Power from Layout to the LED

The first thing I need ot figure out to do is get power from the accessory bus on my Free-mo modules to the LED's. Of course you cannot just directly plug the LED's into the bus wire, well I guess you could if you wanted to see them explode.

So the first step is to get the power in the bus down to a usually voltage that won't cook anything. Free-mo standards state:

"S4.11 Accessory power shall be approximately 16 volts AC or DCC. The bus is wired straight through. A bridge rectifier and filtering capacitor may be used to convert AC or DCC signal to DC. Applications that require AC or DCC signal may utilize power directly from the bus. ( FAQ S4.11)"

"FAQ S4.11  Don't you mean AC & DC for the accessory buss?

Accessory bus can carry either an AC signal or a DCC signal. Many groups use a booster to power the accessory buss."

Ok, so I need to get the 16Aac or DCC  stepped down to a usable voltage, what usable voltage should i use? 

After a brief internet search I found an article Gregg Fuhriman about a signaling system for Free-mo. Amongst his drawings and diagrams he had an drawing showing how to wire up a Bridge Rectifier and step the voltage down to +9 Volts DC. Here is my attempt at redrawing the diagram:

OK so now I need to get the components and see if I can get my voltage to step down to 9 volts.

Also I just want to make sure if anyone knows diagrams is this thing correct? I also assume I would hook up my LED to the gray and Black lines next to the +9 Volts DC?

LED`s use 3

LED`s use 3 volts............some even less..............if you use 9 volts you will burn them up in just a few seconds...............and just like DCC decoders, once you let the smoke out of them they are no good.

On to the LEDs

I went to the National Train Show this year and checked out the Ngineering booth as he was showing off some of his items and making lamps. One thing I noticed was the specialized tools he had to work on the Micro and Nano LEDs. In talking to him he had a kit available to get someone, like me, almost everything they need to start wiring LEDs. At the time I had already spent my monies on other things, but kept the kit in mind for the future. After getting a little extra for Chirstmas I ordered the kit, Free shipping on orders over $100. The kit comes in a cardboard box similar to some resin freight cars. 

Along with what is in the kit the only other major tools needed are a 34-40 Watt Soldering Iron, sharp knife, scissors and small vise. Of course good lighting and magnifying devices also are a great idea for any modeling project.

Here is what is inside the box:

There is also a 17 page print out that is information off their website that is very useful to someone who is new to LEDs. I have read it through once and will keep it near me when I try my hand at Soldering these tiny things. I also think I will print off a few of the charts and other information from the site to pin to my workbench for future reference.

Good So Far!

That kit from Ngineering is an excellent place to start. I have parts of it. Also, Ngineering is a good source for neophytes to get LEDs.

Now you will blow up some LEDs, and have more questions. 

Also, your 9V power supply looked fine. Be sure you check the pin-out diagrams on the components that you get.

Resistors

BR GP30 2300

Yeah I will need to use the handy dandy 9v Resistance Wattage chart to figure out what resistor to use that Ngineering includes. The Ngineering LEDs look to range from 1.7 to 3.3 Volts all at 20ma so with that I will be using the two formulas to check the R value and also the P value to make sure I select the optimal resistor.

LEDs are current devices.

LEDs are current devices. While you want DC, it doesn't have to be precisely regulated or even filtered, as long as you know what the DC voltage is (DC voltmeter is good enough to measure this).

The quoted operating voltage of the LED is only approximate, just a number to plug into the resistor calculation, and as long the supply voltage is a lot higher than (say, at least twice) the LED voltage the formula will be close enough. It's the current you have to get right (though of course, even a little variation in that will only make the LED a bit brighter or dimmer). Common LEDs tend to be 20mA operating, 30mA max.

BTW: if you're using red/green bicolour LEDs, and want a good yellow (not orange) when both are on, you'll probably have to use a higher resistor (i.e. lower current) on the red side to dim it down.

Ngineering LEDs

The LEDs I am going to start to play around with are the Micro and Nano LEDs that Ngineering included in their starter kit. Most of them are already a specific color and in their information state the colors are set at the factory. I am not sure how they set them but I would assume once set they are not adjustable other then brightness? 

