Help Converting to LED for my passenger cars

It appears you're using a 6.3V capacitor (marked on the component).  You should be using a capacitor rated for 35V or more.  He appears to be using a 50V capacitor. 

I'm impressed the little choke isn't dying, I guess the cap goes so quick it doesn't get a chance.

Stan is right on this one, use the proper voltage rating and all will be well.

Stan, how did you see his photos, they don't show up for me?

He even posted the part numbers and I bought exactly what he posted. He gives you and gunrunner a lot of the credit then makes it bad by posting the wrong part numbers. WOW

List of components used with DigiKey part numbers in brackets.  
Note the LED strip was from Amazon, not DigiKey.

22uH CHOKE [495-5557-1-ND]
1A FULL WAVE BRIDGE RECTIFIER [DF005M-E3/45GI-ND]
470uF CAPACITOR [P5508-ND]
1.5A LM317T Voltage Regulator [497-1575-5-ND]
5k TRIM POT [3362P-1-502LF]  (optional)
47 ohm ¼-watt resistor [adj per # of LED's]
LEDwholesalers 5 Meter Flexible LED Strip 12 Volt/Warm White/3100K/2026WW-31K [Amazon]

Thank you Stan and John. I'll try again.

This 35V 470uf Electrolytic will work a lot better!

The other parts appear OK.

Did you already buy in quantity for your project? 

If not, in addition to up'ing the voltage rating on the capacitor, I'd increase the voltage rating on the bridge rectifier.  The DF005 is rated 50V blocking voltage.  This will work but for the same price you can get a part rated for 100V, 200V or more.  This gives a little extra protection for the nasty spikes you see on the rails...

Also, if you're in no great rush most/all these parts are maybe 1/4 or 1/3rd the price of DigiKey if you're willing to use eBay or similar Asia sources.

Yeah I did. I bought 50 and blew up 3.

Thank You again. I can't say that enough

Well, before you rush out and order "just" capacitors, can I ask how you know if the 47 ohm resistor (which sets brightness) will be suitable for you? 

I see from the parts list there's an optional potentiometer/trimmer resistor presumably to adjust brightness?  The value shown is not suitable for adjusting brightness in the circuit.

If all you have is the 6.3V capacitors (47 of them left!) you can stack, say, 5 of those 6.3V capacitor in series to "make" a ~30V capacitor strictly for the purpose of experimenting to see if the brightness is suitable with 47 ohms. This might tell you if you need to order different resistors or whatever to save yourself more parts ordering even after you resolve the capacitor voltage issue.  Let us know your thinking on this issue and there are a bunch of us that are able to help you out!

You are amazing. Thank you for that info . I will try that. Is the trimmer pot and the resistor redundant or can I eliminate the resistor and just use the pot?

I suggest you just make the 30V capacitor and use the 47 ohm resistor to get started.

The recommended pot is needless to say a variable resistor with range of 0 to 5000 (5k) ohms.  This is much too large an adjustment range when the desired value is in the neighborhood of 47 ohms or so.  In other words barely turning the pot will surely change the resistance too much given than one-turn moves it 5000 ohms!

So per above suggestion just use a 47 ohm to get a baseline brightness.  Then if too bright put 2 resistors in series (47+47=94 ohms) and that will cut brightness in half.  If too dim, put 2 resistors in parallel (47/2 = 24 ohms) and that will double brightness.

To your point, a good engineering design when using a pot will have a resistor plus the pot.  This is because one end of the pot range is 0 ohms and this will try to drive "infinite" current into the LEDs.  Adding a 1 cent (or whatever) fixed resistor in series with the pot eliminates this possibility.  For example, GRJ's LED lighting boards have a fixed resistor plus a pot so that even if you set the pot to "full" brightness you do not run the risk of setting the total resistance to 0 ohms which is simply bad manners.

Here is the actual circuit I use for my lighting modules.  You'll see that Stan is clearly right, a 5000 ohm pot is twenty five times the value I use.

The 27 ohm resistor is the one that Stan mentioned to keep people from self-destructing, it limits the maximum current out to around 45ma.  The 200 ohm pot in series allows adjustment from the maximum 45ma to around 5ma minimum current out.

