Digitrax board - plug in adaptor

[The_Ghan]

Some time ago I mentioned to one of you guys (Cap'n, Martijn or KenS, I think) about doing a custom board to plug in Digitrax components and then wire into screw terminals instead of soldering to the spade connectors on the supplied edge board connectors.

I've downloaded pad2pad software (because I don't know what else I can use) and come up with this (see image below).  Sorry, not very good at this as I'm an architect, not an electrical engineer.

What are your thoughts?

Cheers

The_Ghan

[CaptOblivious]

So, would the Digitrax boards stand perpendicular to this board here? Looks fine to me. No need for the traces to be so thick, unless they are transmitting several amps of current. Could be neatened up a bit, but that is a nitpick.

Never used pad2pad. If you don't mind a learning curve, EagleCad is a good (and free for non-profit use) choice. Still, you seem to have gotten results from pad2pad, so perhaps you oughtn't change just now...

[Dani]

I don't know exactly what kind of "Digitrax components" are you referring to, but if they are standard you can use a perfboard and solder standard connectors to it. It's fast, easy and cheap. The one with straight tin tracks will avoid "bridging" holes.

That's what I'm using in my layout:



Hope it be useful!

Dani.

[CaptOblivious]

Dani,

The_Ghan is referring to beasts as these:

http://www.digitrax.com/prd_powerman_pm42.php

The cards have edge connectors, and this thing you can slide onto the edge connectors with solder lugs. Neither is particularly easy to solder to, and neither permits other kinds of connection. The_Ghan wants a doo-dad that would slip into the edge-connector and provide screw terminals for ease of installation.

[The_Ghan]

That's right Cap'n, a doo-dad!

The whole point is to avoid soldering.  I prefer Plug-And-Pray and my whole layout, except for the Digitrax components, is wired that way.  The Digitrax products are good, but the idea of soldering wires to the spade connectors is ill-founded in my opinion.  The pin spacing on the edge connectors is 3.96, so they won't plug into a standard 2.54mm board.  Also, the screw terminal connectors have a 2.54mm spacing compatibility.  The result is the need for a custom board.

The problem with using pad2pad is that the software is proprietary and will only export to DXF.  It has features to order on line etc.  BTW, 10 x will cost me about $23 each while 100 x will cost me less than $5 each, delivered to Australia.  I'm looking at other CAD systems so that I can give the Chinese a go at pricing this.  I might even see if I can get them all pre-fab, so I don't need to solder the components onto the board - about $1590 with pad2pad - which is way off my dial.

Cheers

The_Ghan

[The_Ghan]

Cap'n,

Yes, it could be cleaned up.  I was using a .064" grid, which doesn't work with the 0.1" spacing of the screw terminal pins.  I'll give it a go with some other software.

Also, I went for 0.1" traces because the doo-dad will also be compatible with the PM-42.  That puppy will manage several amps per channel anyway.

Cheers

The_Ghan

[CaptOblivious]

That is far too high a price to pay. Look at Seeed Studio [sic] or iTread Studio, good prices (depending on size, as low as 50USD for 10!) and good quality. They accept Gerber files which Eagle (free, but limited to 100mm x 80mm max size) or KiCad (unconditionally free, but not as many components available) will generate.

That's right Cap'n, a doo-dad!

The whole point is to avoid soldering.  I prefer Plug-And-Pray and my whole layout, except for the Digitrax components, is wired that way.  The Digitrax products are good, but the idea of soldering wires to the spade connectors is ill-founded in my opinion.  The pin spacing on the edge connectors is 3.96, so they won't plug into a standard 2.54mm board.  Also, the screw terminal connectors have a 2.54mm spacing compatibility.  The result is the need for a custom board.

The problem with using pad2pad is that the software is proprietary and will only export to DXF.  It has features to order on line etc.  BTW, 10 x will cost me about $23 each while 100 x will cost me less than $5 each, delivered to Australia.  I'm looking at other CAD systems so that I can give the Chinese a go at pricing this.  I might even see if I can get them all pre-fab, so I don't need to solder the components onto the board - about $1590 with pad2pad - which is way off my dial.

