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Amfleet Upgrades
JohnBoy
Joined: May 14, 2008
Topics: 110 Replies: 517 Topics: 110
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posted Nov 24, 2008: 
The Amfleets are my favorite passenger cars, and I finally got around to detailing some of them. This was inspired by the beautiful work that David Friedlander did on his Amfleet interiors.

In this case, I painted the interior with a simulated "velvet" blue to approximate the fabric used on these cars, and the matching carpet.





A touch of silver paint was applied to the top of each armrest. I think David did a much nicer job on his, as he left each entire armrest/divider unpainted, which I was too lazy to do. I printed out little Acela logos, but with the Amtrak name (which seems to be the direction they are heading recently.) I do not think that this logo on the headrest napkins is prototypical, but I liked it enough to do it.





These were printed onto full-sheet self-adhesive labels, and then cut to size on my paper cutter, and applied to each seat. Thanks to David for this idea!





I also printed out some payphones, and interior doors with the push-button for automatically opening them. And I was always fascinated as a kid by the little water dispensers with the paper-cone cups.





Then some people were added to give it a little life. It's funny how invariably the scenes we make can look so convincing until you add that first O-scale figure.

My next step is to figure out what I want to do with the lighting - I think I want to string up some white LEDs in there, to be more compatible with command-control running. But I haven't figured out if I want to wire them up in series, with essentially no resistors, or parallel, with each LED soldered in with a resistor.

After that, I'll install the black window gaskets, and the diaphragm strike plates.

Thanks for looking...

John
 
JohnBoy
Joined: May 14, 2008
Topics: 110 Replies: 517 Topics: 110
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posted Nov 24, 2008: 
I decided to go with parallel wiring for the LEDs, so I wired in a bridge rectifier. I got these for really cheap a while back, but they are larger than can typically fit into O-gauge items. However, they fit perfectly inside this recessed hallway:





I soldered the DC leads from the rectifier into the modular plug on one end of the light rack, effectively converting the two copper strips into a DC bus.

I had to disconnect the modular plug from the other side, since that would interfere with the DC signal. But this would mean losing the benefit of feeding from both pickup rollers. So I soldered two wires on top of the frame to connect them:





Then I set about soldering in 7 white LEDs. I thought about wiring them in series, and this would have saved me from having to solder in resistors for each LED. I believe it also would have been a more efficient use of current. But it also would have meant less protection for the LEDs in the event that they were accidentally fed more than 18-20 volts.





As such, these standard (and inexpensive) white LEDs produced the dreaded blue glow, further exaggerated by the blue upholstery:





So I started experimenting with the white LEDs. This photo shows some of the tests I did:





- To the far left is just a plain white LED with no paint on it. Quite blue.

- To the far right is a white LED with yellow paint on it, to counteract some of the blue and provide some "warmth". Quite yellow.

- The second from the left is probably the best for general purposes, as it appears nicely white. This was accomplished by painting it with a cheap acrylic paint that was just slightly off-white. Call it cream. Anyway, this still looked rather blue in the test Amfleet car, due to the blue interior colors.

- The middle one is painted with a mix of the cream-white, and orange. This was a bit too rich of an amber, and also I did not water it down enough, so the LED lost a lot of its light.

- The second one from the right is perfect. I mixed less of the orange with the cream-white, and watered it down further.





So I mixed up some more of this color, and proceeded to paint not only the LEDs themselves, but also the roof of the shell, so that even the reflected light would get an "amber boost".





More to come...
 
JohnBoy
Joined: May 14, 2008
Topics: 110 Replies: 517 Topics: 110
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posted Nov 24, 2008: 
I was in for a couple of pleasant surprises when I wrapped this project up. The first thing I did was just put the LED car on the track and apply 18 volts. One nice thing about the Z4K transformer is it has built-in amp-meters. At 18 volts, the LED car eats .30 amps.

Then I put on an Amfleet that just has the stock incandescents in it. At 18 volts, that car eats .60 amps. So my LED car - even though I wired them in parallel with individual resistors - consumes about half the electricity as the incandescent bulbs.





Next, I put both cars on the track and left them at 18 volts for several hours. The roof of the incandescent car was almost uncomfortably hot, while the LED car was almost imperceptibly warm. That's got to be better for my plastic shells.

The lighting itself is, IMO, vastly superior to the incandescents, and this is what surprised me the most. I was not expecting to like it as much, but I actually like it much better. The light is more even, since I used 7 LEDs instead of the 4 bulbs. But the brightness and hue are much more realistic-looking with the LEDs, to my eyes.





Another pleasant surprise: I had always noticed that all of my Amfleet cars (I have three sets of these) flicker rather badly when they roll on the track. This is especially severe when rolling the cars very slowly. I always assumed this was due to dirty or poor pickup rollers, bad track, etc.

