Arduino project · Fire, gas and safety · Medium
Overcurrent Cut-off with Relay
The relay switches the load on. If the current goes above 3 A, the relay turns the load off and an alarm sounds.
What you will learn
- How fuses and circuit breakers protect circuits
- How to watch a value and cut the power
- Why a protective device must be reliable
How it works
The relay is switched on. When the current goes above 3 A, the program switches the relay off and turns on the buzzer and red LED.
Try this next
- Make it latch so it stays off until a reset button is pressed.
- Add an LCD with the current.
- Use a lower limit for a small load.
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
An overload protector
If the current gets too high the relay cuts the load and the buzzer sounds.
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.
- Current sensor = the current
- Relay = cuts the load
- Buzzer + LED = the warning