Atlas B40-8 with TCS AMD4...front & back headlights reversed?

[peteski]

TCS decoders have pretty good (and tunable) lighting effects.  You should be able to get a good rotary beacon simulation and a much simplified circuitry (no additional circuitry needed besides the LED and resistor).  Look into the TCS documentation for instructions how to select and fine tune the lighting effects.

[ryan_wilkerson]

Those are just the details to get me going, thank you. Since this B40-8 comes with a stock beacon, I'll wire up a small white LED and see how it looks shining up the beacon's base from within the cab.
I'm an LED newbie and have a basic question about resistors....if I wire a resistor in and the LED is too bright, do I need to replace the resistor with a more restrictive one or can I add a second resistor? Beacons weren't that bright so I don't want to overwhelm. Thanks for your help once again!
-Ryan

In the TCS documentation it shows the pads to use (http://www.tcsdcc.com/Customer_Content/Literature/Decoders/N_Scale/Atlas_N/AMD4_Web.pdf).

Just program either CV-51 or CV-52 to a value of 36, depending on which wire (in this case pad) you choose. Make sure you include a drop resistor to cut the voltage. Be sure to wrap the exposed leads on the resistor to prevent shorting on the frame or decoder with capton tape or heat shrink tubing.

The S.

[ryan_wilkerson]

Will do, this should be a fun experiment! Thank you.
-Ryan

TCS decoders have pretty good (and tunable) lighting effects.  You should be able to get a good rotary beacon simulation and a much simplified circuitry (no additional circuitry needed besides the LED and resistor).  Look into the TCS documentation for instructions how to select and fine tune the lighting effects.

[sizemore]

Those are just the details to get me going, thank you. Since this B40-8 comes with a stock beacon, I'll wire up a small white LED and see how it looks shining up the beacon's base from within the cab.
I'm an LED newbie and have a basic question about resistors....if I wire a resistor in and the LED is too bright, do I need to replace the resistor with a more restrictive one or can I add a second resistor? Beacons weren't that bright so I don't want to overwhelm. Thanks for your help once again!
-Ryan

You can just use a higher resistor, you will want to experiment. Also the light intensity may be configurable via the decoder.

The S.

[ryan_wilkerson]

I guess I should invest in a variety of resistor specs!

[sizemore]

Find yourself a resistor calculator for your smartphone such as LED Resist and also get ResistorCode. It's a good way to figure out what the resistor value is, or to check your calculations. Get the appropriate resistor for the LED, then control its intensity with the decoder.

The S.

[peteski]

If you are planing on doing many decoder/headlight installs then having an assortment of resistors makes that job much easier.   LED resistors calculators are very helpful but you first have to know what current you want to pass through the LED.  With white LEDs you never really use their rated current (the LED would be too bright). So, the way to do this is visually. Use a resistor that results in a realistic brightness.  I used to be an electronic technician and electronics is one of my hobbies so I have literally thousands of electronic components (which makes finding some specific resistor really easy). 

In your specific case, you could get some standard resistor values for your installs. Then just choose the best one for that particular installation.

I would recommend the following values:

680, 750, 820, 910 (ohms), 1k, 1.5k, 2.2k, 2.7k, 3.3k, 3.9k, 4.7k, 5.6k, 6.8k, 7.5k, 8.2k.  That should give you a nice range of values to arrive at the desired brightness.    In most cases resistors with power dissipation of 1/8W will be robust enough ti handle the job.  But you coudl also get 1/4W (but those are physically larger).  As inexpensive as they are, you could probably buy a set of 1/8 and 1/4 W ones.  If you want to go with surface-mount (SMD) resistors, the 1206 and 805 size woudl be equivalent of 1/4 and 1/8W respectively.

Just get 10 or more of each size (the price per resistor drops dramatically when they are purchased in quantity from suppliers such as Mouser Electronics or Digikey).

As far as the beacons not being very bright, I disagree.  Beacons are designed to attract attention by being bright and by flashing.  Just like the old police gumball lights, they are made up from a headlight-like sealed beam lamp which rotates. It is not very bright until it lines up with your eyesight. Then you get a very intense flash of light. Same with the Xenon strobes. They are fully turned off, then they give you a bright flash of light (just like a camera flash).

So, I wouldn't make their LED too dim. The decoder's lighting effect circuitry will keep the LED dim until it is supposed to flash - automatically.   Keeping the resistor value not too high will allow the decoder to send a bright burst of light through the LED.