Hi, I’m new to the site. Can anyone suggest a good book on the use of LEDs in an HO scale layout (mostly related to scenery such as signals, structure lighting, etc.)?
[#welcome]
NOPE. No good books. LED lighting such as we do it is a very nitche subject, and so I am sure that there are no really good books for you to read. Or if you do find one it will be so technical as to be of no use to you.
The premise is simple howerver, and so I will tell it to you.
The LED is first of all a DIODE, a light emitting diode. It will pass current in one direction, but not in the other. So Think of a rectifier instead of a light bulb. It passes electricity, it does not consume it.
Light bulbs increase their brightness the more voltage you apply to the circuit. Too much voltage and the thing burns out in a flash.
LEDs are different. They may require 2 or 3 volts dc to light it, but if the current is too high (and it is) you will burn it out instantly. So ANY VOLTAGE between 3 and 24 volts will work just fine, but you MUST put a resistor in series with the device to limit the current. While they do act like rectifiers, passing voltage in one direction only, they really cannot be used as a rectifier since a revers current can also kill it.
The LED above is a T1 (a convention used by the lighting industry… it means a tubular shape 1/8th inch in diameter… it says nothing about the electrical characteristics of the lamp.) Most LED manufactures will now call it a 3mm LED. The Larger size is a T1.5 or 5mm.
Looking again at this LED you will see that it has a large flag inside of it (left) a small gap, and then a small flag. If you were to look at it from the top you would see the actual LED element resting on top of that large flag as if in a little frying pan. The Large flag is the cathode, the negative pole of the LED, and it has the shorter lead coming from the device. The smaller flag then is the annode, is positive, and has the longer lead.
LEDs that you are likely to use have either a rounded top which acts like a spot light, or a flat or more properl
Lion wrote you a treatise, but in case he missed anything here are a couple of more useful links:
http://www.trainweb.org/girr/tips/tips7/white_led_tips.html
An LED tester is a very handy tool to have if you are going to play around with LEDs.
I can not find the same type that I bought years ago at Micro-mark but it clips to a 9v. battery and has two mini-grippers. I like this style because I use a lot of “axial” LEDs for signals and I can check them without bending the leads.
There is this type as well and the nice thing here is you can check the brightness against varying current.
I have hundreds of LEDs around and many are the “water-clear” variety and the only way to know the color is to light it up.
Of course, you can make your own LED tester but some of the ones available out there are SO cheap it’s almost a waste of time.
Buy a few assorted bags of cheap LEDs and start experimenting (many sellers throw in 1K resistors, a handy rating to use with most LEDs at 12v)
LION pretty much covered everything you need to get started…
Have FUN, Ed
You don’t need a book.
Everything you need to know can be found on the Internet.
Just Google for what you are searching for.
And ask questions here on the forum as issues arise.
That is honestly the best way to approach this subject.
Rich
WOW… .thanks so much for the tutorial. I copied it and will refer back to it when I get that far on my layout. I work at Home Depot and bought a bunch of the Christmas LED light sets at phenominal savings. Thanks everyone for your input! I think I’m going to like this forum.
Like CNWman, I am new to this forum but frequently visit the Classic Toy Train Forum since my interest is in prewar O guage railroading using AC as my power source. I came to your post (ROAR) while searching for info regarding the use of LEDs and thoroughly enjoyed studying your response to CNWman. The following is a copy of a post I placed on the CTT forum yesterday. I have not had a response and knowing DC is the power source typically used by members of this forum, was reluctant to post here. However, nothing ventured, nothing gained, so here is the post and perhaps you or another member can assist me.
For some time I have considered incorporating LED lighting in my layout. I have seen after market offerings for LEDs operating between 5 -19 VDC, prewired universally for AC or DC power sources, (http://www.modeltrainsoftware.com/bl-212.html). The circuitry includes bridge rectifier, capacitor, resistor and lamp and I have been tempted to make a purchase. However, I would rather learn something in the process as opposed to simply hooking up a finished product. I am no electronics or electrical craftsman but can reason and follow instructions. I have 50 ea. 3.3 volt 0.066 watt LED lamps from an extra Christmas string rated at 3.2 watts and 0.027 amps that I would love to play with. Is there a generic schematic that shows the correct placement of the various components necessary to wire an LED using variable AC and how do I determine the proper specifications for the components?
Thanks for your input,
swede
The 3.x volts is the minimum voltage needed to light the LED. Any voltage (3 - 20) will work just fine, but you MUST limit the current. The math mavens and electricl engineers will tell you exactly what resistor goes with your circuit, but the LION does not care. You can use a DC wall wart and it will light 100s of LEDs, just put a 1000 ohm resistor in series with each LED and you are good to go.
The LION has many circuits on the layout of him, all of them use a common ground, grounded to the building system. With out a good ground you would have all kinds of stray voltages on your common circuit.
So run the negative circuit around your layout, and ground it. Connect the positive circuit to your LEDs and you are good to go. (Remember the story of the Annode and the Cathode).
