Hi all,
I'm working on my first board design with Eagle and have now reached the point where I need someone to tell me if I've done anything wrong or if some improvements could be made.
Is there a better section of the forum than this to post a request?
What files should I post for review (and how do I get them from Eagle)?
The circuit and sketch are working on breadboard, and I will, of course, explain the purpose and proposed manufacturing method.
Thanks!
Paul
Post an image of your schematics and layout. Screen capture or export is fine. Don't post the original files because not everyone can read them, or will bother if they have to open them somewhere else. When you post images, try to keep them less than 1000 pixels width unless doing so makes them unreadable.
Here or General Electronics should be OK.
File:Export Image, Window view, size it so that width is about 1000 wide.
Or, attach the .sch and .brd files to your post.
In the schematic, run the error check, see that everything you want connected actually is.
In the board, run the design rule check, it will confirm you're not violating the widths & clearances you set up under Edit:Net Classes.
I use iteadstudio for a board supplier. They have .dru (.drc?) & .cam files that you can run to make sure you are not violating their capability, and for creating the proper gerber files.
See the Download tab here.
http://imall.iteadstudio.com/open-pcb/pcb-prototyping/im120418001.html
Put the files in the appropriate folder in eagle (or, just browse to them when you want to use them).
Thanks CrossRoads & SirNickity!
First, here is the schematic. The circuit I've chosen to help me learn Eagle is a 4x4x4 LED cube (single colour). The LEDs are driven by a max7219. The max7219 is driven by an ATTiny85. The ATTiny can be programmed by connecting an Arduino to the board and the sketch uploaded using ArduinoISP. Alternatively, the ATTiny could be omitted and the max7219 driven directly by an external Arduino.
Power can be provided by the same header connector used to program, or via a micro-usb socket. This would enable the cube to be powered by an external Arduino, 3x or 4xAAA NiMh cells or a cheap mobile phone charger.
Here is the board layout. The 4x4x4 cube structure is a little different to the most common designs, to accomodate the max7219. The cube is actually in two halves, each half being a 2x4x4, i.e. each layer is 2x4 LEDs, 4 layers high. This is working great on a breadboard as I write.
I have kept the board single-sided. I am considering etching at home using a toner-transfer method.
Let me know if you need to see alternative views of the board.
Here are the DRC errors. What do these mean?
If you double click the errors it will highlight it on the schematic
You can then see what it's moaning about
The "no value" messages can be ignored
On the board I would change right angle bends to 45 degrees
Look at any PCB that's what "real" engineers do!
Having said that, not bad for a first effort!
Schematic errors, go thru & add a junction where noted, only takes a minute or two.
Board, the hole size used violates the size selected in Net Classes.
Click each one & see where it is, could be a problem getting a wire in a whole or something later or, or just a via that is too small.
The schematic, use of the MAX7219 in halves is quite clever. The layout & routing do look pretty nice.
I would add a 10uF cap in parallel with the small cap you have now per the datasheet.
Thanks CrossRoads & mmcp42.
Changes made in this version:
Clicking on the 4 "Errors" on the board layout shows they are something to do with the 4 mounting holes I put in the corners, don't think they can be very important.
The scematic warnings still have me puzzled. They refer to the jumpers, but I can't figure out what they are indicating as a problem. Its as though it thinks the jumpers have two connectors each!
So... can anyone experienced in home-made toner-transfer PCB techniques please tell me: will this work OK with that method, or is it too complex/detailed?
Oh, just noticed I have an air-wire. Its between the GND pin of the ATTiny and cap C2.
As a result of this I've realised I don't understand how using a polygon to create the ground plane works after all. I though it was a "flood fill" algorithm, meaning every part of the ground plane is connected to every other part. But that air-wire shows that the part of the ground plane where cap C2 is located isn't connected to the other areas...
Edit: I figured out what the flood-fill is doing, I think. Its flood-filling outwards from every connection on the GND net, i.e. every component leg connected to GND. But you must connect all those flood-filled areas together if they are unconnected.
What's the best way to do this in Eagle? I can't find a component that represents a wire link. I know I could put a couple of vias in and connect them on the top layer. But if I then send the board off to be manufactured, rather than etching at home, I don't want the manufacturer to think that it is a double-sided board and charge me more!
Crikey!
I had meant you to use 45degree corners
But quadrants look pretty neat too
home-made toner-transfer PCB
I, would not never use a ground plane with this method.
Why not? Ground plane means a ton of copper that does not need to be etched away.
For that one airwire, add a jumper from a pad near C2 to a pad near J15.
Ground planes are great when using photo plots.
Its the "toner method" that I have an issue with.
