Small light question

[cudaken]

 OK, I know I have been bugging you folks a lot lately, sorry about that.

 Getting ready to work on some more Athearn RTR engines. I am planing on not using the light board that comes with the engines this time around. Engines will be a Rio Grand SD-50 and a SD 40-2, they use the small 1.5 volt (I think) bulbs. So if I use the stock bulbs do I need to add a resistor and what value?

 Does anyone make a LED that I could use instead? I rather use LED's

 Thanks for the coming answers.

           Ken

[tstage]

Ken,

If you aren't going to use the built-in light board then you can just hard wire in the LEDs with a 1K ohm resistor.  It will look MUCH better because the beam is directional.  Since you are using more modern locomotives, I would use the plain white or sunny-white LEDS.

If you use the stock 1.5V incandescent bulb, Ken, then - yes, you'll need to use a resistor.  3mm LEDs are 3-4V.  So, you'll then need something more than 1K ohms of resistance for the 1.5Vs.

3mm (T1) Sunny white LEDs can be obtained from Ulrich Models or Empire Train & Hobby (Empire Northern Models). Also, Ulrich has a nice primer on a SD70ACe conversion on their web site.  You don't have to buy the kit but it will at least give you some ideas.

Hope that helps, Ken...

Tom

[narrow gauge nuclear]

This thread saved me a posting.  I plan to just light a very few cars and cabs with warm white LEDs.  I am new to DCC but have long been into model railroading, jumping in an out. 

 So, as long as I stay under the fixed ~13 - 15 volt track voltage's current rating for my zephyr's stock 2.5 amp supply, I can light, at will, constantly "on" LEDs.  These can be in cabooses or passanger cars.

Each LED might draw about 15-20 ma of current with the dropping resistor in place.  I plan on no more that 8 such permanent lighting apps on my trains.  Thus, I will shunt off only .16 amps of draw in my lighting scheme and won't need a DCC controller for each car or cab lighting.  I think this is right.

I was a little worried about the control code wave packet being affected by the diode action of the  (LEDs), but it really is all about the dropping resistors appearing as the real load so far as the voltage on the rails is concerned.

As far as LEDs....  I tend to use the Jameco part #2033164 - $1.90 for ten (3.2mmX1.6mm).  This is a truly microscopic surface mount LED.  Special skills will be needed to solder on leads, but the effort is worth it.

[richg1998]

Plenty of info on light bulb and LED lighting in the below link. I use 520 ohms for 1,5 v bulbs.

http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm

The LED will not be affected by the DCC. Most use a full wave bridge rectifier with capacitor to filter the DCC signal out and give just DC. Many include stuff like a super cap for flicker free. I think you will have to consider flicker free before you venture to far into this. There are commercial kits and you can build your own.

I never run any components at their max value which in this case is 20ma.

With a 1 k resistor, the current is  about 9 ma.

Rich

[richg1998]

Car lighting circuits.

http://www.awrr.com/lighting.html

Rich

[cudaken]

 Tom, thanks for the links but I don't think they will fit. From what I read on Ulrich site the 1.5 volt bulbs are 1.5 MM. I got that information from this item.

http://www.ulrichmodels.biz/servlet/the-608/LED-Light-with-Fiber/Detail

 While the LED/ Fiber Optic kit would work $7.95 X 4 is a little steep.

 Could I just glue a surfaces mount LED say that is 3 to 4 MM to the inside of the shell? Engines I want to install the LED in, the 1.5 bulbs actually stick through the opening in the shell. 

 Any other ideas?

 Thanks for looking and trying to help.

                Ken

[rrinker]

 The problem with Athearns is that the light bulbs they use ARE the lense for the lamp, which is why the Ulrich repalcement kits have the short bits of fiber optic. You can certainly DIY it all the way, have to dig throught he Walthers book or someplace to find the correct MV lens to use so it doesn't look liek there's a hole in the loco, and glue on surface mount LEDs behind the light openings.

 Or keep the factory boards, plug the decoder into the 9 pin, and leave the lights. I haven't decided what to do with my RS-3 yet, it was super easy to just plug a decoder in, but I'm not happy with the lights using the stock bulbs. Plus I'm already doign other work, like adding cab roof drip strips and repalcing the horn with the correct one, so what's a little work around the lamps as well..

                                     --Randy

 

[cudaken]

 Thanks Randy, maybe see if I can find my own fiber optic. Or just stay with the bulbs.

 Ken