LED Headlight replacement for postwar Lionel locomotives

Stan, I didn't think of the 317, an interesting point.  You could also "tune" the current if desired. 

The 0805 resistors are actually cheaper at Digikey, and if you're already buying parts there, shipping is free.

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A 47uf tantalum cap jumps the parts price way up, the 100uf was over $9/ea, so I dropped to 47uf, still pretty pricey!  Given this cost, I don't think they're practical for anyone except the "cost no object" folks.

• (1)  2.62000
• (10)  2.12100
• (25)  1.92800
• (50)  1.85100

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So, I looked at the LM317 SOT223-4, it turned out it's a bit larger in actual footprint.  However, by shrinking the connection points I was able to actually shrink the board a tiny bit.  I even knocked a couple cents of the PCB blank.

Those caps really do run up the price! That's more than I was expecting, quite a bit more too.

Tantalum caps are pretty spendy when you get up into the higher voltages and capacities.  They're OK for lower voltages and capacitance, and they are smaller than the aluminum caps.

When your DRC finds the floating bridge AC input...while the schematic editor is open, here's another cheap shot from the peanut gallery

If you add another R, and a single pad J, the board can support voltage-output mode.  With some re-arrangement board stays same size or a mind-boggling 33 cents!  Then a single pad K provides a raw rectified DC output sort of like "PV" on MTH boards.  New J and K holes might fit between the bridge legs.  All this assuming plated holes don't add cost.

For cost-no-object folks that absolutely need lower tantalum profile, do C1 pads support the common footprint?  Not worth hassle to make custom footprint but if rules allow pads on pads maybe something as shown.

For anybody I get PCB's from, I've never been charged by the hole, only for odd routing shapes, slots, or gold plated connector fingers.

I'm curious about the ears you added to the capacitor pads, why couldn't you solder the tantalum cap to the existing pads?  Are you trying to parallel two tantalum caps of lower value?  That might reduce the cost of higher capacitance.

When your DRC finds the floating bridge AC input...

Oops, rushed that one into production.   Interestingly enough, the DRC didn't pick that up!

Here's Stan's recommend upgrades.  A little jiggering to make that all happen, had to move things around.

GRJ thank you for your efforts designing these circuits and board layouts. I am going to order a few boards and sets of parts for the first design. Since I will be ordering from Digikey would you (or anyone) happen to know a pn for warm white 3mm led suitable for loco headlight? Bright would be good as long as I don't over load the CV board.

Any last minute changes I should know about?

Richard

Since you'll be waiting for boards from OSH Park several weeks, I'd recommend eBay for the LED's.  eBay: 191903315320, 99 cents for twenty warm white 3mm LED's.

gunrunnerjohn posted:

 

...I'm curious about the ears you added to the capacitor pads, why couldn't you solder the tantalum cap to the existing pads?  Are you trying to parallel two tantalum caps of lower value?  That might reduce the cost of higher capacitance...

.

Oops, I missed your question.  I didn't look up the SMD tantalum examples you found but the idea being that some tantalums have wider pads relative to the electrolytic as illustrated above.  And, yes, to your point that having wider pads would/could allow paralleling 2 low profile tantalum caps if cost and availability conspire to make an advantage.

Well, the wider pads on the cap aren't an issue, they'd work fine anyway.  However, I thought maybe you were going for a parallel configuration.  Not a bad idea, but it turns out if you're going tantalum already, it's a pretty linear relationship between capacitance and cost, so not much savings to be had doubling them up.  Looks like the tantalum crowd can just solder to the existing pads for the aluminum electrolytic, the pads are plenty to secure the capacitor.

Thanks John....I will add the Leds to my order. Are you going to put your board on OSH Park or should I upload your zipped file and order that way? Am I correct if you decide to upload it will be in "Shared Projects?"

Richard

Here's the latest design, it should be slightly cheaper and has more flexibility.  You can simply upload the attached gerber files to OSH Park. 

