Introduction: Dark Detecting LED Decoration

About: I like making things and I'm good at breaking things.

This project is highly customisable. I’d be taking advantage of the hexagonal box I've got at home, but chances are you might not have one. So feel free to change the design or whatsoever. I mean, upcycling is about turning some random unused material at home into something useful isn’t it?

Things you'll need:

  • Cardboard
  • White LEDs x 3 - feel free to add more
  • Some wires you got at home
  • Phototransistor x 1
  • 100kohm resistor x 1
  • 2N3904 transistor x 1
  • 3 AA batteries
  • 3 AA battery box
  • Wax paper
  • Hemp string (optional)


  • UHU (or whatever glue you have)
  • Solder
  • Soldering iron
  • Electrical tape
  • Tape
  • Cutter
  • Ruler
  • Pencil
  • Scissors

The original circuit, which uses red LED, is from the Make Magazine.

Step 1: The Circuit

Pretty self-explanatory - just follow the circuit diagram and solder the parts together.

(I recommend trying it out on a breadboard first before soldering)

Step 2: The Cardboard

Mine is hexagonal, and I modified it so it becomes pentagonal because not much light would go through the ‘holes’ (whatever you call them) if I use hexagons. But again, you can always customise it or take advantage of what you have at home.

Cut strips with width 1.5 cm, then glue the ends together to form a pentagon. Repeat the steps and finally, stack them together and glue.

Afterwards, glue the wax paper inside.

Step 3: Fit the Electronics Part In

I’m going to put all the batteries, wire and stuff inside the ‘lid’ of the box. Again I’m taking advantage of the box, and you can always customise this step. Make sure that the phototransistor is outside the lid though.

Step 4: Done!

You can either place it on a table as a decoration, or tie it with a hemp string

Sensors Contest 2016

Participated in the
Sensors Contest 2016