Okay--I've designed my shield, I've made an Eagle-printable layout, I'm well excited to make this thing nicer than my current perfboard mockup...
And I can't find a particular part, curse it.
I'm building a serial-to-USB shield (to make a "hardware driver" for an old serial game controller). I can get every part I need through Maplin in the UK (which may not be the top choice of everyone, but at least they are fast; I got my last order the day after I placed it).
The problem is that to interface with the DB-9 female socket on the device, I need my PCB to have a through-hole mounted male DB9 plug. Maplin doesn't carry these; they only have the straight-through version. I think I found the right part at Digi-key (http://ordering.digikey.com/Ordering/LineItem.aspx?itemSeq=69772816), but having never ordered from there before I've spent literally hours trying to figure out what I need (not just the DB9, but resistors and the like; that's the problem with the 5,000 options every component seems to have at digi-key), and the rather pricey shipping to the UK combined with the mysterious "VAT will be due at the time of delivery" makes me nervous and takes away much of the price advantage (and there's a Maplin about 20 minutes away for walk-in grabs of stuff... but of course not this part).
I've seen the straight-through plug (like these: http://www.maplin.co.uk/Module.aspx?ModuleNo=1113 mounted on the edge of a PCB (like the MiniPOV3 kit does; see the relevant bit here: MiniPOV3 - Soldering). But I'm nervous about the durability of plugging that on and off, not to mention that it requires a two-sided PCB (and I'm not sure how to handle that in Eagle or in my kitchen while I try to etch it; since Eagle seems to be able to make a single-layer of my current board and I've never etched before, I'd prefer the PCB mountable one).
I don't want to pay for international shipping (and incur a decent delay) just for that one part in a one-off (or few-off) project, but I can't find it in the UK yet. Any suggestions from our UK hackers?
I'm in Oxford. I don't want to put you to too much trouble, though (and I may need more of these connectors as I may have to make a few boards for friends, so I want to find a supplier), so no need to rip up your modem on my account. Besides, you may need that awesome high-speed communication later!
Actually, RS online may have what I need... if I can figure out their labyrinthine catalog. I keep seeing female connectors pictured with descriptions saying "male" (or "plug" and "socket" when it's clearly the female part (with holes) whigh plugs "into" the male part (with pins)), such that I'm now no longer sure which is the right name for what I want (the one with pins!). I think the right sequence of buzzwords is "9 way through-hole right-angle male with threaded inserts" (so that you screw the retaining screws of the cable into this) but I'm really baffled by now... it may be this guy (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2593273, but the picture's what I would consider a female, while the description says "male", so I'm scared of ordering...
They have a £20 minimum order for Internet/credit card orders, but the will normally deliver on the next working day. They definitely have the PCB mounting D-connectors, because I got one from them for use in a CAN-bus gadget (CAN to RS232).
But yes, the descriptions are tricky to get right! My pet peeve on Farnell is the terrific parameter-based searching (search for capacitors of 0.1uF, for example), ruined by the almost random selection of parameter syntax (0.1uF, 100nF, 0.10uF, 100000pF, all considered unequal by the search).
I see why you are confused, that picture is what I would think is a female connector.
That wasn't nearly as confusing, though, as the "9-way" plug that both picture and drawing revealed to have 20 pins.
I found what I think is the right part (crosschecked the supplier part number with the supplier catalog) and ordered from RS; we'll see what I actually get. At any rate I think I'll have enough to try my first etch this weekend. Scary stuff for the first time, but enough good tutorials out there that it should go OK... I'll try the single-side version of the board first time out (some delicate traces going between adjacent pins that I'm not crazy about, so it may not work, but I may be able to jiggle it a bit).
Glad you hear that you've got the connector sorted out! Do let us know how you get on with the PCB etching, too. I've done three boards now using Toner Transfer, all of them for AVR chips and all successful. Photos here:
Thanks, mem! I used junk-mail paper! It was thin, flimsy and cheap, but glossy. It's the glossy coating that matters, because that's left behind, stuck to the copper by the toner. The thin paper washes off very easily and the toner sticks to the board much more strongly that I expected.
I'm a little anxious about the etching to be honest; it's a very simple circuit, but either requires a two-sided board or fairly delicate traces going between adjacent holes, etc. I'm pretty nervous about trying a two-sided board as my first etch, not to mention traces would have to be REALLY fine to make it between holes. I curse the max233, which seems to want some pins wired to each other but requires traces to cross (at least it looks that way to me). Here's an early draft of the single-sided board:
... it's what Eagle did with autorouting after I got frustrated and gave up.
Am I being unduly frightened away by two-sided boards? Looking at my blobby soldering of my protoboard with the IC, I'm not sure I can keep traces between solder points clean.
I don't think eagle has done you any favours. I think you can get a much simpler single side board if you do some manual routing and perhaps add one or two jumpers. If you can post the eagle files somewhere, you may even get one of the eagle experts here to give you a hand.
Yeah, probably true--and admittedly, this is my first ever use of Eagle, Arduino, etc (nothing like digging in to serial and USB comm on a first project, I guess). So I'm sure I'm making lots of simple mistakes. There are a couple more mods to the board I'm planning on (a line between pin 1 and ttl in on the max233, and microswitches on pin 0 and 1 so I can turn off the external serial port when reprogramming) but basically it's that. I'll play with it and put up a "aaaugh, help me!" in a day or so.
Am I being unduly frightened away by two-sided boards?
