There are two things about this experiment / activity that I really like:
- It's attractive and educational for all audiences: for toddlers and grandparents, college students and high school kids.
- The lamps give a great opportunity for kids to explore and wonder, without the direct need to "produce the right answer".
In the video, three 10 year old Dutch girls explore the lamps and the way the colors mix. They unravel the mystery of the yellow shadow by themselves, by covering the lamps one by one. I only interfere by asking questions about what they observe. The conversation in the video between the kids and me is in dutch. I'll add english subtitles later on...
Step 1: Tools and materials
- Three Ikea Jansjö spotlights (Ikea US, Ikea NL). I bought them for €5 each as a discount item. Regular price in NL is €10,-
- Leds: red, green and blue. I used 5mm superflux leds because I already had them. Beside the leds, you also need the specifications of the leds, which are easy to find on the internet. More generally speaking: You need superbright leds with a flux of around 4 lumen for red and green, and 2 lumen for the blue led. Red and green leds are around €0,50 / US$ 0,70. Blue leds cost around €1,50 / US$ 2,-
- Resistors to adjust the current through the leds. I used 22 Ohm for the red LED, and 10 Ohms for the green and blue LEDs. More on calculating the resistor-value in step 3.
- A plastic sheet, 2mm or so thick
Leds and resistors can be bought at Conrad, Farnell or RadioShack
If you want to be able to dim the lamps (step 8 and further), for each lamp is needed:
- 2x capacitors 10 nF
- 1x transistor BC547(B)
- 1x transistor BC557(B)
- Resistor 5k6 (or 4k6, if you want to dim the leds to zero)
- Resistor 10k
- Resistor 330k
- Potentiometer 50k
- Jumper wire
- Nuts, bolts and spacers to mount the pcb in the casing.
I haven't finished building the dimmers yet. The prototype circuit in step 8 does work, however.
- Soldering iron and solder
- File: a small one with sharp corners (I used a file with a triangular cross section)
- Drill and drillbits: 1.5mm and 12mm
- Screwdriver (philips screw)
- Straight screwdriver or blunt knife to lift the lens cap from the spotlights.