Power/DCC Bus Taps - Does Anybody Make One Like This?

[C855B]

This is what I need to expedite bus tap wiring:



Does anybody make something like it? The dimensions on the sample may be a little off because I didn't bother to measure the screw terminal blocks I have sitting around, but they're close. The 1" x 2" board is a reasonable goal, and end cost needs to be under $2. Main bus is 12AWG while the taps need to accommodate 18 to 26AWG.

Doing this on my own through the custom PCB houses looks like around $3/ea., and that's at medium production volumes with a minimum of 75 boards. If there were someone already making such a board at commercial/retail volumes, maybe it could save a bit of cash.

[railnerd]

You can get PCBs for about $1/piece if you are willing to wait for China Post…

https://www.seeedstudio.com/fusion.html

-Dave

[John]

Take two pieces of copper / brass ..  one for each polarity, mount on a small piece of wood or other material, drill some holes, tap and put in screws .. same thing . real cheap

[mmyers]

Home made bus bars like John showed or Positaps are going to be the most economical. A positap will allow several tap wires per unit.
I don't think you can get the boards done with the mounting terminals installed for $2 each. It would take a tremendous quantity production run to get the final price down to $2.

Martin Myers

[C855B]

Oops. I apparently gave the wrong impression. I'm specifically after what I drew, using PC board screw terminal blocks. The objective is not to arrive at the cheapest way out, but the least expensive way to get to the design. @railnerd had the right idea in referring an inexpensive board house. I had based my ~$2 on "medium run" PCB quantities from oshpark.com, but this did not include the terminal blocks. I was aware of seeedstudio.com, but they require Gerber files, and I'm still looking into freeware to generate Gerbers for this simple project.

This idea isn't original. I have run across a very similar board in my MRR travels around the web, but cannot for the life of me remember how I got to it. What I do remember is it had three tap pairs and was priced around $1.80 in quantities of 10. With the Chinese board house and similar sourcing for the terminals, I think I can get near that price point.

[John]

Mike .. just curious .. but why a PC board vs any other solution ..   I suppose it would make for neat wiring.   If I was going to the trouble of doing this, I might add detection coils / logic to it as well and kill two birds with one kills

[TerryN@StDave.org]

I can't help you on the source, as I am using Positaps myself.  But I would certainly be interested in buying something like that in quantities of 100 or so.

It is a great idea, and might even be enhanced by providing multiple outlet pairs for each bus cable.

[basementcalling]

How does it work given only the black feed seems to connect to the bus?

[C855B]

...I suppose it would make for neat wiring.   If I was going to the trouble of doing this, I might add ...

Bingo. Neat wiring. I am an an absolute stickler (i.e., hopelessly anal) about wiring. Worked on too many layouts and other equipment wired without regard to maintenance or modification. Another objective is speed and ease of operation. You have to bear in mind I'm working on a very large layout, so quick and easy plus neat and obvious are priorities. As far as detection, I'm dealing with large detection blocks, with 3 or 4 feeders per block. There may be a tap run from the main bus to the detector, but then the detector has to fan out to its own tap block.

If I'm going to add anything, it'll be a socketed mini-ATO fuse protecting the taps. This isn't just for DCC, it's also for my DC buses (5V and 12V). Taps used for DCC will have a jumper wire instead of the fuse socket.

How does it work given only the black feed seems to connect to the bus?

You're not seeing the shadow of the corresponding red bus on the backside. This is a two-layer board.

[mmyers]

How about split bolt connectors? Multiple feeders and bus will fit. No need to cut the bus. Bolt could be glued to the bottom of the layout base.

Martin Myers

[PennsyPride]

Here is a link to an other idea.
https://www.adafruit.com/products/737?gclid=CM6R3v3DqNACFQoPaQod0RQNVg

[Scottl]

The Adafruit product looks ideal, one for each pole.  Can't beat a ready made solution.

[parkrrrr]

Looks like you can get a 5cm x 2.5cm 2-layer board done by dirtypcbs.com for $28 qty 50, and they say they'll make Gerbers from your Eagle files. Their "test site" at http://dangerousprototypes.com/store/pcbs might be even cheaper. (They're associated with Seeed Studio somehow, though; I'm not sure how all of that works.)

(Disclaimer: I've been looking to eventually get a smaller quantity of a slightly larger, more complicated PCB made, so this manufacturer was in my bookmarks, but I have no experience with them.)

Those, plus these terminal blocks, gets you pretty close to your $2 goal: https://www.digikey.com/product-detail/en/phoenix-contact/1935161/277-1667-ND/568614 Getting smaller blocks for your load wires might get you even closer, but since these are 12-26 you could use them in both positions.

[C855B]

Yeah, dirtypcbs.com was on my "A" list for this. They have the 5cm x 2.5 cm option, and a 5x5 option which is super-cheap, too. I was looking at those exact Phoenix terminal blocks, too!

The Adafruit thing is great... for large wires. That bus bar is spec'ed for a minimum of 20AWG. That's the conundrum for layout wiring. We need large wires to mitigate voltage drop for long runs, but local distribution is small. The world is thinking current-carrying capacity, where bus fuses also protect the branches. Connecting a 24AWG branch to a 12AWG-rated bus (20A) would give electricians everywhere the heebie-jeebies.

Still tweaking the design. The original sketch is great if the physical approach to the bus is strictly linear - a "straight through" bus - but after working on it last night I might be better served by something where both the bus in and out are on the same edge of the card. That could complicate things dimensionally because there won't be room for two tap pairs and the mounting holes in 1" (2.5cm) using 5.08mm pitch terminal blocks.

I need to keep it skinny because it's looking like there will be 4 buses - track DCC, accessories DCC, 12VDC, 5VDC. Not all distribution points will need all buses to fan-out, but there are enough that will have all four on the same local electronics panel.

[peteski]

What will you need 5VDC for all over the layout? Instead of running it all over the layout why not provide 5VDC only where needed from 12VDC by using a simple 3-terminal voltage regulator (like 7805)?

The other thing I'm puzzled about is what hi-amperage boosters will feed your monster DCC bus?  I'm worried about the ability to trip the short circuit protection when the short occurs on the track fed by thin feeder wires.  Also high-amperage and N scale seems like a bad combination. I see melted models in the future.