# Pathways — Master Shopping List

*A standalone parts guide for the entire curriculum: 15 STEAM modules + 10 effects-pedal modules + the Science Lab, Body & Mind, Space, and Growing Lab units + the oscilloscope and Breathing Coach tools.*

Copyright © 2026 Ryan Frazier. All rights reserved. · Provenance: PP-PATHWAYS-2026-original-work

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## Start here: pick your path

This curriculum was originally written for the **Piper Computer Kit V4B with Sensor Explorer** — an all-in-one wooden-kit Raspberry Pi with sensors included. That kit is wonderful but not cheap. **You do not need it.** The exact same projects run on a bare Raspberry Pi plus a handful of inexpensive parts, and several modules (plus the virtual oscilloscope) run on *any* computer with a web browser.

Choose whichever path fits your budget:

| Path | Who it's for | Rough cost |
|------|--------------|-----------|
| **A — Piper Computer Kit** | You want the polished all-in-one experience, the build-the-computer story, and the sensors bundled. | ~$250–300 + a few add-on parts |
| **B — Bare Raspberry Pi + parts à la carte** | You're comfortable buying components and want the lowest cost. Same projects, ~⅓ the price. | ~$90–160 all in |
| **C — Use what you already have** | You have a Pi (or any computer) and some parts already, or only want certain modules. | $0–60 to fill gaps |

> **Keeping Piper in the picture:** Every module still references the Piper kit where relevant, and all the Piper instructions still apply if you own one. The lists below simply add the generic-component equivalent so you can choose. Wherever a module says "Piper Computer Kit," read it as "your Raspberry Pi (Piper or bare)."

---

## 1. The computer (choose one)

### Option A — Piper Computer Kit V4B with Sensor Explorer
- **Piper Computer Kit V4B** — includes a Raspberry Pi, screen, battery, buttons, and the build experience. (~$250–300, playpiper.com or education resellers)
- **Sensor Explorer add-on** — bundles the ultrasonic, color, and temperature sensors. (Often included; confirm at purchase.)

*This single purchase covers the base computer AND most of the sensors in Section 2.*

### Option B — Bare Raspberry Pi (lowest cost)
- **Raspberry Pi 4 (2GB or 4GB)** or **Pi 5** — recommended. A **Pi 3B+** also works and is cheaper used. (~$35–60)
- **microSD card, 32GB**, with Raspberry Pi OS flashed. (~$8)
- **Official USB-C (Pi 4/5) or micro-USB (Pi 3) power supply.** (~$8–10)
- **A screen + USB keyboard + mouse** — *or* run "headless" over your laptop via VNC/SSH (free). Any HDMI monitor and spare keyboard/mouse work. (~$0 if you have them)

### Option C — Any computer you already own
- The **app itself** (`index.html`) and the **virtual oscilloscope** (`oscilloscope.html`) run in any modern web browser — no Pi required, no install.
- The **software-only learning** (waveform theory, the oscilloscope experiments, quizzes, lesson reading) needs nothing but a browser.
- You only need a Pi + parts when you want to run the *physical* sensor and audio projects on real hardware.

---

## 2. Sensors

*Included in the Piper Sensor Explorer kit (Path A) for the STEAM modules. Buy individually for Path B/C. All are common hobby parts from Adafruit, SparkFun, Amazon, or AliExpress. Plan only the modules and units you'll actually teach.*

### Core STEAM sensors (M1–M15)

| Part | Used in modules | Qty | Approx. each | Notes |
|------|-----------------|-----|--------------|-------|
| **HC-SR04 ultrasonic distance sensor** | M1, M4, M9, M12, M13 | 1 | $2–4 | The workhorse. Buy a 2-pack so you have a spare. |
| **TCS34725 color sensor** | M2, M8, M10, M11, M14, M15 | 1 | $7–9 | I²C. Adafruit #1334 is the reference part. |
| **Temperature sensor — TMP102, TMP117, or DS18B20** | M3, M10 | 1 | $5–8 | Any of the three works; the code notes which library to import for each. DS18B20 is cheapest. |
| **Capacitive soil-moisture probe** *(optional)* | M10 | 1 | $6–9 | Only for the Plant Whisperer extension. Get the **capacitive** type — resistive ones corrode in weeks. |

