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Build your own Circuit Board

PostPosted: Sun May 28, 2017 2:22 am
by Andrew Davie
Going to take a little side-track here and learn how to build my own circuit board. I have a "lash-up" working nicely, and now I want to transfer it to a minimal-size circuit board. I'd been planning to use the veroboard-type things and lay it all up manually. But I'm already making mistakes, and I hate building up tracks with bits of wire. I'm inevitably going to make mistakes this way, and have all sorts of weird track crossings etc. Better to do it properly, learn how to use some circuit design software and how to etch some boards.

So, that's what I'm going to write about in this thread.

The process seems fairly simple

  • Design a circuit, preferably with some software suited for purpose, but you can skip this step
  • Print (or draw) the circuit onto some shiny paper (or overlay/transparency) using a laser printer or photocopier
  • Transfer the pattern to a shiny, clean copper-covered "blank". If you're really gung-ho you can just "draw" your circuit direct onto the blank, with appropriate marker pen
  • etch the circuit in appropriate chemicals. The uncovered copper will be removed, leaving your circuit as copper traces
  • wash off the ink with some sort of thinner
  • drill holes as appropriate

So that doesn't seem too difficult.

EAGLE seems to be commonly mentioned as free software for drawing. I know it's available on OSX as I installed it a few months back. I did intend to learn it, but forgot. So, that's the software I'm going to go with for now.

The shiny paper - I'll look at using some sort of transparency. More to come on that.

Copper blanks and chemicals I can get from Jaycar for now. I might order some from AliExpress in batch once I have a clear idea of size requirements.

Etching chemicals - there appear to be several options
  • Ferric Chloride - seems to be the standard
  • Ammonium persulphate - sold by Jaycar
  • 1-part pool acid (muriatic acid) to 2 parts hydrogen peroxide homebrew. Seems rather caustic

My goal is to create an easily shareable and reproducible circuit that has all of the "modules" of my lash-up televisor as it stands now. I expect this will take me a few weeks, give or take. I'll document the progress here.

Re: Build your own Circuit Board

PostPosted: Sun May 28, 2017 2:53 am
by Andrew Davie
I recommend watching this YouTube video if you would like a rundown on how to use Eagle...

Re: Build your own Circuit Board

PostPosted: Sun May 28, 2017 11:36 am
by Steve Anderson
That tutorial may be useful. After Eagle was mentioned here a few weeks back I had another go at it. I had some printed tutorials...but still got effectively nowhere. To me it is totally non-intuitive, but many say that about AutoCad when first using it. But I've been using AutoCad for over 30 years and I can use it in my sleep. I hope in short order I'll be able to use Eagle with the same degree of ease.

I just need to knuckle down and get on with it.

Steve A.

Well, I've watched to video, boy does he go through it fast!! Also at the end he mentions a show coming up in 2013 so the version he was using is probably some years old, but like AutoCad each successive version is much like the previous.

Re: Build your own Circuit Board

PostPosted: Sun May 28, 2017 7:42 pm
by Klaas Robers
I always design my PCBs in "Paint". After you made the first one, it is always
- copy a small part,
- paste it somewhere else.
I like to lay my connections anyway on the place where I want to have them.

Re: Build your own Circuit Board

PostPosted: Sun May 28, 2017 8:59 pm
by Andrew Davie
Could use paint, but I would like to see if I can learn how to use Eagle.

Some notes:

Eagle manages a "schematic" and a "board". These are inextricably linked together. When you change one, the other changes.
The schematic is a conceptual view of the circuit; the board represents the physical implementation.

The approach seems to be to do the schematic first. The UI is not exactly intuitive, particularly on OSX.
Basically the first thing to do is add components. There are a gazillion different components available in the inbuilt library, and you can also add new libraries. You can search for your component name - I'm at a bit of a disadvantage because I don't know the generic names for the components (e.g, a 2-pin connector into which I screw incoming wires is a .... ?). So you need a bit of experience here.

First, then, lay down the components.

The next thing is to use the "NET" tool (NOT the line tool!) to connect components together. An important concept is that you design sub-parts of your circuit as stand-alone - the schematic is NOT the place to design/connect the whole circuit, traces and all. What you are doing is a conceptual design.

If you have a part with pins, you CANNOT or at least should not connect another part to it. You put the two parts down, and then you connect them with a NET connection. This is the correct way to do it. At the end of a NET connection, if it is not connected to anything, you can add a label/tag to it. This is essentially a short descriptor of where it connects. Any/all NET connections with the same label are connected together when the board view is engaged. So, for example, I can have a dozen GND lables/tags all over the schematic. These are "connected" by virtue of using the same label.

Similarly, if I have something connected to pin 6 of the Arduino, I can put a NET connection onto pin 6, and then tag it as "SOUND" for example. Then in the circuit subpart that handles the sound, somewhere else... I can put a NET connection to a resistor/capacitor subsection, and label the NET connection SOUND. These are implicitly connected on the board, even if not connected in the schematic.

One gotcha - you right-click (or double-finger-tap on OSX) for bringing up properties. A tag, though it looks like you can click on it -- CANNOT be clicked on. Tags are nothings - it's the NET connection that's actually the clickable object.

Once you have all your components in your schematic and you've defined through net connections and/or tags where everything logically hooks up (and note, you pay NO ATTENTION to physical location in the schematic) then you can go to the board view.

The board view lets you shift components around. It shows the components connected with lines, as defined in the connections (the NET stuff) in the schematic. You can shift, rotate, etc. When you're basically happy with component location, then you can do routing of the lines. You can do double-sided, or n-layers, or single-sided. The routing does what it can automatically (and yes, you can control the thickness of traces and set various spacing constraints). Things that it doesn't manage to connect remain as those connection lines, and you can manually fixup those issues.

