Source For N Scale 12V Street Lights

[freescopesdad]

It seems all I can find on Amazon and eBay are 3V street lamps which require a resistor to be soldered into the circuit. Is there a source that I am missing, other than the WS Just Plug system, that has the resistor preinstalled? My age, eyes and arthritis are a hindrance in this regard. Thanks.

[Maletrain]

Have you considered getting a 3 v DC power supply?

For instance: https://www.ebay.com/itm/264425078563 or https://www.ebay.com/itm/276729176909

[peteski]

Have you considered getting a 3 v DC power supply?

For instance: https://www.ebay.com/itm/264425078563 or https://www.ebay.com/itm/276729176909

It really isn't best practice to directly power white LEDs from source of 3V. Why? because different diodes have varied forward voltage. It also does not give you any control over the brightness.  We all know that many small novelty and mini flashlights using coin-type 3V lithium cells power the LEDs directly, but those batteries have such a high internal resistance (they supply very  low current even when their terminals are shorted) that they pretty much act as a source of voltage *AND* the current limiting resistor.

But if you have let's say a 3V 500mA supply, Some LEDs at 3V will be greatly overdriven at relatively unlimited (for a single LED) current, and the LED will glow way too brightly and maybe even heat up and burn out. Unlike incandescent bulbs LEDs are non-linear current (not voltage) devices and a resistor acts as a buffer to limit the current.   While LEDs greatly advanced mode illumination, they should really have that resistors in the circuit.

[Maletrain]

Peteski,

Not to argue with your post about LED current, but wondering how the WS Just Plug system deals with that physical principle, given that you "just plug" a variety of LEDs into the same system.  Is there already a small value resistor in their individual LED assemblies?  For that matter, what are the directions for powering the "3 volt" street lights that the OP has bought?

Personally, I want some resistor in my lighting to let me adjust the brightness.  I may set it up with a variable resistor and then measure the resistance chosen so that I can replace the variable with a cheaper and smaller fixed value resistor in the final installation.

But, the OP is hoping to avoid soldering.

One other no-solder possibility is to run one of the wires from each LED to a pair of terminal blocks, with a resistor between the blocks for each individual LED circuit.

[peteski]

We discussed that Woodland Scenics lighting  system recently, and Max found some details of the power supply design.  See https://www.therailwire.net/forum/index.php?topic=58878.msg810822#msg810822

To summarize, the light fixtures have a series-connected  680 ohm resistor. The outputs of the lighting hub each have a transistor circuit to further adjust (lower) the brightness.

[Rasputen]

Faller brand street lights can be connected directly to 12V power, according to their product description.

[freescopesdad]

Thanks all for the comments and discussion. I have not bought anything yet, but one more reason to power the street lamps on a 12V circuit is that I already have a supply of 12V led's with resistors that I plan to use for interior lighting in this area of the layout. Powering everything at 12V just seems simpler. I did find a brand called Rock Island Hobbies that sells 12V street lamps. They seem plentiful on eBay at about 3 bucks each.

[peteski]

Thanks all for the comments and discussion. I have not bought anything yet, but one more reason to power the street lamps on a 12V circuit is that I already have a supply of 12V led's with resistors that I plan to use for interior lighting in this area of the layout. Powering everything at 12V just seems simpler. I did find a brand called Rock Island Hobbies that sells 12V street lamps. They seem plentiful on eBay at about 3 bucks each.

Since white LEDs will burn up when connected directly to 12V I suspect that those 12V street lamps either have built in resistor, or the seller supplies the lamps with separate resistors to be installed.  I hope that they have integrated resistors for ease in installation.

EDIT: I looked at the items from Rock Island Hobby and judging by the product photos, the 12V N scale lamps do have resistor covered with heat shrink on one of the leads.  For the power source I would recommend 12V DC.

[freescopesdad]

I went ahead and ordered a 10-pack of 3V street lamps from Evemodel and found that soldering in the included resistor not that difficult. Added 22g red and black wire extensions, sealed with black shrink tubing, finished and tested all 10 with a 9V battery in about 1.5 hours. I'm sure I can cut down that time significantly for the next batch. One thing I've learned in this model railroad journey is that an insurmountable task is never so. Ron

[freescopesdad]

I had ordered 6 n scale 2-bulb lamps from Model Train Stuff made by a company called Rock Island Hobby, which arrived today. Their website says these are 12V with a resistor already installed. Question... Each lamp contains 2 bulbs, and 4 wires (2 red 2 blue) out the bottom. All the same length and impossible to tell which pair goes to which bulb. How do I wire these? Thanks.

EDIT... Well, every picture of this product on Ebay or elsewhere clearly shows a resistor in black shrink wrap in the wires coming out the bottom. Mine do not. I guess these got through QC while someone was sleeping. I blew up 2 bulbs in one lamp by connecting to a 9V battery, so I guess that kinda indicates these only take perhaps 3V. Back they go to Model Train Stuff.

[peteski]

If there are 2 bulbs (LEDs) in each fixture then knowing that LEDs have polarity, that would imply that red and blue wires are showing the polarity.

You could simply tie both red and both blue wires together, then add a series resistor to either the blue or the red wire pair.  While not ideal, if both LEDs are identical, they can be powered in parallel, but they still need a resistor in series with the LED combo.  As you have noticed in the photos, you can likely tell is the resistor was installed at the factory or not.

I guess you found out the hard way that no resistor and 9V battery releases the magic smoke from LEDs.  Seems that either the product description is incorrect, or someone screwed up not installing the resistor. Sorry to hear that.

[Maletrain]

It just seems like we should not be taking anything for granted when buying things with LEDs that we need to power.

That is why I always do a trial hookup with a variable resistor in the circuit, turned to maximum resistance, and then turn down the resistance until I get the light intensity that I want.  I can then just use a multimeter to measure the desired resistance across the variable resistor to determine what fixed value resistors to add to that particular circuit to get the effect I want.

Variable resistors are cheap enough.  For example, see https://www.ebay.com/itm/203687232017 for an assortment at a low price.

[freescopesdad]

I guess you found out the hard way that no resistor and 9V battery releases the magic smoke from LEDs.  Seems that either the product description is incorrect, or someone screwed up not installing the resistor. Sorry to hear that.

Well, they apologized and sent me a prepaid label for a full refund. I should have been able to discern that no resistor would fit inside the narrow upright tube. Good news is that I've received 10 similar lights from EveModel and I know to install resistors in their products. Lesson learned.