### Science Lab sensors (S1–S10)

*One flagship sensor per scientific field. All are I²C unless noted, so they share the same four wires (3.3V, GND, SDA, SCL).*

| Part | Module | Approx. | Notes |
|------|--------|---------|-------|
| **BME280** temp/pressure/humidity | S1 Barometer | $8–12 | I²C. The weather station. |
| **ADXL345** accelerometer | S2 Seismograph | $5–7 | I²C. |
| **Raspberry Pi Camera Module** | S3 Night-Sky | $15–25 | CSI ribbon cable. Reusable for Growing Lab time-lapse. |
| **QMC5883L** magnetometer | S4 Magnetism | $4–6 | I²C. (HMC5883L also works.) |
| **AS7341** spectral sensor | S5 Spectrometer | $12–16 | I²C. |
| **MAX30102** pulse/heart sensor | S6 Heart *(also B1, B2)* | $4–6 | I²C. Shared with Body & Mind. |
| **SGP30** air-quality sensor | S7 Air | $12–16 | I²C. eCO₂ / TVOC. |
| **AMG8833** thermal camera | S8 Heat | $30–40 | I²C. The priciest sensor — skip if budget is tight. |
| **GSR (skin-response) sensor** | S9 Stress *(also B2)* | $7–10 | Analog → needs the MCP3008 ADC (below). |
| **IR break-beam sensor (pair)** | S10 Gravity | $3–4 each | Buy **two**. GPIO digital. |

### Body & Mind (B1–B4)

*The Breathing Coach (B1) runs in any browser — **no hardware required**. The rest build on the heart (S6) and stress (S9) sensors.*

| Part | Module | Approx. | Notes |
|------|--------|---------|-------|
| **MAX30102** heart sensor | B1 *(optional)*, B2 | see S6 | B1 needs none; sensor is optional biofeedback. |
| **GSR sensor + MCP3008** | B2 Calm Dashboard | see S9 | Fuses heart + skin. |
| **Momentary push button** | B3 Reaction | <$1 | From your button assortment. (Optional LED + 220 Ω.) |
| **MLX90614** IR thermometer | B4 Body's Weather | $8–12 | I²C (0x5A). Non-contact fingertip temperature. |

### Space — software-defined radio (SP1–SP5)

*One dongle powers the whole unit. SP1 (FM/scan) and SP2 (aircraft) work with the dongle's included antenna alone.*

| Part | Module | Approx. | Notes |
|------|--------|---------|-------|
| **RTL-SDR USB dongle kit** | all SP | ~$30 | Get the "RTL-SDR Blog V3/V4" kit — includes antennas. The one essential. |
| **V-dipole antenna (137–146 MHz)** | SP3, SP4 | $8–12 or DIY | Two ~53 cm rods in a 120° V. Easy and cheap to build. |
| **1420 MHz LNA** (e.g. Nooelec SAWbird+ H1) | SP5 Hydrogen line | ~$25 | Low-noise amp at the antenna. **Essential** for radio astronomy. |
| **Dish or horn antenna** | SP5 | $0–40 | A repurposed satellite dish or a built horn. |

### The Growing Lab — agricultural sensors & actuators (G1–G6)

*The soil sensor and GSR both use the shared MCP3008 ADC. The automated modules use a relay so the Pi can safely switch a pump, light, or heat mat — each on its **own** power supply.*

> ⚠ **Mains safety:** buy the **low-voltage** versions (USB 5V or 12V DC) of the grow light and heat mat so students only ever handle low-voltage wiring. Most cheap seedling heat mats are 120V wall-plug models. If that's what you have, **never** wire it into a breadboard relay module: use an enclosed GPIO-controlled outlet built for the job (e.g. the Digital Loggers IoT Relay, ~$30), so the Pi only touches its low-voltage control input, and an adult plugs devices in.

| Part | Module | Approx. | Notes |
|------|--------|---------|-------|
| **Capacitive soil-moisture sensor** | G1, G2, G6 | $4–6 | Analog → needs MCP3008. **Capacitive only** (resistive corrodes). |
| **BH1750 light sensor** | G3, G6 | $3–5 | I²C (0x23). Reads lux. |
| **DHT22 temp/humidity sensor** | G4, G6 | $4–6 | Single GPIO data pin (+ 10 kΩ pull-up). |
| **DS18B20 waterproof probe** | G5 Compost | $4–6 | 1-Wire (+ 4.7 kΩ pull-up). |
| **Relay module (1-channel, 5V)** | G2, G3, G4 | $2–4 | GPIO-switched. Buy **3** for the automated modules. |
| **Small 5V water pump + tubing** | G2 Self-Watering | $8–12 | Needs its **own** power supply through the relay. |
| **Low-voltage LED grow light** (USB 5V or 12V DC) | G3 | $8–15 | Switched by relay, own low-voltage supply. Wall-plug lights: use an enclosed GPIO outlet instead. |
| **Low-voltage seedling heat mat** (USB 5V or 12V DC) | G4 | $10–15 | Switched by relay, own low-voltage supply. Wall-plug (120V) mats: use an enclosed GPIO outlet instead. |

