Athearn BB F7s - constant headlight forward only - LEDs??

[Soo Line fan]

Mark R.

Hook the LED straight to the rails through a 330 ohm resistor. That resistor will hold the LED up to about 11 volts and will begin to light between 1.5 and 2 volts.

It will also be directional this way, but you have a 50/50 chance of getting it right the first time depending on which direction it runs. If it lights when going in reverse, just switch the leads.

 

Mark.

 I do the same thing and it works well. Only difference is I use a 470 ohm resistor. Simple and very effective.

[Mark R.]

Hook the LED straight to the rails through a 330 ohm resistor. That resistor will hold the LED up to about 11 volts and will begin to light between 1.5 and 2 volts.

It will also be directional this way, but you have a 50/50 chance of getting it right the first time depending on which direction it runs. If it lights when going in reverse, just switch the leads.

 

Mark.

[DigitalGriffin]

richg1998

LM3334Z.

Operates From 1V to 40V

http://www.pollensoftware.com/railroad/

Mouser sells them also. Mouser has the PDF for both devices. Check the specs.

 

That would work quite well Rich.  Except there's a difference between input and output voltage. is between 1 to 1.25 Volts.  Add 3.3 Volts for the LED to the base and you end up pretty darn close to where you were with the current regulator.

 

Either way it's a viable alternative.

[richg1998]

LM3334Z.

Operates From 1V to 40V

http://www.pollensoftware.com/railroad/

Mouser sells them also. Mouser has the PDF for both devices. Check the specs.

Rich

[DigitalGriffin]

You'll need the LED + 20milliamp current regulator IC (http://www.mouser.com/ProductDetail/Supertex/CL2N3-G/?qs=Plqv86A3fKMm41oemcboMA== )

The problem with using the current regulator is it will take about 5Volts before the LED will light.  So your train might start moving before the headlight comes on.

hook the input of regulator IC to the right rail pickup.  Trim middle leg off.  Hook the last leg to the long leg on the LED.  Connect the short leg of the LED to the left rail pickup.

 

right rail->regulator IC pin 1 

regulator IC Pin 3->LED+ 

LED- -> left rail

[Jersey Southern RR]

Just want to rig up headlights for a A-B-A lashup in DC.  Would like to be directional so no light in reverse. Know lots of ways to do this with the headlight on all the time. what do I need in resistors and/or diodes to do this with some leds (or bulbs) ?