But the LED version of this car does not flicker in the slightest. I don't understand why, but it sure does look a lot better, as the lighting stays perfectly constant as it rolls - no matter how slowly.

Anyway, now I just have to repeat this 9 more times!

Next up: the exterior upgrades...

John
 
stan
Joined: May 18, 2008
Topics: 17 Replies: 16 Topics: 17
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posted Nov 26, 2008: 
Looks good John. But if you're drawing 0.3 Amps and using 7 parallel LEDs (with individual resistors), this means you're drawing 0.3 / 7 = 43 milliAmps average current thru each LED? This seems a bit aggressive for standard 5mm diameter LEDs. Just curious.

Separately, I realize the convenience of the parallel bus on the ceiling, but before you mod the rest of your cars, is there any way to series the LEDs? I figure you don't have enough voltage to drive 7 LEDs in series, but maybe 2 groups of 4 LEDs in series. This would cut your current by 4x... and would save several Amps with 9 cars. Just a thought.

Finally, what is your approach to shutting down the passenger car lights? Back the cars onto a section of unpowered track, manually switch off the lights for those cars that have the slide switch under the chassis, etc.. I've pondered this for quite a while. Using the aftermarket Lionel TMCC decoder boards can get quite expensive to allow remote lights on/off.



 
JohnBoy
Joined: May 14, 2008
Topics: 110 Replies: 517 Topics: 110
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posted Nov 29, 2008: 
Thanks Stan - lol, I think you have far greater ambitions than I do for these passenger cars, at least for now. At this time, I'll be happy just to have Amfleets that are better-looking on the interiors, populated with some passengers, and illuminated in a way that is more compatible with DCS operation, as eventually I plan to run these with an AEM-7 that I want to convert to PS2 electronics. You know, when the Dow goes back to 14,000 or so...

But I am confused about the current going through the LEDs. My comprehension on the electronics is rudimentary, but I thought that if you place a resistor (in this case, 470 ohms) in series with a LED, it will cut the voltage down to the necessary level to safely run it.

I wonder - is the 43 mAs running through each LED also counting the current that is converted to heat by each resistor?

No doubt that wiring the LEDs into banks of 6 in series would be much better - at least in terms of electrical efficiency. But then I would have to figure out a way to protect them from getting fed more than 18 volts. In my environment, which involves kids, I could easily see the throttle getting knocked up to 24 volts and frying all the LEDs in the whole string of cars.

There are ways to prevent this, I'm sure. Maybe a programmable voltage regulator in each car, to cap the voltage off at 18V?

My main goal was to just get the lighting to be better, and ready for DCS. The fact that each car now consumes half the current, and almost no heat, is victory enough for me.

But I'm interested in better ways to do things, that's for sure!

John
 
stan
Joined: May 18, 2008
Topics: 17 Replies: 16 Topics: 17
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posted Dec 3, 2008: 
John, I suppose declaring victory is in order since you cut current in half...that's a bigger drop than the Dow from 14,000 to 8,000. Ouch.

Anyway, with one resistor per LED (the parallel method), the same current flows thru the resistor as the LED. Since a white LED runs at about 3.5V that means the resistor is 'eating' most of the ~18V available on your bus. So in round numbers the resistor is consuming 5x the power of the LED and that's all going up in heat...you know, global warming

So if you, say, put 4 LEDs in series running on the same 18V bus, the LEDs would require 4 x 3.5V or about 14V. Operating at the same current (all the series LEDs and the resistor get the same current), the resistor value would go down and it would only eat about 4V rather than 15.5V. With 2 strings of 4 LEDs (8 total), you ought to be able to lower your per-car current to less than 0.1 Amps so all 9 cars would draw less than 1 Amp.

The resistor still functions to limit current into a strings of LEDs. But to your point, there are other techniques like a Voltage Regulator to provide a more precise limiter for someone accidentally leaving the transformer to 24V.

To dig a bit deeper, IMO the correct way to drive LEDs is with a current-regulator for which there are a range of solutions from Cadillac to Yugo. This because LEDs brightness if proportional to current, not voltage. Double the current, double the brightness. This is true over remarkable range - well over 1000 to 1. OTOH, double the voltage, blow up the LED!

A resistor is a current regulator albeit a poor one but it costs pennies. By poor I mean the brightness changes somewhat with track voltage. Semiconductor chips (LM317 is probably the best known for hobbyists) run about 50 cents but are quite precise; brightness will be constant with track voltage. Think of these as a resistor which automatically adjusts its resistance to keep the current at a fixed level. Note that any unused voltage still goes up as heat.

The top end approach would use a so-called switching regulator which pulses energy to the load as needed rather than dissipating the unused voltage as heat. This in concept eliminates the resistor. You would essentially feel no wasted heat. Unfortunately the parts cost alone would be several dollars per car so not really for the hobbyist - or not until the Dow hits 20,000?

