What about Dual Mode Marker Lights ??

[Mike-NC]

HO scale Dual Mode Marker Lights ??

OK, I see that many locomotives are being produced now with dual mode (DC/DCC) for the modelers choice of operation, even sound locomotives. This is great for the front of the train and marker lights can be added to the locomotive decoder for the engine and/or tender.

What about the other end of the train? Do they make a dual mode (DC/DCC) marker light kit for the Caboose and Observation car (with NO battery). How can you make one? What parts are needed? LED or 1.5 volts?

Utah Pacific / Tomar Industries make a 1.5 volt marker light.
Can this be made to work in dual mode DC/DCC (with NO battery)?
I see that they also make a LED version.

What about this wiring diagram (attachment)?
HELP ! ! ! !

 

[Artieiii]

Mike,
I just finished a project wiring LED's inside my NJ transit passenger cars. Your wiring diagram is correct. On a DCC track the lights will be on all the time (full power). I also added a small 330uF capacitor in parallel with the LED's so that the lights would not flicker if i hit some dirty track. If you want really simple you can just hook the track pickups to a resistor (to drop voltage) then your lights. DCC alternates voltage similar to AC so an LED will operate fine. On a DC system you need the bridge rectifier so that if the engine is going forward or backwards (reversal of polarity) the lights will stay on. However in DC mode the light intensity will vary with the throttle setting.
-Art

Forgot to mention:
if you use incadescent bulbs you can skip the bridge rectifier for both DC and DCC. Incandescents can light with the polarity in either direction.

 

[AyTrane]

You could try one of the TCS accessory decoders; most of them are dual-mode. That would also give you the option of being able to turn the lights off if need be.

 

[Mike-NC]

Thanks Art, I am using the Utah Pacific with 1.5 v bulbs. I have already installed them on my Observation Car and I just want to get them to work on DC for now. On hooking this up, a diagram would be more helpful for me.
---------------------
Thanks, Mike

 

[diburning]

If you want the ability to turn the lights on and off, then a switch or a DCC decoder will be needed.

As far as LEDs or bulbs, you don't need any special wiring to use them on DCC, just use a resistor. Polarity would be an issue however, when used on DC if you use LEDs.

 

[Artieiii]

Thanks Art, I am using the Utah Pacific with 1.5 v bulbs. I have already installed them on my Observation Car and I just want to get them to work on DC for now. On hooking this up, a diagram would be more helpful for me.
---------------------
Thanks, Mike

Mike,
Here is a pic of my aparatus. You can't see the wiring on the bottom but I have included a wiring diagram for you. The red leads go to the track power pickups. Black goes to the negative on the LED's and white goes to the positive on the LED's. Someone on another forum suggested adding a 100 ohm resistor to one of the red leads to help isolate the apparatus from the DCC system (not in the wiring diagram). My solution will give the LED's power in either direction on a DC setup as well as a DCC setup. But the lights will be on all the time for DCC and the intensity will vary depending on the throttle position on a DC system. Hope this helps.
-Art

 

[PatOC]

resistor to use

Fellas - I am also in the process of trying to add the same marker lights to a heavyweight I custom painted and decaled and found your discussion. My question is: what size resistor would be most suitable? Having fried one light already, I'm wary of experimenting too much. It seems like I want to drop the voltage from 12v (I'm on DCC) to around 1.5v, based on the option to use a AA battery in the included instructions. If I use a 1000k, the bulb doesn't light, if I use a 200, it lights and seems to burn ok. Does that size seem suitable?

Also, if I wire the lights together by soldering two wires together (I believe this is called "in parallel"), put one wire directly to the track, and put the resistor on the other and then to the track, does that changes the size of the resistor I should use? I would prefer to wire it this way instead of separately and having to use two resistors.

Thanks for any advice or help. It's the time of the year when I resume working on my dream railroad and I feel like I have to learn everything all over again.

-Pat O'Connor

 

[diburning]

Here's a bit on series vs parallel:

Bulbs at 1.5 volts typically run at 15 milliamps, so an 820 ohm resistor per bulb will work at 12 volts. If you hook both bulbs together in series, you can use a 680 ohm resistor.