### Shared add-on — analog-to-digital converter

| Part | Used in | Approx. | Notes |
|------|---------|---------|-------|
| **MCP3008 8-channel ADC** | S9, B2, G1, G2, G6 | $3–5 | The Pi has no analog input; this chip bridges analog sensors (GSR, soil moisture) to the Pi over SPI. Buy one or two — it's reused across units. |

---

## 3. Audio input & output

| Part | Used in | Qty | Approx. | Notes |
|------|---------|-----|---------|-------|
| **USB microphone** | M4, M6, software pedals P1–P6, scope | 1 | $10–20 | Any plug-and-play USB mic. A clip-on lavalier is fine. |
| **Headphones or small speaker** | most audio modules | 1 per station | $5–15 | Headphones strongly recommended in a classroom — audio modules get loud. |
| **USB audio interface — Behringer UCA202** | P7, P8, P9, P10 (hardware pedals), `guitar_scope.py` | 1 | ~$30 | The classroom standard. Needed to get guitar-level signal into the Pi cleanly. The UCA222 is identical. |

---

## 4. Electronic components

*The backbone of the breadboard pedal builds (P7–P10) and several sensor/audio modules. A single "electronics starter kit" from Amazon (~$25–35) covers most of the resistors, capacitors, LEDs, jumper wires, breadboards, and buttons below — often cheaper than buying à la carte.*

### Breadboards & wiring
| Part | Used in | Qty | Approx. | Notes |
|------|---------|-----|---------|-------|
| **Breadboard, 830-point** | M5, M6, P7–P10, most builds | 1 per student pair; **3+ for P10** | $4–6 | P10 (capstone) chains three pedals, so that pair needs three boards. |
| **Jumper wire assortment (M-M, M-F)** | nearly every module | 1 pack (120 ct) | $7 | Get a multi-color pack; the diagrams use color to mean signal/power/ground. |

### Resistors (a single assortment kit covers all of these)
| Value | Used in | Notes |
|-------|---------|-------|
| **220 Ω** (×10) | M6, M7, M8, M13, M14 (LED current limiting) | Red-red-brown |
| **1.5 kΩ** (×2) | P7 buffer | Brown-green-red |
| **4.7 kΩ** (×2) | P9 overdrive | Yellow-violet-red |
| **10 kΩ** (×6) | M7 pull-down, P9 virtual ground | Brown-black-orange |
| **100 kΩ** (×2) | P8 fuzz | Brown-black-yellow |
| **1 MΩ** (×4) | P7, P8, P9 | Brown-black-green |

> A **resistor assortment kit** (~$8, hundreds of values) is the easy buy — you'll have every value above and spares.

### Capacitors
| Value / type | Used in | Notes |
|--------------|---------|-------|
| **0.05 µF (50 nF) film** | P9 | bandwidth shaping |
| **0.1 µF film** | P8, P9 | coupling |
| **1 µF film** | P7, P9 | coupling — film, *not* ceramic, for clean audio |
| **10 µF electrolytic** | P8 | polarized — watch the + / − legs |

> A **film + electrolytic capacitor assortment** (~$8) covers these with spares.

### Semiconductors (the heart of the pedal builds)
| Part | Used in | Qty | Approx. | Notes |
|------|---------|-----|---------|-------|
| **2N5457 JFET** (or J201) | P7 buffer | 1–2 | $1 ea | Buy a few — easy to mis-pin while learning. |
| **2N3904 NPN transistor** | P8 fuzz | 1–2 | $0.25 ea | Comes in cheap 50-packs. |
| **TL072 op-amp (8-pin DIP)** | P9 overdrive | 1–2 | $1 ea | Buy spares. |
| **1N4148 silicon diode** | P8, P9 | 4+ | $0.10 ea | Comes in cheap 100-packs. |

### Potentiometers (control knobs)
| Value / taper | Used in | Qty | Notes |
|---------------|---------|-----|-------|
| **10 kΩ audio taper** | P8 (volume) | 1 | |
| **100 kΩ audio taper** | P9 (volume) | 1 | |
| **500 kΩ audio taper** | P9 (drive) | 1 | |

