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DCC lighting for passenger cars

Greg Harter
 

I've wired a passenger car with an LED lighting unit, but it flickers as there is no capacitor in the circuit to keep the car lit over track gaps, etc.  I'm using metal frame trucks, and the axle points go into the truck dimples, and I've connected wires from the truck frame screws to the light board.  I've put Conducta-lube in the truck dimples.  Works fine as long as I don't move the car!!!   Can I install a capacitor in the circuit, where the circuit board is that supplies light to the LEDs?  I know capacitors don't work on AC.  There are two open solder points on the board that test at 2.4VDC.  Would putting a capacitor there be of any help?  This is a Walthers LED lighting unit for passenger cars.  Capacitors come with voltage and microfarad ratings, what should I use?  Size not really a problem, lots of room in the car interior.  Thanks for any help/advice!
Greg Harter
John Bishop
 

Put a capacitor at any point across the printed lines that go to the LEDs. This will be on the DC side of the rectifier. Size shouldn't matter much as the current is low, but get the polarity right. I just experimented with caps I happened to have, the more Mfs the longer the lights will stay on after you turn off the power.  (I use Golden Gate lighting strips because I'm in O scale. They now come with caps built in, but this was earlier.)

John Bishop

On Thursday, February 24, 2022, 06:10:34 AM PST, Greg Harter <greg1462@...> wrote:


I've wired a passenger car with an LED lighting unit, but it flickers as there is no capacitor in the circuit to keep the car lit over track gaps, etc.  I'm using metal frame trucks, and the axle points go into the truck dimples, and I've connected wires from the truck frame screws to the light board.  I've put Conducta-lube in the truck dimples.  Works fine as long as I don't move the car!!!   Can I install a capacitor in the circuit, where the circuit board is that supplies light to the LEDs?  I know capacitors don't work on AC.  There are two open solder points on the board that test at 2.4VDC.  Would putting a capacitor there be of any help?  This is a Walthers LED lighting unit for passenger cars.  Capacitors come with voltage and microfarad ratings, what should I use?  Size not really a problem, lots of room in the car interior.  Thanks for any help/advice!
Greg Harter

Gene
 

One thing you should check is the cleanliness of the wheels. Give them a good cleaning by hand running over a paper towel laid on the tracks dampened with 90% IPA (alcohol not India Pale Ale). I then ingest the India Pale Ale. This works for me but others may have other ideas. 

Have fun,

Gene J
Don Weigt
 

While a capacitor across the traces that power the LEDs will help, the voltage range over which the LEDs light is small, so the capacitor can't deliver power very long before the LEDs dim and then go out. I don't know anything about the Walthers lighting units, but if the rectified diodes are connected to the leads from the rails, then you have about 12V DC after them somewhere on the board, and one or more resistors setting the current to the LEDs, which operate at about 3 volts. If you can attach the capacitor to that higher DC voltage PCB lands, then it can power the LEDs with little change in brightness as the capacitor discharges a few volts. I think you'd like that better.

The disadvantage is you need a capacitor rated for 15 volts or more. Higher voltage caps are bigger, but the capacitance (microFarads) can be much lower to store the same amount of power.Actually, their volume is about the same for the same energy storage capacity, which makes sense. A capacitor rated for at least 100 uF (microFarads) and 16 or 25 volts should help a lot this way, where directly across the LED power lands, you'll want 1,000 uF or more, but only about 6.3 volts. An even lower voltage rating would be better. of you can find them, but they should be rated for at least 4 volts, and I'm not sure anybody makes caps with those ratings.

Don Weigt

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Don Weigt
Connecticut
Tom O'Hara
 

Thanks for the suggestions. There turn out to be no real complications that I was anticipating, so I am able to move forward with what's there and your ideas.

....Tom
Greg Harter
 

Don's advice was perfect.  installed 16V1000mfd across rectifier outputs.  Thanks!

greg harter
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