Arduino project · Distance and parking · Easy
Ultrasonic Switch with Relay
Wave your hand near the sensor and the relay switches on.
What you will learn
- How a no-touch switch works
- How a relay switches a larger load
- How to use distance as a switch
How it works
When something is closer than 15 cm the relay and green LED turn on. Move away and they switch off. The relay lets you control a low-voltage lamp or a small pump with a separate supply.
Try this next
- Make it toggle on each wave (needs a variable).
- Add a delay so it stays on for 5 seconds.
- Use it as a touch-free lamp.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
Caution: single-phase mains (230 V AC). The wall socket, relay contacts and load in this circuit carry mains voltage, which can kill. Work only with an adult, with the plug out of the wall, switch the LIVE wire only, fit a fuse or MCB, join Earth to metal bodies, use a closed insulated box, and have an electrician check it before you power it. In the simulator everything is safe. In real life, test with a low-voltage lamp first.
Parts: sensors and actuators (tap to show or hide)
Try the inputs (virtual sensors)
Pins (you can change them)
| Part | Arduino pin (change it here) | How to wire it |
|---|
Every wire, one by one
Red rail = 5 V from the Arduino 5V pin. Black rail = GND. The coloured wires carry signals. Match the wire colours on the drawing to this list.
| # | Colour | From (part and leg) | To |
|---|
Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.
Quantities come from the parts you added. The store links open a search for that item on Robu.in, Amazon.in and ThinkRobotics, so you always see what is in stock today. Check the model, voltage and price before you order.
| # | Item | Qty | Search term | Buy / compare |
|---|
The PDF has the circuit sketch, pin table, every wire, sequence, full code, the parts list with store links, do’s and don’ts for each part, and the safety notes. The project file lets you come back and keep editing.
In the real world
A car backing towards a wall
Move the distance slider. The car in the real scene drives closer to the wall as the distance falls, with sound waves from its sensor, exactly like a parking sensor.
Tip: use the gold tab at the bottom of the circuit drawing to pull the real-world view up over the Arduino board. Your parts stay visible above it, so you can press a button and watch the real scene react.
- Distance sensor = the sensor on the car bumper
- LEDs, buzzer, display = the warnings you see and hear in the car