LED Resistor Value Calculators

It as been mentioned on MRH before, but there are several OK LED resistor value calculators on the web. Just search for LED Resistor Calculator and you will find several sites like: http://www.electricaltechnology.org/2014/02/LED-resistor-calculator.html.

Although you are planning on adding a regulated DC supply (your schematic looks correct), in applications where you may not have a reliable DC source, you can also get LED drivers (current sources) such as the MicroChip (Supertex) CL series of devices. These and similar devices have working voltages from ~4 to> 90 VDC and set output currents of 15, 20, 25 30 mA. No resistor needed. 

Enjoy learning about LEDs.

Thanks guys!!'

Ken

Both of those are great resources and I will be sure to be utilizing the calculator. I will also keep the LED driver for use in a stand alone situation. 

Paul

As stated above I have no idea what I am doing just trying to follow the instructions to keep things working. I am not sure why they require the step down to 9v but it seems to be a common voltage for items. I will just play nice and make sure to include it. 

About LED colour

Sorry if I introduced some confusion, Greg. Yes, any given LED has a set colour that's a basic characteristic of the emitter device. However, you may run across multi-colour LEDs that combine several emitters of different colours in the same package (e.g. LED Christmas lights that change colour). A common configuration is a three-wire device with red and green emitters -- obviously useful for lighting up single-head signals. If you turn on both red and green at the same time it will give you a range of yellow/amber/orange, depending on how much current you feed the red vs. the green. (If you've seen DigiTrax sockets, the track status LED is a red/green bi-colour).

My kit from Microluminata

came with current limiters. Consider them smart resistors. They are Ngineering products I believe, as the are in their packaging, but these little doo dads automatically limit the current into the LED to 20ma and the proper voltage, no matter how much current is in the wiring. Well I wouldn't try them alone with straight AC, but you can drop one in between the LED and the + source of 12 volts from, say a toy transformer or wall wart, and no need to worry about letting the smoke out of the LED.

I'll follow this thread with interest as I too am starting to work on lighting a few scenes on my layout and figure if I let the smoke out of the LED, as long as I can keep it in the layout room I am still good.

Clarity and possibilities

Steve,

Ok that makes sense, I have seen the bi-color LEDs referenced in signaling and was kind of aware of how the change in voltage affected the lights. One thing I would like to do, at some point, is add signaling to some of my modules, but I figured one thing at a time.

Peter,

That is defiantly a product I will have to look into, I think I will us up the resistors I have as I think it is a good exercise in learning something new. If it is a complete failure I might fall back on the current limiters. Yeah I figure I will burn up a few, hopefully I can save someone else from burning up so many?

The expirment begins

I had a little time this afternoon and decided to try the first step in soldering wire to my LEDs. It call for tinning the Magnet Wire using silver solder. I set my soldering iron up using a tabletop vise so I would not have to hold it and the wire at the same time.

I then got out the other tools I thought I would need and set them nearby for the next step.

Next I cut some magnet wire starting with six 6" long pieces, three red and three green. I was not sure how well it would go and did not want to spend to much time just tinning the wire. I figured I could cut it shorter if I needed to try again. With the wire cut and the iron hot I applied the Silver Solder to form a bubble, as the instructions state, near the tip. I put on my Optivisor, as the magnet wire is very very small. I then quickly dipped the end of the wire into the solder and back out. The goal is to melt the coating and tin the tip at the same time. I think I was successful, but I guess I will not completely know until I try to solder them to an LED.

LED's

Greg,

There's an excellent (and FREE) book available on the web on LED's for beginners by Colin Mitchell at 'Talking Electronics' called '30 LED Projects'.

I would suggest that you grab a copy and delve into how to operate a LED. The book has several projects that can be used with model railways.

BTW, you will need a resistor of approximately 470 ohms to run a standard LED on a 9vdc circuit.

Have fun,
 

Good Set-Up

That's a good set-up you've got. I learned that the directions that come with the Ngineering are correct, and the small soldering iron doesn't get hot enough to tin the wires. I take it that you also have some sort of magnifier.

To figure out LED voltage requirements and resistor value.......

........why not use an old power packs (PP) variable DC and a meter to figure out the voltage needed for the LED and then the correct resistor to get there from whatever voltage you start with?

