Hi
I have a couple of projects I'd like to make PCBs for. Can someone recommend a pcb manufacturer that will let me make small amounts of 2 or 3 different boards, say 50 pieces?
There's at least one thread on the subject! Found a place for cheap pcb manufacturing - Products and Services - Arduino Forum
ok so the simplest project i have is this one, do I need to adjust the wires/tracks for the pcb before sending it to them?
You need to draw the traces - all I see there is the airwires (showing connections that you haven't drawn a trace for yet) - if you generate gerbers from that and send it off, you'll get back a board with no connections between the parts.
You should add a groundplane too if possible, topside since this is a through-hole board.
What PCB design package is that?
Thats Fritzing. Do you mean I should add a perf board to the design? Its mounted on a breadboard like so:
No, you need to draw the actual tracks. You have "wires" that cross in that PCB image. You can't cross wires in a single layer of copper - it just comes out with one big spider of copper that shorts everything together.
F**ing makes it easy. They will get it manufactured for you. I've never tried their service but I expect that you will get back exactly what you designed.
Haven't we told you before to never use the breadboard view of F**ing? Please use the schematic view if you wish to show the circuit.
Ok so what you're saying is I should straighten out the wires in Schematic view, not Breadboard view?
That is still nothing but a schematic, and a somewhat poor layout schematic at that. You cannot expect a board house to guess what you want, but sending them a fritzy might get some chuckles.
Surely you have seen a pcb before. Remove all the components, and that is what your design needs to look like. There will be layers for pads, silk, soldermask in the design program you use.
So I modified the PCB layout to this:
and I got these files created from it...
Archive.zip (1.69 KB)
You need to send a special format file, called 'gerber'. The following is taken from Elecrow's ordering page:
The following files would be needed for the 2-layers PCB production:
Top layer: pcbname.GTL
Bottom layer: pcbname.GBL
Solder Stop Mask top: pcbname.GTS
Solder Stop Mask Bottom: pcbname.GBS
Silk Top: pcbname.GTO
Silk Bottom: pcbname.GBO
NC Drill: pcbname.TXT
Mechanical layer : pcbname.GML
Note:
The Gerber file must be RS-274x format, The format of the drill file can be Excellon Board outline must be included at least in one layer if there isn't GML/GKO layer.
There is a Java program floating around called 'Freerouting'. Initially a free online service it has been taken down but the source is still available. That will route your design for you. There is also a free design program called 'FreePCB' which does the other bits you need to do. The only fault that I found with it is that it isn't easy to add ground planes.
Marciokoko:
So I modified the PCB layout to this:and I got these files created from it...
I suggest using thicker traces for power and ground (lower inductance), the decoupling capacitor should be
right next to the supply pin on the chip (less inductance between chip and capacitor), and give the board
a groundplane if possible (gives a lower inductance to all the signal paths), keeping most of the signals on
one side.
For logic speed circuits stray inductance is not completely negligible (its the reason circuits on a breadboard
start to misbehave above 10 to 20MHz for instance). It may not matter for this circuit, but its a good habit
to get into.
Presumably orange and yellow represent the two sides of a 2 layer board. It looks like you have yellow wires crossing yellow. That can't happen. Swap one of them to the other side.
It also looks like you have a trace that jumps from orange to yellow with no via or component leg to carry the current through the board.
A tool like Eagle can alert you to these errors as well as many more subtle mistakes.
MarkT, what is a ground plate?
MorganS, are you referring to the bottom left corner of the tiny?
That Gnd pin goes to 3 places:
Battery ground
Piezo ground
Flex ground
So it seems like it's switching from Orange to yellow but I'm not sure how it should look but they should all be connected
Ground Plane (sometimes called a "pour") is when you have all the unoccupied space on one or both sides of the board filled in with ground. I know how to do that in Eagle, but not in whatever program you're using - generally, you tell it which signal the pour is and draw it on the board, then the layout program fills it in, avoiding other signals and automatically connecting it to anything of the same signal.
Using a ground plane is good design practice, and also makes the routing process easier, since the thing you have to connect to basically every part is done for you. You do have to be on guard for cases where the layer is split by some other trace, such that the ground plane on one side of the board can't be connected to the one on the other side. In thise case you'll see an airwire between them, and need to adjust the layout to ensure that they're connected.
I usually put a ground plane on both sides of the board unless there's a compelling reason not to.
Where is the 0.1uf ceramic capacitor between supply and ground, which must be located right next to the ATTiny85? I think you forgot about it; you must include this decoupling capacitor, otherwise your sketch will not function reliably (ie, it may or may not reset itself or hang, and you may or may not be able to program it in system). I have had to throw out boards I had made for the tiny85 because the traces to the decoupling cap were too long... Basically every digital IC requires a decoupling cap between supply and ground, and these should be right next to the chip (obviously, there are exceptions - the datasheet will mention, usually in the pin descriptions or example circuits, what is required here)
Also, you should include the 6-pin ISP programming header on the board so you can program the chip in place. Otherwise, you'd have to unplug it from a socket, plug it into a programmer board, program it, then unplug and replug it. That's 4 opportunities to bend or break the pins, and a lot more work than just plugging your USBAsp onto the 6-pin ISP header on the board. In hand-wired designs, wiring up the 6-pin header is annoying; when you're getting boards made, there's no cost to adding it (especially in a board like yours where you seem totally unconcerned with board size)
ok i think I understand what you mean, ive seen those in some pcbs from stuff ive taken apart (the ground plane i mean).
Thanks for the tip about the 0.1uF cap, ill wire that in.
As for the 6-pin header for ISP programming, how do you mean? Are you saying I should add an extra socket on the board for ISP programming, or wire the existing socket to program my tiny?
Add a 6-pin connector to the board, and connect the pins used for ISP programming to it. That way you can just plug a USPAsp (or other programmer with that standard connector pinout) into it to program it, without having to remove the chip or anything.
This is the pinout I mean:
ok i understand that I would want to be able to program my tiny while its still sitting on the pcb where it will normally operate. So you are suggesting I add some connections from the tiny's header pins on the pcb, to a header connector elsewhere on the pcb where I can connect my UNO as ISP cables in order to program it.
But as it currently stands, there is no more space on the pcb since its made to be a very small portable device. I guess im being unreasonable though because Im sure I could work some header pins in there somewhere, I just worry about the routing. Ill give it some thought because I know itll be handy. Working on this project Ive despised having to move my tiny between the prototype pcb and the breadboard for programming.
THanks! ill definitely post back when Im done.
The point of a ground plane is to provide the return path for all the signals moving around (every circuit
needs a return path, unless its an antenna - you normally don't want your circuit to radiate unless its
meant to be an antenna. If the return path is near to the signal you get less interference transmitted
or received by that signal.
Rather than have a return wire for each and every signal, on a multilayer board its much simpler to have
a single layer to do the job.
Ground planes also reduce coupling between nearby signals by diverting the electric fields surrounding
the conductors to ground plane locally.
This all matter more at higher frequencies, but modern logic circuitry is very high frequency, signals
change in a few nanoseconds.
RF circuitry for instance usually simply won't work without good groundplanes - cannot be breadboarded