Ever stubbed your toe at 2 a.m.? Yeah, me too. It’s like your furniture waits for darkness to attack. But don’t worry — today, we’re fixing that with a simple night light circuit that automatically turns on when it’s dark.
And the best part? You can drop this circuit right into your 3D prints — glowing dragons, spooky pumpkins, sci-fi helmets — whatever your imagination (and your soldering iron) can handle.
What We’re Building
This project is a small LED night light that uses just a few basic components — a transistor, resistor, and light-sensing diode — to detect when it’s dark and automatically power on. It’s simple, fun, and gives you that “evil genius” feeling without needing a secret lair.
I’m using my new Fornarsi soldering iron for this one. It’s got a wild temperature range, USB and DC power options, and it heats up faster than I can find my tweezers. Seriously, it’s like a lightsaber in pencil form.
⚠️ WARNING: This video is for demonstration and educational purposes only. Always exercise caution when working with electronics, soldering equipment, or power sources. These projects should be attempted only by qualified individuals or under the direct supervision of a professional. Maker Build It and its creators assume no responsibility for injury or damage resulting from misuse or improper handling.
Components You’ll Need
🧰 Gear Used (Affiliate Links):
• BC547 Transistor - https://amzn.to/47HKil5
• 47kΩ Resistor - https://amzn.to/3JeLdRV
• LDR (Light Dependent Resistor) - https://amzn.to/43ahX5u
• LED (your choice of color) - https://amzn.to/47T7b6i
• 9V Battery - https://amzn.to/47jagfK
• 9V Battery Connector - https://amzn.to/47jJLH4
• Fnarsi Soldering Iron - https://amzn.to/3X7Tzhj
• Helping Hands Soldering Tool - https://amzn.to/4nygpJO
• Solder - https://amzn.to/4hFMFcI
Building the Circuit
Start by bending the ends of your resistor so it’s ready to connect. Then solder your light-sensing diode (LDR) and resistor together — this combo helps detect how much light is in the room.
Next, solder your LED into place. The negative leg goes on one side, and the positive runs down the other. Bend the positive lead outward so it’s easier to connect. Grab your helping hands tool to keep everything steady while soldering.
Now, solder in that 47 kΩ resistor and make sure all your joints are solid. Once that’s done, wire your battery connector to the circuit and give it a quick test.
Cover the light sensor with your finger — if the LED lights up, congrats! It works. You just built a night light circuit that powers on automatically when it gets dark.
How It Works
The light-sensing diode (LDR) changes its resistance based on the amount of light hitting it. When it’s bright, it lets less current flow. When it’s dark, it allows more current, triggering the transistor to turn on your LED.
Basically, the circuit “knows” when it’s dark and decides to light up — simple, clever, and incredibly satisfying to build.
Integrating It Into 3D Prints
Here’s where things get really fun. You can embed this circuit directly into your 3D prints:
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Give your dragon eyes that glow when the lights go out.
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Make a mini haunted house that flickers like a ghost electrician is at work.
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Add soft night lighting to custom props or cosplay pieces.
If you want to take it further, I’ve got more videos on integrating LEDs into your 3D prints — check the links below.
This little LED circuit doesn’t just save your shins — it opens up a ton of creative possibilities for your next 3D printing project.
⚠️ WARNING: This video is for demonstration and educational purposes only. Always exercise caution when working with electronics, soldering equipment, or power sources. These projects should be attempted only by qualified individuals or under the direct supervision of a professional. Maker Build It and its creators assume no responsibility for injury or damage resulting from misuse or improper handling.
🧰 Gear Used (Affiliate Links):
• BC547 Transistor - https://amzn.to/47HKil5
• 47kΩ Resistor - https://amzn.to/3JeLdRV
• LDR (Light Dependent Resistor) - https://amzn.to/43ahX5u
• LED (your choice of color) - https://amzn.to/47T7b6i
• 9V Battery - https://amzn.to/47jagfK
• 9V Battery Connector - https://amzn.to/47jJLH4
• Fnarsi Soldering Iron - https://amzn.to/3X7Tzhj
• Helping Hands Soldering Tool - https://amzn.to/4nygpJO
• Solder - https://amzn.to/4hFMFcI