Learning Objective
Measure temperature and humidity using a digital sensor.
Atmospheric Sensing (DHT11)
Hardware: MakerBuddy DHT11 Temp & Humidity Sensor
Dashboard: DHT11 Sensor Cards
See How the DHT11 Temperature and Humidity Sensor Works
Read the picture from left to right: the change in the world → the sensor signal → a useful action.
1 · What it notices
The air's temperature and relative humidity (how full of water vapor the air is).
2 · How it works
Two parts inside react to heat and moisture, and a small chip turns them into digital readings.
3 · Why it matters
The same temperature feels different in damp or dry air.
Where might we use it?
- Classrooms and homes
- Greenhouses
- Server and storage rooms
Student sentence: A DHT11 reports the air's temperature and its relative humidity.
Teacher/parent prompt: Ask, “What changes on the left, what does the sensor turn it into, and what could happen next?”
Theory: Temperature and Humidity
Building on Your Sensor Knowledge
You have used buttons, the potentiometer and the LDR. The DHT11 is an environmental sensor: it measures the air around you. It is your first multi-function sensor, measuring temperature and humidity at the same time.
How the DHT11 Works
Inside the blue grid are a thermistor, a resistor that changes with temperature, and a capacitive humidity sensor. Its layer soaks up water vapor, which changes how much electric charge it stores. A tiny chip turns both readings into a digital signal for the ESP32.
DHT11 vs. DHT22: The Specs
Your kit has the DHT11, and MakerBuddy is set up to read a DHT11 only. Its "big brother," the DHT22 (AM2302), costs a bit more but has a wider range and better accuracy:
| Feature | DHT11 | DHT22 |
|---|---|---|
| Temperature Range | 0°C to 50°C | -40°C to 80°C |
| Temperature Accuracy | ±2°C | ±0.5°C |
| Humidity Range | 20% to 80% | 0% to 100% |
| Humidity Accuracy | ±5% | ±2% to 5% |
| Sampling Rate | 1 Hz (1 reading / sec) | 0.5 Hz (1 reading / 2 sec) |
On MakerBuddy you get a fresh DHT11 reading about every 2 seconds. The dashboard cards update every 2 seconds.
Understanding Humidity: The Water in Air
Humidity is the amount of water vapor (invisible water gas) in the air. Relative humidity (RH%) compares it with the most the air could hold at that temperature. At 100% the air is full, so dew forms or rain falls. Your breath carries lots of water vapor, which is why mirrors fog up when you breathe on them.
Real-World Applications
Smart thermostats, weather stations and greenhouses.
For Teachers
Humidity is invisible, but students can feel it: muggy versus dry. Link it to the water cycle, and compare DHT11 readings with a classroom thermometer.
For Parents
Your child learns to measure temperature and humidity. It explains why humid summers feel hotter and winter air indoors feels dry.
Try It: The Breath Test
Interactive demo · no kit needed
Play with a pretend MakerBuddy board and its web page, right here.
Follow the steps one at a time. Got the kit? You can switch to the real board inside.
Hands-On Activity: DHT11 Setup
Activity Duration: 20-25 minutes
Connect the DHT11 and watch the live readings.
Step-by-Step Instructions:
- Identify the DHT11: Find the DHT11, with its blue plastic grid.
- Locate the Connector: Find the 3-pin connector marked 25 on the right edge of the board. That is where the DHT11 goes.
- Connect the Sensor: Unplug the USB cable first. Plug the DHT11 into connector 25. The plug only fits one way, so never force it. Then plug the USB cable back in.
- Open the Dashboard: Find the two DHT11 cards: Temperature (DHT) in °C and Humidity in %. If both show 0.0, the board is not getting readings: unplug the USB cable and check the plug in connector 25.
- Record Baseline Values: Without touching the sensor, note the room temperature and humidity. This is your baseline.
- Wait for Stabilization: The DHT11 gives a fresh reading about every 2 seconds. Indoors, the values stay fairly steady.
- Create a Data Table: Note the readings every minute for 5 minutes.
What Students Should Observe:
- Temperature usually 20-25°C in a comfortable classroom
- Humidity usually 30-60% indoors
- Small jumps even when nothing changes (sensor resolution)
- Both values updating about every 2 seconds
Challenge
Your Mission: The Atmospheric Detective
Be an atmospheric scientist: test how temperature and humidity react.
Experiment 1: The Breath Test
- Note your baseline values
- Breathe gently on the DHT11 for 3-4 seconds from a few centimeters away. Don't blow or spit: keep the board dry.
- Watch both readings change
- Note the highest values. How much did each rise?
- Watch for 2 more minutes. Readings fall back slowly; humidity can take a minute or more to reach your baseline.
Experiment 2: The Hand Warmth Test
- Cup your hands around the DHT11 without touching it
- Hold for 20-30 seconds
- Watch your body heat raise the temperature
- Does humidity rise too? Why or why not?
Discussion Questions:
- Why does breathing increase humidity? (Breath carries water vapor from your lungs)
- Why does humidity affect comfort? (Sweat can't evaporate in humid air, so we feel hotter)
- What happens on a rainy day? (Higher humidity, maybe cooler)
- Why measure both values? (Temperature alone doesn't show comfort)
Bonus Challenge: Using your readings, design an "ideal comfort zone" for your classroom: which temperature and humidity range feels best? (Hint: most people like 20-22°C and 40-50% humidity.)
Science Connection
Your breath is about 90% humidity because your lungs add moisture. On cold days that water vapor turns into tiny droplets, so you can "see your breath."
Key Takeaways
✓ Temperature Measurement
The DHT11's thermistor measures the air temperature in degrees Celsius.
✓ Humidity Concept
Humidity is the water vapor in the air, shown as relative humidity (RH%). High humidity makes heat feel worse.
✓ Digital Sensors
The DHT11's chip sends digital data, not a changing voltage like analog sensors. That cuts noise and improves accuracy.
✓ Environmental Monitoring
Logging readings over time shows patterns, so smart buildings and farms can react automatically.
Coming Up Next Week:
Week 11: Precision Temperature (DS18B20)
Learning Support
Use this quick guide to help every learner understand, practice and explain Atmospheric Sensing (DHT11).
For students
Try it in three steps
- Say it: explain the main idea in one simple sentence.
- Show it: With the USB cable unplugged, plug the DHT11 into connector 25. Read the Temperature (DHT) card in °C and the Humidity card in %.
- Stretch it: "The Breath Test" - trigger temperature and humidity spikes via exhalation.
Checkpoint: What was your input, what decision or process happened, and what was the output?
For teachers & parents
Coach without taking over
- Before: ask the learner to predict what will happen and why.
- During: use prompts such as “What changed?” and “What could you test next?” instead of giving the answer.
- After: ask for a 30-second explanation, one piece of evidence and one improvement.
Look for: safe handling, correct vocabulary, a result the learner can demonstrate, and an explanation in their own words.
Did you get it?
Three quick questions. Pick an answer to see whether it is right, and why.
1What two things does the DHT11 sensor measure?
2What does humidity tell you?
3Why does breathing gently on the DHT11 make the humidity reading jump?