Cheers

The_Ghan

[Dani]

The Digitrax products are good, but the idea of soldering wires to the spade connectors is ill-founded in my opinion.  The pin spacing on the edge connectors is 3.96, so they won't plug into a standard 2.54mm board.  Also, the screw terminal connectors have a 2.54mm spacing compatibility.  The result is the need for a custom board.

Hi again!

I still don't see the necessity to make a custom PCB, 3.96 is a completely standard gauge in electronics. The photo from my last post is a 3.96 spacing perfboard and connectors. I use this gauge because tin tracks are wider and better to run 2 or 3 Amp. on there. I guess that's the same reason for Digitrax to use it also.

Here you can see 3,96 gauge perfboards (you have them in all size and shapes): http://www.ondaradio.es/esp/detalle.aspx?id=1198

And here you can see standard connectors prepared for 3.96 spacing: http://www.ondaradio.es/esp/catalogoConsulta.aspx?pagina=999;1

I think 2 - 2.54 - 3.96 - 5.08 are the standard gauges in electronics.

Regards!
Dani.

[The_Ghan]

Dani,

Most people here will know more about electronics than me.  I can see that you are one of them.  I don't have an electronics background, so please be patient with me.  Your help will be appreciated.  My master plan is for a 5.6mx 3.92m (18' x 13' approx) "donut" shaped layout built in stages.  At the moment I'm building the first stage which is 2.8m x 1.68m (9' x 5'6") front, centre piece.  It has a subway, urban/rural node and shinkansen lines. I'm going to implement signalling as well.  For stage 1 alone I need the following Digitrax components:

• 1 x PM42 Power Manager
• 7 x BDL168 Occupancy Detector
• 7 x SE8C Signal Decoder
  

... all of which use the same Edge Card Connector

So, for Stage 1 there will be wiring for 15 cards.  For the whole layout in the future, it will probably be more like 40 cards.  So, what do you think is the best way for me to go about this, being a novice at electronics and all?  If I can get, say, 50 boards pre-fab and save the soldering time then that might be worthwhile for me.  If I make my own boards how do I do the traces?  They need to be able to handle several amps for the PM42.  Also, I couldn't find screw terminals and PCB boards at 3.96 pitch on eBay.  Please show me where I can get them.

Your help is greatly appreciated.

Cheers

The_Ghan

[Dani]

Hi Ghan!!

I think you have nothing to learn from me, for sure!! I'm just a newbie in everything, also electronics!!! But I'm very lucky and I have a huge electronic components store near with very nice personal who answers all my "connectors" questions, and all you in the JNS forum for the rest (I don't need Mastercard).     

I never buy electronic components in internet because there are always too much similar articles but with million of distinct characteristics to choose from, and directly in the shop they give me the solution. So if I were you I would go to the biggest electronic shop with the Digitrax connector as a sample (but as you said it's a standard EDGE CONNECTOR 22 WAY, 44 CONTACTS, 3.96 LEAD SPACING => http://uk.farnell.com/itw-mcmurdo/305-044-500-202/edge-connector-22way/dp/145148) and I would say: "Listen guy, I want a protoboard with straight lanes to solder this connector in one side, and screw terminals in the other".   

They will sell you a 3.96 pitch protoboard (5€ costs mine, and I cut it so I can make 3-5 boards from each), screw terminals for 3.96 pitch to solder in the protoboard, and may be they also have a leaned edge connector to be parallel to the protoboard, but this is up to you. The digitrax connector can be soldered directly to the protoboard like the screw terminal connectors. Also for the screw terminals, you can choose them straight or "leaned" (I mean by leaned like in an "elbow" form instead of straight, my English hasn't enough technical vocabulary).

Sorry I can only give you an idea, but no concrete specifications!!

I'm happy to help (or just trying to) an experienced modeller like you.

Dani.

