Here are some LED Light Frequently Asked Questions

Why Switch to LED’s?
There are many reasons to switch to LED’s instead of regular incandescent lighting!

• LED’s do not get hot like an incandescent, so you will not melt the roof of your
  building or the housing of your train, water tower, model emergency vehicle or model airplane!
• LED’s last and last!!  Over 10 years  (100,000 hours!) per light.  So, you will not have to take apart your building locomotive, passenger car, model, or diorama to change out the lighting when it burns out!  A standard incandescent bulb will last  about750 hours or so.  We at Evan Designs guarantee our lights for two full years with free replacement if run at the correct voltage.
• LED’s give a lot of light in a very small package.  The LED’s we sell have a minimum of 5000 millicandels of light, approximately 1.45 Lumens.  Some colors, like white, have 15,000 mcd.   Compare that to a GE 14 volt Midget bulb which gives approximately .3 lumens (mscp).  Check the brightness information before you buy any LED.  There is a huge variation of brightness sold today... be wary of any vendor who does not publish brightness numbers right out front.
• LED’s are tough and durable.  There is no filament to break, and the diode is encased in solid epoxy.  You can use pliers to install these lights if you need to.

What Do I need to do in order to connect LEDs to power?

If you are planning to run your LEDs on a 9V DC or 12V DC battery or a 12V DC wall adapter, then you will want to get a small resistor and some connector wire. 
Most people know how to hook an LED to DC power, just trim the two leads on the LED and solder a resistor and some connector wire to the LED leads.  Depending on the voltage you plan to apply, and depending on the color of the LED, a 470 ohm or 560 ohm resistor will work fine.  Use a calculator you can find on the internet (sorry I cannot put the link for the calculator in this guide).  Be wary of vendors who give away 100 ohm resistors with their LEDs.  I have no idea what use that small resistor is, they probably get a good deal on them :)

The resistor is typically put on the positive or "hot" lead, although I have been told that this does not matter.

  You can tell the positive lead on an LED because the leg on that side of the LED is longer.  Also, looking at the diode, the positive half of the diode is smaller than the negative.

A few things to keep in mind when soldering LEDs: 

• Do not solder too close to the bulb, the recommended distance away is at least a few millimeters.  
•  Do not let your solder gun temperature get over 240 degrees Celsius.  Check what temperature your soldering gun gets up to since LEDs are heat sensitive.  
• LEDs are also sensitive to static electricity (before the resistor is added), so try not to give them "a shock" when you are handling them.  Solder in a humid room if possible, or wear a static wrist guard, and don't drag your feet across nylon carpet.

If you are running your LEDs directly on your railroad track, as in the Locomotive or passenger car, of if you plan to hook them to the accessory outlet on your train's AC, DCC or DC power pack, then you will need the to do some more to protect your LED.  Even DC Trains tend to switch polarity (whenever you back up) and the lights are also subjected to voltage "spikes" and surges and the occasional interruption and re-start when the track is not perfectly clean.  To protect the lights from all of this, you will need to add a full wave bridge rectifier in addition to the previously mentioned dropping resistor.  So even if you have a DC train, and you only plan to run your train at 12 volts or less, like the N Scale Kato power supplies, we still recommend you use bridge rectified LEDs.  You could use a single rectifier diode like 1N914, to block the reverse polarity, but there are two problems with this approach: 

• The LED will only be half as bright because it is only on for half the time.  This did not sound right to me, but it is true!  I have tested this fact with a light meter so I know it is true. 
• The LED will flicker slightly because it is going on and off rapidly.  You may not see the flicker easily, or you may be used to flicker from looking at your TV, but when the LED moves, (in a loco or passenger car) you will see it flickering.

If you are going to run one of the new Integrated Circuit Flashing LEDs on AC or DCC power, there is another step to take as well.  I have found with a lot of testing that the IC Flashing LEDs need a small .1 (uF) capacitor in addition to the full Bridge Rectifier in order flash reliably with AC or DCC.   

Another thing to check on when you are looking at buying flashing LEDs is the flash rate.  For older diecast models and for Model Trains, models of radio towers, water towers, warning signs, etc. a nice relatively "slow" flash rate is 1.5Hz or one and a half flashes per second.  A lot of the LEDs produced today have a faster rate, 2.5Hz (2.5 flashes per second) or even faster!  A 2.5Hz flasher will make a great modern emergency vehicle flasher or simulate a strobe light on a RC Helicopter.  Faster than 2.5Hz, the flash is pretty much just too fast for most model applications.  So be sure to Check the flash rate as well as the brightness information when you are buying IC flashing LEDs.