Single LED REG2 Gerber.ZIP

Ok John....I will upload to OSH Park the "latest version 2" zip file. Things got a little fuzzy as you were changing the version 2 design. Would you list the correct parts  please. e bay leds already on the way.

Richard

So we're all on the same page, I believe this is a DIY situation?  GRJ  has gone above and beyond the call with the PCB design and presumably no one is under the impression that assembled-tested boards are in the works. 

Anyway, for anyone ordering DigiKey resistors I'd suggest using R1=82 ohms which sets the current to about 15 mA (rather than 20 mA as would be using R1=62 ohms).  This is for heat management as the flicker-tolerant version with the large capacitor dissipates more power than the Evans design all things being equal.  Resistors at DigiKey are only 19 cents for a strip of 10, so why not stock up on values for 5 mA, 10 mA, 15 mA, 20 mA.  240 ohms, 120 ohms, 82 ohms, 62 ohms respectively are common values.  LED brightness is exactly proportional to current.

Presumably these are used to replace omni-directional incandescent bulbs so for headlights in particular the directional output of LEDs will more than make up for driving the LED at 15 mA rather than 20 mA. 

stan2004 if the above post is directed to me I do not understand a word of your post. Am I missing something?

Richard

Believe me Stan, the LED headlights are a LOT brighter than the bulbs that are consuming 3-4 times as much power.  I rarely drive LED's at a full 20ma, I choose to run them somewere in the 15ma range, they probably last longer there and I have a margin of error on any calculations.

Yes, this is a DIY all the way, I'm not doing anything about ordering parts for this one.

Most of the parts are the same, here's the Digikey List for the fixed parts.  The resistors are all 0805 footprint resistors, you have to select the value you want, depending on the current.

• 493-2203-1-ND   CAP ALUM 100UF 20% 35V SMD: (1) .38, (25) .22
• MDB10SFSCT-ND   IC BRIDGE DIODE 1000V 4-MICRODIP: (1) .40, (25) .32
• 587-2036-1-ND   FIXED IND 22UH 255MA 490 MOHM: (1) .13, (25) .11
• 296-12602-1-ND   IC REG LINEAR ADJ 1.5A SOT223-4
• Digikey search for Stan's List of selected resistor values

 That's all you should need, adding the PCB from OSH Park of course.

No, not directed at you. 

I guess my comments are premature - just enthused that the board will soon be available to all for a whopping 35 cents. I'm planning to recommend it to DIY enthusiasts as GRJ graciously accommodated some of my ideas which would make this useful for more than LED headlights in on-board applications!  

John.......You know what. I like the 1st circuit for my simple application. a simple replacement for a 18v bulb on a classic Hudson. All I want is a CV module for a bright LED. I will report back on how it works out. With lead time for parts it might take a couple weeks.

Richard

Rppoind posted:

John.......You know what. I like the 1st circuit for my simple application. a simple replacement for a 18v bulb on a classic Hudson. All I want is a CV module for a bright LED. I will report back on how it works out. With lead time for parts it might take a couple weeks.

Perfect.  Then we've got both bases covered! 

I've got the 2nd circuit on order in both 0.8mm (1/32") and 1.6mm (1/16") board thickness. 

And, no kidding...the boards are indeed 35 cents each and that includes shipping. 

Stan2004. I have ordered from OSH Park before. Very economical. I hope your version does the job for you. As I posted I just need a CV board for a single bright led.

Richard

I love those guys for really small boards, the price really runs up with larger boards.  In larger quantities like 200 or so, I can get boards for about 60 cents a sq/in, OSH Park gets $2 sq/in for larger orders.

John....they have found a neat niche market for guys that like this stuff. I will place a small order for your accessory actuator tomorrow. my layout is about 6 or so months off so my needs are small at this time. I am primarily an RC modeler in large giant scale aerobatic and 3 D flying models but at 71 years old  the trains are looking better and better. I am a PW Lionel collector TCA since 81 and plan is to start operating a bit with LTI and newer Lionel customized to my liking. You have been an inspiration to me no kidding. 

Richard

Thanks Richard, these projects keep me out of the bars.

