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Thread: Playing around with DCC powered things.

  1. #21
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    Ah good questions.

    First, it will run off 5-15v AC or DC. So yes, some kind of wall wart would be fine for a fixed blinker.

    The board is “expensive” for a fixed application due to the super capacitor. It’s job is to deal with dirty track, plastic frogs, etc. it’s not necessary for a wall powered application. It would be easy to make one without it though.

    As for multiple LEDs, yes, it could drive more than one. The problem here is I’ve built the resistor into the board to make it easier for a FRED. That would need to be removed for multiple LEDs so correct external ones could be added. So probably not good for multiple LEDs.

    There’s no reason I couldn’t make a larger board suitable to drive multiple LEDs with small variable resistors so the user could adjust the flash rate and even dual outputs for like a crossing signal pair of lights. But my thinking is various other folks fill that niche. Just plug is a great structure system. Circutron makes a number of cool little boards.

    I just wanted a bettter FRED. The firefly one is quit good and fairly priced. There are a couple of other options that are ok, if you like bending wipers and adjusting trucks. I thought if I could make a better board and use Kato caboose trucks to get needle point pickup it would be a better solution for me, and maybe I can hook up a few people on here along the way.
    --
    Leo Bicknell

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  3. #22
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    Quote Originally Posted by bicknell View Post
    Got some more time to play with this today, and man am I impressed with the state of the world.
    Me too, mate, me too... cheap prices for high quality parts for everyone to order.

    Quote Originally Posted by bicknell View Post
    I've been recommended to try jlcpcb, macrofab, and pcb:ng to make the boards. I wanted to try jlcpcb as they can do the thinner 0.4mm boards. But jlcpcb says their SMT assembly is not available right now. So I went on to PCBNG and gave that try.
    I don't know where Macrofab or PCB:NG are located, but if they depend on China like JLCPCB, be prepared for some wait time there as well. The new Corona virus basically shut everything down, and because many companies were on holiday when it hit, it took them some time to update their production schedules and a lot still is unclear.

    Good luck,
    Heiko

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    @bicknell - is it just me, or is the LED polarity backwards on your circuit diagram?
    Tim Rumph
    Modeling the Southern Railway in N-Scale

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    PGB:NG is supposedly 100% in Brooklyn, NY. So they seem to be fine.

    I uploaded the design to Macrofab who didn't have any warnings about delays right now. But their price was approximately 50% higher for both the small and large quantity boards. My friend tells me he always tries all three because the pricing is sometimes a bit "random".

    JLCPCB won't even give me a quote right now, as they state their production is in China and they are just trying to get out things that were already ordered.

    My guess is I'll get the prototype 6 from PCB:NG, run them on the layout, make sure the board is all good. And if that checks out see if by that time I can go to JLCPCB and get their thinner board for a "production" run. That is assuming folks want to buy some.
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    Quote Originally Posted by Tim R View Post
    @bicknell - is it just me, or is the LED polarity backwards on your circuit diagram?
    Good eye, and it's worse than that. It's all wrong! Ha, that was my first draft of turning the bread board into a schematic, and I wasn't too careful.

    The timer goes high for 0.83 seconds then low for 0.13 seconds. We want to light the LED on the low, so it's actually connected between +3.3v and the timer output. I drew it the other way, between GND and the timer output, which would get the durations backwards. And the LED was backwards for that!

    I had to move to KiCad to design the boards, so here's the current schematic in KiCAD:



    Track obviously goes in TRK-A and TRK-B, polarity doesn't matter. The FRED is connected to the 3.3v and the FRED-. After digging around to find smaller, cheaper components I swapped out the regulator for a LP2985 and the 555 for a TLC555CDR. Caps and resistors are all the same I think.

    Here's a 3D render of the finished board:



    --
    Leo Bicknell

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  9. #26
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    Please correct me if I'm wrong, but C1 would also filter out most of DCC signal, right, to keep it out of the 555? Not that the 555, being analog, would care that much. ...

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    My parts arrived, and there were some non-surprises and some surprises!


    First I swapped the TTL 555 for the CMOS 555 and tested the circuit. No issues there.

    Then I swapped for the 3.3v regulator and test that. No issues there.

    Then I swapped the super cap for the chip cap I bought to test. No issues there.

    Then I went to mount the LED to a small board that will let me plug it into my bread board, and.....

    It's small.

    Like really small.

