I have managed to solder 36 white LEDs in series. I connected them to 120 volts for a few seconds at a time and they seem to light up, flicker a lot and did not burn. My goal is to have a large number of series LEDs in series to use it with either a 120 or 220 volt AC source or both. I want them to be as energy efficient as possible, use a limited amount of extra parts, keep cost down and have the longest service life time as possible, up to the 50 and 100 thousand hours that this technology advertises ! Having the LEDs flicker a lot/significantly (60 Hz ?), I wanted to connect them to the 120 volt source using a bridge rectifier. I connected the leds to the + and - sign of the square bridge rectifier (one part) I bought from Radio Shack (400 volt rating) and the alternative source current to the two ~ signs on the rectifier ! It made a flame, loud noise and killed the electrical circuit in the wall flipping the circuit breaker in the breaker box. I also constructed a bridge rectifier with four 1000 volt rated rectifying diodes and had the same thing happening ! Can anyone give me some hints or ideas on how to make use of the bridge rectifier ? I am trying to limit the use of resistors and capacitors for cost and energy efficiency reasons and reduce the amount of work time/complexity needed to put these long led strings together, but I would like to learn more about the benefits and disadvantages of other designs as well.

 

We consider circuits that are powered directly from the line to be too dangerous to discuss. Do you figure your life is worth less than the cost of a transformer? As you have seen, these experiments can be lethally dangerous.

You must use a transformer to limit energy as to provide galvanic isolation from the AC line.