Author Topic: Analog circuit component layout on single side through hole?  (Read 371 times)

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Djentronio

Analog circuit component layout on single side through hole?
« on: October 12, 2017, 03:04:25 PM »
I've spent probably about 3-4 hours over the course of the last two weeks trying to find any information on designing single side analog circuit boards. I think the best thing I've come up with so far is pictures of older guitar pedal circuits from major name brands that used through-hole and where they placed parts. About the only thing I can find to learn from. Everything else involves multilayer PCB, SMD, and printed-in resistors and capacitors.

Are there any rules for through hole? Is it just a wild west of component placement (apart from the decoupling caps as close to voltage pins as possible)?

Part of the reason for my asking is that design constraints often help me get a project finished quicker. Its easier to take something from start to finish with some constraints. Like the way you clearly define goals to reach them, having clearly defined limits seems to help me put together a circuit. On stripboard I could place objects anywhere, so it bogs me down in the details and permutations of arrangement. But If I take a stripboard and make some hard rules like "always cut the trace next to V+ and V- to only allow a distance of 1 hole for the jumper wire", it seems to help. It might be an arbitrary limitation that could interfere with the 'optimal solution for circuit miniaturization' but it gets me going.

With all that said, are there any good rules of thumb for through-hole analog circuit design so that a tightly packed circuit will perform well?
« Last Edit: October 12, 2017, 03:08:47 PM by Djentronio »

GGBB

Re: Analog circuit component layout on single side through hole?
« Reply #1 on: October 12, 2017, 03:45:08 PM »
Yes. Forum member and diy pedal pioneer RG Keen published a book on stompbox PCB design that is available from Small Bear I think. There are some basic principles that some know and follow for PCB design. But stripboard and PCB are not the same, so the limitations of stripboard may mean that general principals are applied differently. I don't use stripboard, but I'm sure others will chime in soon.

Fancy Lime

Re: Analog circuit component layout on single side through hole?
« Reply #2 on: October 12, 2017, 03:47:41 PM »
Hi Djentronio,

layouting of any sort (pcb, stripboard, whatever) is an art that needs experience to get really good at. I kind of suck at it but others on this forum make absolutely amazing layouts and some do or have done it professionally for major companies, so they will be more competent to answer in detail.

Some general guidelines that I find useful:
Place the most complicated components first. That is generally ICs before transistors before everything else. A good measure of "complicated" in this context is how many other things are connected to the component. A dual op amp with its 8 pins can have a lot of connections. In a tube screamer there are 14 other things connected to the op amp. So the op amp brings with it the most restrictions in terms of its surroundings. If on the other hand a single op amp is used as a non inverting buffer, you may only have to other components connected to it and use as few as 4 pins. So that can be place late in the layout because it can go anywhere. If you want to make it compact it helps to ask: Have you ever loaded a moving truck? Put the bulky, awkwardly shaped stuff (like the many connections op amp) in first, you can always fit the small stuff with few connections (resistors and caps) at the end where there is room.

Make modules: Many transistor stages look very much alike, give or take a few extra components. So you can lay them out all alike once you found your favorite way. Try to make the modules be most area efficient in an imaginary rectangle. This way you can more easily combine various modules without playing too much Tetris. A good example where this works elegantly is the Big Muff.

Look at other peoples boards and try to figure out which ones are well designed and which aren't. Successful commercial stuff like Boss pedals, Tube Screamer, Big Muff etc are a good school because they have had many different layouts for the same basic circuits over the years and there is an army of clones out there. And they all range from bloody awful to mind-blowingly wonderful pieces of art. So you can compare many different layouts for the same circuit. Deducing good and bad design principles from looking at the end results is a bit of work but really educational imho.

Please hold the line, one of our layout professionals will be with you shortly  :icon_wink:

Good luck,
Andy
Sound is like a complex number. It consists of a real and an imaginary part but that does not mean that the imaginary part does not exist. The unit for measuring the imaginary part is called 'mojo'.

PRR

Re: Analog circuit component layout on single side through hole?
« Reply #3 on: October 12, 2017, 07:55:42 PM »
Draw your schematic. Pick some philosophy like "signal flow left to right, power rails top and bottom, controls on left, jacks on right". Draw it again, clearer. Combine things like 2 stages in one dual chip. And draw it again. Keep it orderly. Try to have about the same space between parts (this will be re-visited when you start to pencil real-size parts). From there you can "nearly" draw a fairly compact and easily proof-read and de-bugged board layout.

