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Build the Smart Parking System

At a glance

What you'll build: a single parking-spot prototype — a distance sensor watches for a car, a "spot taken" LED lights up when it's occupied, and a servo gate opens only when an authorized RFID card is scanned.

Smart-city pillar: 🚦 Smart Mobility & Traffic Systems

Prerequisites: Distance Sensor lesson, Servo Motor lesson, RFID Reader lesson.

Time: about 60 minutes.

Overview

Two independent behaviours running in one program:

  1. Spot detection. The ultrasonic sensor sits over the parking spot and constantly measures the distance to whatever's beneath it. Empty spot → distance to ground (large). Car parked → distance to car roof (small). The system decides "taken" or "empty" and lights the LED accordingly.
  2. Authorized gate access. The RFID reader watches for tagged cards. When an authorized card taps the reader, the servo opens the gate for 5 seconds, then closes it. Unauthorized cards (or no card) → gate stays closed.

In a real lot, you'd have many spots and many gates — your prototype is one of each.

Components needed

All from your Flowlence IoT Kit.

Component Quantity
ESP32 Plus board 1
Distance Sensor (Ultrasonic) 1
Servo Motor 1
RFID Reader 1
RFID Card or Fob 1+ (use the cards/fob from your kit)
White LED module 1
3-pin Dupont cables 4–5
USB-C cable 1

Wiring

Plug each module's 3-pin cable into the matching G/V/S header on your ESP32 Plus shield at the pin numbers below.

Smart Parking wiring — Ultrasonic, Servo, RFID, and White LED on the ESP32 Plus shield

Sensor ESP32 Plus pin
Ultrasonic — TRIG IO 12
Ultrasonic — ECHO IO 13
Servo Motor IO 14
RFID Reader I²C header (SDA / SCL near top of board)
White LED IO 5

Disconnect USB before wiring

Always unplug, wire, plug back in. Moving wires while powered can short pins and damage the board.

Step-by-step code

We'll build this in three stages. Test after each stage before moving on — that way if something breaks you'll know exactly which piece caused it.

Stage 1 · Spot detection (ultrasonic + LED)

This stage proves the basic sense → decide → act loop.

Stage 1 blocks — Ultrasonic reading lights the White LED when a car is detected

The block-by-block:

Block What it does
when Arduino begin Program starts
serial 0 begin baudrate 115200 Open Serial Monitor for debugging
init ultrasonic TRIG IO12 ECHO IO13 Tell Flowlence the ultrasonic's pins
forever Repeat forever
set var distance to (read ultrasonic distance cm) Read the sensor
if (distance < 10) then ... else ... Decision threshold (10 cm)
set pin 5 to HIGH (in then) LED on — spot taken
set pin 5 to LOW (in else) LED off — spot empty
wait 0.2 seconds Don't poll too fast

Test it: upload, then move your hand close to and away from the ultrasonic sensor. The LED should follow — close = on, far = off. If it never turns on, lower the threshold; if it stays on, raise it.

Why 10 cm?

A real parked car is much closer to a ceiling-mounted sensor than 10 cm — but for your tabletop prototype, you'll be using your hand or a small object as the "car." Tune the threshold to whatever distance feels natural.

Stage 2 · Add the gate (servo)

Now add the servo motor as a gate. We'll have it default to closed, and we'll prepare a "open then close" routine that future code will trigger.

Stage 2 blocks — Spot detection plus servo gate that opens for 5 seconds

What's new:

Block What it does
init servo on IO14 Tell Flowlence the servo's pin
set servo IO14 to angle 0 Default position — gate closed
Custom block: Open the gate Sets servo to 90°, waits 5s, returns to 0°

For now, manually trigger the gate by pressing a button block, or just to test, drop the "Open the gate" call inside the loop temporarily so it cycles.

Test it: the gate should swing open, hold for 5 seconds, then swing closed.

Stage 3 · Authorized access (RFID)

Final stage — the gate only opens for cards we've authorized. You'll need to first read the IDs of your kit's RFID cards so you know which ones to allow.

Stage 3 blocks — Full system with RFID-authorized gate access

Two-step build:

A. Find your card IDs. Add a temporary serial print block that prints the ID of any card scanned. Tap each card and fob from your kit, write down the IDs. They look something like 34 A2 4F 9B.

B. Authorize specific IDs. Replace the print block with an if that compares the scanned ID to your authorized list. If matches → Open the gate. If not → do nothing (or buzz a denied sound).

Test it: tap an authorized card → gate opens. Tap an unauthorized card → gate stays closed.

Testing

Once Stage 3 is uploaded, run through this checklist:

  • [ ] Move hand close to ultrasonic → LED turns on
  • [ ] Move hand away → LED turns off
  • [ ] Tap authorized RFID card → gate opens, holds 5 sec, closes
  • [ ] Tap unauthorized RFID card → gate stays closed
  • [ ] Both behaviours work simultaneously (LED tracks while RFID is also responsive)

If all five boxes check, you've built a working smart-city parking node. 🎉

Extend it

Pick one and run with it — the BGC judges value extensions over polish.

Extension 1 · Multi-spot lot

Use the second ultrasonic sensor and another LED to add a second spot. Show both statuses on an LCD: "Spot 1: TAKEN / Spot 2: FREE."

Extension 2 · Audio feedback

Add the Active Buzzer. Two-beep tone for a successful unlock, single long buzz for a denied card.

Extension 3 · Visitor log

Print a Serial Monitor log every time a card is scanned: timestamp, ID, allowed/denied. Real lots store this for security audits.

Extension 4 · Gate timeout adapts to car

If the ultrasonic detects a car still under the gate after 5 seconds, hold the gate open longer. Real gates do this so cars don't get stuck.

What's next?

  • More smart-city sensors → Smart Safety, Smart Temperature
  • Add this to a smart-city dashboard → coming in a future curriculum once Flowlence Cloud is ready