Would there be any problems running LEDS in passenger cars using DCC track power? I know they are polarity sensitive with DC voltage. But they seam to work fine on AC voltage from a DCC system.
Just wondering. Thanks, Truck.
The Answer is Yes and No...
Let me explain. I just took a 3mm Golden White LED and hooked it up to an old Atlas DC power pack. I also hooked up a Multi-Meter to measure the voltage as I turned the dial on the DC power pack "slowly". I noticed that the LED looked really good at about 3 volts of power. As I slowly turned the dial, the LED got brighter and brighter. The LED burned out at about 8.2 volts. RIP LED....LOL
We know that DCC runs at a constant 15 + or - a few volts of power.
If you attempt to run your passenger cars with LED lighting at DCC power, you'll blow them in a as soon as DCC power is applied to the tracks. the trick is to run a resister inline with the LED to 'step down" the power. My guess is that you want the total power getting to the LED to be no more than 3 volts.
Hope this helps answer your question
Mike
I add small 1 Amp bridge rectifiers to the circuit along with appropriate resistors, usually 1K Ohm. The bridge rectifier changes the pulsating DCC square wave into DC, so the LEDs last longer.
Warm White Inverted Cone LEDs, which can be had in bulk this time of year as Christmas light sets at all of the major stores, are better for passenger car lighting than a typical LED because they radiate light in a 360 degree pattern instead of being a point source.
You've got to have a resistor in series. Something like 680 Ohms probably, maybe a little larger. As far as a recitfier goes, it's not a bad idea, since it will protect the LEDs from reverse voltage, and will allow them to be lit all the time, rather than half the time.
Jeff But it's a dry heat!
I DO USE RESISTERS. I was pretty much wondering if AC current was bad for the LED's.
Yes, it is. Regular rectifier diodes usually have large peak inverse voltage ratings - 100, 200, or 400. They can handle that much voltage in the opposite direction without melting down. LEDs usually do not handle large inverse voltages.
Simple trick for AC: two LEDs back to back (cathode of one to anode of other, anode fo first to cathod of second), connect pair to track power through a resistor. Now each neither LED will get too much inverse voltage - it will see onyl the forward voltage of the other LED as an inverse voltage, so about 3.1-3.5 volts. No problems there.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
AC can be bad for the LEDs. At DCC voltages probably not, though you will most likely be beyond the guaranteed spec. To avoid any question you can put a diode parallel to the LED, conducting the opposite way, or use a rectifier so it doesn't see reverse voltage.