ROAR
Thanks for the quick response, ROAR, For the fun of it, I will rummage around here for an obsolete, but suitable wall wart, do some soldering with 1000 ohm resistors, following your earlier directions, connecting the short lead (cathode) and resistor to ground and longer lead (annode) to power. Will report my success!
For information or curiosity sake, I would still like to learn what the circuity and component specifications would be for a 5v -19v Universal AC/DC hookup, if someone could tell me.
Thanks again, swede
swede,
I’d think circuits suitable for DCC would work with AC. Many people think they’re the same, but they’re not. But for something like lighting with LEDs, I’m pretty sure a circuit I used in my passenger cars will work. If you need something less than 12 volts, the spookshow website link I posted earlier shows a simple adjustable DC output circuit that could piggyback on top of this one. It’s about a 3rd of the way down the page and is drawn with markers.
http://cs.trains.com/mrr/f/88/t/213765.aspx?page=2
It’s set up to provide power to the 12 volt dc LED strip light segments, but with a voltage regulater can do other voltages.
Yes, LION uses LEDs in passenger cars. Since cars can travel either way through the layout, you need to put a full wave rectifier in the circuit. The AC side of the rectifier connects to the track power, and then you will always have + and = dc inside of your car.
LION is still working on a circuit to keep the lights lit while the train is stopped. Him will report on that when (not if) he is successful.
ROAR
Thanks for the response, Mike. I don’t utilize DCC, but based on what I have read, it is sort of modified AC and I believe you are correct, this approach will work. Your diagram and part call outs will get me trying this approach as well as the wall wart one. I really enjoyed going through the entire thread on Night Lights. I don’t believe I will get to the level of lighting sophistication on my layout as you and others have displayed but I have bookmarked this thread and will be following it. Who knows, lighting may become as important to me as the trains and their movement around the track are.
swede
Thanks for the response, ROAR. Yes, lighting in passenger cars as well as other cars was a concern on my part. The schematic that Mike had previously posted and included in his response to me substantiated what I suspected was the layout utilized in the after market universal AC/DC LED hookup.
Will be back, and again, thanks.
swede
Mike and Roar, just for experimental purposes, I hooked up a 9 VDC wall wort with a 1000 ohm 1/2 watt resistor in series with a Christmas LED, then 2 LEDs hooked together + to - with the resistor and AC power and then built the circuit Mike suggested using AC power, all three worked just fine. Now I’ll get busy and see how many Christmas LEDs I can realistically use on the layout. I truly appreciate your assistance.
swede
LION has more than 1000, and is still putting them on the layout. Each of about 200 signals has three LEDs, Each of the station platforms is well lighted, some only an inch apart. Station platforms on the Route of the Broadway LION are four feet long. (Subway trains you know.)
These were made with a coffee stirrer (the kind with two chanels in them) an LED, and a thumbtack, painted to match the posts and with the point cut off.
(I found the point to be pointless, you know)
ROAR
I understand the pointed pointless point. Do you use superglue to glue the pointless tops to the LED or something less permanent? What is the base material the stirrers are attached to? The edge looks like a squashed piece of corrugated paperboard that has been painted.
swede
The platform is indeed a piece of cardboard. It is resting on a strip of ceiling tile. I uses an aul to drive a hole through the platform and the table top which is also lightweight tile material. The Stirer goes clear thorugh, with the end and the wires coming out the bottom of the table, and connected to the bus wires. I then can adjust the height of the light fixtures.
ROAR
LION you’ve been a great help to me in answering my nubie questions about LEDs. I bought some LED Christmas light sets at Home Depot just after the Holidays… they were closing them out so I got a good deal. I’m now awash in little LEDs! Time to do something with them. What is the best way to power them… by the AC accessory terminals on one of my power packs, or maybe buy a little DC starter transformer on E-bay and use that strictly for power? Won’t the lights last longer on DC power? Thanks- KD
You have to run the LEDS you salvaged from Christmas Tree lights on DC only - AC will not work. Indeed, I have been tested my reclaimed LEDs with a plain old battery, as I am trying to figure the best combo of resistor/LED (looks like the old standard - 1KΩ - is the best, although they work OK on 2KΩ). LEDs are in parallel, I’m going with the now standard two “rail” (brass pieces) along the structure interior roof, LEDs & resistor attached across the rails, cone pointed down, as needed. LEDs as stated are voltage directional, I believe the larger triangle within the LED is the Cathode, and this page seems to confirm that.
I’m mostly wondering about current draw, I believe each LED is running 35mA; with 100 LEDs, that’s 3.5A, which is not insignificant.
Running a white LED with a 1K resistor on a 12V DC power supply results in about 9ma per LED. 4.25ma with a 2K resistor. Not sure how you got 35ma per, the LEDs are typically only rated for a max of 20-25ma and at 35ma they wouldn’t last too long.
12V - 3.5V LED forward voltage (typical white LED) =8.5V 8.5V /1000 ohm resistor = 8.5ma.
–Randy