› M9 Hardware
Smart Sensor Network
Temperature, light, and motion — three senses working together so your bot can decide, not just react.
Competency: Multi-sensor input + Threshold logic + Autonomous decision-making
~$28
Individual DHT22, LDR, and PIR sensors — cheapest way to get all three inputs
View List~$62
Same three sensors in better-made modules + prototyping shield + project box
View ListWhat you're building
Three sensors feeding your microcontroller at once: a DHT22 for temperature/humidity, a photoresistor (LDR) for ambient light, and a PIR module for motion. You'll write logic that combines all three readings to make one decision — the first real step toward an autonomous bot.
Decision Tree: What Do You Have?
🔧 Do you already have an Arduino or Raspberry Pi from M7?
Great — M9 reuses it. No new microcontroller needed; your budget goes entirely to sensors.
🔌 Do you have leftover breadboard + jumper wires from M7?
Perfect, skip wiring purchases entirely. Three sensors fit comfortably on one 830-point breadboard.
📦 Want everything in one box instead of three separate purchases?
Skip straight to the Premium tier's 37-in-1 sensor kit — it includes the DHT22, LDR, and PIR plus dozens of sensors for future projects.
🎯 Tight Budget Tier (~$28)
Three separate sensor modules, cheapest reliable option for each. Reuses your M7 microcontroller, breadboard, and jumper wires.
Temperature + Humidity (DHT22)
Digital sensor, reads both temp and humidity on one pin
DHT22 (AM2302) Module
Why this one: More accurate than the cheaper DHT11, still under $10, huge library support.
Ambient Light (LDR)
Photoresistor (LDR) 5-pack + resistors
Why this one: Simple voltage divider circuit, analog read, no library needed.
Motion (PIR)
HC-SR501 PIR Motion Sensor
Why this one: Industry-standard PIR module, adjustable sensitivity and delay, digital HIGH/LOW output.
Wiring (if you don't already have it)
💚 Budget Tier Total: ~$28
Assumes you have: microcontroller, breadboard, jumper wires from M7. If starting fresh, add $10–15.
⭐ Recommended Tier (~$62)
Better-made sensor modules with screw terminals, a prototyping shield to keep wiring tidy, and a project box to protect the build.
🌡️ Temperature + Humidity: DHT22 Breakout Module
Pre-wired breakout with pull-up resistor built in — one less thing to wire wrong.
💡 Ambient Light: LDR Sensor Module
Pre-built module with onboard comparator — usable as digital or analog input.
🏃 Motion: HC-SR501 PIR Motion Sensor
🧩 Prototyping Shield (Optional, Recommended)
Screw-terminal shield that stacks on your Arduino Uno so sensor wires can't shake loose mid-project.
📦 Project Box
Keeps the sensor network protected and mountable — useful once you start testing it around the house.
⭐ Recommended Tier Total: ~$62
Sturdier build, cleaner wiring, and a box that protects it — worth it if you plan to keep the sensor network running.
What If Something's Unavailable?
❌ DHT22 out of stock?
DHT11 works as a drop-in substitute (same wiring, same library, just lower precision). Both use the same code pattern.
❌ PIR sensor out of stock?
Any HC-SR501-compatible module works — look for "PIR motion sensor module" with the same 3-pin (VCC/OUT/GND) layout.
❌ Can't find a 37-in-1 kit at a good price?
Buy the three individual sensors from the Recommended tier instead — same lesson, just without the extras for later.
❌ OLED display too complex to wire?
Skip it — print sensor readings to the Serial Monitor instead. Add the display later once the sensor logic works.
Next Steps
- 1Pick your tier (Budget / Recommended / Premium).
- 2Add items to your cart using the links above.
- 3While parts arrive, review M7 wiring — M9 builds directly on that setup.
- 4When parts arrive, continue to M11: Full Stack Bot to see how the sensor network feeds into motor control.
› Questions?
Stuck or need help?
Check the Learning Guides for wiring diagrams and troubleshooting, join our Discord community, or email support@hibot.space.
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