But not from partaking, I hope.

I plead the 5th.   I leave it for you to decide which 5th I'm referring to.

stan2004 posted:

Rppoind posted:

John.......You know what. I like the 1st circuit for my simple application. a simple replacement for a 18v bulb on a classic Hudson. All I want is a CV module for a bright LED. I will report back on how it works out. With lead time for parts it might take a couple weeks.

Perfect.  Then we've got both bases covered! 

I've got the 2nd circuit on order in both 0.8mm (1/32") and 1.6mm (1/16") board thickness. 

And, no kidding...the boards are indeed 35 cents each and that includes shipping. 

Dumb question, why two thicknesses? What is gained/lost by ordering the different thicknesses?

If you just happened to know someone (possibly a forum acquaintance that asks a lot of questions) that had never ordered a PCB before, what thickness would you imagine them ordering?? 

gunrunnerjohn posted:

I love those guys for really small boards, the price really runs up with larger boards.  In larger quantities like 200 or so, I can get boards for about 60 cents a sq/in, OSH Park gets $2 sq/in for larger orders.

Funny how they do the small ones so inexpensively and then they go up so much for larger sizes. I'm sure they know what they are doing, but the pricing structure just seems kind of odd. I would kind of expect it to be the other way around? But, I am not complaining by any means and sure hope they keep it up this way. 

I order most of the stuff I do in the .031" board stock.  Why make the board any thicker than it needs to be?  I'm always trying to squeeze a little space out of a design.  The Super-Chuffer is still the .062" stock, that's just because I didn't think of it when I ran the first batch.  Since it would cost me several hundred dollars to change the tooling, I just left it alone.  The most recent insulated track signal driver is also .062, in that case I figured that there was no space constraints, and the thicker board is a bit more robust.  Everything else is done on the .031" board stock.

rtr12 posted:

Funny how they do the small ones so inexpensively and then they go up so much for larger sizes. I'm sure they know what they are doing, but the pricing structure just seems kind of odd. I would kind of expect it to be the other way around? But, I am not complaining by any means and sure hope they keep it up this way. 

The pricing isn't odd at all really.  They charge $5 sq/in for three copies of the board.  The latest version of the lighting board is .28" x .725", or .203 sq/in.  So, that board is just over $1 for three or 35 cents each.  They detect a "slightly" larger board, I guess whatever tolerance the Gerber files have.

Detected 2 layer board of 0.73x0.29 inches (18.59x7.29mm). $1.05 for three.

That computes to $1.0585 for three, so they're even giving me a penny break.

gunrunnerjohn posted:

I order most of the stuff I do in the .031" board stock.  Why make the board any thicker than it needs to be?  I'm always trying to squeeze a little space out of a design.  The Super-Chuffer is still the .062" stock, that's just because I didn't think of it when I ran the first batch.  Since it would cost me several hundred dollars to change the tooling, I just left it alone.  The most recent insulated track signal driver is also .062, in that case I figured that there was no space constraints, and the thicker board is a bit more robust.  Everything else is done on the .031" board stock.

I guess some of this will become more clear to me in a few days.   I agree with not making anything thicker than needed and the extra thickness providing more ruggedness. I also can see the tooling fees and not wanting to change there. That is really a lot just for changing board thickness!! Is that a one time fee that you can have additional runs made without having to pay another fee? I would surely hope it includes multiple runs.

Anyway, I am still curious as to what Stan is up to with the two thicknesses? I know he must have something good up his sleeve here. And OSH Park sure makes this affordable, that is a real bargain.

gunrunnerjohn posted:

rtr12 posted:

Funny how they do the small ones so inexpensively and then they go up so much for larger sizes. I'm sure they know what they are doing, but the pricing structure just seems kind of odd. I would kind of expect it to be the other way around? But, I am not complaining by any means and sure hope they keep it up this way. 

The pricing isn't odd at all really.  They charge $5 sq/in for three copies of the board.  The latest version of the lighting board is .28" x .725", or .203 sq/in.  So, that board is just over $1 for three or 35 cents each.  They detect a "slightly" larger board, I guess whatever tolerance the Gerber files have.

