# Adding Headlight to Athearn Blue Box



## DavefromMD (Jul 25, 2013)

I'm considering removing the cab light and adding a headlight to a couple of 
HO Athearn GP 38-2s. I can figure out the wiring fine. 
I run DC.

I'm considering incandescent and LED.

For incandescent - what size and wattage to use and how big do I need to drill the headlight hole. Do I need to add insulation around the bulb to prevent melting the plastic?

For LED - what size and what ma rating should I use. What size resistor or are there premade setups available? Any other electronic components needed? Drill size, and is insulation needed?


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## T-Man (May 16, 2008)

Prepare for an adventure. One simple way is to use a grain of wheat bulb 12 volt and wire it in. Then it goes downhill fast.
Engines are the hardest to light up with LEDs. You have direction and polarity changes plus voltage surges form the motor changes speeds. You need four diodes to solve the polarity problem and a capacitor over the motor leads.










The image shows the capacitor between the LED leads but you can place it over the motor leads then to the diodes. The capacitor is a .1uf bipolar I think. The positive wire to the Led is the low one. These are 5 mm LEDs for a headlight 3mm will work. I have to check on the drill size. Somewhere aroun 3/16th hole. unless you have a 3mm drill.

This is the thread


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## shaygetz (Sep 23, 2007)

1.6 mm LEDs are a press fit and look awesome...my Chessie Geep on the club layout some years back....










1/4 watt 470 ohm resistor for every two LEDs.


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## DavefromMD (Jul 25, 2013)

I seem to have found a site that has LEDs with all the electronics already built in:
http://www.modeltrainsoftware.com/bl-212.html

Are these the right thing?

Otherwise, it sounds like just using a grain of wheat bulb may be the easy answer.


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## T-Man (May 16, 2008)

I would still use a capacitor over the motor leads. They look fine. I buy components in mass quantities and do different things. To keep it simple it should work for you. I used a 20v dc tyco transformer and I blew out a few LEDs that way. Using a modern transformer may be easier on them. I am just wary to say just use an LED and a resistor and it will work. This is where other suggestions would be helpful. I worked on that 4 years ago.


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## DavefromMD (Jul 25, 2013)

What voltage grain of wheat bulb? I see 3.5v, 14v, 12-16v. 

Running Railpower 1370 transformer with 15v DC, 18VA output.


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## T-Man (May 16, 2008)

I have used 12 volt in coaches. 14 volts will last longer but will lose brightness. The others are usefull in DCC applications with resistors. . These are low amperage bulbs and expel less heat than a common 52 screw bulb of the same voltage.

This electrical aspect can be a whole new hobby. It depends on how deep you want to dive. You start with a solder iron and solder. I bought string lights at a yard sale in the plastic tube. They were 6 volt grain of wheat. LEDs I buy cheep at sales or Xmas discount or e bay. A meter is handy for voltage checks etc. I use wall chargers as power supplies. I cut the plug off and solder it to the board I am making. The meter tells me the positive wire and voltage.

What started me is I wanted LEDs and I wanted to make them flash.


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## DavefromMD (Jul 25, 2013)

Is that Chessie Locomotive with the LED lighting DC or DCC?


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## shaygetz (Sep 23, 2007)

DavefromMD said:


> Is that Chessie Locomotive with the LED lighting DC or DCC?


I wired it up for DCC...I would recommend a higher value resistor, personally, the "Death Beams" look from the 470 ohm resistors was too cool to resist. I put them on all my locos at the time...


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