Coach Lighting Version 3 is a Keeper

I was not quite satisfied with the light flicker that coach lighting version 2 suffered from. A large capacitor could maybe help some, but I had my doubts. It stemmed more from bad DCC pickups. The pickup was from the axle, on 4 wheels, but from just one side of the rails per bogie:

— A — A — — — — o — o —
— o — o — — — — B — B —

Now, if there is the slightest tilt in the rail, in a curve or with turnouts, A or B can easily become disconnected. Probably it would be more reliable when A and B both have a pickup per bogie:

— A — o — — — — A — o —
— o — B — — — — o — B —

But that would mean 4 wires need to be led inside through the bottom of the coach. And even then probably this is not ultimately reliable.

The new idea was really as simple as can be. A wire was planned to run out of the loco anyhow, to switch the lights via DCC. Well … if there is already 1 wire between the loco and the coach, why not have 2? The LED’s will be fed now via the wheel pickups of the loco, which has the following configuration, which is most reliable:

— A — A — — — — A — A —
— B — B — — — — B — B —

Two thin wires that run to the coach are soldered inside the loco. The funny thing is, I have 2 very cheap locos, they were just €59,95, including a Zimo decoder! These cheap loco’s have 4 nice extra solder pads on their PCB where the blue ‘+’ and the green AUX1 can be picked up. Alas the much more costly NS 1830 does not have such a nice feature! We’ll have to improvise. I used the loose purple AUX2 wire to run to the coach. The blue ‘+’ could be connected somewhat ‘clandestine’ on the PCB, to an existing front lights resistor.

There’s a mini connector between the loco and the coach, such that they can still easily be taken apart.

While the hood was off the NS1830 and the solder iron was still hot anyhow, I also added a cabin light. Three LED’s cut off the strip, added a resistor, connected to the same blue ‘+’ spot on the PCB. The other end connected to AUX1. For that I cut the green wire off of the 8 pin connector and connected it to the LED’s.

The schematics … I don’t think it can become much simpler! 🙂

The whole DCDC converter is gone. It was there for the ease of tuning the light level. Not needed anymore, since light level can now be tuned via a CV value in the decoder. There’s also even an option for a slow fade in/out effect! 🙂

If maybe you’d like to try this too, in your case the 470 ohm resistor may need to be a different value. It depends on your DCC voltage, LED strip type, number of coaches to light and max light output you want. Just experiment a bit with different values.

Result: see the video.
+ Simplest schematics imaginable.
+ Price for 3 coaches: $1,- (3 feet of LED strip plus 1 resistor).
+ Lights can be switched on/off via a loco function.
+ No light flicker. No capacitor needed (on my layout, with this loco that is, may be situation dependent).
+ Nothing in sight inside the coaches.
+ Light output can be tuned via a decoder CV value (may depend on decoder type in use).
+ Light can have a subtle fade in/out effect, also via a CV value (may depend on decoder type in use).
– 2 wires run between the loco and the coach, with a connector in sight. Same connectors are used between the coaches.

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