Solar I-V Explorer Kit

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

Activity engagement

120–180 minutes. Explore 20–35 min · Build 40–60 min · Test and discuss 60–85 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
• 6V - 100 mA (70 mmx70 mm) Solar panel — 1 solar panel
• DT9205A Digital Multimeter with Probes and Battery — 1 multimeter
• 100 Ohm 1 W Through-Hole Power Resistor — 1 resistor
• 220 Ohm 1 W Through-Hole Power Resistor — 1 resistor
• 470 Ohm 1 W Through-Hole Power Resistor — 1 resistor
• 1000 Ohm 1 W Through-Hole Power Resistor — 1 resistor
• 10K Ω 1/4 Watts (10 PCS) — 4 resistor (individual units)

What you learn

• Panel voltage changes with illumination and load.
• For a known resistive load, current is approximately V/R.
• Maximum measured power is a property of the tested conditions and available load points.

Connection guide

• Panel positive → two 10 kOhm resistors in series → GPIO34 node → one 10 kOhm → panel negative. Panel negative → ESP32 GND. A fourth 10 kOhm is a supplied spare.
• Use the 100, 220, 470 and 1000 Ohm 1 W resistors one at a time directly across the panel; the divider remains in parallel.
• Meter in DC volts mode across the panel; COM and V sockets only. Do not use current mode across the panel.

Steps to make it

1. Disconnect all power and identify the supplied part labels and pinouts before wiring.
2. Verify the 3:1 divider before connecting the solar panel and confirm its open-circuit voltage is no higher than 9 V.
3. Power ESP32 by USB and compare ADC-derived panel voltage against the meter; adjust dividerFactor if required.
4. Under fixed illumination, disconnect the panel before changing each load; enter its measured resistance in the local sketch.
5. Record load voltage and calculate load current/power; then repeat one load with partial shading.
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.

Uses the selected board core libraries.

Download starter sketch

Test challenge

Compare at least four load points under the same light, then repeat the highest measured power point in shade.

Observation task

Illumination condition, load resistance, meter voltage, ADC voltage, calculated load current and power.

Expected result

Each resistor gives an approximate operating point. I=V/R refers to the selected load branch; divider current is a small additional branch.

If it does not work

Check divider orientation and stop if panel open-circuit voltage exceeds 9 V. The 1 W load resistors are required; do not substitute tiny 1/4 W parts.

Try next

Plot I against V and P against V; explain why four points do not locate the exact maximum-power point.

Use and supervision

Use only the supplied 6 V/100 mA panel, no batteries or charging circuits. Keep panel open-circuit voltage at or below 9 V for this divider. Switch off/disconnect before changing loads; 1 W resistors may become warm.

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.