Home etched double sided boards are doable. I don't bother with complex designs that require toner transfer on both sides; it looks like too much work to get them aligned. Here's what I do:
lay out the board with maximum traces on one side. if I have PTH and SMT parts, I end up with PTH on one side and SMT on the other.
put no vias on IC pins, since you won't have PTH
arrange vias so that any traces on the other side are straight and, if possible, make them all parallel (or perpendicular, if you can't manage that). The idea is simplicity - you'll draw these by hand later.
make the via pads a bit larger than default, to make life easier for yourself later
do toner transfer as usual for the complex side
drill holes through vias as small as possible (I used the uselessly small bits in the Harbor Freight set I bought)
using the holes as endpoints and a straightedge, connect the dots on the simple side of your board, and draw a pad for the via. (I used the PCB marking pens and didn't like them; I prefer paint pens). I also put a paint dot on the complex side of the board to prevent the etchant from attacking the copper edge exposed by the drill.
etch the board (I like HCl + H2O2 much better than FeCl)
clean as usual. I usually end up using acetone for the toner and naptha for the paint.
solder "Z-wires" into the via holes. I use a drill for the "connect the dots" stage so small that I must redrill the holes. I use discarded component leads (resistors, caps, etc) that tend to be lying on the bench, in the floor, even after I clean up...
Take a look at the single sided arduino serial version 2 board layout, if it's still around. IIRC, it has about 4 traces on the top side, and they're all straight lines. Look at this board after reading my babbling and maybe it will make sense.
No, that makes sense (and the single-sided serialduino made me say "oh, that works much better" with the idea of jumpers on the top surface). Having seen that, your explanation of "toner the bottom, manually draw the top" works very well--although mine is so simple that I can probably just jigger the design a little bit and do it with a soldered jumper rather than doing proper vias, at least on the first go. Thanks for the idea, though--makes good sense.
Now I just want to learn to get Eagle to
Play nice with multiple grounds (right now it seems to want to connect every single ground together; I need to play with adding the second ground connection on the "digital pins" side of the shield template and connecting components to it as well, for two separate "ground nets" that are actually connected on the Arduino board, not the shield)--ie specify that "this contact is connected to an external ground" rather than "this contact needs to be connected to an external ground, if that makes sense).
Play nice with autorouting and manual jumpers. I'll play with manual routing as well of course, but it'd be nice to learn how to do most of it myself and then auto the rest. It sounds like setting a preferred direction on one side of the board and upping cost will probably do it (there's a script on the cadsoft site, "1layer.ctl", that looks to do this although you can of course always do it manually).
You can mess with the eagle autorouter settings to force all the traces on one layer, but I didn't have a lot of luck with that.
You can autoroute at any time - if you have part of the routing done, the autorouter will do the rest. This is definitely the time to save the design first, though, so you can "undo" the autorouted part if it's too ugly.
I'm not sure I know exactly what you mean, but the multiple ground pins can be a bit obnoxious, or they can actually help, as it some circumstances (the last board I etched, for instance) you can use the arduino ground connections to "jumper" ground from one side to the other. Sometimes I ignore an airwire if it goes from a ground on one side of the board to the ground on the other, or even twiddle the net names to make it come out neat.
It sounds like setting a preferred direction on one side of the board ...
In Autorouter Setup, set the preferred direction for the side of the board you don't want traces to 'N/A' – all routing will then be on the other side of the board.
Yeah, that's how I generated the above actually. It worked, but is just a bit untidy (and runs things between adjacent pins, which I'm not crazy about).
the multiple ground pins can be a bit obnoxious, or they can actually help, as it some circumstances (the last board I etched, for instance) you can use the arduino ground connections to "jumper" ground from one side to the other.
Yeah, that's what I mean; effectively having the two grounds jumpered but not appearing on the board, so that I can label everything that should be ground as "connected to ground" so Eagle won't freak out during electrical checks, but happily route things to either ground point (or have the autorouter to so) because it knows both pins are grounded.
One way might be to manually jumper them in Eagle on a layer that the autorouter doesn't know about (tell the autorouter it can't use it, then turn off the jumper layer when printing since it just doesn't really exist). Seems a bit of a hack, but I bet it would work.
I think you'll need much wider traces if you're going to do this with Toner Transfer. My thinnest traces were about 15mil (15 thousandths of an inch), and they were tricky. There's no penalty to making the traces much, much wider, and it'll make the TT easier.
As for the routing, I used the GNU PCB program and it "just worked", although I did all the routing by eye. Then, I printed out a 600dpi version on the laser printer (HP LaserJet 4+).
not to mention traces would have to be REALLY fine to make it between holes.
The traces can be thick; the gaps need to be narrow. You can always cut away extra copper using tools ranging from knives to dremel tools, but putting back more copper is harder. I'm a big fan of wide traces, and wrote some suggestions on modifying design rules for hobbyist fabrication here: http://www.instructables.com/id/Make-hobbyist-PCBs-with-professional-CAD-tools-by-/
I curse the max233, which seems to want some pins wired to each other but requires traces to cross (at least it looks that way to me).
Yes, I had the same problem. I didn't notice till I had already made a PCB without the necessary pins connected Here's what I ended up with (untested, but perhaps good for ideas anyway) (the two traces going up off the top are the TTL-level rx/tx; this was an rs232 single-sided serial arduino design...) (The top traces are intended to be jumpers.)
Nice instructable, Westfw! I'll keep that under advisement, revamp the board (adding the DIP switches, a couple jumpers, and a couple of other things) and see what I come up with. Exciting stuff!
Here's what I ended up with (untested, but perhaps good for ideas anyway) (the two traces going up off the top are the TTL-level rx/tx; this was an rs232 single-sided serial arduino design...) (The top traces are intended to be jumpers.)