Temperature and Humidity Sensors

📊 Popular Sensors for African Farmers

🛒 What You'll Learn:

🌡️ Compare the most popular sensors for African farms
💰 Understand cost vs. performance trade-offs
✅ Choose the right sensor for your specific use case
📋 Build the perfect sensor kit for your budget

🌡️ DHT22 - Temperature + Humidity Sensor

💰 Cost: $5-7
🌾 Best for: Crop storage monitoring, greenhouses, weather stations
🎯 Accuracy: ±0.5°C temperature, ±2% humidity
⭐ Why choose it: One sensor gives you TWO measurements - temperature AND humidity. Perfect for small farms wanting maximum data from minimum equipment.

💡 DHT22 Pro Tip:

The DHT22 is much more accurate than its cheaper cousin DHT11. For farming, spend the extra $3 — it's worth it for reliable crop decisions!

🌡️ DS18B20 - Digital Temperature Sensor

💰 Cost: $4-6
🌾 Best for: Soil temperature, water temperature, cold storage
🎯 Accuracy: ±0.5°C from -55°C to +125°C
⭐ Special feature: It's waterproof! You can bury it directly in soil or drop it in a water tank. Multiple sensors can share one wire (OneWire protocol).

💡 DS18B20 Pro Tip:

Connect up to 10 DS18B20 sensors to the same GPIO pin! Perfect for monitoring soil temperature at different depths or different zones across your farm.

🔌 NTC Thermistor - Budget Temperature Sensor

💰 Cost: $1-2
🌾 Best for: Budget projects, air temperature monitoring
🎯 Accuracy: ±1-2°C after calibration
⭐ Why choose it: Extremely cheap. Great for learning and for farms where you need many sensors on a tight budget.

⚠️ NTC Note:

NTC thermistors require a voltage divider circuit and calibration. They are NOT waterproof. Good for air temperature only, not for soil or water.

🌱 Capacitive Soil Moisture Sensor

💰 Cost: $8-12
🌾 Best for: Irrigation automation, precision watering
⭐ Why it's better: Unlike resistive sensors, capacitive sensors don't corrode over time. They last for years in soil.

⚠️ Avoid Resistive Soil Sensors!

Resistive sensors cost $2-3 but corrode in 2-4 weeks. You'll buy 10+ per year. Capacitive sensors ($8-12) last 3-5 years — cheaper in the long run!

📋 Quick Selection Guide

💰 Low budget (~$10 total)
→ NTC Thermistor + Resistive Soil Moisture
⚠️ Resistive sensor will corrode — replace every 1-2 months
⭐ Best value (~$15 total)
→ DHT22 + Capacitive Soil Moisture
✅ Recommended for most small farms — lasts years!
🏆 Professional farm (~$25 total)
→ DS18B20 (soil temp) + DHT22 (air temp/humidity) + Capacitive Moisture
✅ Complete monitoring solution — soil + air + moisture

📖 Case Study — Sensor Selection Saves $500/Year, Uganda:

A farmer started with cheap sensors ($10 total):

❌ Problem: Resistive sensor corroded every 3 weeks → bought 12 replacements ($36/year)
❌ Problem: NTC thermistor was inaccurate without calibration
✅ Upgraded to: DHT22 + Capacitive sensor ($15 one-time)
💰 Savings: $36/year on replacements + better data = higher yield

"I wasted money on cheap sensors. The capacitive sensor and DHT22 have been working perfectly for 2 years. Buy quality once!" — Farmer, Wakiso District

        📊 Sensor Comparison Summary:
        🌡️ DHT22: Best all-around — temp + humidity, accurate, $5-7
🌊 DS18B20: Best for soil/water — waterproof, multiple sensors on one wire, $4-6
🔌 NTC: Cheapest — $1-2, but needs calibration, not waterproof
🌱 Capacitive moisture: Best for irrigation — lasts 3-5 years, $8-12
⚠️ Resistive moisture: Avoid — corrodes in weeks, false economy!

    

💡 Where to Buy in Africa:

🌍 Online (international): AliExpress, Amazon (2-4 weeks shipping)
📍 Local electronics shops: Check major cities — often faster but more expensive
📦 Bulk buying: Buy 5-10 sensors at once to save on shipping
🤝 Farmer cooperatives: Group buying reduces cost per sensor

🎯 Key Takeaways:

✅ DHT22 = Best all-around sensor (temp + humidity, $5-7)
✅ DS18B20 = Best for soil/water (waterproof, multiple sensors on one wire)
✅ Capacitive moisture = Lasts 3-5 years (resistive corrodes in weeks!)
✅ Best value kit: DHT22 + Capacitive moisture = $15 total
✅ Low budget: NTC + Resistive = $10, but replace resistive often
✅ Professional farm: DS18B20 + DHT22 + Capacitive = $25 complete solution
✅ Quality sensors pay for themselves in 1-3 months through water savings

💡 Key Takeaways:

Apply these concepts directly to your farm or project.
Take notes on important details for the quiz.
Use the button below to track your progress.

← Previous Lesson 📝 Take Quiz →