Adding LED on PS3 locomotive

I would not tap off the headlight for the firebox glow.  First off, different LEDs have different operating voltages, so trying to run dissimilar LEDs in parallel is an exercise in futility.  The headlight drive is also current limited, so adding loads will create different issues as well.

I suggest you run from track power with a 22uh choke, diode, 220uf 35V capacitor, and current limiting resistors.  I'm somewhat surprised that the red LED and the flickering LED's are working in parallel, the red LED usually operates at a lower voltage.  In order to run them in parallel, I'd use a separate current limiting resistor for the red LED and then the two parallel flickering LED's. 

Ok. I did see your posts on the other threads and have the components all set up.  I believe the 3mm red LED is 5v.  What would the circuit look like if I have that added into the mix?  I have the LEDs already CAed to some plastic.  Could I run the red LED in parellel and just add a 100ohm resistor in series with the LED on the positive side, John?

Also, based on your circuit diagrams running off of track power, if the LEDs are 3V (red one is too) and the track voltage is 18V, and the LEDs are 25mA, if the three were in parallel that would be 75mA.  Doing the math, would it be 18V-3V= 15V.  Divide that by .075 amps, you get 200 ohms.  Or do I have to take into account the capacitor at all? Would that work for the resistor after the diode, and then if the red LED is too bright, just put a 100ohm on the positive side just before the red LED only?  Just getting a sanity check.  

Actually, common LED are maxed out at 20ma, and you don't really need that much current to light them properly.  Also, when you have 18V on the track, the capacitor charges to the peak voltage, so you'll have around 13 volts maximum after the filter.   I'd suggest a 470 ohm 1/2W resistor for the two flickering LED's in parallel, and I'd go a separate 1K resistor for the red LED.  I think you'll find they look pretty good at those levels.  Here's an example...

Awesome stuff, John! Thanks, I'll give that a try and see how it looks.  

Also, have 470ohm-1/4w resistors. Think that would be ok with just two tea light LEDs?

I'd want a 1/2W one there, the actual power dissipation is about .2 watts, too close to the 1/4W rating.  It'll get pretty toasty...

Yeah, true.

gunrunnerjohn posted:

Actually, common LED are maxed out at 20ma, and you don't really need that much current to light them properly.  Also, when you have 18V on the track, the capacitor charges to the peak voltage, so you'll have around 13 volts maximum after the filter.   I'd suggest a 470 ohm 1/2W resistor for the two flickering LED's in parallel, and I'd go a separate 1K resistor for the red LED.  I think you'll find they look pretty good at those levels.  Here's an example...

Would this circuit above albeit somewhat modified work for a single self flashing led to be used as a beacon like you see on some sd 40-2's? It would go in a ps3 gp-35. As soon as i had track power it would come on which is fine with me

I have used that circuit on a number of flashing LED's.