Adding rear marker lights to Kato Superliners, N scale

[peteski]

Here are couple of simple circuits.


SuperlinerEOTlights.jpg

If you choose the top one and it lights up in the wrong direction, just flip the track pickup leads.
You should be able to pick up all the components in Radio Shack. Any red LED will work. You should pick ones which will be the easiest to install.  Electrically, all red LEDs are pretty much identical. I decided to hook up the LEDs in parallel in order to have them start glowing at a lowest possible voltage (since you are running on DC).

[Ike the BN Freak]

Thanks...seems easy enough

[PAL_Houston]

Lots of wasted parts in there:  you only really need one resistor, and can skip the bridge rectifier if you are willing to use 4 LED's and do some soldering.

[peteski]

Lots of wasted parts in there:  you only really need one resistor, and can skip the bridge rectifier if you are willing to use 4 LED's and do some soldering.

=

If I understand you correctly, you want to use 4 LEDs arranged as a bridge rectifier, with a single resistor connected between positive and negative bridge outputs?  Interesting idea.  But depending on the polarity, only 2 out of the 4 LEDs would light up. So, each marker light would have to be illuminated by 2 LEDs.  Hmmm....

I also gave a clear reason why I wired the LEDs in parallel.

[DKS]

Lots of wasted parts in there...

Seriously?

Peteski's version: 5 parts (1 bridge rectifier, two resistors, two LEDs)

Your version: 5 parts (1 resistor, 4 LEDs)

Using Peteski's version means not having to mess with arranging two LEDs for each marker.

[Ike the BN Freak]

I'm going with Peteski's method, just gotta find some LEDs now.

[PAL_Houston]

=

If I understand you correctly, you want to use 4 LEDs arranged as a bridge rectifier, with a single resistor connected between positive and negative bridge outputs?  Interesting idea.  But depending on the polarity, only 2 out of the 4 LEDs would light up. So, each marker light would have to be illuminated by 2 LEDs.  Hmmm....

I also gave a clear reason why I wired the LEDs in parallel.

Peteski:
You are right.
My comments were a bit hasty and ill-considered.
And probably a bit brusk and impolite.

My apologies.

[peteski]

Peteski:
You are right.
My comments were a bit hasty and ill-considered.
And probably a bit brusk and impolite.

My apologies.

Thanks Paul. I was somewhat surprised by your comments.  All is well. 

[Ike the BN Freak]

If I were to add a capacitor to the second one that Peteski posted, would I add it before or after the bridge rectifier.  I'm guessing after.

Also any particular size capacitor I should get?

[peteski]

The capacitor would be added after the bridge rectifier (make sure to pay attention to the polarity of the capacitor).  You should also add another resistor to limit the inrush current.  A 100 ohm 0.25W resistor would be a good value. The resistor would be added between the positive output of the bridge rectifier and the positive lead of the capacitor. The LED resistors would then be also hooked up to that positive lead from the capacitor. All the negative leads would then be tied together (Bridge rectifier, cap, and 2 LED cathodes).

As far as the cap value goes, the larger, the better. I would start with around 500 uF (micro Farads).  The cap should be rated at least for 16V (I use 20V caps for safety margin).  Since larger values caps are rather bulky, you can gang several smaller caps in parallel.  The total capacitance will then be the sum of all the caps. So four 150 uF caps in parallel would give you 600 uF total capacitance.  But this setup will not give you any long lasting illumination. Maybe few seconds with a large cap.  But a cap will nicely reduce flicker.