Single Resistor?

Sure, just have to size it properly.  Since they're all in parallel, you'll need a lower value but higher wattage resistor.  Assuming 18V track voltage, I'd wire three of the LED's with one polarity and the other three with the opposite polarity.  This eliminates them putting a DC offset on the tracks and also allows the LED's to provide protection for each other from excessive reverse voltage.

On to the resistor rating and value.  I'd go for 60ma, considering three LED's light on each half-cycle, that's about 150 ohms.  The actual power dissipation is .54 watts, so you'll need at least a 1 watt resistor, I'd probably stick a 2 watt one in so it'll run cooler.

@gunrunnerjohn posted:

Assuming 18V track voltage

John, thanks for the reply. If you remember the track voltage thread, I’d like to assume the track voltage could be 22 VAC if the MTH transformer handle is all the way up.

Brian NY

Well you could switch out the large 2 watt resistor for a smaller 1/8 watt one and wire the LEDs in series. As John mentioned, make sure you reverse the polarity on a few to protect the LEDs and balance the load on the AC line.

For 22 volts use a 220 ohm resistor in the series circuit.

I think the series wiring was problematic due to the way the bulbs are mounted.  220 ohm 2 watt for 22 volts would be a good choice.

@gunrunnerjohn posted:

I think the series wiring was problematic due to the way the bulbs are mounted.  220 ohm 2 watt for 22 volts would be a good choice.

Thank you Sir

Looks good to me!

@gunrunnerjohn posted:

Looks good to me!

John, you may remember in another post where you suggested I add a diode before the resistor because the resistor was getting very hot. This 2W gets hot too. Should I put the diode before these as well?  

Brian NY

By my calculations, your 2 watt resistor is a tiny bit overloaded:

I'd recommend a 3 watt resistor. You could also use a higher ohm resistor (say 220), that should reduce the amount of heat that needs to be dissipated from the resistor. The downside is the LED's wont be as bright. Adding a diode before the circuit will drop the input voltage and effectively make your 22 volts about 20.8, this would also help but that resistor will still get plenty warm.

I'd up the value of the resistor, I suspect the lights are very bright.  One thing about a series connection, that would have dropped the power dissipation of the resistor a bunch.

@MCD4x4 posted:

... On the subway engines, the engine cover has six glass bulbs that I want to replace with LED's.

Out of curiosity is the swap to LEDs motivated by power consumption, ease-of maintenance (tired of replacing bulbs), shift color temperature to cooler white, etc.?

I appreciate the hassle of modifying the voltage rails to put the LEDs in series.  But here's the thing.  With the parallel method the single resistor is burning over 5 times the power of the LEDs.  That is, in broad terms, you are asking the resistor to drop 18V (from the track) to 3V (that LEDs use).  OTOH with bulbs, all 18V of the track voltage goes to the filaments and hence to generating light.  Yes, LEDs are much more efficient in terms of lumens per Watt.  The numbers are still on your side (supporting LEDs) but not as dramatic as the 10-to-1 improvement one thinks of when converting from bulbs to LEDs.

@stan2004 posted:

Out of curiosity is the swap to LEDs motivated by power consumption, ease-of maintenance (tired of replacing bulbs), shift color temperature to cooler white, etc.?

I appreciate the hassle of modifying the voltage rails to put the LEDs in series.  But here's the thing.  With the parallel method the single resistor is burning over 5 times the power of the LEDs.  That is, in broad terms, you are asking the resistor to drop 18V (from the track) to 3V (that LEDs use).  OTOH with bulbs, all 18V of the track voltage goes to the filaments and hence to generating light.  Yes, LEDs are much more efficient in terms of lumens per Watt.  The numbers are still on your side (supporting LEDs) but not as dramatic as the 10-to-1 improvement one thinks of when converting from bulbs to LEDs.

Given I have a similar PS2 Subway set, and due to the socket arrangement of the incandescent bulbs being not the greatest contact or design, coupled with the heat of the bulbs right at the roofline of the shell, I would say there is plenty of reason for going LED over bulbs. Again, It's on my list of rainy day projects to glue back in the windows (again, old school second hand PS2 3V), and while the car is open convert to a "regulated" LED setup to replace the factory bulbs and get rid of the brittle and semi fragile original socket and contact system.

The part that is lost in this arrangement as presented in the thread is that there is no anti-flicker or constant voltage/constant current aspect to the LEDs- again as presented in this topic. They will vary in brightness based on track voltage, and maybe that is desired or a feature.

Bottom line, each person is likely to do these mods in a way they feel comfortable and at the cost and effectiveness they feel comfortable with. I likely will do my conversion slightly different but this topic certainly shows one way it can be done.

I did my Red Arrow Liberty Liner cars with LED lighting, I used the narrow LED strips and of course, my LED controllers.

The middle cars got the classic LED upgrade, but the two end units got a special treatment due to the space for the lighting.

@stan2004 posted:

Out of curiosity is the swap to LEDs motivated by power consumption, ease-of maintenance (tired of replacing bulbs), shift color temperature to cooler white, etc.?

