Capstone & Resources · Study deck

Capstone Projects: Agriculture and Environment

A field node and an indoor monitor may share sensors but face different power, weather, and network limits.

Test Tessa is your guide for this deck.

projects
Test Tessa, the module guide, in a scene from this chapter.
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After studying this chapter

Learning objectives

You will be able to:

  • Explain: Calibrated sensors establish the evidence, watering control acts on it, power and connectivity keep the loop available outdoors, the algorithm explains when action is permitted, and documentation preserves calibration, safety, and recovery steps.
  • Explain: The shared capstone approach (reviewable claims, the thin-slice method, and interface evidence) is introduced on the Capstone Projects hub; this part works through the Smart Agriculture System brief.
  • Explain: That changes the review question from "did the system observe correctly?" to "did the system act safely when soil, weather, water level, and schedule evidence disagreed?".
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Major section

Start With the Decision

A field node and an indoor monitor may share sensors but face different power, weather, and network limits.

  • Each project brief must turn those limits into testable evidence.

A field node and an indoor monitor may share sensors but face different power, weather, and network limits. Each project brief must turn those limits into testable evidence.

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Major section

Capstone Project 2: Smart Agriculture System

The shared capstone approach (reviewable claims, the thin-slice method, and interface evidence) is introduced on the Capstone Projects hub; this part works through the Smart Agriculture System brief.

  • The second brief adds actuation.
  • The system should work both indoors (houseplants) and outdoors (garden), with solar power capability for remote deployment.
  • Smart irrigation projects show how IoT can reduce manual monitoring, improve watering consistency, and make resource use visible.
  • Solar power sizing requires matching daily energy consumption with panel output.

Why it matters

Smart irrigation projects show how IoT can reduce manual monitoring, improve watering consistency, and make resource use visible.

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Major section

Capstone Project 2: Smart Agriculture System (continued)

That changes the review question from "did the system observe correctly?" to "did the system act safely when soil, weather, water level, and schedule evidence disagreed?".

  • Your system should demonstrate closed-loop sensing and actuation while still protecting plants from unsafe automated decisions.
  • ESP32 + LoRa transmits once/hour (30s active at 200mA, rest at 5mA sleep).
  • Step 2 — Node publishes readings over LoRa or Wi-Fi.
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Major section

Capstone Project 2: Smart Agriculture System (continued)

With 80% charging efficiency, the panel yields 20Wh/day; under that electronics-only estimate, an 11Wh 18650 could charge in roughly half a sunny day.

  • Include pump run time, sensors, and regulator losses before claiming whole-system autonomy or cloudy-day margin.
  • Step 3 — Gateway or cloud service stores readings and evaluates watering rules.
  • No category can compensate for an unsafe or unreviewable control path.
  • Together those records make the field claim reproducible.
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Major section

Capstone Project 2: Smart Agriculture System (continued)

Calibrated sensors establish the evidence, watering control acts on it, power and connectivity keep the loop available outdoors, the algorithm explains when action is permitted, and documentation preserves calibration, safety, and recovery steps.

  • The must-have path measures soil moisture, soil temperature, ambient temperature and humidity, schedule state, smart watering, and pump or valve control.
  • Those readings and actions must share a traceable zone and time context.
  • The result is a functional system within budget.
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Major section

Capstone Project 1: Smart Environment Monitor

The first brief keeps the system relatively contained: indoor sensing, Wi-Fi/MQTT delivery, cloud storage, and a dashboard that makes room conditions visible.

  • Message Queuing Telemetry Transport (MQTT) is a lightweight method for sending named data streams through a message service.
  • A student build is not a certified safety system.

Key terms

Telemetry
Telemetry is a time-linked record from a device.

Why it matters

With those best-case inputs, the arithmetic produces 136 days, or 19 times the target, but that ratio is not engineering margin for retries or display use because those costs were omitted from the active window.

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Major section

Capstone Project 1: Smart Environment Monitor (continued)

A bright chart is easy to build, but it can hide an unplugged sensor or a value with the wrong units.

  • The deeper sections guide design, parts, data flow, tests, and review so the final project states what it proved and what remains outside scope.
  • The system should provide real-time dashboards, historical analytics, and automated alerts when conditions exceed healthy thresholds.
  • Meeting the 7-day battery life target requires careful power budgeting.
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Major section

Capstone Project 1: Smart Environment Monitor (continued)

Its separate 2 kohm by 100 pF sensing time constant is 200 ns.

  • Indoor environment monitoring helps facility teams spot poor ventilation, comfort problems, and air-quality trends before they become persistent operational issues.
  • Your system should turn raw sensor readings into clear dashboard signals and actionable alerts.
  • Step 1 — Sensors provide temperature, humidity, CO2, particulate, light, and noise readings.
  • Step 2 — ESP32 validates and publishes readings over Wi-Fi using MQTT.
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Deck summary

Key takeaways

A field node and an indoor monitor may share sensors but face different power, weather, and network limits.