This is only if your track voltage is at 12 volts DCC. Some aftermarket boosters for DCC are adjustable (for example, some blocks at the club are 16 volts)

If you have multiple boosters that can give off more than 12 volts or have a DCC system that gives out inconsistent voltage or spikes, make sure to measure all around the layout, and calculate the resistor size based on the highest voltage coming from your layout. If you only have one DCC command station and no boosters, and it puts out 12 volts reliably, you can use the values I described above.

 

[PatOC]

Eric- thank you for the informative reply, that's exactly what I need to know. My layout is pretty small so I'm pretty confident I am getting 12 volts consistently across it.

Can you tell me how you were able to calculate 820 and 680 ohms? Every calculator I've looked at online confuses me to no end.

Thanks again
-Pat

 

[diburning]

I used this LED resistor calculator:

http://ledz.com/?p=zz.led.resistor.calculator

I know you're using bulbs and not LEDs, but the math is the same. Just input the bulbs' specs into the calculator and you'll get an answer.

Supply voltage: 12 volts
Voltage Drop Across LED: 1.5 volts
Desired LED current: 15 milliamps
How many LEDs connected: 2

Hit calculate and it will give you the precise resistance you'll need to not blow the bulbs, then they'll give you the next highest resistor (resistors are made in standard "sizes")

You'll also need to look at the resistor wattage. The more volts and amps you're trying to drop, the more heat will be generated. The wattage GENERALLY (but not always) corresponds to the actual physical size of the resistor. (a half watt resistor would be larger in physical size than a 1/4th watt resistor). If the calculator calculates that you'll need a half watt resistor, but you only use a 1/4th watt resistor, the resistor would overheat and burn out. More wattage = more capacity to withstand the heat generated

It's also a good idea to mount resistors next to the metal frame/weight to help dissipate the heat since it is possible for the resistor to get hot enough to melt a plastic shell (although that usually only happens if you use a resistor without the appropriate wattage)

To find how many milliamps your bulbs run at, look at the package, it should say (especially if they were made by Miniatronics). From what I've seen, most 1.5 volt grain of wheat bulbs are 15 milliamps.

Using those examples above, it is your best bet to wire the bulbs in PARALLEL. However, do NOT use the wiring diagram on the LED calculator page. Instead, use a separate resistor for each bulb. I'll tell you why later.

Here are the pros and cons of wiring them in series.

Pros:

You'd only need a 1/4th watt resistor at 680 ohms.
You'd only need one resistor.
Slightly less wiring

Cons:

If one bulb blows, neither of them will light.
Both bulbs are connected so if you need to remove one, you may need to remove both. (although you'd probably want to do so anyway to figure out which one blew)

Here are the pros and cons of wiring the bulbs in parallel with TWO resistors

Pros:

If one bulb blows, the other will still light
You can use the same calculation for one bulb and apply the result separately to each bulb
Easier to manage as each bulb is separate, only hooked together at the power source.

Cons:

You'll need two resistors
More wiring to do, so it may get a bit crowded on the power source end.
Draws more power from the power source.

Here are the pros and cons of wiring the bulbs in parallel, but only using one resistor and having branching connections for bulbs:

Pros:

You only use one resistor

Cons:

The resistor would have to be large (higher wattage) since all of the bulbs drawing power would put strain on the resistor causing it to heat up.
If one bulb blows, the resistor may not drop the voltage and current enough to stop the other bulb(s) from blowing so it's possible to end up with all blown bulbs

(It's really late and I just got home from work so if anyone more knowledgeable than I am sees anything incorrect with the info up above, feel free to correct me)

 

[PatOC]

Eric - thanks again, this is great information. One other question: where do you (or anyone else) buy your resistors from? My local hobby, model railroading stores and Radio Shack do not carry any, and the one time I ordered some online they turned out to be the tiny wafer-like squares (Ngineering brand) that I find near impossible to solder. I'd prefer the everyday cylindrical ones, I find them much easier to solder.

Thanks,
-Pat

 

[diburning]

Radio Shack should carry them in the drawers that they sell LEDs and toggle switches in.

I generally use LEDs and get the Miniatronics ones which come with two resistors per LED.

If you need specific resistors (can sometimes cost less than buying a multi-pack or assorted-pack) you can get them from a DCC store such as Litchfield Station, DCCTrain, or Traintek

The square surface mount resistors sold by NGineering are not hard to solder to, you just have to flux the hell out of the pads to make the solder stick in a short time.