What are 5mm, 3mm, and 1.8mm LED Lights?
The size of the light is measured across the base of the bulb.  The size measurement refers to the diameter of the bulb.
5mm (T 1 3/4) is a larger sized light, for building lighting, passenger car lighting, or larger scale train running lights.
3mm (T 1) lights are smaller in size, and better suited to street lighting, warning lights, and train running lights in smaller scales.  Brightness-wise there is little to no difference between the 3mm and 5mm size. 
1.8mm LEDs are really very small and most useful in N scale and other smaller models where there is not much space to fit a bulb.  The 1.8mm we have are still bright at 3,000mcd.  I do not know of an incandescent that is as small as these 1.8mm LEDs

What are 12 Volt pre-wired LEDs?
 An LED bulb can only handle 2 - 3.5 volts of power, depending on the color of the LED.  White can handle more voltage than red, for example.  If you were to connect an LED bulb straight to a 12 Volt power source without a resistor, you would see a very brief bright flash as the LED burns out.  We have soldered a color-specific resistor to the LED so that it will work with your 9 or 12 volt power source without harming the LED.  Our 12 Volt DC LED's can run on anywhere from 6 to 14 Volts and are fully guaranteed to work, with a 2 year Replacement Guarantee if run at the correct power.

Why do you sell 18 Volt Universal Input Lights?
An LED alone can only handle 2-3.5 volts of power.  AC Trains,  Digital Command Control layouts and  DC trains have power supplies that run at a high voltage, 8-25 volts, depending on how the Layout is set-up.  To handle this bigger voltage supply, we have added a full wave bridge rectifier and a greater ohm resistor to the LED assembly to handle both the higher forward voltage, and the switching polarity of AC and DCC trains.  The great thing about the Bridge Rectifier is that these lights stay lit even when the trains are run in reverse!

Can LEDs work outdoors?
 Yes!  These LED’s are the same ones you see around car license plates and in flashlights.  The Light Emitting Diode in an LED is completely encased in tough epoxy.  Our "Garden LEDs" also have a marine coating on the electronic parts for years of carefree use.

Can I wire these into my rolling stock?
 Yes, you can.  Refer to the diagram that came with your locomotive to check where to attach the leads for your particular loco.  To light a passenger car, you will need to run the wire down to the track through the "truck".  In general, the red wire goes to the positive the black wire goes to the negative.  Check the internet and magazine issues for articles on how to proceed with installing.

Does Reverse Polairy Damage LEDs?                                                                                              Yes, it does.  Not immediately, but over time reverse polarity will burn out an LED.  This is the case when you run an LED without a single diode rectifier or a full wave bridge rectifier on AC or DCC current.  Both AC and DCC switch polarity from + to - and back again many times per second.  The LED will run fine under this condition for 12 hours, sometimes even longer but after time it will dim and burn out if you do not have a rectifier.  The rectifier acts as a 1-way valve to only let the + polarity through to the LED.

How many LED's can I wire in parallel?
 The LED’s we sell draw less than 20 milliamps of power.  So check your power source.  If you have a small wall plug power source with 500 milliamps of power you can run (500 / 20) or 25 lights in parallel!  We have a light board that we bring to shows, there are 38 lights in it and it runs very brightly indeed on our 500 milliamp wall adapter.

How about in wiring LEDs series?
We do not recommend wiring LED lights in series.  We have tried it, with poor results.  For one thing, the assumption you are making is that the LEDs will share the incoming current equally.  So if you have 12 Volts coming in,  you should be able to connect 4 LEDs, right?  In practice this does not work.  The first LED in the string will get more power, so you will have a "gradient" of brightness with the last LED dimmer.  Also, since that first LED is getting more power than it should, it burns out very quickly.  There are other problems with this system, if you do not have exactly the right power source, the LEDs will be too dim or burn out too quickly.  Adding a resistor to each LED ensures that each LED is getting exactly the correct power to burn efficiently and for 100,000 hours.  Series really does not work well.

Can I get more light spread?
 The LED’s we sell are “wide angle” LED’s,  most have an average of 35 degrees of light spread.  If you find you need more light spread on an LED, you can gently sand off the epoxy that makes the rounded top on the LED to change the shape from "rounded top" to "flat top".  Unlike an incandescent, you can take away the top of the LED without harming the diode.  Just be careful when you are sanding not to get anywhere near the diode inside the epoxy.

Can I fit my LED into a really  tight space?
 Yes, LED’s can be bent at the stalk up to 90 degrees to perpendicular and still light!  That is how LEDs are fit into computer keyboards, cellphones, etc.   If you need a really small light, try out our new super bright 1.8mm LEDs.

How much power do these lights draw?
 The LED's draw only 20 milliamps of power.  So you can connect quite a few of them to your power source without dropping your power to your models!

Can I mix colors, sizes, flashing and solid in the same model?
 Yes! You can mix any color solid light with flashers and any size of light in the same model.  We do this all the time when we modify die cast emergency vehicles with white headlights, red tail lights, some flashers in the dome and 1.8mm interior lights.  We have a gallery on our website with some great examples that customers have sent in of their projects.  You will see lots of examples mixing LEDs in trains and more!

What Can I used LEDs in?
 You can use LEDs in Locomotives, passenger cars, buildings, emergency vehicles, model boats, model airplanes, model dioramas, RC Boats, Planes, Helicopters, Trucks.  The durability, low heat and extremely long life of LEDs make them by far the best choice for every type of modeler!

 Still have questions? Contact us!  We will be happy to answer your questions!