in this instructable i made little LED lights for some nice lightening effects

i used recycled batteries because it was free but you can use whatever battery you want :)

Step 1:

It all started when I went around the container for used batteries and I was wondering how many of them are actually useful

so ask my teacher if I could test them with some school meters in his lab and he agreed

Step 2: First Measuring

inside was a lot of rubbish and used lightbulbs,

I was impressed some batteries was even new :)

exactly half of them was able to output 100mA and hold their voltage between 1.5-1.1V

(current 100mA was given by variable resistor, one LED need only around 20mA)

there was also few rechargeable batteries which were probably used only once (i tested them at home and capacity was pretty close to the description on battery )

when I finished my measuring I packed all of the useful batteries and return a container with remaining bad ones in his place

it seems nobody registered half of them is gone :)

Step 3: Second Measuring

after I arrived home I measured batteries once more and I sorted them by their voltage

Step 4: Schematics and Some Info

I used only best batteries with 1.5V for this project rest could be used in some other projects

you can even use worse batteries if you add joule thief but I didn't have that many components for the build.

All that I used was just two batteries, switch and LED

you can also use battery box with switch and just add LED and batteries

I bought 10pcs on eBay for $5 here

green, white and blue LED could be powered by 3V without a resistor other colors need one

50-100Ω should be enough for other colors (only if you use 3V power source)

if you don't know much about electronics you can use this nice page for calculating resistor http://www.ohmslawcalculator.com/led-resistor-cal...

I also add a picture with LED voltage for each color

Step 5: Assembly

It took a few finished pieces until I learned the effective method, after that I was working faster and the assembly of 20 lights took less than three hours