John is C1 35 volts or higher say 50 vdc Alan

John Thank You to you and Stan for all your help. Hopefully this dummy will get it working.

Yes, 50V will work fine.  Lower than 35V is a problem as with 18 VAC in, you get a bit over 25 volts charge on the cap.  If you have 20VAC on the track, the cap charges to about 28 volts.

I didn't see this mentioned so just a FYI here, the variable resistors are available with different numbers of turns needed to adjust them through their entire range. More is better for fine adjustment. I learned about the 'one turn' pots the hard way when I ordered a few each of several ranges to experiment with. Luckily I only got a half dozen of one range with a single turn adjustment. Unfortunately it was the one I wanted the most out of the whole batch.

Not that I know much, but I have also learned most all of my train electronics from Stan and GRJ and some others here. They offer very good advice and I have learned a lot from their posts. They are also always very willing to try and help everyone with their projects, which I for one really appreciate. I try to read all their posts on the workings of the electronics and learn more with each thread or post.

I have also watched (and still enjoy watching) Bobot's videos. He seems pretty knowledgeable as well. He also does a good job of explaining things in his videos, IMO. Maybe he just made a mistake or typo in the parts list?

Using a variable resistor (aka pot, potentiometer, trimmer, trimpot, etc.) in the LM317 LED circuit, while touched on in various threads, could use some additional discussion in my opinion.

So here's a side-by-side of the GRJ's module (available from forum sponsor Hennings Trains) with a mock-up of a DIY version including the trimpot to adjust LED brightness.  It looks like the reference design shows a picture of an 18" LED strip.  So if your car isn't 18" long - like a caboose which might only need a 6" LED strip - you'll probably want to change the resistor value or use a trimpot to set the brightness.

In this hypothetical example (driving an 18" strip vs. a 6" strip), if you don't change the resistor value, the current "pushed" into the strip remains constant so each LED will be 3 times brighter.  LED brightness is exactly proportional to LED current.  So 1/3 the number of LEDs means each LED is driven with 3 times the current.  Since you are illuminating a smaller space in a caboose (or whatever) than a long passenger car, you probably want to reduce the overall current....hence either change the resistor or use a trimpot.

The 3362 is a very popular family of trimpots manufactured by a variety of vendors.  The pins on this part drop right in to a 0.1" grid prototype board.  If you choose to follow GRJ's schematic which uses a 200 ohm trimpot (vs. the 5k or 5000 ohm trimpot in the reference design), that would be DigiKey 3362P-201LF-ND

To be clear, I absolutely recommend GRJ's lighting board as the fastest and easiest way to convert your cars to LED.  But if messing with electronic components and learning about circuits makes the hobby rewarding/enjoyable for you then this is a great DIY project.

I absolutely recommend DigiKey and have used them for almost 40 years!  But if you're on a tight budget and are willing to wait for parts and deal with occasional hassles associated with getting parts from Asia via eBay or the like, you can get each component of the reference parts list for about 1/3rd the price...and maybe 1/10th the price of Radio Shack.

So in this example photo there is a resistor and a. trimmer pot. What I read was this "....hence either change the resistor or use a trimpot". The key word was  "or" If I use a trimmer pot can I just not use the resistor because the strip of LEDS have a resistor for every three LEDS?

Or does at least 1 resistor need to be there before it gets to the LEDS.          I think I get that I can adjust the brightness by adding additional resistors or use a trimmer pot. Right?

That's an astute observation that the LED strip itself has a resistor per 2" section...that is, why doesn't that "count" as a resistor?  Unfortunately it gets a bit messy to explain why it doesn't count. 

See if this makes sense.  The LED circuit you have chosen is a current-regulator; it is designed to deliver some fixed level of current (set by the resistor or trimpot).  What this means is it will apply whatever voltage it takes to push the programmed level of current into the LED strip.  Now here's the rub.  The LED strips are commonly used in automotive applications or accent lighting where you have a 12V DC voltage source; in fact these strips are typically called 12V LED strips.  The resistors on the strips are used as a low-cost method to regulate the current into the LEDs when driven from a 12V supply.  But wait!  If you drive the strips with a current-regulator, the current-regulator will overwhelm the resistors on the LED strip making them ineffective.