That's the basic gist of it. It's frustrating finding names for components, and knowing the "correct" way to do things. For example, you need to add a "SUPPLY" which can be 5V or whatever. But I'm not quite sure how to handle this properly yet.

Still, I can see it's extremely powerful and versatile. Hopefully I'll pick up some skills in the next week or two that lets me build something.

Re: Build your own Circuit Board

PostPosted: Sun May 28, 2017 9:58 pm
by Andrew Davie
The following is a series of video tutorials for Eagle. It starts out very simple. Episodes are short and sweet. I find it easy to follow and thought I'd share as a worthwhile starting point for anyone following along...

Re: Build your own Circuit Board

PostPosted: Mon May 29, 2017 6:32 pm
by Andrew Davie
Another how-to link to peruse.

Re: Build your own Circuit Board

PostPosted: Tue May 30, 2017 12:31 am
by Andrew Davie
Frustrating, but getting there!

Here are some results - I've tried to do a small bit of my project - the Arduino (ATMega32U4), and the RC capacitor & resistor. Also input connectors for the 12V and for the speaker out. I was stuck for a long time with an "only one pin connected" problem, and that turned out to be the 12V and GND were not connected to an input. Fixed that, and the error went away. Wasn't very intuitive, though. Anyway here are some screen grabs - the first is the schematic. Then there are two boards (single sided for now). The red one is with a groundplane (red) and the other is just barebones traces.

eagle3.png (46.37 KiB) Viewed 5746 times

eagle1.png (41.62 KiB) Viewed 5746 times

eagle2.png (46.86 KiB) Viewed 5746 times

Re: Build your own Circuit Board

PostPosted: Tue May 30, 2017 12:45 am
by Steve Anderson
Well, all I can say is that's far further than I have got, but I haven't spent that much time on it.

Steve A.

Re: Build your own Circuit Board

PostPosted: Tue May 30, 2017 9:09 pm
by gary
How do you intend to manufacture the board Andrew?

I only ask because if you are doing it yourself (I have done dozens if not hundreds with all sorts of methods) you really want the spacings and traces to be as wide as possible as there is printing - (possibly developing) - transferring - and etching to be done all having a crack at eating away at your traces.

Eagle normally produces a format optimised for production houses (namely their own) and are not necessarily the best format for home production especially noobie home production.

OTOH production houses - especially in the US - are now so cheap you would be mad to do your own (except for the fun of it - and it IS fun except for hole drilling). Having said that I don't know that those production houses are available to Aussies (cheaply) as I haven't checked for at least 10 years - we seem to be about 20 years behind in those sorts of things and even then only via China.

Re: Build your own Circuit Board

PostPosted: Tue May 30, 2017 11:28 pm
by Andrew Davie
I'm skilling-up on Eagle, and starting to enjoy playing with it. It's a bit "back to front" - normally I would select an object and then an operation on it. With eagle you have to get used to selecting an operation and then an object. To copy an object you select copy first, then the object. Takes some getting used to, but I'm finally making some progress. I did a video of an attempt to do some manual routing, sped up 4x because essentially it's really boring. Hard to see for the first few seconds until I zoom in. Watch it full-screen - should give you some idea of how Eagle works for this feature.

Re: Build your own Circuit Board

PostPosted: Tue May 30, 2017 11:36 pm
by Andrew Davie
gary wrote:How do you intend to manufacture the board Andrew?

I'll try to keep it single-sided. I will use Ferric Chloride or whatever is safest. A laser printer to make the mask on a transparency, then iron-on to the board. If I have to do double-sided, I'll do one side, cover the other. Then drill a few pilot holes, then repeat. As you can see with the video just posted, I'm using lovely thick traces, so should be just fine. If I have to make more than one then I'll go through a production house, probably - just to see how it works.

My eventual goal is to have a dozen or so made so that I can send to anyone who wants one to build their own.

Re: Build your own Circuit Board

PostPosted: Wed May 31, 2017 1:20 am
by Andrew Davie
Routing a circuit board manually is kind of therapeutic! I spent way too long finding optimal routes and parallel lines.
Currently I have the motor, IR (in/out) and sound worked out. Except the sound doesn't include the amp, which I plan to place on-board somehow.
Great way to learn how to use the tool, though - it does have auto-routing, but so much more fun to do it manually.

board2.png (250.27 KiB) Viewed 5718 times

Re: Build your own Circuit Board

PostPosted: Fri Jun 02, 2017 11:03 pm
by Andrew Davie
Slow progress. I have added the PAM8302 "module" at upper left. Took me a while to figure out how to include this.

routing3.png (121.29 KiB) Viewed 5699 times

Still required - the nextion connection, the LED matrix, and the SD card connection. These are lots of wires, and I can't see any possible way of keeping this single-sided unless I put in some dummy 0 ohm resistors, so the traces can go under/through. Might be an ok solution.

Re: Build your own Circuit Board

PostPosted: Sat Jun 03, 2017 2:06 am
by Andrew Davie
I have now added the Nextion and SD card. Still to do: the LED matrix. It's apparent that I cannot make this work with a single-sided board without kludging wire-bridges. I am thinking I might as well bite the bullet and go for a double-sided board. It's not that much more complex to make. This may be the last single-sided iteration - here I have not connected the IR-receive pin (#7) to the diode, because there's no way to do that without crossing stuff. That's the thin yellow line. The IRF540 is actually a IRL540 - I need to learn how to build my own library modules for bits that don't have definitions.

routing4.png (151.32 KiB) Viewed 5696 times