Read this book snippet (or buy the book) Chap 38 (pg 385 on). I like the idea of "paper dolls", though for 2- 3- and 8-leg parts you can sketch on grid-paper quicker than cutouts.



Do not obsess with making it "small". I have always regretted that.

R.G.

Re: Analog circuit component layout on single side through hole?
« Reply #4 on: October 12, 2017, 11:47:58 PM »
1. Consider the mechanical constraints first, before ever placing anything else. It's almost impossible to stress this enough. There is nothing quite so frustrating as finishing a layout that won't fit in the box. Likewise, visualize and place the mechanical supports to hold the board in the box before every placing a hole or trace. Likewise, visualize how the board will interact with user controls and jacks. This is critical if you use on-PCB pots and switches, but also important with controls on flying wires off the board. If you don't know how it will fit in the box, either the box is really big, or it will only fit if you're lucky.
2. Partition the circuit up into what I call "postage stamps" - small bite-sized pieces of circuit that have minimal interaction with one another. The design automation researchers call this "partitioning into a minimal cut-set." This guarantees the maximum freedom in moving circuit blocks around on a plane.
3. Assign room on the PCB for the full set of postage stamps. Guess at how big each one is, then assign it a space.
4. Arrange the spaces so the signal flows through the "stamps" in a logical, smooth route. You don't want to have to run a trace back through 15 circuit blocks because you placed the stamps in an illogical order.
5. Route each stamp to fit in its area. This is unlikely to succeed the first time for any stamp. But the work tells you what to adjust.
6. Refine and rework, perhaps many times. This is the part where you'll really appreciate working with drawing software or PCB layout software. You really don't want to be moving real parts around to see how the fit. Even pencil and paper plus "paper dolls" is better.
7. Iterate. Go back to 4 or 5 as needed and keep adjusting until it all fits. I generally get a new layout nearly perfect in a few hours, then may spend days coming back to it to refine it.

Read. The book I wrote was aimed at specifically the needs of this forum, and it hits in detail a lot of things, including my version of your "constraints" oriented layout. But what I wrote was not the end-all of PCB layout books. I still have one of the books I learned from back in the mid 70s. There are lots of them. Learn from them all. Forums are not a particularly good place to learn something like this, because there is a severe limitation on how much anyone will type on a topic - including me and Mark.  :icon_lol:
R.G.

Quick IQ Test: If anyone in a governmental position suspected that YOU had top-secret information on YOUR computer, how many minutes would you remain outside a jail cell?

anotherjim

Re: Analog circuit component layout on single side through hole?
« Reply #5 on: October 13, 2017, 05:44:37 AM »
If you haven't already, give perfboard building a try - and make your own layout. This should teach you how to use components as track jumpers and ways to avoid parts leaving no room for others.

There are effect layouts out there giving you three methods - Strip, perf and single side pcb. You will notice the pcb layouts are only copies of the perfboard ones.
"So lets stay within the limit of sureness: lets consider the fuses you have available and lets see what you have to do to light them up..." Farfisa Partner 15 drum machine manual.

merlinb

Re: Analog circuit component layout on single side through hole?
« Reply #6 on: October 13, 2017, 06:54:03 AM »
If you're making a single-sided board it's probably a simple circuit. And simple circuits are usually non critical, so usually you can put your components almost anywhere and you'll be OK. Slap a big ground plane on and you're done. But anything with high gain or digital signals will of course be more stringent.

If you use a modern layout program then you'll get little 'elastic bands' called 'netlines' on screen, showing what is connected to what, so by moving things around you can make it so the netlines shrink and become as short as possible. This is a visual cue that you're placing things probably sensibly.
But if you're using a simple program or even pen and paper then you don't have this luxury. Place the fixed components first. Then group components together into clusters (gain stages, functional blocks etc). Feedback caps are often important for stabilising an opamp, for example, so should be right next to the IC. Then put your decoupling caps nearby (they rarely have to be 'right on the pins' though, a couple of centimeters is OK). Then you can group your clusters together in a logical pattern for signal flow (left to right, horseshoe, or whatever), and finally start nudging the components again so the clusters tesselate together better.

Djentronio

Re: Analog circuit component layout on single side through hole?
« Reply #7 on: October 13, 2017, 02:11:30 PM »
This is all quite helpful. I've been trying to fit a 5 band EQ in a 1590B for a while, and Im so, so close. I just found some of my others which are roughly the same shape but upscaled, probably 125B and I think those will actually work.