  • The shared capstone approach (reviewable claims, the thin-slice method, and interface evidence) is introduced on the Capstone Projects hub; this part works through the Smart Agriculture System brief.
  • That changes the review question from "did the system observe correctly?" to "did the system act safely when soil, weather, water level, and schedule evidence disagreed?".
  • With 80% charging efficiency, the panel yields 20Wh/day; under that electronics-only estimate, an 11Wh 18650 could charge in roughly half a sunny day.
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Retrieval practice

Recall check 1 of 6

Test Tessa says: answer from memory, then check your reasoning.

Q1The hardware list specifies 'Capacitive (not resistive!)' soil moisture sensors. Why is this distinction critical for a long-term agricultural deployment?

ACapacitive probes are always factory-calibrated more accurately than resistive probes
BCapacitive probes usually cost less once waterproof cabling is included
CCapacitive probes automatically draw less power during every measurement
DResistive probes can corrode as DC current passes through wet soil over time
Show answer

Answer: D When a resistive probe passes DC current through wet soil, electrochemical effects can corrode exposed electrodes.

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Retrieval practice

Recall check 2 of 6

Test Tessa says: answer from memory, then check your reasoning.

Q2A soil-moisture sensor is stuck reporting dry even after watering, so the controller repeatedly evaluates a dry condition. Why does MIN_INTERVAL_HOURS matter?

ATo cap daily water use even when every soil zone reports consistently dry
BTo prevent repeated watering from one bad dry reading
CTo allow time for the water to soak into the soil before measuring again
DTo synchronize watering times across multiple zones
Show answer

Answer: B The stuck-dry signal would keep requesting water.

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Retrieval practice

Recall check 3 of 6

Test Tessa says: answer from memory, then check your reasoning.

Q3An agricultural sensor is 200 m from the farmhouse, outside tested Wi-Fi coverage. A LoRa gateway at the farmhouse has passed a link trial to that location, and the sensor sends small, infrequent readings. Which factor favors LoRa?

ALoRa provides longer range and lower power beyond Wi-Fi coverage
BLoRa is selected because it sends dashboard data faster than Wi-Fi
CLoRa simplifies deployment by connecting the field node directly to the cloud service
DLoRa is preferable because its protected telemetry path better suits watering commands
Show answer

Answer: A The LoRa link is tested at the field location while Wi-Fi has no coverage there; small infrequent readings fit LoRa's lower data rate.

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Retrieval practice

Recall check 4 of 6

Test Tessa says: answer from memory, then check your reasoning.

Q4An environment monitor already uses an I2C BH1750 light sensor and OLED display, and its alert design needs pressure context as well as temperature and humidity. The candidate DHT22 costs $5 and BME280 costs $15. Which factor should most influence the choice?

AAlways choose the cheaper option to minimize cost
BUse the BME280 mainly because pressure readings may become interesting later
CUse the DHT22 because examples online remove most integration uncertainty
DUse BME280 when I2C wiring and pressure context reduce risk
Show answer

Answer: D The BME280's I2C interface is crucial when you're also connecting a BH1750 light sensor and OLED display on the same bus.

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Retrieval practice

Recall check 5 of 6

Test Tessa says: answer from memory, then check your reasoning.

Q5Looking at the MQTT topic structure above, why is each sensor value published to a separate topic (e.g., environment/{device_id}/temperature) rather than all values in a single JSON payload to environment/{device_id}/all?

ASingle-value topics use less bandwidth than JSON
BMQTT brokers cannot route messages that contain multiple sensor fields
CQoS levels can only be configured when each value has its own topic
DSubscribers can filter by sensor type without parsing unused fields
Show answer

Answer: D Topic-per-sensor allows selective subscription.

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Retrieval practice

Recall check 6 of 6

Test Tessa says: answer from memory, then check your reasoning.

Q6The Environment Monitor stores sensor data in InfluxDB (a time-series database) rather than a general relational schema. With 5 sensors publishing every 5 minutes, you'll have 525,600 data points per year. Which requirement most directly supports evaluating a time-series-oriented design?

AInfluxDB is free while PostgreSQL requires a license
BUse time-series retention, compaction, and downsampling
CPostgreSQL cannot store numeric sensor values
DInfluxDB provides built-in visualization that PostgreSQL lacks
Show answer

Answer: B Retention, compaction, and downsampling are first-class time-series requirements that InfluxDB is designed to express.

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Print reference

Answers 1 of 2

Answer key.

  1. D · When a resistive probe passes DC current through wet soil, electrochemical effects can corrode exposed electrodes.
  2. B · The stuck-dry signal would keep requesting water.
  3. A · The LoRa link is tested at the field location while Wi-Fi has no coverage there; small infrequent readings fit LoRa's lower data rate.
  4. D · The BME280's I2C interface is crucial when you're also connecting a BH1750 light sensor and OLED display on the same bus.
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Print reference

Answers 2 of 2

Answer key.

  1. D · Topic-per-sensor allows selective subscription.
  2. B · Retention, compaction, and downsampling are first-class time-series requirements that InfluxDB is designed to express.
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