Upgrading Intermountain Passenger cars to Track powered Lighting.

[CodyO]

I recently decided to upgrade all of my Rapido and Intermountain cars to track powered(DCC) Lighting

I`m going to be using these to add wheel wipers to one set of trucks on each car
http://store.sbs4dcc.com/sbs4dccnscalep4w-mt-440flat4-40mountwheelwiper.aspx

Then into Ngineering`s tiny bridge rectifier
http://www.ngineering.com/accessories.htm

Then into a series of 5 capacitors totaling 1,100uf
http://store.sbs4dcc.com/SBS4DCC220uF16V2917SMDCapacitor.aspx

And finally though a resistor to drop the voltage down
And then into either the board on the car or direct to the LEDs
I`m planning on keeping the existing lighting setup in the cars to keep it simple for the 30-40 cars I want to upgrade.

One of my main questions is can I keep the full board already in each car, hook my wires to the old battery leads and use the magnetic reed switch as an on/off switch for the lighting?

Here`s a shot of it so you don`t have to crack open your cars...
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[peteski]

That is nice, but with the amount of cars you have to convert you might want to try a much cheaper (and smaller) solution.
https://www.therailwire.net/forum/index.php?topic=29654.0

I'm also working on a track-power retrofit for Rapido Easy-Peasy light boards which will retain the reed switch function (and which will "remember" the setting for several hours even after the power is disconnected).  I have the circuit bread-boarded - I just have to come up with a way to solder the components on the existing board, take photos and do the writeup.

[nkalanaga]

Replacing the batteries with your track pickup and caps should work fine.

[peteski]

Replacing the batteries with your track pickup and caps should work fine.

Not quite. The battery-based circuit is designed to work with 3V DC. If you feed it rectified 12V DCC or variable DC voltage which often exceeds 3V, the LEDs will lglow very brightly and then let their magic smoke out.

[narrowminded]

On this subject, does anyone know a good source for a suitable latching reed switch for similar applications?  As usual, size matters.

[peteski]

On this subject, does anyone know a good source for a suitable latching reed switch for similar applications?  As usual, size matters.

True latching reed switches are hard to find.

The circuit in Rapido Easy-Peasy ligths uses a standard reed switch. The toggling is done by a small electronic chip which contains a flip-flop that changes state upon each reed switch closure.  That flip-flop then controls an on-chip transistor which supplies power to the LED.

[narrowminded]

True latching reed switches are hard to find.

The circuit in Rapido Easy-Peasy ligths uses a standard reed switch. The toggling is done by a small electronic chip which contains a flip-flop that changes state upon each reed switch closure.  That flip-flop then controls an on-chip transistor which supplies power to the LED.

Thanks Pete.  Sounds logical.  I will eventually be attempting such a device for miners in a man trip car with lights on their helmets.  Yeah, I know.   Any quick direction on that without making a project out of it?

[Lemosteam]

Not quite. The battery-based circuit is designed to work with 3V DC. If you feed it rectified 12V DCC or variable DC voltage which often exceeds 3V, the LEDs will lglow very brightly and then let their magic smoke out.

So to use the current system, he only needs to add a resistor to the incoming power?

[CodyO]

So to use the current system, he only needs to add a resistor to the incoming power?

Thats what I`m getting from this, though I thought that it was 1.5v LEDs in the car

That is nice, but with the amount of cars you have to convert you might want to try a much cheaper (and smaller) solution.
https://www.therailwire.net/forum/index.php?topic=29654.0

Not sure how that is cheaper and smaller?
I`ll have to replace the LEDs in each car and I`ll still need the parts I listed above

[Sokramiketes]

Scroll down farther on the Ngineering page and you'll see N90CL2-2, a 20mA constant *current* source.  That may allow you to reuse the existing 3V circuitry since it will limit the current to the LED's.

[peteski]

Thats what I`m getting from this, though I thought that it was 1.5v LEDs in the car

Without getting too deep into technical details, LEDs don't run off a specific voltage - they need to be feed a limited current, and they drop a voltage across their terminals.  That is why a resistor is used - it is the current limiter.  Most red, green, yellow, and amber LEDs will usually drop around 1.7 to 2.1 volts. Blue and white LEDs drop around 2.8-3.2 volts.  In order for the LED to even illuminate the supply voltage needs to be at least as high as the voltage drop across it.

