Does any company sell White LED headlights for HO locos without them standard?
Radioshack sells white leds and most stores stock them.
You’ll need a dropping resistor to install an LED in a locomotive. Otherwise, track power could fry it.
Yes, you need a dropping resistor. And also a polarity device. There are different ways to do this depending on if you use dcc or dc. Experiment with red leds at fifty cents versus $5 for a white one. I still use lightbulbs because white leds are more trouble than they are worth, cost way too much, and are not really white, but bluish white… I have a white LED flshlight and it is really nice, is bright, light,and easy on AA batteries. But they are too complex and costly for any benefit as a loco headlight.
flee307 “But they are too complex and costly for any benefit as a loco headlight.” That comes as a bit of a facer. I had heard that they were brighter than bulbs, and not as complex as a constant brightness circuit in dc.
BTW, the original question was an HO reference, but does Radio Shack stock white LEDs suitable for N?
Constant brightness in DC for bulbs require 4 silicon diodes to set up a 1.5 volt drop across the motor circuit. That’s it, 4- 5 cent 1n4001 diodes and a 1.5 volt lamp. In dcc all one needs is a 12v bulb. As to brightness, LEDs might put out more lumes per watt, but for ultimate brightness (if that is what you are after) small 12v halogens outshine all. Remember though, if the light is too bright it shines through even painted plastic. You can get them and white leds from www.allelectronics.com/ along with lots of other parts like low rpm ac motors. I think all current white LEDs are t-1 3/4 which are kind of big for N, but you could notch your frame. But to use an LED you also need include a full wave bridge for polarity control and a dropper resistor. That’s a lot to pack in an n. And what’s a facer?
I use white LED’s that I purchase from Jameco Electronics for around $2.95 each. I am running DCC and use a 1k resistor to keep the voltage from burning out the led. If you are running analog (dc) you need a voltage regulator to get the voltage higher to light the LED at lower speeds. The LED’s work great with DCC. The have virtually no draw, no heat and are really bright. The sometimes have a bluei***int to them, but I do not find it offensive. I am starting to use fiber optics as lenses with the LED’s. The light is bright and projects well.
I use white LED’s and fiber optic headlights on my engines. I get them from the local electronics supply house ($CAD 9 - ouch!) or when they have them, the Hobby shop ($CAD 2). The $9 ones are brighter, but not that much!
For DCC, a 1K resistor needs to go in line with the LED.
For DC, if the engine doesn’t have a directional lighting circuit, add a diode rated for the full track voltage in parallel with the LED, in the opposite orientation to the LED (positive to negative, negative to positive), and a 1K resistor in series with both. If you don’t do this, the LED will pop the first few times you reverse the engine.
If you do have a directional lighting circuit, you can dispense with the diode and possibly the resistor, depending on the output of the lighting circuit.
It’s sort of a “build to suit” situation, but anyone who knows a little about electronics can help you get going, and the results are great.
Quote: "I use white LED’s that I purchase from Jameco Electronics for around $2.95 each. "
Do they ship them free? I couldn’t find a shipping charge quote on their site but have found that on lots of mail order stuff the shipping + parts is more than the parts locally. And if it don’t work you then pay shipping back too.
As for DCC only needing a 1K resistor, I disagree. My DCC shows AC voltage at the light terminal which frys LEDs. And as to using 2- 1K resistors and a diode on DC, my results showed lots of dimming at low speeds and burnouts at over 16V.
Rocky, could you explain the use of fibre optics as lenses for you locos. It sounds interesting. I’m missing a few lenses for my Ho trains and I’m looking for an alternative.
thks
Huh? Every decoder I’ve seen has DC function outputs. Using my Atlas Master system (which puts out a higher voltage to the rails than most), I get no higher than 14-16VDC on the function outputs. Haven’t had a problem yet.
I didn’t say two resistors, I said one in series with both the LED and the straight diode, which are in parallel with one another. This whole circuit is then placed in parallel with the motor. Now, I’ve only bench-tested this, but I went to +/- 18VDC with no burnout. Dimming/dropout at starting voltage is the Achilles heel of this version, though, and I should have mentioned that. My bad.
