@Chuck K. posted:You can get away with doing what you are doing. But just so people know, you should generally avoid any situation that reverse biases an LED. it is typical that they be safe up to about 5 volts reverse bias, but might have the breakover voltage at 12 to 20 volts at which point the LED is destroyed. Also, a resistor would normally be used for limiting current to a safe value. What is happening with the string of diodes is sort of a "workaround" where there are enough forward voltage drops of the series LEDs so there isn't enough voltage across any LED for it to overcurrent. And the reverse bias is divided between all the LED's (theoretically anyway) so any one LED shouldn't see a very high reverse voltage.
That's why you need to start around 8 leds for 18v. That will be as bright as you get add more leds to dim it down. But like I said I don't use this I don't like the 60hz. Three years ago I hooked those in my photo up to the transformer and left them on non stop for nearly two months. The passenger cars I gave to the grandkids all have this scheme for lighting. It's stable. j