So back to the circuit at hand.  To clarify, I should have said use either

(1) a fixed resistor if you know what current/brightness you want

"or"

(2) a fixed resistor plus a trimpot if want adjustability

A fixed resistor costs about 3 cents at DigiKey or 1 cent on eBay.  A 3362 type trimpot of 200 ohms runs about 75 cents on DigiKey or about 25 cents on eBay.  In fact on eBay the trimpot is probably the most expensive individual component (more than the bridge, more than the LM317, more than the 35V capacitor, etc.).

So answering your question yet another way, even if using a trimpot the fixed-resistor limits the maximum current you force into the LED strip...because the fixed-resistor(s) on strip itself do not perform that limiting function in the presence of a current-regulator.  Sorry for the techno-nerdy answer and maybe there is an easier way to state it. 

But bottom line is if using a trimpot, the cost of that fixed resistor (albeit a couple extra solder joints) is negligible.

FWIW, the component values on my board were somewhat of a compromise.  I had to decide what would be the best range of current adjustment for typical passenger cars.  Most passenger cars are in the 12-21 inch range.  With that in mind, I went for the best compromise (IMO of course) of brightness vs. car length.  For 18" passenger cars, I personally use from 20-30ma of current to light all the LED's for the lighting level I like.  Some like them brighter, and some like them dimmer. 

If I find the lowest limit of current is still to bright on a 12" passenger car, for instance, I just add a resistor to the end of the LED strip to soak up some current.  Usually something in the range of around 470 to 1,000 ohms does the job nicely, and it's dirt simple to just solder it to the end of the LED strip.

My thinking was that I had purchased a set of 4 heavyweight passenger cars and the had some lighting issues(using standard lighting). So my thinking was that I would fix the lighting issues by replacing the conventional bulbs with LED's and by doing this I will use less current to light them. I watched Bobot's trains video and without understanding the technology I could duplicate what he did. Seemed simple enough right? Well he had posted all the parts you need with a drawing of the circuit. Low and behold he had the wrong Cap listed and I didn't know any better to double check his parts list and to be honest with you I probably wouldn't realize that something was amiss. I guess in short I figured that if I could duplicate a successful project I could learn my basic electronics as I  watch my passenger cars go around the layout. 

Well, you have most of the components, you just need some better caps.

Understood.  But I guess I wasn't clear on my question. I was asking about your thinking on the brightness issue or whether you need to also order additional (different value) resistors and/or trimpots.  I don't think DigiKey has a minimum order but the shipping charges can add up if you order one component today, another tomorrow, and another the next day, etc..  That is, I was trying to organize the procurement phase down to one more order to DigiKey to carry on.

Also, you mention 4 heavyweights. Did you order 50 caps for other lighting projects?  If you care to share what those are perhaps we can suggest some other components to get.  One thing I've learned about LED lighting conversions is that one-size does NOT fit all!  There are so many different types of cars, with different bulbs, operated in different environments (conventional, command, AC, DC, etc.), additional lighting needs such as marker lamps, and so on.

A cheaper alternative, one that I use, is the Chinese AC-to-DC buck converters.  After building about a dozen power supplies, I discovered them on line.  Output voltage is adjustable.

Do note that some schematics limit output voltage and others limit output current.

Sorry misunderstood question. I started with wanting to convert the heavyweights to LED because the conventional bulbs were not bright enough to illuminate the whole car, because they have green tinted windows. Also these care are sleeper cars so there is a divider between the compartments and a hall that goes the entire length of the car and the hall would get no light. I thought if this works I could apply this to other cars I have 4 MTH and 3 other Lionel passenger cars as well. All with conventional lighting. Even better I thought, Why not convert My Cabooses and any other cars to LED. So I ordered 25 of all that was on that list except the CAPS. It was actually cheaper (price total) for 50 instead of 25) so I ordered 50. I had no idea one size doesn't fit all. I was just thinking I would either put in 3LEDs, 6LEDs, or how ever many I thought I would need or would fit into the car. Sorry for the long winded explanation.

