track power for lights

[Terry Toenges]

If I want to use track power for lights on some cars what size resistor do I need?
I have some 3 volt Christmas lights that I'm using on flat cars and gondolas. Right now I'm using batteries. I'm using the cars with my DCC Mogul.
Someone also suggested a zener diode. Do those come in different sizes? I know nothing about them.

[trainman203]

Why don't you just use 16 V bulbs and get rid of the resistors.

[Terry Toenges]

Because they are strings of miniature Christmas lights and trees. How would I do that?

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[Ralph S]

I have not tried to connect lights to my DCC track power.  I take that back.  I do have lights on my Hayes bumpers (44593) that are connected to the DCC track power.   I have been specializing in keeping all lighting from the track DCC power. 
 Frankly, I wonder if my DCC controller could handle any additional current draw other than the locomotives. 

As for the zener diode, know this.   A diode is a semiconductor that conducts current in a single direction only.  Mainly used to convert AC into DC.  Where a zener diode conducts current in both forward and reverse current directions.  If a normal diode is placed to function in reverse, it will fail.   If a zener diode is placed to function in reverse current, it will conduct in both positive and negative directions and that's normal expectation of the zener diode.   Yes, zener diodes come in many different sizes.  The ones I worked with were of the 250 amp in 480 V to 12 KV applications.

That's about the best I can do for you.   Keep us informed if you pursue this venue, I haven't been involved in the very small zener diodes.

Sorry I couldn't help more...

[rbturner]

Start with a 1000 ohm resistor. How many bulbs will you be operating? The total current draw will affect what size resistor you need. If you are powering the bulbs pictured you'll need a good sized resistor. At least 1 watt. Do you have any specs other than 3 volts?

[trainman203]

Sorry, Terry, I misunderstood what the point of your lights on the car were. I get it now.  With all the adaptations needed to try to get power from the track up through the trucks through some kind of resistors to finally get to the lights, I'm not sure if just using the battery like you are now isn't the best and easiest way.  If that was my project, that's how I would do it. See below.

I'm retired now. I like easy. I despise work. Of any kind. 😂😂

[jward]

Are you running them off DC or DCC track power?

[Terry Toenges]

DCC track power for the On30 Mogul which is pulling these. I switch controllers when I'm running DC stuff but I don't have any DC On30 locos.
I'm thinking I'd better off just staying with batteries. I thought it would be easy to just add like 1000 ohm resistor. It's hard to hide the batteries. I have two more cars to do - another gondola and another flat with different type of light strings.
No other specs on the lights. The batteries are 3 volts. That's how I know they are 3 volts.

[trainman203]

Just hide the battery under some kind of load like a crate or a load of lumber.

Or even better, seats with Santa and Mrs Claus and the elfs.

[Terry Toenges]

I'm trying to do that. I have to make sure the switch is accessible.
The one gondola has the trees.. I had to fit all the wires in there. I cut down the AAA battery box to keep just the switch. I used CR2032 batteries for power instead because they are smaller. Then, I covered the wires with pieces of styrene. I couldn't shorten the wires because they are so small and soldering them would have been impossible for me to do.

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[jward]

DCC track power for the On30 Mogul which is pulling these. I switch controllers when I'm running DC stuff but I don't have any DC On30 locos.
I'm thinking I'd better off just staying with batteries. I thought it would be easy to just add like 1000 ohm resistor. It's hard to hide the batteries. I have two more cars to do - another gondola and another flat with different type of light strings.
No other specs on the lights. The batteries are 3 volts. That's how I know they are 3 volts.

The problem comes in the fact that DCC (constant voltage and polarity) and DC (variable voltage and polarity) must be treated differently if you are going to use track power to power your lights. LEDs only conduct in one direction, if the polarity is reversed they go dark. LED stands for light emitting diode. ON DC you'd need to have other diodes to route power of the proper polarity to your LEDs, and that gets a little complicated. ON D, as long as the resistors drop the voltage to what the LEDs can handle you wouldn't need anything else in the circuit. Being as you are running a dual mode layout, you're better off sticking with the batteries.

[Terry Toenges]

Thanks Jeff. I'll stick with the batteries.

[trainman203]

TheBattery in the middle of the green flatcar could be made it look like a big gift wrapped present with a big bow and ribbon

[Terry Toenges]

I might put an elf on the box. I have some miniature garland coming to  put on the car around the trees.