wvg_ca as a guess, he went to pads that had 12v or so to them, he mentions using a 470ohm resistor ... you could alwaya leave a comment on that video ??
as a guess, he went to pads that had 12v or so to them, he mentions using a 470ohm resistor ...
you could alwaya leave a comment on that video ??
wvg_ca he actually didn't go straight to the loco [DC] in the video .. he went to the pads on a TCS decoder [DCC] with keep alive
he actually didn't go straight to the loco [DC] in the video ..
he went to the pads on a TCS decoder [DCC] with keep alive
I found another video that does a great job on how make your own LED + leads and install in the headlamp openings. Lighting looks awesome in the locos! Unfortunately, he didn't show how he completed the final wiring from shell to the locomotive... Grrr...
Shouldn't have pulled the trigger so fast. After further review, I have canceled the order as I don't care for all the light in the cab and there's very little room to add a light block. Plus the LED leads are rather short which makes it difficult to attach/take off a shell with attached LEDs.
Those will certainly work. But they are only 1 LED per end, not double, Which is another way to do it - several companies make clear lenses, and you can put one LED on the inside and have both holes filled and illuminated.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Randy, thanks for your discussion and always great advice!
I came across a good deal for a newbie like me on ebay. I purchased this: https://www.ebay.com/itm/PARTS-Athearn-Blue-Box-locomotive-warm-white-LED-head-lights-DC-DCC-EASY-INSTALL-/202466058665?oid=202421016879
This will outfit front and rear lights of both of my athearns on Front and Rear lights. Provides directions for DC connection and then how to change when upgrading to DCC. Has nice set of directions. May be a bit overpriced but for a newbie, it's perfect given the well described directions and easy way of converting between DC and DCC! Do you agree, did I read it right?
As one of the comments rudely states, to which he rudely replied - he doesn;t show that kind of important bit of information. Makes the electrical portion of the video pretty much useless.
Unless thoose LEDs already have resistors in line somewhere, it would appear he is hooking 2 LEDs in parallel and then using one resistor. This is probably the least favorable way to do it, but it will work. The issue can be that the two LEDs are not well matched, especially if you buy the cheap Chinesium ones. They may not have equal forward voltages, so one may end up brighter than the other. It would be better to put two LEDs in series and use a smaller than 1K resistor if you want to reduce the number of resistors used.
As for the ditch lights, looks like he's doing a BC Rail model, so it's OK what he did, but if you are modeling a different railroad such as Conrail, NS, or CSX, you don't want to combine the two ditch lights, you want each light on its own function output so they can alternately flash. Canadian railroads don't do that, so they can be wired together.
i'd need to see how he connects the LED so the decoder
greg - Philadelphia & Reading / Reading
Thanks for the discussion, most appreciated.
Here is the youtube video that I watched: https://www.youtube.com/watch?v=j46QbNDG4I0
Note each LED has a black and red wire. Near the end (4:45) he describes soldering the wires in parallel (ie the two blacks are soldered together then the two red ones). Earlier he shows the resistors but not show them being attached. Oops, I missed that the first time... (probably because I had be looking at LEDs with attached resistors prior to watching the this video). With his wiring approach, where will he install the resistors? Thanks
IDRickThe locomotive had twin headlights so he mounted a separate LED + 1000 ohm resistor in each slot then connected them in parallel to the decoder.
seems like this is what he's saying
decoder -----|----R--------LED---------| |----R--------LED---------|--- Blueso why not do this?
decoder ----------R----LED-----LED---- BlueMark R.Two LEDs soldered together in series with a single 470 ohm resistor
Mark R.Two LEDs soldered together in series with a single 470 ohm resistor
The physics isn;t wrong - 2x 1K resistors in parallel will yield 500 ohms. However, when you have an LED and a 1K resistoor in parallel with another LED and a 1K resistor - the resistors are not in parallel with each other. The entire circuit of a resistor in series with an LED is in parallel with the entire other circuit of an LED in series with a resistor. You have to account for the LEDs as well. Then the math actually does work out.
For a single LED in series with a single resistor, the current is calculated by (Source voltage - LED voltage drop)/resistance. For typical DCC decooders and white LEDs, it works out to be around 9ma with a 1K resistor. A pair of 9ma circuits in parallel with each other, will draw 18ma from the source. The voltage drop across each resistor will be the same because parallel circuits each get the same voltage - it's not split. So you have the same voltage at twice the current = half the resistance! But that's measured across the entire circuit - each LED still has 1K, not 500 ohms.
It's actually not quite that simple, but for fairly trivial circuits it happens to work out.
and the LED. Some of those cheap-as-chips chineseium ones on ebay need a bit more in the resistance department.
But hey, when you get a pack of 50 or 100 for $5 ... a little trial-and-error time is fine.
-Dan
Builder of Bowser steam! Railimages Site
I've done installs in three methods, all with long term success ....
All three methods work just fine and have lasted years in my own installs. Which method I use depends on the application more than anything.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
The way I see it, each LED, resistor circuit would have 12 vdc across it whch would have about 9 ma current flowing through each circuit which is normal. I have done a few of those, single and dual. No interaction between circuits. The decoder can handle it.
I did resistor LED measurements a number of years ago when I started working with LED's in 1972.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Mark R. The two resistors themselves aren't in parallel. The two circuits (resistor and LED) are in parallel with each other from the power source .... different math. Mark.
The two resistors themselves aren't in parallel. The two circuits (resistor and LED) are in parallel with each other from the power source .... different math.
What is your answer then? Been a long time since I had physics...
I'm a dairy guy, not a electronics whiz.
richg1998 The OP might be interested in the below link. I hope it does not cause any confusion. http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm Rich
The OP might be interested in the below link. I hope it does not cause any confusion.
http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm
Makes sense that a 1000 ohm resistor in series will yield same circuit current flow as two 1000 ohm resistors in parallel. Thanks for the link Rich!
I am a DCC newbie and need be quiet before making myself more of a fool...
Okay, thanks. The 70's were a long time ago...
After cheating by reading my friend Google, the series equivalent current = Voltage/500 ohms. The sum of current through two parallel resistors equals Voltage/500 but individual resistor would receive receive a current = Voltage/1000 ohms.
nope .. that's is right
one 1000ohm resistor per led
I watched a neat youtube video tody that discussed converting bulb lighting to LED. The locomotive had twin headlights so he mounted a separate LED + 1000 ohm resistor in each slot then connected them in parallel to the decoder. My memory from college physics (70's vintage) is that two 1000 ohm resistors in parallel will have a series equivalent of 500 ohms (1000/2). Isn't that too low for LEDs? Seems like most recommend a 1000 ohm resister for a single LED. To achieve this with twin headlights, one would need to wire two 2000 ohm resisters in parallel, correct?