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Lighting Effects for the Atlas 341 Decoder
One of the nice things about the Atlas 341 decoder is that you can add lighting effects to your locomotive very easily.  We present here, how to add front and rear headlights to your locomotive using those small grain-of-wheat bulbs. 
One of the things you should always remember with lights.  When the bulbs are switched on, they are hit by a momentary surge of electricity that is greater than the rated voltage of the bulb.  Turn the bulbs on enought times and the bulbs will burn out.  To prevent this, we use a couple of resistors to reduce the impact of the surge.  The resistors will not visibly affect the brightness of the bulbs. 
You can also use these instructions to create a small test light using a pair of miniature alligator clips should you choose not to install lights at this time.  This will ensure that your motor wires are correctly oriented when installing the decoder. 

The Atlas 341 Decoder has two solder tabs on the inside at each end of the decoder for lights.  After you have installed the decoder on the locomotive, you can now install the lights.  Use a 12 or 16 volt grain-of-wheat bulb in series with two 22 ohm ¼ watt resistors.  (If you use 1.5 volt bulbs, use two 220 ohm ¼ watt resistors.)  Before soldering the motor wires, ensure that each light comes on in the appropriate direction.  All exposed wires should be covered with 3/16" shrink tubing. 
Do not use black electrical tape or double-sided sticky tape.  Only use heat-shrink tubing.  Do not use a 250 watt solder gun!!!  Use a 25-45 watt pencil soldering iron - unless you've got a good supply of decoders.  Be careful with the soldering iron.  Remove all handrails and other plastic parts that can be removed. 
We assume no liability if you choose to follow these instructions. 
Here are the details. 

Prepare the Grain-of-Wheat Bulb
  • Using the back of your soldering iron, melt the plastic insulation off each lead on the grain-of-wheat bulb about 2" from the bulb.  You want to expose the bare wires. 
  • Don't try to strip the plastic insulation using a pair of wire strippers or cutters - unless you've got a good supply of bulbs. 
  • Cut the ends of the bulb leads about 1" from the places you have melted. 
  • Gently pull back the plastic insulation to expose the 1" of wire.  As you pull back the insulation, twist the wire strands of each lead
Solder the Grain-of-Wheat Bulb to Two 22-ohm ¼Watt Resistors
It's best to do this part using a vise to hold the resistors.
  • Wrap the bare wire of one lead of the grain-of-wheat bulb around one of the leads of a resistor.  Push the wrapped wire up against the body of the resistor.  Put solder paste on the leads and solder the leads.  Don't linger too long with the soldering iron!
  • You'll now have about 1" of resistor lead hanging out the end you just soldered.  Carefully cut this excess lead snug to the solder joint.  Make sure you don't cut the bulb lead. 
  • Using another resistor, repeat this wrap-solder-cut process.  You have now fastened two resistors to the grain-of-wheat-bulb and it looks like this. 
  • Cut two pieces of 3/16" shrink-tubing about 1/8" long, or long enough to cover the solder joints. 
  • Slide them over each of the resistors so that they cover the solder joint. 
  • Gently heat the shrink tubing with a butane lighter.  Don't linger too long.  It is best to apply heat several times, rather than all at once. 
  • Using a 9-volt battery, make sure the light works. 

Prepare the Resistors for Soldering to the Decoder
This step involves cutting the other ends of the resistor leads so that they will fit into the solder holes of the decoder. 
  • Hold the lead of one resistor with a pair of small needle nose pliers right against the body of the resistor. 
  • Bend the lead to a 90 degree angle.
  • Cut the lead about 1/16" from the bend. 
This is what the grain-of-wheat bulb/resistor assembly now looks like. 
  • Prepare another grain-of-wheat bulb/resistor assembly for the other end of the decoder. 