### Other components
| Part | Used in | Qty | Approx. | Notes |
|------|---------|-----|---------|-------|
| **LEDs (assorted colors, 5 mm)** | M6, M7, M8, M13, M14 | 10+ | $5/bag | Pair each with a 220 Ω resistor. |
| **Momentary push buttons** | M5, M7 | 3+ | $5/bag | Tactile breadboard-friendly type. |
| **Piezo buzzer (active)** | M7, M9, M11, M13 | 1–2 | $2 ea | Active = makes its own tone. |
| **9 V battery + snap connector leads** | P7–P10 | 1 battery + clip per pedal | $10 | Rechargeable 9 V is worth it long-term. |
| **¼-inch mono panel jacks** | P7–P10 | 2 per pedal | $1 ea | For guitar in / amp out. |

---

## 5. Guitar gear — only for the advanced pedal builds (P7–P10)

*Skip this whole section unless you're doing the breadboard pedals. Your school may already own guitars and amps.*

| Item | Qty | Approx. | Notes |
|------|-----|---------|-------|
| **Electric guitar** | 1+ to share | $0 if borrowed | Any working electric guitar. The school music department may lend some. |
| **Guitar amplifier (battery-powered preferred)** | 1+ to share | $0 if borrowed | Battery amps (Roland Micro Cube, Fender Mini) are safest for students. |
| **¼-inch instrument cables** | 2–3 | $8 ea | Guitar→pedal and pedal→interface. |
| **RCA-to-¼-inch adapter** | 1–2 | $5 | The UCA202 uses RCA jacks; this adapts to ¼-inch. |

---

## 6. Tools (one shared set per classroom)

| Tool | Approx. | Notes |
|------|---------|-------|
| **Digital multimeter** | $15–30 | Essential for the pedal modules' debugging steps. |
| **Wire strippers** | $10 | Only if you're cutting/stripping your own wire. |
| **Small screwdriver set** | $10 | For the Piper build and general use. |
| **Magnetic parts tray** | $6 | Saves the "where did the JFET go" panic. (It's on the floor.) |

---

## 7. Software — all free

Nothing here costs money. On a Raspberry Pi, most of it is pre-installed or one command away.

| Software | For | Install |
|----------|-----|---------|
| **Raspberry Pi OS** | the Pi itself | flashed to the microSD with Raspberry Pi Imager (free) |
| **Python 3** | all modules | pre-installed on Pi OS |
| **Sonic Pi** | M1, M2, M3, M5 audio | free Raspberry Pi package from sonic-pi.net (no longer pre-installed on Pi OS) |
| **A web browser** | the app + virtual oscilloscope + quizzes | any browser, any OS |
| One-time Python setup | all Python modules | `sudo apt install -y python3-venv python3-lgpio python3-gpiozero` · `python3 -m venv --system-site-packages ~/pathways-env` · `source ~/pathways-env/bin/activate` · `pip install rpi-lgpio` |
| Python libraries | various modules | `pip3 install numpy scipy sounddevice pygame python-osc adafruit-circuitpython-tcs34725` (inside `pathways-env`) |
| Unit libraries | Science Lab / Body & Mind / Growing Lab | `pip3 install adafruit-circuitpython-mcp3xxx adafruit-circuitpython-dht adafruit-circuitpython-mlx90614 adafruit-circuitpython-bme280 smbus2` |
| SDR tools | Space unit | `sudo apt install rtl-sdr` · dump1090-fa via FlightAware's apt repository (flightaware.com/adsb/piaware/install) · SatDump for Meteor LRPT (satdump.org) · `pip3 install pyrtlsdr numpy skyfield` |

> **Why the one-time setup:** current Raspberry Pi OS (Bookworm and later) blocks system-wide `pip` installs, and the original `RPi.GPIO` library doesn't work on a Pi 5. A single `pathways-env` environment (created with `--system-site-packages`, so the preinstalled `gpiozero`/`lgpio` stay visible) fixes both; `rpi-lgpio` provides `RPi.GPIO` so every module's code runs unchanged on any Pi.