    Like really, really, really, really small.

    I picked it because it was 1ma. I liked it was small. But the amount of small didn't register. As a reminder it is 1mm x 0.6mm. To put that in context, the whole part is smaller than one of the pads for the IC in the lower left with 8 legs!

    I honestly wasn't sure I could solder it. I lost the first one to my table. Who knows where it went. So small, so small. But attempt #2 was successful. I soldered it to my little prototyping board and put it in the circuit. Success!

    So I did a rundown test. I let it run with power for 5 minutes making sure the super-capacitor was fully charged. Then cut power and started a timer. 1:52 seconds later it was dim enough it was no longer useful, and right about the 2 minute mark it stopped blinking completely. Wow. That's longer than I expected!

    It was so long I went and found the largest tantalum capacitor I could find in a surface mount package. 680uF. I have a 680uF electrolytic here, so I tried that. Hold up time was 6 seconds. It would work for dirty track, but wouldn't provide any significant runtime. And, the tantalum 680 is more expensive than the 11mF supercapacitor!

    So, here's where I am at:

    Design looks good, everything works, run time with the super-capacitor is phenomenal.

    The light I was going to use for the FRED is a a scale 4", which is great if you want to be realistic, and not so great if you want to solder it. I suspect 99% of the people would have no interest in trying to solder wires to it, and would want something better. Plus N scale couplers are oversized, so do we really need scale?

    Where my mind is right now is to go down two paths:

    1 - find a bigger LED, it will probably be 2 or 5ma, that is easier to solder magnet wire to. Make an oversized FRED with 3-D printing like I was going to do that "matches" the amount of oversize of an N scale coupler.

    2 - Make a "circuit board" that is just the LED with a copper pad on each end. Have them made by someone that can pick and place with a robot. I'm not sure any of my board fabs can do a part that small though. But then use a dremel to sand the board down even with the left and right edges and as tall as a real life FRED. Solder magnet wires to the board, and paint. The board material is 10 scale inches thick (for the 1.6mm), and the back could be shaved. I can almost get a 100% scale FRED this way, and then just paint the whole thing yellow. Put it on a z-scale coupler, and wow, it would look pretty amazing. But is it worth the trouble?
    --
    Leo Bicknell

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  12. #28
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    Quote Originally Posted by Paul Schmidt View Post
    Please correct me if I'm wrong, but C1 would also filter out most of DCC signal, right, to keep it out of the 555? Not that the 555, being analog, would care that much. ...
    The DCC signal is already gone after the power has been through the bridge rectifier (which I made with 4 discrete diodes here). There's only DC power coming into C1, possibly not 100% constantly due to the alternating arrangement.

    But you are correct that C1 would be described as an input filter capacitor. It's job is to soak up some electrons when the power is there, and give them back when it momentarily isn't so the linear regulator sees a closer to constant voltage. Pretty much all regulators have a minimum capacitance on input and output to meet their specs for +- on the output voltage.

    Here C3, the SuperCap, does the job on output. If we weren't trying to hold up the circuit, it would just be a copy of C1, a small little filter on output.
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    Leo Bicknell

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    LEDs were sized... 0402 and 0603
    I recall 0402 was hard to solder
    and that 0603 was a lot easier

    with the smaller 0402 I had the solder wet the LED to the iron... ick.
    I made a wire 'clamp' or finger thing to hold the LED down
    a brass brick of about 1/2 inch sq 1/8 inch thick with a copper wire to hold the LED down

    the tiny LEDs are a special pain

    victor

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    Quote Originally Posted by victor miranda View Post
    the tiny LEDs are a special pain
    You can say that again!

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    So try this on for size:





    The idea being that the purchaser would cut the board along the white line. One part is the circuit as I showed before. If you want to use your own LED go right ahed. Use a giant 5mm if you want! But for those who want fine scale, they could then carefully cut out the LED on the right from the part they cut off. That white box is 6 scale inches by 24 scale inches, which I think is just about right for a real life FRED. Note that there are two vias to the back side, where there are large (ish!) solder pads. The idea is the user would solder their magnet wire (probably #36 would be fine) to the back. The whole thing could then be painted yellow, minus of course the teeny lens of the FRED light. Simply glue it to the side of a coupler for a prototypical appearance.

    Total cost addition, $0.15 for the LED. The additional board, copper, vias, they are all free as the board is under the minimum charge size already.

