Environmental Sensing


Environmental Monitoring for the Internet of Things

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Dive into Environmental Sensing & Control

With its built-in sensors, microSD card slot, ESP32 wireless capabilities, wall-mountable enclosure, and ample examples and documentation, EMIT accelerates the development of environmental sensing and control applications, like a greenhouse controller, a central heating thermostat, or an environmental data logger. Its easy expandability also makes EMIT an ideal platform for teaching and learning about the hardware, software, and design aspects of IoT product development.

Plug Your ESP32 Into the World Around It

EMIT has been built around the popular 30-pin DOIT ESP32 DEVKIT V1, which is a low-cost, low-power, dual-core, wireless IoT module with integrated Wi-Fi and Bluetooth connectivity. The ESP32 module itself is extremely well supported, of course, and you will find a number of websites and blogs that offer tutorials on both Python and Arduino development.

The 30-pin version of the DEVKIT V1 is affordable and easy to find, both on Amazon and elsewhere. Its schematic has been published online and there are many websites with additional information about the board.

All the bits. (Click to expand)

In addition to the ESP32, a microSD card socket, and a DC input connector, EMIT includes several key components related to environmental monitoring and control: an AM2302/DHT22 temperature and humidity sensor, a 5 A relay with a status LED, two user-programmable LEDs, and a 12-pin expansion connector with which you might add a soil moisture probe, an ambient light sensor, an additional relay, a camera, or some other peripheral that is not integrated into the board itself.

Looking the Part

Like many products, EMIT started life as a simple breadboard project — a quick way to log the temperature and humidity of our basement so we could determine just how cold things got in winter. However, I soon realized two things: first, that we could use it for many other purposes, especially if I added a relay; and second, that I would need to make it a whole lot better looking if I wanted my wife to let me hang it on a wall.

EMIT mounted on the wall

After three iterations, EMIT v1.2 is now stable, reliable and easy to use. It has been designed to fit inside a low-cost, vented, wall-mounted enclosure that looks good just about anywhere.

Supporting Every Stage of Your Project

We know that developing hardware that connects to "the Internet of Things" (IoT) isn’t easy. Every new project or application needs a lot of different elements, including hardware, firmware, infrastructure, brokers, application software, etc., to work seamlessly together.

So, as part of this project, to help make life a little easier, we have also created detailed guides, example firmware, a free-to-use public MQTT broker, and even a simple web application, so you can dive right into the parts of the project that interest you the most.

Typical Applications

Features & Specifications

Temperature Measurement
Range-40° to +80° C
Resolution0.1° C
Accuracy (Typical)+/- 0.5° C (+10° C to +55° C)
+/- 1.5° C (< 10° C or > 55° C)
Max Error+/- 2.0° C (at < 10° C or > 55° C)
Repeatability (Typical)+/- 0.2° C
Read Frequency2 seconds max
Humidity Measurement
Range0 to 99.9 %RH
Resolution0.1 %RH
Accuracy (Typical)+/- 2 %RH (20% to 80%)
+/- 3 %RH (< 20% or > 80%)
Max Error+/- 5 %RH (at < 20% or > 80%)
Repeatability (Typical)+/- 1 %RH
Read Frequency2 seconds max
Power Requirements
Voltage Range6 to 12 VDC
Power Consumption50 mA typical
Physical Dimensions
Width81 mm
Height81 mm
Depth18 mm


EMITArduino MKR Wi-Fi 1010 + AM2302MXCHIP AZ3166 IoT DevKit
Components EMIT Board + ESP32 Module An Arduino MKR Wi-Fi 1010, an AM2302 sensor, a relay Module, and a microSD PCB An MXCHIP AZ3166 IoT DevKit, a relay Module, and a microSD PCB
Published schematicsYes Yes Yes
All-in-one solutionYes No No
Enclosure availableYes No No
Operating voltage6 - 12 VDC 7 - 12 VDC 5 V (USB only)
Temperature Sensor40° to +80° C (integrated) 40° to +80° C (separate PCB) 40° to +80° C (separate PCB)
Humidity Sensor0 to 99.9 %RH (integrated) 0 to 99.9 %RH (separate PCB) 20 to 80 %RH (separate PCB)
Relay5 A SPST (integrated) 10 A SPDT (separate PCB) 10 A SPDT (separate PCB)
SD Card holderIntegrated Separate PCB Separate PCB
LEDs2 1 2
ADC pins4 6 2
ADC resolution16 bits 12 bits 12 bits
Arduino supportYes Yes Yes
MicroPython supportYes No No
Dimensions (LxWxH)81 x 81 x 18 mm 69 x 54 x 15 mm 140 x 100 x 21 mm

Program in Python or Arduino(C/C++)

EMIT can be programmed using either MicroPython or Arduino (C/C++). We have published a step-by-step firmware development guide for both languages so you can develop EMIT applications in your preferred language.

Support & Documentation

Our goal is to make EMIT the perfect starting place for your next IoT project, regardless of your ambitions or skill level. When we designed EMIT we also created:

All documents and code examples are available in the EMIT GitHub repository!

More information is available on the website, and of course, you can always reach us through the Ask a question form on our campaign page.

In the Press

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Produced by ControlBits in Wales, United Kingdom.

Sold and shipped by Crowd Supply.

EMIT - Board Only

A dev board with a socket for a 30-pin DOIT ESP32 DEVKIT V1 (not included), an integrated temperature and humidity sensor, a microSD slot, an I/O expansion socket, and an 5 A SPST relay.

$29 $8 US Shipping / $18 Worldwide

EMIT - Full Kit

A Wi-Fi- and Bluetooth-enabled ESP32-based dev board with an integrated temperature and humidity sensor, a microSD slot, an I/O expansion socket, and an 5 A SPST relay. Includes a 30-pin DOIT ESP32 DEVKIT V1, a custom enclosure, an 8 GB microSD card, and a USB cable.

$59 $8 US Shipping / $18 Worldwide

About the Team


Wales, United Kingdom  ·

At Control Bits we're dedicated to building great IoT products that are open to everyone through education, hardware development kits, and open source software. Along the way we aim to build an open and vibrant community.

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