Single alkaline button cell can supply 1.55V when new. That would not work with white or blue LEDs, and you might get a very faint glow from the other color LEDs.  I don't have the IM lighting board handy but I know that the Rapido Easy-Peasy boards have 2 button cells in series (for the total of 3.1 volts).  If the IM boards use white LEDs then I suspect they also use at least 2 button cells in series.

Not sure how that is cheaper and smaller?
I`ll have to replace the LEDs in each car and I`ll still need the parts I listed above

Well,, you got me here. I assumed that electronic components purchased from model RR suppliers are usually overpriced. I get my components from an electronic supply company which has pretty low prices.  But the 220 uF tantalum cap you found as sbs4dcc costs only a buck - that is a good price. But I suspect the rectifier and the resistors are cheaper where I buy them.

One thing I'm worried about is the 16V rating for the capacitor. I prefer to have a larger margin of safety and I use caps rated at 20V. Tantalum caps are very sensitive to voltages approaching their rated voltage and they self-destruct in a rather spectacular way (they blow up).

I would also recommend using the inrush-current-limiting resistor and then a 2nd current limiting resistor going to the LEDs (as shown in the schematic in the thread I pointed you to).  Limiting inrush current is especially important with large capacitance you want to use.

When you are using the existing lighting boards, how many LEDs are on them, and do you like their color?  Using the inexpensive LED strips gives you choice to select a color temperature you like and they might give you more even light distribution inside the car.

[nkalanaga]

Peteski:  He also had a dropping resistor on his list, which I left out of my comment.  So, as he described it, it should work.  And, with his capacitors, there shouldn't be any voltage spikes getting through.

[peteski]

Peteski:  He also had a dropping resistor on his list, which I left out of my comment.  So, as he described it, it should work.  And, with his capacitors, there shouldn't be any voltage spikes getting through.

I'm worried that any overvoltage will destroy the explosive tantalum caps (not LEDs).  Cody didn't mention whether he would use 2 resistors (one to limit the inrush current when the 1,100 uF capacitor bank is charging, and 2nd resistor to control the current going to the LEDs).

[randgust]

Wow, for me this is almost painful to read, having converted every lit Kato, Atlas, etc., passenger car I own over to Rapido light boards.   And lovin' it.  I think I've had one battery corrode a bit that had to be removed for cleaning.

OK, so I had to make sure I could still get the roofs off for battery replacement.   No problem.  I think two batteries in four years over 20 cars.  Less labor than wheel cleaning, for sure.

I also have no fewer than eight lit cabooses with pickup wipers, capacitors, and Richmond Controls units in them for markers and interior lights.  Those puppies stay lit for hours even with the power off.  It's a brilliant and effective solution.   Still requires wheel cleaning about once a year.  No flicker whatsoever until the wheels get so bad you can peel it off with a knife.

Jim Hinds has beaten this one for DCC, DC, whatever.   The only reason I put them in my cabooses for the marker lights was the Rapido units don't come that small and are pretty much near impossible to modify.   He's got a unit solution for passenger cars with capacitors and track supply power if you want to go that route instead of batteries or a DIY modification of the stock boards.  Not saying this doesn't work, but as it wonders off into the technical weeds there is a less painful approach, if not less expensive.

If anybody wants any leftover Kato lighting parts, strips, reflector tape, or light bulbs, I'll make such a deal.  I'm never going back to that for sure.

[CodyO]

I'm worried that any overvoltage will destroy the explosive tantalum caps (not LEDs).  Cody didn't mention whether he would use 2 resistors (one to limit the inrush current when the 1,100 uF capacitor bank is charging, and 2nd resistor to control the current going to the LEDs).

I didn't because I wasn't planning on it but now on will as the last thing on want is to blow up part of my cars!

I like the color and how they look, there is 2 leds in the car one on each side of the diffuser(?)
The observation car will have 5 leds though do to 1 for the drumhead and one on each side for the markers.

@randgust I like the ease of use for battery lights but would rather go to truck powered. I do plan on doing cabin cars after this. And the senator if I can ever finish it.(Have you seen my emails?)