[The_Ghan]

Dani,

Jaycar is the only electronics company that I know in Sydney that sells components.  I might have to ask around a bit.  I've now found suitable 3.96mm terminals to go with the card edge connector, but I'm coming up short on a 3.96mm PCB.

Cheers

The_Ghan

[Dani]

Hello,

Yesterday I asked a friend who is a Master in electronics about this gap spacing issue, and he answered me:

* 2.54 mm is the standard gap between chip legs (IC, processors, ...), that's the reason why most prototyping boards are prepared just for that spacing, and it's the only supported grid spacing by most designing software.
* 3.96 mm is the standard gap for all kind of connectors prepared to mount on PCB. That's not logical when IC have a distinct gap, but that's how it is.... 

And I asked him how to deal with it when you want to use prototyping boards, and answered that the common solution (when you can't find 3.96 or 3.8 gap board, or you are prototyping a board with chips and connectors) is to use 2.54 spacing board and drill new holes or make bigger the needed holes (with a dremel or similar tool) for the connectors.

My mother always said "You will never go to sleep without learning something new"....   

Cheers,

Dani.

[The_Ghan]

Thanks Dani,

That brings us full circle, I think, to the point where there is so much work to do on the boards that I may as well get them custom made.  In model railways everyone usually suffers from one or more of these constraints: time, money, or space.  In my case, it is definently time, which is why I'm going to get the boards custom made.

When I get a moment I'll redraw the board neaty using Eagle.  I'm also sourcing some Chinese board manufacturers.

Cheers

The_Ghan

[Dani]

Hi!

I've been preparing more feeders for the new tracks, but this time I'm using pluggable connectors because these feeders will have difficult access to screw or unscrew feeder wires.

Ghan, I know it's not a possible solution for you (mainly because you cannot find this wider gauge protoboards), but anyway I post a photo if someone wants to adopt my solution.



More info in my blog: http://clubncaldes.blogspot.com/2011/09/tips-for-connectors-and-feeders.html

Cheers,

Dani

[The_Ghan]

Good idea Dani.

I've gone pluggable throughout my layout with Molex connectors because they are cheap.  The connector you show is expensive in Australia.  But if I could get them cheap that is exactly what I would use.

Cheers

The_Ghan

[KenS]

Ghan, I've never been able to find anything better than soldering to the blue card connectors. And that's a pain because they really don't take larger than 20 ga wire, and I often want to use larger wire (Digitrax's solution is to use short wires to adapt to the thicker ones where needed; electrically viable, but a nuisance to do).

I'm in the middle of doing my PM42/BDL168 assembly, but I only have a total of 13 boards (14 with the eventual SE8C I plan) so I'm not quite as bad off as you.  It's still a huge amount of work which causes me to avoid doing it at all so it's taking me months, and a screw-terminal adapter would be a really nice option to have. I spent over an hour last night working on one PM42, something I could have done in half the time with a screwdriver.

BTW, I use 1" angle brackets to mount my connectors to a sheet of plywood, so the circuit board lies parallel to the plywood.  One thing I don't like about PCB solutions is that they usually assume the board would stick up away from what it was mounted to, and that's problematic when space is a concern.

[The_Ghan]

Ken,

You sum up the problems pretty well.  I just had a quick look at your article.  I'll have a good read of it overnight.

Are those RX4s operational yet?  They look pretty close together.

Cheers

The_Ghan

[KenS]

None of it's been tested yet, as there's no functional track connected to it yet.  But the specs indicate a two-inch spacing (not separation, but center-to-center spacing) and that's what I used for the set mounted to the underside of the table.  I'm now working on mounting the new ones on a separate board (the latest Musing on my site has a picture of the as-yet-empty board) and for that I have more room so I'm using a 2.5" spacing.  I'd have used more, but with two sets the length of the wires bacame a limiting factor unless I wanted to locate the BDL in the middle of the board, and that would have made other wiring messier.

I probably ought to test the first of the new boards after I build it, with some test track if nothing else.

[The_Ghan]

I'm looking forward to testing RX4s myself.

Cheers

The_Ghan