Arduino project · Motion and security · Medium
Motion Light That Works Only in the Dark
The light comes on when someone moves, but only if the room is dark.
What you will learn
- How to combine two sensors
- How a later step can cancel an earlier one
- How to save energy in daylight
How it works
The PIR step turns the LED on when it sees motion. The next step turns it off again if the room is bright (light above 40 percent). So the LED is on only when there is motion AND it is dark.
Try this next
- Add a delay so the light stays on for 10 seconds.
- Use a relay to switch a lamp.
- Add a buzzer for night intruders.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
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 light that only comes on in the dark
The lamp lights only when someone is there AND it is dark. Change the light slider and move the person.
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.
- PIR sensor = a person
- Light sensor = daylight
- LED = the lamp