I connect my LED to the pp and slowly turn it up until I get the exact brightness (or color if using voltage controlled color) that I want.  I them measure the voltage with my meter.  Remove the LED and attach the meter to your DC output and increase your pp to the starting voltage you need, say 12.  (I use 5 for QSI Titan lighting output)  Now find the correct resistor to get the 12 volts down to the LED's voltage.  To make this easier I have soldered a bunch of marked resistors (in a fan pattern) together at one end *which is clipped to one meter lead and by touching the other lead to the single resistor wire, find the one that drops your voltage to what the LED needs.  Mark this down somewhere if you are using a lot of the same make and size LED. 

Using this method is pretty foolproof as I have only fried an LED when a twitch made me turn the pp up too high!

Peter

*I had planned to make a permanent tester using a 12 position rotary switch with 12 different value resistors but as I use the same LED's at the same voltages I never bothered 

One quick word of warning.

One quick word of warning. In your original circuit diagram, near the start of this thread, you have a 330uF capacitor on the output of the bridge rectifier (red and black wires) but you do not state its maximum voltage rating. Depending on the bus source, e.g. 16V AC output from an old controller, this could peak at 30V or more. If you only use a 16V rated capacitor, it will eventually go pop.

For a good read, and general introduction to electronics for railway enthusiasts, I can recommend this free download:

http://www.merg.org.uk/ebook.php

Ian Morgan

Hampshire

England

Thanks again

Neville-

What a great online resource, I downloaded the recommended book and skimmed it last night. It goes very in depth, but has lots of pictures and is written in a way that is understandable. I also see he has another online book of 75 model railroad projects that looks to have some interesting projects too.

TIm-

I have a set of Optivisors I am using, I am also thinking of adding an additional light as this stuff is darn small

Peter-

That is an interesting idea, I will have to see if I can locate my DC transformer, I know I had one for a Christmas Train Set I had awhile ago. I would like to see a picture of your resistor setup.

Ian -

I have a recommend part number for the Capacitor and will check its peak voltage. Most setups have been using a DCC booster to power the Accessory Bus, but it is a great idea to make sure if that is not what is being used I don't make things go "POP." I will also check out the book, another great value...FREE!

And away we go...

After pre tinning he wire I could not resist trying them out, so I stayed upa little bit to late last night trying to successfully wire up an LED.

I started with a Yellow Micro LED, they come in these neat little carriers that each LED can be cut off the strip and the reaming returned to the package. One thing they made clear in the instructions is that once you misplace the LED from the packaging their is no way to determine what they are unless you hook them up to a power source.

After cutting one LED and placing it on some styrene so hte handy grabber things could pick it up I took a picture to show the size.

(That little fleck is the LED, also there is one size smaller the Nano.) 

I used the provide LED holder, which is one of those simply yet effective tools I can really appreciate. It has two small clamps, one with rubber cover jaws, o na piece of brass that can be held by a desktop vise.

Then came the fun part...placing a pre tinned wire into the rubber cover clamp and seat it onto the tiny soldering pad. Next was to touch the soldering iron for no more the 2 seconds to the wire to get it attached to the pad. This took a couple of tries as I broke a few wires from moving them and found out not all of them were well tinned. I did not try it this time but may take the recommendation of using a toothpick to apply liquid flux in a minute amount to wick the solder onto the pad. Also make sure you have a well tinned iron that is clean and ready to go.

Once this was completed I took the LED out of the clamp and flipped it around placing back in the holder. The process was then repeated in attaching a wire. I followed the recommended practice of soldering a Green with to the Cathode side to try to keep things within spec. 

So after a few bad soldering joints, and a broken wire from mis handling I finally got the wire attached to the LED. Not until I tested it could i claim a victory, or at least a small victory.

Next was to use the LED Tester that was included in the kit. This has two spring loaded catches and a built in Resistor of some sort to keep things from blowing up. It plugs into a 9V battery and is quite clever and simple. There is also a spot to test different Resistors on the board.

So after attaching it to the leads this happend, YAY!

Just to get a feel of how much light these little LEDs put out I placed it inside a house that I plan to install LEDs inside. So far, pretty impressed.

Next will be to work with some resistors to see what I come up with. Then it will be on to wiring up more LEDs and installing them into a couple of buildings.

I'll post a couple of pictures when I find them..........

Peter