Does it matter where in the wiring that I place the resistor for my Bachmann steam locomotive headlight? I have always seen them wired to the LED but since all the goodies, decoder and speaker are in the tender I would just rather place it there rather than in the locomotive. I don't see what difference it would make but then I am electronically challenged so there may be a good reason I am not aware of.
Doesn't matter where between the board and the LED it is. Just make sure it's spliced into the correct wire.
As long as it is in series with the LED e.g. resistor then LED or LED then resistor there is no problem. Issues appear if you have other components in between the two or you connect the resistor to both legs of the LED. Russ
Again, remember the analogy of a garden hose moving electricity. A resistor is like squeezing the hose. It does not matter where you squeeze the hose
As pointed out, the resistor can be on either leg of the LED. The voltage across all components in a series circuit equals source (bus or feed) voltage, so the total of voltage drops across the LED and the resistor must equal 15 volts. Because the resistance of the LED and the resistor are different, each will have a different voltage drop across it. White LEDs run about 3.5 volts, so the drop across the resister will be about 11.5 volts in a 15 volt system. Any other device on either leg between the LED and power source will require a different size resistor, so keeping both legs clear of anything but the resistor will produce the proper intensity of light. Image supplied is simplified schematic of the circuit. Please remember this is a quick and easy explanation. There is a lot more involved in powering an LED, but for the sake of understanding where to mount a resistor this should be enough.
