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Lesson plan

Sensors and measurement lesson plan

Intermediate: thermistors and RTDs, strain gauges in a Wheatstone bridge, light and IR, current on a shunt and an INA219, ADC resolution and noise, and calibration, finished with a power instrument you check against Ohm's law.

3 chapters, 7 lessons, about 4 hours, on the Arduino Uno R3. Every lesson runs in the browser, with nothing to install.

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The unit

Objectives and materials

By the end, students can

  • Temperature, strain and light, each turned into a resistance or a voltage.
  • Current on a shunt, the limits of an ADC, and calibration against a known value.
  • A power instrument checked against Ohm's law, with a latching trip.

Materials for the whole unit

  • Arduino Uno R3
  • Battery: AA, coin cell, LiPo
  • Bench power supply
  • Buzzer
  • Character LCD with I2C backpack
  • Current monitor, INA219
  • DC voltage source
  • Full-size breadboard
  • Half breadboard
  • LED x 2
  • Line sensor, TCRT5000
  • Load cell with HX711
  • Multimeter
  • Photoresistor sensor module
  • Piezo speaker
  • Potentiometer
  • Pushbutton
  • Relay module
  • Resistor x 4
  • Slide switch
  • Thermistor, 10k NTC x 2
  • Traffic light module
  • Voltage sensor, 0 to 25 V

Every part is already on the simulator’s bench, so there is nothing to buy or hand out. The counts are the most any one lesson uses, if you build it on real breadboards too.

Chapter 1. About 1 h 45 min

Sensing the world

Temperature, strain and light, each turned into a resistance or a voltage.

LessonTimeWhat students do
Thermistors and RTDsA 10 k NTC bead on a meter and in a divider on A0: what "10 k" means, why the curve bends, how the divider turns ohms into volts, and when a platinum RTD is worth the money.35 min
  1. Run it: the room
  2. What "10 k" means
  3. The curve bends
  4. Ohms into volts
  5. Warm it up
  6. When to use an RTD
Strain gauges and the Wheatstone bridgeFour 350 ohm strain gauges in a Wheatstone bridge: how a 0.2% change becomes millivolts, why two or four active gauges beat one, and how the bridge cancels temperature.35 min
  1. Run it: balanced
  2. Stretch one gauge
  3. Two active gauges
  4. A full bridge
  5. Temperature cancels
  6. mV per V
Light and IRA photoresistor module on a dusk switch and a TCRT5000 reflective IR sensor: light as a voltage, a comparator with a threshold, and infrared that bounces off white and vanishes into black.35 min
  1. Run it: daylight
  2. Dusk
  3. The DO lamp
  4. Bounce some infrared
  5. Black swallows it
  6. Why remotes flash at 38 kHz

Materials

  • Arduino Uno R3
  • Character LCD with I2C backpack
  • Half breadboard
  • Line sensor, TCRT5000
  • Multimeter
  • Photoresistor sensor module
  • Resistor x 4
  • Thermistor, 10k NTC x 2

Check for understanding

Each student finishes "Light and IR" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go.

Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Why remotes flash at 38 kHz".

Chapter 2. About 1 h 40 min

Measuring it well

Current on a shunt, the limits of an ADC, and calibration against a known value.

LessonTimeWhat students do
Current sensing with a shunt and an INA219A battery gauge with an INA219: a 0.1 ohm shunt turns amps into millivolts, a meter reads the same millivolts, and a heavier load shows why time left falls faster than percent.35 min
  1. Run it: the battery gauge
  2. Ohm's law says
  3. Read the shunt yourself
  4. A heavier load
  5. Why 0.1 ohm
  6. Run it flat
ADC resolution and noiseA 0 to 25 V voltmeter on an Uno: what 10 bits buy you, the smallest step it can see, what happens past the top of the range, and how averaging fights noise.30 min
  1. Run it: 12 V
  2. One step
  3. Below one step
  4. Past the top
  5. Noise and averaging
CalibrationA kitchen scale on an HX711: the offset that tare removes, the gain error that only a known weight finds, a check at a second point, and the noise left over.35 min
  1. Run it: tare
  2. Weigh 500 g
  3. An offset error
  4. A gain error
  5. Check a second point
  6. Work out the new factor

Materials

  • Arduino Uno R3
  • Battery: AA, coin cell, LiPo
  • Bench power supply
  • Character LCD with I2C backpack
  • Current monitor, INA219
  • Half breadboard
  • Load cell with HX711
  • Multimeter
  • Piezo speaker
  • Resistor
  • Traffic light module
  • Voltage sensor, 0 to 25 V

Check for understanding

Each student finishes "Calibration" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go.

Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Work out the new factor".

Chapter 3. About 40 min

Boss project

A power instrument checked against Ohm's law, with a latching trip.

LessonTimeWhat students do
Boss: a calibrated power instrumentA bench supply monitor on an Uno and an INA219: volts, amps and watts checked against Ohm's law and the shunt, a second load, and an over-current trip that latches until RESET.40 min
  1. Run it: off until RESET
  2. Turn the output on
  3. Where did 40 mV go?
  4. Add a second load
  5. Trip it
  6. Latched, on purpose
  7. What makes it calibrated

Materials

  • Arduino Uno R3
  • Buzzer
  • Character LCD with I2C backpack
  • Current monitor, INA219
  • DC voltage source
  • Full-size breadboard
  • LED x 2
  • Potentiometer
  • Pushbutton
  • Relay module
  • Resistor x 4
  • Slide switch

Check for understanding

Each student finishes "Boss: a calibrated power instrument" on their own, without opening the hints. The simulator checks 7 of its 7 steps as they go.

Then ask each one to explain, in a sentence or two, the last thing it asked of them: "What makes it calibrated".

Your class

Teach this unit as a class

Start a class from this course and its 7 lessons are assigned in one go, in order. Students join with a six-character code or printed login cards, and each one’s work comes back to you.

The class tools are free for 30 days for one class of up to 20 students, with no card. The lessons themselves are free either way.

Start a class from this courseSee the demo class
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