> Library cheat-sheet by need: **rpi-lgpio** (provides `RPi.GPIO`: buttons, LEDs, ultrasonic, buzzer, relays — works on every Pi including the Pi 5) · **numpy/scipy** (M4, M6, P-series audio math; SDR spectrum/FFT) · **sounddevice** (live audio in/out) · **pygame** (the `mic_scope.py` displays) · **python-osc** (talking to Sonic Pi) · **adafruit-circuitpython-tcs34725** + a temp library (color & temperature sensors) · **adafruit-circuitpython-mcp3xxx** (the MCP3008 ADC — GSR, soil moisture) · **adafruit-circuitpython-dht** (DHT22) · **smbus2** (BH1750 light) · **pyrtlsdr** + **skyfield** (Space unit: spectrum scans and satellite-pass prediction). DS18B20 needs no library — it's read straight from the 1-Wire system files. The Breathing Coach needs no install at all.

---

## 8. Per-module quick reference

*What each module actually needs beyond a working Pi. Plan only the modules you'll teach.*

**Audio modules**
- **M1 Ultrasonic Theremin** — ultrasonic sensor, 4 wires, breadboard, headphones, Sonic Pi
- **M2 Chromatic Sequencer** — color sensor (from M8), colored paper, Sonic Pi
- **M3 Thermal Ambient** — temperature sensor, 4 wires, Sonic Pi, cups of hot/ice water
- **M4 Granular Delay** — ultrasonic sensor, USB mic, headphones (numpy/scipy/sounddevice)
- **M5 Drum Machine** — 3 buttons, jumper wires, (optional 3 LEDs), Sonic Pi
- **M6 FFT Visualizer** — USB mic, 5 LEDs + 5×220 Ω, breadboard, ~12 wires
- **M7 Morse Code** — 1 button + 10 kΩ, buzzer, LED + 220 Ω, wires

**Sensor modules**
- **M8 Color-Mood Lamp** — color sensor, 4 wires, colored objects, (optional 5 LEDs + 220 Ω)
- **M9 Treasure Hunt** — ultrasonic sensor, active buzzer, 5 wires, open space
- **M10 Plant Whisperer** — color + temperature sensors, (optional moisture probe), a plant, 4 weeks
- **M11 Memory Color Game** — color sensor, buzzer, colored cards
- **M12 Music Box** — ultrasonic sensor, passive buzzer (or Sonic Pi)
- **M13 Stealth Detector** — ultrasonic sensor, buzzer, (optional LED + 220 Ω)
- **M14 Color Sorter** — color sensor, 5 LEDs + 220 Ω (or screen output)

**Hybrid capstone**
- **M15 Cymatics** — color sensor + ultrasonic, speaker/headphones (numpy, tkinter)

**Science Lab modules** *(one I²C sensor each unless noted)*
- **S1 Barometer's Memory** — BME280, 4 wires
- **S2 The Floor Listens** — ADXL345, 4 wires
- **S3 Night-Sky Diary** — Pi Camera (CSI ribbon)
- **S4 Invisible Field** — QMC5883L, 4 wires
- **S5 Pocket Spectrometer** — AS7341, 4 wires
- **S6 Your Heart, Drawn** — MAX30102, 4 wires
- **S7 What the Air Holds** — SGP30, 4 wires
- **S8 Seeing Heat** — AMG8833 thermal cam, 4 wires
- **S9 The Stress Signal** — GSR sensor + MCP3008 (SPI)
- **S10 Measuring Gravity** — 2× IR break-beam sensors, frame, GPIO

**Body & Mind modules**
- **B1 The Breathing Coach** — *nothing required* (browser tool); optional MAX30102 for biofeedback
- **B2 The Calm Dashboard** — MAX30102 + GSR + MCP3008 (capstone)
- **B3 Reaction & the Nervous System** — 1 push button (optional LED + 220 Ω)
- **B4 The Body's Weather** — MLX90614 IR thermometer, 4 wires

**Space modules** *(all use the RTL-SDR dongle)*
- **SP1 The Sky Has a Voice** — dongle + included antenna
- **SP2 Eavesdropping on Aircraft** — dongle + included antenna (height helps)
- **SP3 Images from Orbit** — dongle + 137 MHz V-dipole
- **SP4 Hello, Space Station** — dongle + V-dipole (shared with SP3)
- **SP5 The Galaxy's Hum** — dongle + 1420 MHz LNA + dish/horn

**Growing Lab modules**
- **G1 The Thirsty Soil** — capacitive soil sensor + MCP3008 (SPI)
- **G2 The Self-Watering Garden** — soil sensor + relay + 5V pump (own power)
- **G3 Let There Be Light** — BH1750 + relay + low-voltage grow light (own supply)
- **G4 The Germination Chamber** — DHT22 + relay + low-voltage heat mat (own supply)
- **G5 The Compost's Heat** — DS18B20 + 4.7 kΩ pull-up (1-Wire)
- **G6 The Greenhouse Dashboard** — soil + DHT22 + BH1750 together (capstone)

**Software effects pedals (no extra hardware beyond mic + headphones)**
- **P1–P6** — USB mic + headphones; some use the color/ultrasonic sensors you already have. All run in Python/Sonic Pi.