Well, that's my 2 cents.
 
JohnBoy
Joined: May 14, 2008
Topics: 110 Replies: 517 Topics: 110
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posted Dec 17, 2008: 
Wow - thanks Stan! You have piqued my curiosity with the LM317 chip. I've done some cursory searches on Google to obtain a tutorial of sorts. Most of the diagrams look like this:





So my monkey-brain first stab at this would be:

- connect track power (converted to DC via bridge rect.) to V-in
- connect a resistor from the ADJ pin to the ground
- the V-out pin will have my fixed 18-volts (or whatever it's programmed to)

But what are the two capacitors for? And it looks like the cap. on the right has a curved bottom line - is that significant?

And what does the R1 resistor do? Is that a fixed ohm-value per spec of the specific LM317 used?

Also, what is the significance of the diagonal arrow through the R2 resistor?

I found this diagram on a site that has a calculator, but it assumes you're feeding it at least 20 volts:

http://www.electronics-lab.com/articles/LM317/

 
stan
Joined: May 18, 2008
Topics: 17 Replies: 16 Topics: 17
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posted Dec 17, 2008: 
The LM317 is one of those parts that won't go away - like the 555. I suggested it as a constant current source...so if you search of "LM317 current source" you'll get zillions of hits where you only need R1 (not R2) and you get a constant current source such as generating 20 mA irrespective of input voltage to have constant brightness to LEDs. The example you show is the standard adjustable voltage configuration for the LM317. The ratio of R1 and R2 sets the output voltage using the calculators. In general, if you want a fixed standard output voltage (like 5V or 12V) you can buy a 'fixed output' regulator where R1 and R2 are embedded in the chip itself for you. The 7805 (5V) regulator that is always brought up on OGR is an example. The arrow in R2 means a variable resistor (aka potentiometer) so that you can set the output voltage. The curved bottom on a cap means that cap is polarized like an electrolytic; as shown that cap has a + sign on the flat line. The input cap has 2 flat-lines because it is not polarized and you can hook it up either way. In general, values above 1 microfarad (1 uF) or so are usually polarized. The capacitors are for what the nerd-herd calls 'stability' which is a technical characteristic of a circuit's ability to respond to varying conditions. Varying conditions means changes to the input voltage such as track input voltage or going over a bad spot of track - or changes to the output such as when additional loads are added to the regulator. Since caps suitable for 99% of LM317 applications cost about 5 or 10 cents these should be used.

As for that 20V input calculator, the input voltage of the standard LM317 must be at least 2V or so above the output voltage. This is sort of a tax on the output voltage that the LM317 charges. There are versions of the LM317 that have lower taxation. I think you might have specified 18V as the output and it said you must supply 20V. If you said you wanted 3.5V as the output, it would say you need to supply it about 5.5V.

I think I got all your questions

Since you have a white-board for prototyping, I suggest you just hook it up and 'play' with it. It is a very robust chip. It's probably not as neat as the 555 but it is nevertheless a remarkably versatile chip and of course is very cheap. There are different versions of the LM317 that handle more power, are more accurate, are more efficient, and so on. Probably the first calculation in choosing a version is the power it can handle. They probably vary from about 0.1 Watts to several Watts. You calculate the power dissipated by the LM317 by multiplying the difference between the input and output voltage by the current delivered to the load. For example, say the output voltage is 3.5V driving a single white LED drawing 25 milliamps (0.025 Amps), and the input voltage is 18V. The power dissipated by the LM317 will be (18V - 3.5V) x 0.025 A = 0.36 Watts. If instead if the output voltage is 14V to drive a string of 4 series LEDs, the power wasted by the LM317 drops to (18V - 14V) x 0.025 Amps = 0.1 Watts. To complicate matters, as mentioned earlier, it is better to drive LEDs by regulating the current to them. The LM317 using just R1 can be set to deliver 0.025 Amps to whatever you hook up to the load. So whether you hook up 1 or more series-connected LEDs the current into the LEDs will be 0.025 Amps. When configured this way, the voltage at the output will adjust to whatever is needed to deliver the specified current. So if you had only 1 LED hooked up, the output voltage would adjust to about 3.5V. If you hooked up 2, the output voltage would adjust to about 7V, and so on. Of course as you add more series-LEDs, you have to have enough input voltage to support the output voltage plus the tax of about 2V. In current-regulator mode, you still must calculate the power burned by the LM317 in the same way and choose an appropriate version or package.
 
King Mouse
Joined: Sep 28, 2009
Topics: 3 Replies: 14 Topics: 3
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posted Dec 31, 2010: 
John,

Nice tutorial!

Dave
 

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