6.9020 HTMAA
Final Project

Objectives

My aspiration is to create an artistic but functional soil-sensing device that connects to my research on peatlands in Northern Ireland. As a design object, I will include this piece for display in an exhibition on this research later this year.

The research associated with this exhibition, which is also the subject of my MCP / MS EECS thesis and my MAD Fellowship project, deals with peatland restoration in Northern Ireland. Peatlands are the most efficient terrestrial carbon stores on Earth, and while Northern Ireland has a high coverage of them (about 18% total peat soil coverage), the vast majority (estimated at 18%) are degraded. The newly released Northern Ireland Peatland Strategy to 2040 follows recent measures in England, Wales, and Scotland to coordinate peatland restoraiton as part of a broader investment in Natural Capital across the UK.

My project follows the technical, social, and historical dimensions of this restoration effort. Peatlands have strong cultural significance, especially in Ireland. This is manifested in the poetry of Seamus Heaney, the ancient bodies preserved in bogs for centuries, and the archeological treasures the bogs have preserved.

Across time, boglands have held a variety of social meanings; they have been interpreted as mystic grounds for worship and sacrifice, as wastelands in need of improvement, as fuel sources to be drained, cut, and dried for bricks to burn, and most recently as powerful carbon sinks in need of large-scale rehabilitation.

In the present, the interpretation of these landscapes integrates all of the forementioned historical vestiges as well as new layers of remote sensing, government-subsidized restoration, and speculative new modes of land valuation in a "Stack" that extends from the soil to the state to the satellite. As peatlands become re-saturated as a part of broader decarbonization efforts, these cultural and technical touchpoints are opportunities for expansive thinking about the way that people feel about their land, and the structures of property and governance that formalize that affinity.

Soil and Peatland Monitoring

Peatland monitoring is essential to peatland restoration in the UK, and many resources have been produced in order to make this practice accessible to landowners and citizen scientists. The Northern Ireland Peatland Collaborative Network published the following Minimum Monitoring Guidelines based on the IUCN UK Peatland Programme's Eyes on the Bog Manual for baseline and continuous bog monitoring. Both sources emphasize that monitoring of the water table height, peat quality and saturation, and other soil qualities should be conducted regularly and thoroughly, however the Eyes on the Bog Manual observes that restored and natural peatlands are highly sensitive to trampling-- this means that damage to fragile vegetation can be caused even by the annual visiting of the same site.

In response to the dual needs for both continuous monitoring and minimal trampling, I am proposing a modular, convertible monitoring kit that is not anchored to a single site but rather mobile across an entire monitoring area. It takes inspiration from various monitoring techniques, for example: "Rust rods" as shown above are anchored in peat for months at a time, developing rust at the level of the water table. My device will offer a way to sense changes in moisture at a single moment in time and at different locations. Additionally, the "Von Post" test performed above involves simply squeezing peat samples in the hand to determine how much soil mass disintegrates. The spade used to collect such samples will be an inspiration for this project.

Concept Development and History

Device Design

In Week 1 I developed a conceptual diagram for the device I would like to build, describing its sensing, sampling, and location tracking capabilities. The aspiration behind this device is to be able to take a walk through a bog, sensing soil qualities as you go, and to come home with a map of your walk and the data you collected: The component on the bottom of the stick is based on the Russian Peat Corer by Aquatic Research, which can take soil samples using a rotating chamber. The Peat Sampler Set by Royal Eijkelkamp is a very similar device, and the Manual for it describes how it works. Based on my initial designs and the insight from Anthony that a LiDAR or Ultrasound depth sensor would be a good choice (and would therefore need to be located at the top of the stick, while the sensors and sampling equipment are at the bottom), I believe the device will work best as two components: an upper device (with most of the electronics and the depth sensor) and a lower device (with the sampling spade and moisture sensing).

Upper Device: GPS

While I have been warned that GPS sensors are not accurate within very precise distances, especially indoors, the GPS available will be able to track a walk of 1-10km outdoors.

Upper Device: Ultrasound

This Ultrasonic Sonar Distance Sensor from Adafruit is amazing, and it can sense distance within a few centimeters. My idea is to use this sensor or a similar one to sense the distance from the top of the stick (an arbitrary distance established at boot-up) and the ground. As this distance diminishes, the depth of the corer and sensors (lower device) is calculable as difference between that initial distance and the present one, minus the distance of the sensors and corer from the end of the stick.

Upper Device: Electronics Integration

In class I learned to use the XIAO RP2040 microcontroller with Arduino code. This would be a good option for my project, although I need more pins. Mid-semester, I am planning to use a Raspberry Pi Pico W, which has the same RP2040 processor but additionally offers more pins and Wi-Fi connection capabilities.

Lower Device: Peat Sampling

Below is a photograph of a sample that the US Geological Survey took from the Great Dismal Swamp in 2017, showing the kind of sample a peat borer withdraws: The cores taken from these devices tend to be about 50cm long, which I expect to be too long for a 3D printed part to hold up against. My thinking is to make a this component about 25cm long, so that the force exerted on the stick and the 3D printed tool end is not excessive.

Lower Device: Moisture Sensing

I think sensing the moisture of the soil electronically is an innovation in peatland sensing, as this usually is done using very low-tech methods for water table tracking over time. My best lead for a sensor for this is the Adafruit STEMMA Soil Sensor, which uses capacitive sensing (like a finger pressing a button) to capture a measure from 200 (dry) to 2000 (wet) as well as a built-in ambient temperature reading from the SAMD10 microcontroller. This seems like a great option for integrating with the project, as it can connect to any microcontroller using an I2C interface.

In my understanding, if I buy this, it would mean I have two microcontrollers in total-- the one on my custom PCB (a Pi Pico W) that integrates all the electronics, and the SAMD10 integrated on this sensor. If I can make a sensor like this one, I still need that microcontroller (and wireless connectivity?) in order to receive and align the data from the sensor with my GPS module. In making one I would probably use a Xiao version because I don't need a lot of pins and it is simpler.

The Stick (and adhesion)

My hope is that this two-part device will be able to attach to any stick. To test this, I am amassing a stick library in my garage: Final Project Idea In order to attach to sticks of varying diameters, both parts will need to use some strategy of attaching securely while remaining removable. I do not want to have to modify the stick I think some combination of a rigid adjustable frame with a flexible interior. Maybe this looks like a belt with variable width, that is also stretchy or grippy. I think this may be possible to 3D print with TPU according to the Prusa Website. This Multipurpose TPU Strap by Hans Hiorth seems like a good reference. I could imagine having two of these attached to the housing for both the upper and lower devices respectively. I would probably redesign it to be wider (create more surface area touching the stick) and have a buckle with multiple prongs.

Components and Skills

Below some notes connecting the components of the device to specific skill categories (both taught and not-taught in this class):

Mechanical Design

to develop an adjustable appendage that can capture soil samples.

3D Printing

to create the sample withdrawal component and housing for electronics.

Electronics

to link battery power to GPS, buttons, and sensor(s).

Input Devices

for capacitance (moisture), light, distance or depth (from top of stick to ground), pressure (tap), and GPS location.

Networking

for wireless communication of data.

Embedded Programming

to program behavior of sensors and buttons.

Web Interface Programming

to display instructions access and display sensed data and sample locations on map.

Foraging and Whittling

to locate and prepare a suitable stick.

Checklist of Information:

Checklist of Skills: