What do you do when wintertime comes and you still want to ride your bike, but everytime you find some hours to spare, it is pitch black night outside? You probably need some modern, decent LED bike light, one of those that literally turn night into day. But if you don´t want to pay the exagerated sums that some companies charge for their products, or if you just like to build your own stuff, you could find it interesting to be able to build your own lights.