MRC decoders run the headlights on AC, at lead my digital VOM show its AC. And I read " and a 1K resistor in series with both. " to read 2 resistors ie. one with the led and one with the diode. That’s why LED fried at 16 volts? And another way is to power LEDs off of aaa batteries in HO. I’ll still stick with light bulbs. I never have had one give problem. I follow KISS most of the time.
Weird. I have a couple of MRC decoders, but haven’t connected lights to those ones. Maybe I should see what they have on the function outputs. My TCS, Atlas and Digitrax decoders all put out DC.
flea307: Facer , a Brit expression ( how current I can’t say since we left in 1967) for something that brings you up short. to be brought up short is to be stopped in one’s tracks. So you see, there is a RR link in there somewhere! [:D]
BENT: I did a little research and found dcc controllers works with either DC or AC power supplies. I use a 16VAC MRC powerpack that came with my Prodegy DCC. That may be why my headlight is AC but yours is appears as dc if you are using a dc powerpack. I gather the decoders use “switches” to turn on-off headlight suppling track power to them. I am goint to do an experiment when I get time and swap in a filtered dc power pack and see. I am also going to note if it changes the way no-dcc locos sound.
higssy: Rocky doesn’t seem to have answered yet about the fibre optics and lenses.
Here’s my take on what he may have meant.
Hold the end of a piece of plastic fibre optic material not far from a hot soldering iron. Watch what happens. That blob of plastic that forms makes the lens. You can cut off a stem for mounting the lens if all you’re after is a replacement for a jewel. Or you can thread the fibre through the opening where the light would be, pull the lens into the light fitting, and arrange the free end against the light source inside the loco.
All this assumes that you drill out the back of the light fitting on the locomotive to receive the lens and fibre, or lens and stem. If you’ve ever searched the floor for a fallen jewel, you’ll likely appreciate the extra handle a stem provides!
Thanks der5997, that’s very informative. Should the fibre optics be available at the local hobby store or am I looking at Radio Shack or something like that?
The end your talking about at the light source, do you mean glued?
Fibre Optics: I use a lighter to heat the tip. It will form a convex “lense”. I use .040" and .060". I pick the size that is slightly smaller than the opening and heat the fibre optic with the lighter until it is of diameter to seat in the opening. The soldering iron should work also.
1k (1,000-ohm) resistors: I read an article from Railroad Model Craftsman (sorry MR) “Demistifying DCC, Part 8”. It covered how to use and care for LED’s and bulbs. Works perfect with no problems. I have not lost an LED yet!
Jameco: The more you order, the cheaper it is. 1 led is 2.95 ea, 10 leds are 2.65 ea…shipping is reasonable. You can pick which method you want: FedEx, USPS, UPS, air, ground…I pick the cheapest.
I also use heat shrink to keep LED light out of the cab.
Answering the debate on whether or not the light output is AC or DC.
The output signal is varying from o volts to plus (insert 10-18 volts depending on P’supply input.)
It does not go below zero volts, therefore in one sense it is varying DC voltage, and will measure as DC on a DC input to your meter. However if you measure it on an AC meter, then the waveform looks roughly like a sine wave and will measure as AC.
However the reality is that it is DC, that is if you put a LED (or diode) across it, then one end of the Diode will always have positve jolts, while the other has negative jolts. Therefore care must be taken to get the polarity right.
Note that measurements obtained on either DC or AC meters are not accurate. The DC meter is only averaging what it sees., and the AC meter is cailbrated to read sine waves, not complex waves. For the purpose of calculating resistor values for 1.5v bulbs, the best bet is to build the little experimental resistor matrix that was a recent MR mag article.
Same arguement applies to pulse controllers, the output goes from zero to plus 12-16 volts with a variable pulse width determining the energy available to drive the DC motor. Throw the reverse switch and the output is still zero to 12-16 volts, but the zero changes from the left to right rail or vice versa. Again you can measure an inaccurate DC voltage or AC voltage.
Try All Electronics (www.allelectronics.com) for LEDs of all shapes, sizes, and colors at surplus prices. For example, a white 3mm LED (Catalog Nr. LED-83) is priced at $2.85. Radio Shack probably doesn’t even have this size LED in stock, and would want nearly $5 each if they did.