Hi Team - Has anyone taken a plain Jane DC locomotive and added LEDs to them? I'm building a locomotive from the ground up, so I don't have a circuit board, just old school motor and some wires. I've seen people say just put a 1000 ohm resistor between the power and LED and you're set, but have seen others recommend adding a regular diode as a safeguard for the LED, and others have said LEDs don't work well in the setup I'm describing. So - I'm looking for someone that's actually done this to set me on the right path. Anyone out there? Cheers -Mike
It isn’t difficult, especially for directional. At a minimum, all that is needed is the resistor to ensure you limit the current, and that you have the leads hooked up correctly for direction of travel. That is all the most basic DC boards do.
Simple indeed. I cheat and get 12v LEds already wired with the resistor and 6 or so inch long leads. I think I paid 3 or 4 euros for a pack of 10 last time I was at a train show.
Okay - thank you both for the confidence boost. I was looking at the 12V pre-wired LEDs last night which got me thinking about this, but they didn't have the resisters included. Is 1000 Ohm the right way to go then? And is there a favorite style/model/size of LED that works best, or are they all pretty much the same, just varying degrees of brightness? I like the smaller surface mount sizes as I'm envisioning putting them inside the light tunnel of my locomotive but I don't want them to be too dim.
What I suggest is wiring up some LEDs and connect them to your track at a “normal” operating setting on your throttle. That will give you an idea on brightness. SMDs can be very bright. Choosing the right LED is more a function of the space and location you want to mount in.
Isn't there at least sometimes the need for an additional component to protect the unlit LED from sudden voltage spikes when running in the opposite direction when on straight DC?
White LEDs are very susceptible to reverse voltage spikes. Some motors generate some rather strong back EMF voltage spikes. Those will definitely zap the LED without some additional protection. I learned this the hard way. Adding an additional diode to shunt the reverse voltage spikes and a small capacitor will ensure that your LED won't be harmed.
What is the capacitor for? Is it to keep the LED from flickering? You can also use an LED driver and not worry about resistors, but you still need the diode. T.C.
To absorb the spiking electricity. Capacitors charge and discharge more quickly than batteries, but don't store power reliably for long periods of time. But they are like batteries in one regard--they absorb electricity.
That does interest me - I'll have to take a closer look into that. I got my parts today and rigged up a quick test. The LEDs I ordered already had the 1k ohm resistors installed, so my order of resistors was unnecessary. These are 1x1.5mm SMDs, perfect size for what I'm planning and super bright. I'll have to create a light tunnel to see how it travels thru clear plastic but I'd say it's going to work out just fine: Thanks to all for providing some guidance. I'll post more as this project develops... -Mike
I have found 1500-3000 ohms (in total, depending on specific LED) yields a much more realistic brightness.