Detected 2 layer board of 0.73x0.29 inches (18.59x7.29mm). $1.05 for three.

That computes to $1.0585 for three, so they're even giving me a penny break.

Ok, I've got it now. It really is more for the smaller quantities at $5 sq/in. and the price does go down for more quantity of larger boards. It's just more than other places. That does make sense. I remember reading your post earlier about how OSH Park does the small quantities so cheaply. Still, anything these days that's 3 for $1 is a real deal!

Thanks for the explanations here, interesting stuff!

Most PCB assembly tooling charges are a one-time charge, additional runs of the same board layout don't incur the extra charges.  Since the Super-Chuffer is a two-sided board with components on both sides, changing the thickness was a problem.  I did change the lighting regulator to the thinner stock after the first run, but being a board with components on one side only, that didn't throw them. 

When you have assembly of board done, you pay a setup fee of typically $5-8 a part for each run, that is for setting up the parts magazines, reels, etc.  Then there's a per board fee for running them, usually between 5 and 10 cents a connection.

rtr12 posted:

Dumb question, why two thicknesses? What is gained/lost by ordering the different thicknesses?

If you just happened to know someone (possibly a forum acquaintance that asks a lot of questions) that had never ordered a PCB before, what thickness would you imagine them ordering?? 

Absolutely nothing nefarious about my choice to order different thickness.  It pops up on the OSH Park order page as a no-cost adder/option so since I was already splurging for $1.05 why not double-down!

For someone ordering a board first-time I suspect they would order the 1/16" thickness since that appears to be the default on the OSH site.

But for manually-building a few tiny boards for trains I'd think the goal would be as small as possible so 1/32".  For more demanding applications such as a RF/hi-frequency or multi-layer circuit there can be electrical design considerations with using 1/32" vs. 1/16" boards (noting that OSH Park doubles the copper thickness on the thinner board).  But for the low-power, low-frequency applications being discussed here the 1/32" boards seems the way to go.

As GRJ points out there can be logistics/manufacturing issues if changing horses mid-stream.  OSH Park also charges the same which other board houses might not do for these small "hobby" jobs.  The two thicknesses are obviously built separately so I suspect the boards might even come separately.  I already got a message saying one went to production so presumably the other is waiting on a few more orders of that thickness to fill up the panel.

I am extremely pleased with the responses to and the ultimate outcome of my request for assistance. I had no idea that such a request would generate so much thought or that it would result in the product so generously offered by GRJ and Stan.

Thank you very much, swede  

stan2004 posted:

But for manually-building a few tiny boards for trains I'd think the goal would be as small as possible so 1/32".  For more demanding applications such as a RF/hi-frequency or multi-layer circuit there can be electrical design considerations with using 1/32" vs. 1/16" boards (noting that OSH Park doubles the copper thickness on the thinner board). 

One of the nice things about the .031" boards is the doubling up of the copper thickness.  For stuff like my YLB (TMCC battery), it was nice to have twice the copper as some of the currents are peaking at 1/2 amp.  I could run narrower traces and still have the current carrying capability and the thinner board.  It was a win-win all around.

swede, I hope we didn't drive you nuts with all the back and forth.

And I second that to John and Stan this is a nice addition to my current project very much appreciated.

I also own Stan an apology. I have reread and now do understand what he was posting about design 2. I have ordered the version 2 boards and parts today.  

Richard

Rppoind posted:

...I also own Stan an apology. I have reread and now do understand what he was posting about design 2...

Not sure what you're apologizing for! 

The 2nd circuit is more of a kitchen-sink approach to allow the circuit to do more.  For the headlight application the 1st circuit works fine.  In the event the fixed 20 mA current turns ought to be too bright for whatever LED you have, obviously there are physical remedies to dim/mask the output.  Or if you want to do so electronically you can put a 2-cent 330-ohm 0805-size resistor across the LED which will cut the LED current in half (to about 10 mA).