I appreciate the hassle of modifying the voltage rails to put the LEDs in series.  But here's the thing.  With the parallel method the single resistor is burning over 5 times the power of the LEDs.  That is, in broad terms, you are asking the resistor to drop 18V (from the track) to 3V (that LEDs use).  OTOH with bulbs, all 18V of the track voltage goes to the filaments and hence to generating light.  Yes, LEDs are much more efficient in terms of lumens per Watt.  The numbers are still on your side (supporting LEDs) but not as dramatic as the 10-to-1 improvement one thinks of when converting from bulbs to LEDs.

I’m looking to cut back on the amps drawn. From past experience, an 8-10 track layups for six car trains with all those glass ceiling bulbs requires a Z4000. Ya pull another train in and it trips it.

@gunrunnerjohn posted:

I'd up the value of the resistor, I suspect the lights are very bright.  One thing about a series connection, that would have dropped the power dissipation of the resistor a bunch.

John, what resistor should I go up to? 260 ohm 3 watt? Higher ohms? Have a look at the bottom, I posted two videos. I don’t think they look to bright. Also in an earlier post you provided a link to the little white MTH headlights. I believe they were on Digi-key. I think it 30 gauge wire.

Brian NY

@gunrunnerjohn posted:

I did my Red Arrow Liberty Liner cars with LED lighting, I used the narrow LED strips and of course, my LED controllers.

The middle cars got the classic LED upgrade, but the two end units got a special treatment due to the space for the lighting.

If a resistor and a diode work, why put the boards in?

Brian NY

@Vernon Barry posted:

Bottom line, each person is likely to do these mods in a way they feel comfortable and at the cost and effectiveness they feel comfortable with. I likely will do my conversion slightly different but this topic certainly shows one way it can be done.

Barry,  keep in mind, it the NYC a subway, until recently, the lights did flicker in the cars when crossing a switch etc.

Brian NY

@MCD4x4 posted:

If a resistor and a diode work, why put the boards in?

Brian NY

The board allows you to adjust brightness, and also has a capacitor to eliminate flickering.

@MCD4x4 posted:

If a resistor and a diode work, why put the boards in?

Flicker suppression, intensity adjustment, DCS compatibility...

@gunrunnerjohn posted:

Flicker suppression, intensity adjustment, DCS compatibility...

John I was under the impression from a post years ago, if you do not use a regular or a pot to adjust the voltage the DCS signal in not interfered with. Is that the case?

also, what resistor should I go up to? 260 ohm 3 watt? Higher ohms? Have a look at the bottom, I posted two videos. I don’t think they look to bright. Also in an earlier post you provided a link to the little white MTH headlights. I believe they were on Digi-key. I think it 30 gauge wire.

@MCD4x4 posted:

John I was under the impression from a post years ago, if you do not use a regular or a pot to adjust the voltage the DCS signal in not interfered with. Is that the case?

I have no idea where that notion came from.  The issue with the DCS signal is typically the capacitor in the power supply affecting the DCS signal.

@MCD4x4 posted:

also, what resistor should I go up to? 260 ohm 3 watt? Higher ohms? Have a look at the bottom, I posted two videos. I don’t think they look to bright. Also in an earlier post you provided a link to the little white MTH headlights. I believe they were on Digi-key. I think it 30 gauge wire.

The great thing is, you can go to pretty much any value above the minimum to achieve the light level you desire.  The higher the value, the less current it draws, and the lower the intensity of the lighting will be.  Since I don't like my passengers to get a sunburn in my cars, a typical 18" car on my RR draws about 25-35 milliamps for the entire car.

@MCD4x4 posted:

If a resistor and a diode work, why put the boards in?

...

Did you reach a satisfactory conclusion?

If so, and for the OGR record, what is your final configuration in terms of the parts required to achieve what you show in the videos.  What resistor did you end up with?  Using a diode?  What kind of LEDs (they look like 5mm cool white)?  Etc.

@stan2004 posted:

Did you reach a satisfactory conclusion?

If so, and for the OGR record, what is your final configuration in terms of the parts required to achieve what you show in the videos.  What resistor did you end up with?  Using a diode?  What kind of LEDs (they look like 5mm cool white)?  Etc.

The original resistors that turned out to be to small, I put two in line and that solved the problem. Moving forward I will use the ones pictured.  They’re 3W but cheaper for some reason than the 2W  

The Digikey "marketplace" is where surplus parts go to die, that's why they're cheap.

@gunrunnerjohn posted:

The Digikey "marketplace" is where surplus parts go to die, that's why they're cheap.

Can you provide a part number from Digikey that you would prefer? I really do not have any knowledge about this subject and that’s why I post in this section for help.

Dropping 15 volts, a 56-ohm resistor will dissipate .4 watts.  I can't imagine you need more than a 2 watt resistor for your 560 ohm resistor.  Rule of thumb is typically twice the actual power dissipation for the rating, surely 4 times the requirement will not run very hot.

Here's a 2W 560 ohm resistor for 31 cents, and next a search for alternatives.

Here's the search for 2W 560 ohm resistors, eight results.

@gunrunnerjohn posted:

Dropping 15 volts, a 56-ohm resistor will dissipate .4 watts.  I can't imagine you need more than a 2 watt resistor for your 560 ohm resistor.  

John the reason I was going to go for the 3W is the price was the same or cheaper than the 2W.  I’ll order these now. Thank you for your time.

That was a 560 ohm resistor, not a 56 ohm one, just so you didn't get confused by my typo!