Niles Project ~ Resistification

Because LED's are diodes and don't behave like a resistor, a current limiting resistor is needed to prevent the current from exceeding the operating limits of the LED's.

Determining the size of resistor to use was simple enough. John McWhirter and I soldered the 4 LED's together in series. Then we attached a best guess resistor in series with them. Then we gave the circuit "the juice". 15 volts DC. We then carefully considered the results. If the lights were too bright for what I wanted, we would then replace the resistor with a" stronger" one. If the lights were too dim, then we replaced the resistor with a "lighter" one.

Actually, it was easier than I'm letting on because John has built a box with an array of resistors in it. A rotary switch switches from one resistor to another. So all we had to do really was connect our LED assembly to it and with a simple flip of the switch, find the the setting that gave me the illumination I was looking for.

Eventually we determined that a 1000 Ohm resistor (brown, black, red, gold bands) provided the right amount of juice to the 4 LED's to achieve reasonable illumination for the interior compartments of the trolley.

For the one headlight, we determined that a 15000 Ohm resistor works best (brown, green, orange, gold bands).

My next objective was to determine the most unobtrusive location to mount the resistors. I can't mount the resistors on the circuit board because they would interfere with the ability of the circuit boards to slip between the bulkheads and the ceiling. It would also be nice if the resistors weren't someplace visible through the windows. So this is where I got clever...

I need a jumper from the blue wire (lighting positive common) bus on the bottom of the circuit board to the LED leads on top of the circuit board. So why not have the resistor fill that bill? The leads to the resistors were bent so that one lead solders on top and the other lead solders on the bottom with the resistor itself on the front edge of the circuit board. Works for me. Yes sir! Works for me just fine!

Dandy

Niles Project ~ Interior Lighting Wiring Schematic

This is going to take a little planing.

Things are getting a little complicated:

• The decoder can't light 8 interior LEDs because of milliamp limitations. So the LEDs are going to be split between two functions of the decoder. Four LEDs on the purple wire, and four LEDs on the green wire.
• The LEDs have to be oriented correctly. Unlike incandescent bulbs, LEDs have a positive and negative side to them.
• The LEDs require resistors.
  
• The blue wire of the decoder is the common positive lead to all the interior lights and to both headlights.
• In attempt to keep things neat and tidy and serviceable, circuit board is being used as a mount for the interior lights, a bus for the headlights, and as a soldering pad for the decoder wires.

So after a lot of trail and error, I drew this schematic to help make things crystal clear:

Okay, so here is where we left off...

This shows the top and bottom of one of the two circuit boards (as it sits in the car). On the top, the copper cladding has been cut vertically to electrically isolate the LEDs so that they can be wired in series. On the bottom, the copper cladding has been cut horizontally. The top strip will be the bus for the blue wire, the bottom strip will be the bus for either the white or yellow headlights wire. The vertical cut provides a soldering pad for either the purple or green wire.

So that's the plan man. Time to put the plan into action. Yes sir! Put this plan to action!

Dandy

Niles Project ~ Illuminatification

Installing interior lighting, LED's this time, and in their prototypically correct locations of all places.

The September 1908 edition of the Electric Traction Weeklys article on the new Niles Cars for San Diego (graciously forwarded to me by Bill Bolton) included an interior shot of these cars. Looking at this photo, I was able to ascertain the locations of the lights in the car (despite the fact that all of the lights weren't shown). Which got me to thinkin' (which could be dangerous) what would it take to light the car prototypically? Would the car look any different/better if it was lit prototypically? Would it be worth the time and effort to light the car prototypically? And why doesn't my spell check like the word "prototypically"? Well, there is only one way to find out. And that is to light the car prototypically (spellcheck be damned!).

This photo was shot in the enclosed section of the California style Niles Cars, probably standing in the doorway of one of the two bulkheads looking towards the second bulkhead. Visible are three lights (or 6 if were counting bulbs). The car is symmetrical so its safe to assume the forth light is just out of frame above.

 

The lights are evenly spaced so, if I continue the spacing into the open end sections of the car, we have a total of 8 interior lights. Seems reasonable enough. As long as the decoder can handle lighting that many lights. Since the lights would be lit more on the dim side, it should.

I've seen traction models with their lights mounted on a strip of circuit board. That seems like a really good idea to me, so that's the route I'm going to take. But because the Niles cars have those bulkheads inside, I'm going to have to split the circuit board into two sections. The bulkheads don't reach all the way into the deck (or clerestory) section, so the circuit boards are able to slip over the top of the bulkheads. But the bulkheads definitely limit the length of the circuit boards.

 

LED's are the way to go. They require less voltage, they don't burn as hot, and last a lot longer, than incandescent bulbs do. But as you can imagine, jamming 8 Christmas LED's into these cars would be ridiculous. So instead, I'm opting for the tiny SMD (Surface Mount Diodes)LEDs (warm white). John McWhirter recommended purchasing the SMD LED's from TrainAidsA. They specialize in electronics for model railroading. I have found them to be very helpful.

 

The circuit board is cut to size. Then holes are drilled for the LED lights and also where the base of the trolley poles pass through the roof. The holes for the lights are filed square to match the size of the LED's. Then the copper clad is notched with a saw to separate the positive and negative sides of each LED. The opposite side the circuit board is notched length wise to act as a bus for the headlights (see photo below).

 

Here are the circuit boards with the LEDs installed. This is actually my second attempt, I had the polarity of the LEDs reversed last time! The round holes are for the trolley pole base to pass through, so these boards have a front end and a back end. The pole holes denote the front end of the circuit board. The white wires are soldered towards the front end, the black wires towards the back end. The back ends of the circuits boards will butt against each other in the center of the car:

 

This test fit revealed the circuit boards fit quite snug between the ceiling and the bulkheads. I don't think any adhesive will be needed to keep them in place.

Next, I have to determine how bright the lights should be. This will determine the size of resistors required. Then we'll have this car illuminating quite nicely. Yes sir! Illuminating quite nicely!

Dandy