Actually, I'm the one that should be apologizing to GRJ for badgering him with creeping features; but I think he's used to it.   I see the 2nd circuit as a DIY windfall for a wide variety of train circuits including a headlight but so much more!   I plan to show how they can simplify life for the "how do I ..." applications which regularly arise.

I think the second circuit was just Stan getting me to do the heavy lifting and designing his circuit board.

Don't worry, I'll get even with him.

gunrunnerjohn posted:

Most PCB assembly tooling charges are a one-time charge, additional runs of the same board layout don't incur the extra charges.  Since the Super-Chuffer is a two-sided board with components on both sides, changing the thickness was a problem.  I did change the lighting regulator to the thinner stock after the first run, but being a board with components on one side only, that didn't throw them. 

When you have assembly of board done, you pay a setup fee of typically $5-8 a part for each run, that is for setting up the parts magazines, reels, etc.  Then there's a per board fee for running them, usually between 5 and 10 cents a connection.

Well that is good the tooling is a one time deal. The rest makes sense too, so the more you have made the less cost per unit as the setup of the reels, etc. are spread out over more units. More interesting stuff and thanks again for explaining!

stan2004 posted:

rtr12 posted:

Dumb question, why two thicknesses? What is gained/lost by ordering the different thicknesses?

If you just happened to know someone (possibly a forum acquaintance that asks a lot of questions) that had never ordered a PCB before, what thickness would you imagine them ordering?? 

Absolutely nothing nefarious about my choice to order different thickness.  It pops up on the OSH Park order page as a no-cost adder/option so since I was already splurging for $1.05 why not double-down!

For someone ordering a board first-time I suspect they would order the 1/16" thickness since that appears to be the default on the OSH site.

But for manually-building a few tiny boards for trains I'd think the goal would be as small as possible so 1/32".  For more demanding applications such as a RF/hi-frequency or multi-layer circuit there can be electrical design considerations with using 1/32" vs. 1/16" boards (noting that OSH Park doubles the copper thickness on the thinner board).  But for the low-power, low-frequency applications being discussed here the 1/32" boards seems the way to go.

As GRJ points out there can be logistics/manufacturing issues if changing horses mid-stream.  OSH Park also charges the same which other board houses might not do for these small "hobby" jobs.  The two thicknesses are obviously built separately so I suspect the boards might even come separately.  I already got a message saying one went to production so presumably the other is waiting on a few more orders of that thickness to fill up the panel.

More interesting stuff!! I think I will follow your lead and order 3 of each investing an entire $2.10. Then I will have both to compare for myself, although I probably won'e be able to tell the difference? But who knows? Interesting that they double the copper thickness on the thinner boards. Seems like it should be the other way around, thicker boards, thicker copper?? Of course I am surely missing something due to lack of know how.

It's really nice of you and GRJ to take the time to explain all this stuff to us (me especially ) and I think a lot of folks here really appreciate the time you both spend educating us. I know I do, and each time a little more sticks. So a BIG thanks to you both. And I really enjoy following your team efforts in threads like this.

P.S. Please don't tell GRJ I said this, but I think deep down he really likes your creeping features, however I am pretty sure he won't ever tell you that here. 

GRJ, you and Stan did not drive me nuts with the back and forth. I did wonder how far you two would take the design, however. Now I know and I hope Stan offers some suggestions as to where this circuitry would really shine. I don't want to wait two years before I learn I have a real need.  

While the discussions were going on, I assembled a LED circuit using just a 1A 50V bridge rectifier, 470 ohm 1/4 W resistor and a 1.8mm LED that were all on hand.  With a little bending I was able to cram it into the space between the smoke unit and armature housing, snake the LED around the smoke chamber and get it into the hole for the lamp lens. Although it must have a constant flicker, I don't see it. When placing my immediate parts order for the "miniature" sized components, you have helped me select, I don't plan to include capacitors. I do plan to build a few of the 2nd design for fun and for use when I learn where I need them.

Again, thank you.

swede