Only up to four LEDs light up. Answered
I've got loads of LEDs and resistors from eBay and using the resistors, only up to 4 LEDs in serial will light. I can't just use more resistors, as I broke open a mains lighting bulb that uses 20 LEDs to provide lighting. Looking at the printed circuit, they are all soldered in series. If I put + at one side of an LED and - at the other with these resistors I have, it lights, two three and 4 work, but on the 5th, it drops dim, after that it won't light at all. Do I need a different resistor, of is something else wrong. Could someone kindly tell my what resistor I need for 20 5mm White LEDs running off 18v (two 9V batteries), and 9v (one)? Thanks! Josh.