Signal Sampling and Filtering 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
• 10 K POTENTIOMETER — 1 potentiometer
• 0.1 µF CAPACITOR (5 PCS) — 3 capacitor (individual units)
• 1K Ω 1/4 Watts (10 PCS) — 2 resistor (individual units)
• 10 µF CAPACITOR (5 PCS) — 1 capacitor

What you learn

• Analog and digital filters operate at different points in a signal path.
• Averaging reduces variation but delays a changing signal.
• Sampling rate and filter bandwidth must be considered together.

Connection guide

• Pot outer pins → 3.3 V/GND; wiper → GPIO35 for the raw measurement.
• Wiper → two 1 kOhm resistors in series → GPIO34; capacitor from GPIO34 to GND. Start with 100 nF.
• Compare 100 nF with the supplied 10 uF electrolytic (positive to GPIO34); two extra 100 nF capacitors can be tested in parallel.

Steps to make it

1. Disconnect all power and identify the supplied part labels and pinouts before wiring.
2. Build both ADC1 inputs, checking that neither can exceed 3.3 V.
3. Upload and view raw, RC and 16-sample-average channels in Serial Plotter.
4. Turn the dial slowly, then make repeatable small step changes.
5. Power off before changing the capacitor; compare ripple and settling delay for the two values.
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 the same dial step with 100 nF and 10 uF; estimate filter delay without assuming the knob is an ideal signal generator.

Observation task

Capacitance, sample interval, raw/RC/average values, settling time and stable-signal variation.

Expected result

The RC and moving-average channels respond more smoothly; larger filtering causes more lag.

If it does not work

Check the shared ground and electrolytic polarity. Keep GPIO35 on the raw wiper side of the resistors.

Try next

For 2 kOhm and 10 uF, estimate fc=1/(2πRC), about 8 Hz, and compare with the 100 Hz sampling rate.

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.