Solder the Bulb-Resistor Assembly to the Decoder
This step involves preparing shrink tubing to cover the solder joint between the resistors and the decoder, positioning the bulb-resistor assembly in the solder holes on the decoder, soldering, and applying the shrink tubing.
  • Cut two pieces of 3/16" shrink tubing about 1/8" long and slide each piece over the leads of one of the bulb-resistor assemblies.   Push each piece up close to the bulb. 
  • Place the bent end of one of the bent resistor leads into one of the solder holes at one end of the decoder. 
  • Apply solder paste and solder the lead to the decoder.  Don't linger too long with the soldering iron! 
  • Put the other bent resistor lead into the other solder hole. 
  • Apply solder paste and solder the lead lead to the decoder.  Don't linger too long with the soldering iron! 
  • Move the shrink wrap tubing over the resistors and onto the soldered tabs of the decoder so that the resistor leads and the tabs are covered. 
  • Gently heat the shrink tubing with a butane lighter.  Don't linger too long.  It is best to apply heat several times, rather than all at once. 
This is what the decoder and lights will look like when the lights are installed. (We've erased the locomotive to make things clearer. )

Fold each light back into the decoder and then back out (the same way you would fold a long scarf) so that the lights are just above the resistors. 
Place the locomotive on your track and make sure that the locomotive is working.  Don't try any of the lighting effects. 

Programming the Atlas 341 Decoder for Lighting Effects
Now that you know the locomotive is working properly, you will have to program the decoder for the lighting effects that you want.  This is done by programming specific CVs (Configuration Variables).  CV51 and CV52 control the lighting effects for the Atlas 341 Decoder.  CV51 determines when and how the lights will come on or off, and whether they will dim.  CV52 determines the level of brightness when the lights are dimmed.  Straight out of the box, the Atlas 341 decoder is programmed for directional lighting (CV51 = 0)
Depending on the type of command station that you have (Atlas, Digitrax, Lenz, NCE, etc) your programming procedures will vary.  Refer to your command station user manual for specific instructions on programming. The following instructions are for the Digitrax DB150 command station and their DT300 throttle. 
Values for CV51 Which Determine Lighting Effects
Values for CV51 and Lighting Results DT300 Key to Turn Light Effects On/Off
CV 51
F0 F1 F4
0 Directional None On/Off N/A N/A
1 Independent None Front On/Off Rear On/Off N/A
6 Directional Dim Front Only On/Off Dim Front N/A
7 Independent Dim Front Only Front On/Off Rear On/Off Dim Front
10 Directional Dim Rear Only On/Off Dim Rear N/A
11 Independent Dim Rear Only Front On/Off Rear On/Off Dim Rear
14 Directional Dim Both On/Off Dim Both N/A
15 Independent Dim Both Front On/Off Rear On/Off Dim Both
Directional - One light goes out, other light comes on when loco changes direction.
Independent - Light(s) stay on regardless of change in loco direction.
Recommended Value for dimming: CV52 = 128  (Range is 0 to 256)
Keys to press on the Digitrax DT300 Throttle to turn light effects on/off:
Press F0 =  twice. Press F1 =  and  Press F4 =  and 
The above CV Values are in decimal format. The following are the associated bits for each CV51 decimal value. 
Bit 3 value (CV51.3) Bit 2 value (CV51.2) Bit 1 value (CV51.1) Bit 0 value (CV51.0)
0 0 0 0 0
1 0 0 0 1
6 0 1 1 0
7 0 1 1 1
10 1 0 1 0
11 1 0 1 1
14 1 1 1 0
15 1 1 1 1
Thanx to Phil Hartung, Idaho Falls, ID for the information on CVs and lighting effects. 
At this point, if you're still with us, and your front lights come on when your loco is moving forward, and your back lights come on when you're moving backwards, you can solder the motor wires to the decoder.  (Shut down your command station!)
If your front light comes on when you're moving backwards, reverse the wires from the motor. 
If you have an older Atlas model, the plastic light bar extends from the headlights/number boards to the middle of the decoder.  The light bar is centred in the locomotive shell by flat "wings" that touch the sides of the locomotive shell.  These wings are an integral part of the light bar. 
  • Two sets of plastic tabs in the roof of the locomotive shell keep the light bar in place. 
  • Using a pair of wire cutters, cut off these plastic tabs flush with the roof of the locomotive shell. 
  • Cut off the part of the light bar between the "wings" and the decoder. 
  • Do not cut off the "wings"! 
  • Your locomotive shell should now fit snugly onto the locomotive chassis. 
  • Set your loco on the tracks, fire up your command station and 
  • Have fun!

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