Keypad PIN Lock Kit

Classes 9-10, typical ages 14–16. Age ranges vary by learner. Guided low-voltage electronics.

Activity engagement

90–120 minutes. Explore 15–20 min · Build 30–40 min · Test and discuss 45–60 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.

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
• Arduino Uno R3 CH340G version compatible Arduino Development Board — 1 controller board
• USB A to B Programming Cable for Arduino Uno/ Arduino Mega — 1 data cable
• 4X4 MEMBRANE KEYPAD — 1 keypad
• Tower Pro SG90 Servo Motor - 9 gms Mini/Micro Servo Motor — 1 servo
• Enclosed Regulated 5 V Servo Supply with Fitted Lead — 1 power supply

What you learn

• A matrix keypad shares row and column wires.
• Input buffering needs clear, submit and length limits.
• A servo model demonstrates a decision but is not a security lock.

Connection guide

• Keypad rows R1–R4 → Uno D2,D3,D4,D5; columns C1–C4 → D6,D7,D8,D10. Follow the supplied keypad ribbon pin map.
• Servo signal → D9; red → separate supplied 5 V supply; ground → that supply GND and Uno GND.
• Keep the external +5 V separate from the USB-powered Uno +5 V.

Steps to make it

1. Disconnect all power and identify the supplied part labels and pinouts before wiring.
2. Wire the keypad using its row/column labels and leave the servo horn unloaded.
3. Install libraries and upload the sketch; enable the separate servo supply.
4. Enter 2468 followed by # to move the servo; use * to clear an entry and enter a wrong code to compare.
5. Change the code, repeat ten valid/invalid trials and document the state transitions.
6. Change only the named parameter for the extension, repeat the controlled trials, save observations and disconnect power afterward.

Programming resources

Arduino IDE: select Arduino Uno and the USB port. Use the supplied USB data cable. Serial Monitor/Plotter: 115200 baud.

Libraries to install

• Keypad
• Servo (Arduino)

Download starter sketch

Test challenge

Test correct, incorrect, overlength and cleared entries; verify the model returns to its resting angle.

Observation task

Input sequence, expected decision, printed feedback and servo angle.

Expected result

A correct submitted code moves the unloaded servo briefly; an incorrect code does not.

If it does not work

Check row/column mapping and separate servo power. This demonstration has a visible code and no physical-security rating.

Try next

Add a limited number of attempts and a timed lockout state.

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.