**Hardware breadboard pedals (the big parts list)**
- **P7 Buffer** — breadboard, 2N5457, 1 MΩ, 1.5 kΩ, 2× 1 µF film, 9 V + clip, 2 jacks, USB interface, guitar, amp
- **P8 Bazz Fuss** — breadboard, 2N3904, 1N4148, 100 kΩ, 1 MΩ, 0.1 µF, 10 µF, 10 kΩ pot, 9 V, 2 jacks
- **P9 Overdrive** — breadboard, TL072, 2× 1N4148, 2× 10 kΩ, 1 MΩ, 4.7 kΩ, 0.1 µF×2, 0.05 µF, 500 kΩ + 100 kΩ pots, 9 V, 2 jacks
- **P10 Studio Chain** — everything from P7+P8+P9 + 3 breadboards + patch cables + USB interface + guitar + amp

---

## 9. Budget scenarios

**"I just want the software + oscilloscope + quizzes" — $0**
Any computer with a browser. Open `index.html`. Done.

**"Bare-bones physical projects (sensors + audio), Path B" — ~$90–120**
Pi 4 + SD + power (~$55) · ultrasonic + color + temp sensors (~$20) · USB mic (~$15) · electronics starter kit with breadboard/wires/LEDs/resistors/buttons (~$30). Covers all 15 STEAM modules and the software pedals.

**"Everything including the hardware pedals, Path B" — ~$160–200**
Add to the above: USB audio interface (~$30) · semiconductors + pots + caps + jacks + 9 V (~$30) · borrow a guitar and amp. Covers the entire curriculum end to end.

**"The polished Piper experience, Path A" — ~$280–340**
Piper Computer Kit V4B + Sensor Explorer (~$250–300) · USB mic (~$15) · USB audio interface for the pedals (~$30) · electronics for P7–P10 (~$40). The smoothest classroom experience with the build-it-yourself story baked in.

### Add-on units (on top of any path above)

**"Add the Science Lab (S1–S10)" — ~$100–150 for all ten**
One sensor per field plus an MCP3008 (~$4) for the GSR module. The AMG8833 thermal camera (~$35) is the single big-ticket item — skip it and you're closer to ~$80 for the other nine. Most are $5–15 I²C boards sharing the same four wires.

**"Add Body & Mind (B1–B4)" — ~$10–30**
The Breathing Coach (B1) is **free** — browser only. Add a push button (B3, ~$1) and an MLX90614 (B4, ~$10); B1/B2 reuse the heart and GSR sensors from the Science Lab, so if you have those, the whole unit is ~$11.

**"Add Space (SP1–SP5)" — ~$30 to start, ~$90 for everything**
An RTL-SDR dongle (~$30) covers SP1 (FM) and SP2 (aircraft) on its own. Add a DIY/cheap V-dipole (~$10) for weather satellites and the ISS, and a 1420 MHz LNA + dish (~$50) for the hydrogen-line radio astronomy.

**"Add the Growing Lab (G1–G6)" — ~$50–75 for all six**
Soil sensor + BH1750 + DHT22 + DS18B20 (~$20) · MCP3008 (~$4, shared) · 3 relays (~$9) · small pump (~$10) · low-voltage grow light (~$12) · low-voltage seedling heat mat (~$13), or an enclosed GPIO outlet (~$30) for wall-plug versions. G1 alone (soil + ADC) is ~$10.

**"The whole curriculum, everything, Path B" — ~$350–450**
All of the above on a bare Pi: STEAM + hardware pedals (~$200) + Science Lab (~$120) + Body & Mind (~$15) + Space full (~$90) + Growing Lab (~$65). Spread across a year and shared among student stations, it's remarkably affordable for 50 modules of hands-on science.

---

*Prices are ballpark estimates as of 2026 and vary by supplier and region. Buying assortment kits (resistors, capacitors, jumper wires) is almost always cheaper than à-la-carte for a classroom. Check Adafruit, SparkFun, Amazon, Micro Center, and AliExpress.*