I find in most passenger cars that the strip of LEDs for the entire length of the car gives the best and most even illumination.

If you want bright and assuming you run command,you may want to consider this circuit. With this method you can circuit the strip LEDs in multiples of 6, so 6,12,or 18 LEDs etc. believe me these would be plenty bright if that is your complaint. They can be dimmed if desired as shown in the link with a resistor.

LINK

Dale H

Are you running conventional control or command control (or both)?  Usually with traditional incandescent bulbs the cars are too bright at command control voltage (18V AC) is too bright.  So when you say bulbs are not bright enough this makes me wonder if you're operating conventional control - this would be a potential game-changer?

Upon clarification of the variety of cars you're working on, I think it wise to consider the trimpot option for at least some of the cars.  Or order a range of fixed-resistor values to have in addition to the 47 ohms... like 22, 33, 68, 100, 150, 200.

As for the sleeping cars with separate walled-off compartments as well as a hallway, I assume it's understood you can cut multiples of 3 LEDs (2" sections) and splice them together.  So with one electronic module, 2 wires would run to say a long hallway strip, then 2 wires would run from the end of that strip to a short strip in one sleeping compartment, then 2 wires from the end of that strip to the next short strip in another sleeping compartment, and so on.  To add to the confusion there are so-called double-density LED strips where each section of 3 LEDs is on a 1" length (2.5cm) rather than a 2" length (5cm).  A 1" strip might be easier to mount to the ceiling of individual walled compartments rather than folding or bending a 2" longer strip.  Yet another option for a lavatory or small room is to use individual LEDs with the 2 wires extended from their solder pads on the strip. 

Low-power, low-heat, inexpensive, compact LEDs allow better and more realistic lighting in passenger cars.  Again, one size does NOT fit all!  It comes down to how much time, money, effort one wants to put into it.  Good eyesight and soldering skills are a big plus!

So if I did use say a 2" strip (3 LEDs with resistor)and then wire another 2" strip. I would wire it as if it was still connected to the one I cut it from, just connected with wire. + to + and - to -.Parallel?

Dear mknight1957

I did something similar earlier this year here is the link. I did an observer car with a similar problem with dividers.  If you look at the rest of the link for "Replacing Incandescent with LED in Passenger Car" might answer some of your question.

Correct.  I found this old photo from a previous thread showing various ways to hook up "loose" 3-LED sections.  This was a different application but for purposes of this discussion the vertical 2-wires +/- on the left represents the current-regulator output.

Exactly, so with a trimmer pot in the circuit we would adjust all from the same pot at the same time.

RJR, Do you have a link to some that you would recommend?

In this post,I describe buck converters to drive things. They will work with LEDs as well. 

LINK

Here is one of many Chinese vendors

LINK2

Dale H

The cheapest alternative is to simply roll your own circuit using a few components.  I posted the diagram, and there have been a number of folks that have packaged the components in unique ways and posted pictures in the forum.  Remember, if you use the AC-DC buck converter, they're not nearly as small as you can package the components.  The module below is 2" long, about 7/8" wide, and almost 1" tall.  Keep that in mind when you're trying to plan any installations.  That's one reason I tried to keep my lighting module a bit smaller.

Absolutely. WE need to be able to fit it into what ever we are trying to light.

These are nice modules, and I've used a number of them, but they are not the smallest solution to the problem.  In many ways, they're overkill for just lighting a passenger car, this module will deliver in excess of an amp of current, far more than is required for lighting a strip of LED's. 

If this is a race-to-the-bottom, I just patched together the following - direct eBay links can be deleted by OGR so this is just a fleeting example of less than $1 per module for raw parts.

I didn't try very hard so I'm sure you can shave a few more pennies per module.

This includes the trimpot for brightness adjustment.  I also included 0.1" grid prototyping board to mount components.  A board of about 3/4" x 1-1/2" ought to do the trick or about 2cm x 4cm (8 sq. cm per module) - hence the choice of board quantity and size.

Obviously there are other costs - wire, solder, mounting screws, maybe heat-shrink for insulation, and so on.  And suitable assembly tools. Also, I think a basic multi-meter is useful - even if it be the Harbor Freight free-with-coupon.