I bought 50 LEDs that can light red or green for $5.00 on ebay. Figure I will use them on the control panel to indicate turnout direction. I attached one LED lead to a 1k resistor and used a 9volt battery to connect the resistor and the other LED lead and sure enough it is green. So I reversed the battery and it turned red. Cool. What I don't understand is in one direction the resistor is on the upstream current direction and in the other it is downstream of the LED yet both light properly. I thought the resistor had to be between the LED and the source. What am I not understanding here?
Upstream or downstream doesn't matter. The resistor just has to be in the stream to limit the current flow.
Joe
ndbprr I thought the resistor had to be between the LED and the source.
Your resistor IS between the LED and the source whether the current is flowing this way < or that > way. As long as it is in series.
I use dozens of two-lead bicolor LEDs for turnout indicators, sometimes two or even three LEDs in series with each other.
In my case the Tortoise switch motor is doing the honors as the resistor so I can simply place the LED(s) in series and only have to contend with a slight voltage drop which the Tortoise doesn't mind.
Inside the LED "package" there are actually two LEDs wired cathode to anode.
Page two, diagram 4 here shows two individual LEDs wired that way but the bicolor ones have all this in one little package:
http://www.circuitron.com/index_files/ins/800-6000ins.pdf
How will your turnout toggle switch be wired and I wonder what turnout "motors" you are using?
Good Luck, Ed
Layout has been postponed due to my wife having a terminal health issue. Turnouts on the two track main will have tortoises. Three Crossings between the mains and 4 locations into industrial areas. It doesn't make sense to use the tortoise connections for indication as the majority will be between 15' and 30' from the dispatcher board. That will require a lot of wire out and back when the LEDs can be wired in parallel to the switch controlling the tortises since the distance there will be about 3" max and probably less.
ndbprrLayout has been postponed due to my wife having a terminal health issue.
Hi ndbprr,
I am very sorry to hear about your wife's situation. Life is not fair.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Thank you. The only thing that ends 100% in death is life. don't tell the government though they would probably ban life.
My sincere sympathies. I know what you are going through, but not wife. In my mid twenties I had a son born with a bad heart and he lasted seven months. Ten year ago now I lost my youngest. At least I have my grandkids to keep me busy.
Give her all the love and understanding you can possibly give.
Pete.
Bicolor LEDs have one common lead, be it anode or kathode. Attach the resistor to the common pin. Both LEDs will work.
know2goBicolor LEDs have one common lead,
There are three-lead LEDs and two lead LEDs (sometimes even four lead [RGB]).
I believe the OP's question was related to a two-lead bi-color LED.
Regards, Ed