No Need For Resistors

[alloboard]

If I added ditch lights or cab lights to the Digitrax DH165A0 decoders with 12V LEDS wouldn't there be no need for a resistor?

[rrinker]

12V LEDs are nothign more than LEDs with resistors already connected, usually in the case. That also makes the LEDs larger - the tiny ones you need for ditch lights aren't likely to come in a 12V variety. You could mount them up inside the loco and use fiber optics to get the light to the ditch light housing, but to me that's more work than just using the smaller LEDs and adding a resistor.

                                                       --Randy

 

[gandydancer19]

 ALL LED's require resistors.  It just may be that some types have them built in.  These are usually larger than regular LED's and found at Radio Shack type stores. They should also specifically state that the have resistors built in or that they do not require resistors.  If in doubt, test them first.  If you put 12VDC on an LED without a resistor, it will have a distorted color and burn out shortly.

If you are using 12 volts DC, you can use a resistor with a value between 470 ohms and 1000 ohms.

I don't know about the decoder you are working with, but most decoder light outputs are 12VDC and they require resistors even if there is an LED function selection.  Read the decoder instructions for full information.

[rrinker]

 Well there are "12V" LEDs and "5V" LEDs - they are just regualr LEDs with the appropriate resostor already included, usually mbedded in the package. But those are usually all 5mm or larger LEDs, way too big to be a ditch light.

 Here, 12V LEDS: http://www.allelectronics.com/make-a-store/category/340600/LEDs/12-Vdc/1.html

 

                                               --Randy

[alloboard]

I'm only using the 12V LEDs for interior cab lighting. How do you use fiber optics to get the LED into the ditchlight housing?, and where can you get the fiber optics and how do they look like?

[richg1998]

davidmbedard

alloboard

I'm only using the 12V LEDs for interior cab lighting. How do you use fiber optics to get the LED into the ditchlight housing?, and where can you get the fiber optics and how do they look like?

 

Are you making stuff up?  There is no such thing as a 12 volt LED.

David B

 

 

 There is if the resistors is included when manufactured or the below link is a lie.

http://www.allelectronics.com/make-a-store/category/340600/LEDs/12-Vdc/1.html

Rich

[Hamltnblue]

davidmbedard

alloboard

I'm only using the 12V LEDs for interior cab lighting. How do you use fiber optics to get the LED into the ditchlight housing?, and where can you get the fiber optics and how do they look like?

 

Are you making stuff up?  There is no such thing as a 12 volt LED.

David B

 

Actually there are thousands of products advertised as 12 volt LED.  Simply google it.  The individual LED isn't but the packaging and required voltage source is.

[richg1998]

As a machine mechanic back around 1999 I use to order LED replacement lamps for some machines that where for 120 VAC indicator lamps. Five LED”s in a small “bulb” arrangement. Exact size replacement.

The LED market is continually everliving as LED's run cooler and use less power.

Start using Google as a "lot" of stuff is continually evolving. Do some homework on your own and go beyond this forum for more knowledge.

Rich

[richhotrain]

davidmbedard

Are you making stuff up?  David B

LOL.  David, you're a stitch !

 

[cudaken]

  Would the fabled 12 volt LED work with a Digitrax SEB? Reason I ask is the track power is 14 volts.

 

            Cuda Ken

[rrinker]

 Measure the voltage output on the function of the decoder. It's a bit less than track voltage due to going through the controller. Now that I have a DB150, its nterstign to see the effect on my lights. The Zephyr's output is slightly more than the N scale setting but slightly ledd than the HO setting. Flipping through the three settings, I see my headlight get brihter. However, since I used a 1K resistor with my white LEDs, nominal 9ma at 12 volts, I have plenty of leeway - even the O/G setting does not result in too much current flowing. This is why you don't select the resistor based on the LED's maximum current - accidently flip the switch to O/G and poof goes the LED.

 This also explains why the answer to the 12V LED question is "maybe". Check the current rating of the 12V LED in question. If it's close to the maximum rating for a similar 'normal' LED that doesn't have the resistor, then it's probably not a good idea to use it on higher voltage. If it's well below the typical maximum for an LED, then there is enough leeway to allow higher input voltage without frying the LED. It all depends on what value resistor they embedded in there, and often they don;t tell you that - but you can tell based on the current.

                                                          --Randy

[WheelSet2]

My wife has a coffee maker that has some really cool lights on the front .I was just thinking would I need a resistor to use these on my loco

[Texas Zepher]

richg1998

There is if the resistors is included when manufactured or the below link is a lie.

http://www.allelectronics.com/make-a-store/category/340600/LEDs/12-Vdc/1.html

I think you are both saying the same thing just with different words.  A quote straight out of the ads referred to on the link, "Bright 5mm round red LED with built-in resistors for 12Vdc...."  which answers the question for itself.   LEDs by definition are diodes first and light emitting second.   Technically (semiconductorly speaking?) there is no such thing as a 12V LED.  It is only if a resistor is included with the LED by the manufacture that it can be advertised as a 12V LED.  That technically makes it is a 12V LED circuit.  Saying 12V LED is very confusing to electronics type people.