    How many of you would be crazy to cut it out and use it?
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    Leo Bicknell

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  19. #32
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    I made a video showing the operation and size of the components. What you'll see below:

    • Initial startup. Notice a small amount of instability as the voltage comes up in the Super Capacitor. The circuit is powered off the AC outputs of my power pack, but I've left the DC throttles up so you can use the green lights on the power pack to tell if it is on or not.
    • Stable operation. We want to make sure the Super Capacitor is fully charged, so I let it run for about a minute.
    • Power removed. I turn off the power pack and watch the run down. The light slowly gets dimmer.


    https://youtu.be/Bxb5ptsfQ7U
    --
    Leo Bicknell

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  21. #33
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    Quote Originally Posted by bicknell View Post
    The idea being that the purchaser would cut the board along the white line. One part is the circuit as I showed before.
    Nice idea! If you succeed in getting 0.5mm PCBs, they can be cut with a pair of (not the lightest) scissors. Now I'm crazy enough to solder magnet wire to 0603 LEDs, so I'd probably just throw the extra away, but...

    [OT]I'm still trying to figure out a FRED to be placed on a coupler after assembling a train, for operations - maybe something with a pair of thin bronze wipers wiping on the railtops, but not getting stuck in turnouts...[/OT]

    Heiko

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    Quote Originally Posted by Heiko View Post
    I'm still trying to figure out a FRED to be placed on a coupler after assembling a train, for operations - maybe something with a pair of thin bronze wipers wiping on the railtops, but not getting stuck in turnouts...
    I think the wipers would be a big issue. If you got the same flashing LEDs the FireFly guy uses and soldered an 0402 resistor directly to the end you would have a super-compact FRED package. But the pickup is still an issue. And there's no battery that small.

    The direction I'm going is I ordered some Micro-Trains "True-Scale" couplers. I hadn't gotten any yet. My plan is to put this board in a car, mount a true-scale to the back, and mount my nearly perfectly scale sized FRED to it. I think that will make the back of the train look awesome. But we'll see how it comes out.
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    Good news: I received notice my board is in production now. I should have them back by next Monday.

    Bad news: I don't think I like the Kato Caboose trucks for what i'm doing here.

    Worse news: SBS4DCC seems to be out of stock on all of their wipers for micro-trains trucks.

    Grumble.
    --
    Leo Bicknell

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    I have an idea you may want to consider...

    https://www.nscale.net/forums/showth...wheel-version)

    I know it is thumping my own stump.
    the solution does work for darned near any truck with a plastic frame.

    I have been working on a set of bowser crown trucks for my PRR h-ish thing.
    in a soon to be posted share of my recent efforts.

    victor

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    Been a while since I updated. My board still shows "In fabrication" on the web site, well past their normal delivery times. No communication from them either about delays. Under normal circumstances I would be rather upset, but given the COVID-19 situation I'm going to assume they have experienced impacts and are struggling to cope. I'll be posting here as soon as they show up.
    --
    Leo Bicknell

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    Quote Originally Posted by bicknell View Post
    1 - find a bigger LED, it will probably be 2 or 5ma, that is easier to solder magnet wire to. Make an oversized FRED with 3-D printing like I was going to do that "matches" the amount of oversize of an N scale coupler.
    There are small LED's available with wires already attached: https://www.amazon.com/gp/product/B0...5-cd78f07a84d8

    This may be an alternative for the FRED part.
    - Gary R.

    President & CEO
    Pinnacle & Western Railroad

    Never under-do the over-kill.

    I don't always stop for trains, but when ... oh wait!, Yes I do.

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  30. #39
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    Today I got this in e-mail from them:

    "The status of this order has changed to: In manufacturing. Your boards are being assembled as we speak. Almost there!"

    I think the boards have been made, and they are off getting components installed now.
    --
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    Interesting. I got an e-mail from them today. They were confused by the super-capacitor part, because I had indicated it was polarized, but the data sheet they found did not indicate polarization. I had a different data sheet which did not say it was polarized, but clearly shows there is a "+" symbol on one end. So they are going to treat it as polarized and put that on the anode side. This is how I have it in my test circuit here, so I'm sure it will work.

    That said, I plan to flip the one in my test circuit and see if it blows up. Maybe the part isn't polarized after all, would be nice to know.

    Which means they are setting up the pick-and-place machines to build the boards. Also kudos on them for clear and fast resolution to this confusion.
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