Power and Energy Monitor Kit

Classes 11-12, typical ages 16–18. Age ranges vary by learner. Guided low-voltage electronics.

Activity engagement

105–150 minutes. Explore 20–30 min · Build 35–50 min · Test and discuss 50–70 min. Estimated time for building, testing and discussion.

What you need

A computer with a USB port and Arduino IDE is required and is not included. Wi-Fi/BLE experiments also require the local network or phone specified in the guide.

Included components

• Small Breadboard / Mini Solderless Board - 400 points — 1 breadboard
• Jumper Wire Combo - Male to Male, Male to Female and Female to Female Breadboard Connecting Wires (10 Qty Each) — 1 set
• Illustrated Activity Guide and Observation Sheets — 1 set
• Fitted Headers and Labelled Connection Leads — 1 set
• ESP32S 38Pin Development Board (WIFI+BLUETOOTH) — 1 controller board
• MICRO USB DATA CABLE — 1 data cable
• CJMCU-219 INA219 I2C Interface No Drift Bi-directional Current / Power Monitoring Sensor Module — 1 sensor module
• 5mm LED - Red Color — 1 LED
• 330 Ω 1/4 Watts (10 PCS) — 1 resistor
• 5 V USB Power Lead with Screw-Terminal Output — 1 lead
• 5V 2A Adapter (Without Cable) - 10W Adapter for Raspberry Pi 3 — 1 power supply

What you learn

• Current sensing is inserted in series with a load.
• Power and energy use different units.
• Energy is estimated by integrating power over elapsed time.

Connection guide

• INA219 VCC → 3.3 V, GND → ESP32 GND, SDA → GPIO21, SCL → GPIO22.
• Supplied separate 5 V load supply positive → INA219 VIN+; VIN− → 330 Ohm → LED anode; LED cathode → load supply GND.
• Load-supply GND → ESP32 GND. Keep its +5 V separate from USB-powered board +5 V.

Steps to make it

1. Disconnect all power and identify the supplied part labels and pinouts before wiring.
2. Wire the current path in series and check it with power disconnected.
3. Install libraries, upload and enable the separate 5 V load supply.
4. Observe volts, milliamps, milliwatts and accumulated milliwatt-hours for two minutes.
5. Disconnect only the load branch with power off, restart and compare the near-zero-load reading.
6. Change only the named parameter for the extension, repeat the controlled trials, save observations and disconnect power afterward.

Programming resources

Arduino IDE: install esp32 by Espressif Systems 3.x; select ESP32 Dev Module for the supplied classic WROOM board. Serial Monitor: 115200 baud. GPIO is 3.3 V only.

Libraries to install

• Adafruit INA219
• Adafruit BusIO

Download starter sketch

Test challenge

Compare integrated energy with average measured power multiplied by the test duration in hours.

Observation task

Elapsed seconds, load voltage, current mA, power mW and energy mWh.

Expected result

Energy accumulates while a valid non-negative load power is measured and resets on board restart.

If it does not work

Check VIN+/VIN− orientation and common grounds. Do not wire the current path across a supply as a short.

Try next

Estimate uncertainty from current-sensor offset and sampling interval; this is not a billing meter.

Use and supervision

Use only the supplied low-voltage DC parts. Disconnect power before rewiring; check polarity and labelled pinouts. No soldering or exposed mains connections. Adult guidance is recommended.

How this experiment works

Download class activity guide

Cover illustrations show component types. Functional animations explain principles and are not recorded prototype tests. Follow the supplied connection labels and pinouts.