagram: @videopixil

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Visit the Adafruit shop online - http://www.adafruit.com/?utm_source=youtube&utm_medium=videodescrip&utm_campaign=3dprinting

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Adafruit Monthly Deals & FREE Specials

https://www.adafruit.com/free?utm_source=youtube&utm_medium=videodescrip&utm_campaign=3dprinting

Join our weekly Show & Tell on G+ Hangouts On Air: http://adafru.it/showtell

Watch our latest project videos: http://adafru.it/latest?utm_source=youtube&utm_medium=videodescrip&utm_campaign=3dprinting

3DThursday Posts: https://blog.adafruit.com/category/3d-printing?utm_source=youtube&utm_medium=videodescrip&utm_campaign=3dprinting

New tutorials on the Adafruit Learning System: http://learn.adafruit.com/?utm_source=youtube&utm_medium=videodescrip&utm_campaign=3dprinting

Music by Dan Q https://soundcloud.com/adafruit

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JST SH Compatible - 1mm Pitch - 3 Pin to Premium Socket Cable - 200mm

long (0:33) https://www.adafruit.com/product/6376

JST SH Compatible 1mm Pitch - 3 Pin to Premium Plug Header Cable -

200mm long (0:33 )https://www.adafruit.com/product/6375

JST SH Compatible 1mm Pitch 3-pin Plug-Plug Cable - 50mm long (1:36)

https://www.adafruit.com/product/6405

JST SH Compatible 1mm Pitch 3-pin Plug-Plug Cable - 100mm long (1:36)

https://www.adafruit.com/product/6404

JST SH Compatible 1mm Pitch 3-pin - Plug-Plug Cable - 200mm long

(1:36) https://www.adafruit.com/product/6406

Conductive Rubber Cord Stretch Sensor + extras! - 3m long (2:19)

https://www.adafruit.com/product/6379

Adafruit E-Ink Bonnet for Raspberry Pi - 24-pin E-Paper Displays

(3:00) https://www.adafruit.com/product/6418

Snap-on Enclosure for Adafruit Fruit Jam (5:28)

https://www.adafruit.com/product/6425

Adafruit SPA06-003 Temperature + Pressure Sensor - STEMMA QT (6:17)

https://www.adafruit.com/product/6420

Adafruit PCM5122 I2S DAC with Line Level Output - HW, I2C or SPI

(6:55) https://www.adafruit.com/product/6421

Slim 19-Conductor Cable - 1.8 meter / 6 feet long (8:52)

https://www.adafruit.com/product/6412

Adafruit Feather STM32F405 Express (9:13) https://www.adafruit.com/product/4382

Raspberry Pi M.2 HAT+ Compact (10:15) https://www.adafruit.com/product/6427

NeoPixel Nano 2020 RGB LEDs - 100-pack - WS2812B (10:56)

https://www.adafruit.com/product/6428

Raspberry Pi 500+ (11:14) https://www.adafruit.com/product/6416

MyoWare 2.0 Muscle Sensor (12:01) https://www.adafruit.com/product/6423

ESP32-S2 Saola 1R Dev Kit featuring ESP32-S2 WROVER (12:52)

https://www.adafruit.com/product/4693

Adafruit STHS34PF80 IR Presence / Motion Sensor - STEMMA QT / Qwiic

(13:39) https://www.adafruit.com/product/6426

Visit the Adafruit shop online - http://www.adafruit.com

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New nEw NEWs New Products, News, and more: https://www.adafruit.com/newsletter #newnewnew

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Visit the Adafruit shop online - http://www.adafruit.com

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LIVE CHAT IS HERE! http://adafru.it/discord

Subscribe to Adafruit on YouTube: http://adafru.it/subscribe

New tutorials on the Adafruit Learning System: http://learn.adafruit.com/

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John Park's Workshop Live 10/9/25

Slow Movie Player

JPPPoW recap

CircuitPython Parsec

tool tips

gear report

and more!

Visit the Adafruit shop online - http://www.adafruit.com

-----------------------------------------

LIVE CHAT IS HERE! http://adafru.it/discord

Adafruit on Instagram: https://www.instagram.com/adafruit

Subscribe to Adafruit on YouTube: http://adafru.it/subscribe

New tutorials on the Adafruit Learning System: http://learn.adafruit.com/

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