farvorite ways to start a pcb design?

[bassist001]

Not sure if this is the right place to post but here goes. What's you favorite ways to start a PCB design? Like in eagle or something. Start with the ic or power or a ground? Hmm... what works good for everyone?

[.Mike]

I tend to spend way too much time designing PCBs, which probably explains why I have only designed a handful so far, but...

First, I like to decide the maximum dimensions of the board, which is usually dictated by the size of the enclosure I'll be using. Then, I make decisions about on-board components-- will it use board-mounted pots... board-mounted jacks... anything else that I plan on putting on the board that needs to interface directly with the enclosure. Then, I like to decide, roughly, where I want my connections to be... in over here, out over there, V+ over here, ground over there.

Then, I like to start laying out components. I usually look at the schematic, and start in the most complicated area-- where the most components intersect-- and then work from there. This makes it less likely that jumpers will be needed in crowded areas.

From there, I like to try to keep the in separated from the out, and keep the signal path as short as possible. I try to put power filtering/regulating elements in one section of the board, audio in another, noisy components in yet another.

Works for me.

Mike

[DrNomis]

I did some PCB designing using a bit of software called Easytrax some years ago,but I'm very rusty on my PCB designing Kung-Fu,maybe I need a good spell in the Dojo...lol...,seriously,I'm a bit out of practice so I'll need to sit down and re-familiarize myself with it,but I tend to use Strip/Veroboard in my pedal builds more than proper PCBs....

What I will do is find a good schematic of the effect I want to build,then I'll either search for an existing Vero layout,or design my own on some 5mm graph paper,yeah I still think the oldschool methods,ie pencil,eraser,paper,brainpower,is the best,I'll try and lay out the components using the schematic as a guide,and then,if need be,make adjustments to it,I might even do a few design iterations before I'm satisfied with the results.....

[mictester]

Not sure if this is the right place to post but here goes. What's you favorite ways to start a PCB design? Like in eagle or something. Start with the ic or power or a ground? Hmm... what works good for everyone?

I generally start with the maximum dimensions of the board. I then put the ICs in the centre of the board, connect the power rails and mid-rail (where required), and then start laying out the resistors, capacitors and other components around the ICs. I try to get the resistors in neat rows, try not to "stand up" any resistors, and am careful to give enough space around electrolytic caps and other larger components to prevent one part impeding another. I make sure that inputs and outputs are well separated (especially with high gain circuits), and NEVER run tracks between IC pins! It's also important to avoid potential ground loops, and always a good idea to provide enough space for additional supply line filtering.

My favourite programme for board layout is the old DOS version of Easy PC - it's the one I've used for 20 years, and it really hasn't been bettered. The Linux PCB programme is getting better all the time, and is now close to the functionality of Easy PC, but I still find it easier to boot a DOS box virtual machine on this computer and go from there.

[Scruffie]

I'm very new to this game but I use express PCB (I just find it very simple to work with) I start out with the Board Dimensions as everyone else, choose if I want a battery or what not so I can add or cut space.

I then put all the components down on the page just to see if there is physically enough space for them on board, it atleast lets me guess if i'm gunna get it all in a bit better.

I have a very set way of doing PCBs cause there's a few things I like, Onboard Pots, No Stand Up Resistors (Maybe on a larger 1590BB PCB with alot i'd allow a few if i'd spent a long time and it wasn't looking like I could avoid it) and I like to try and keep the 9V,Gnd, In & Out in different corners of the board corresponding to how I intend to wire it up, I also like to keep things neat and in rows, here's an example of what my PCB layouts look like, I have no idea if this is a good way to design PCB layouts electrically, but it's how I like them.





From there, i'll normally start with the power section if it has a V.Ref, as I always find I forget this till the last minute otherwise and don't have the space or tracks needed. Then I'll start from the input with the resistor to ground which I give its own row for any other components that get grounded (You can see that long ground track in the above PCB) and move up another row for the rest of the components (I tend to do it in rows from right to left to get it all neat) and then of course when space gets tight or I need to cross a track and avoid a jumper i'll change the orientation of a component.

As all the components are custom sized in Express PCB I don't have to worry about space around components too much as it's already accounted for too.

Not sure if that all makes sense but that's my basic way of doing them.

[madbean]

If it's IC based, I start at the input. Usually I do that section, then the power, then I got to the output and work backwards. Everything in the middle I figure out as I go along.

For stuff that's transistor based, I try to get most of the resistors on a single row that either connect to power or ground at the bottom of the board. Transistors go on a second row above that. Then all the other stuff.

With some IC based stuff, like TS variants, its actually easier to lay out if you do your input section into the second stage of the op-amp, and do the tone stuff on the first stage. You can generally get a tighter layout this way.

I pretty much always put the I/O stuff on the bottom, pots in a row on the top, and I work the thing to death to eliminate any jumpers.

If planning for a 1590B, 2"x1.7" is about the biggest I will go if I want there to be a battery in the enclosure. You can easily get up to 2x2" if you don't care about a battery.

[bassist001]

Wow that's a nice and clean looking board!!

Wow those are all awesome things to keep in mind. I never really though much about keeping in and out away. Bugh gain you could cross talk or something. Does it ever cause problems running +voltages and grounds close? I've started a few designs with an ic and quickly decided it probably wasnt the best choice, but some it was haha. And lots of time find myself needing just one jumper! I can't get away from that one jumper haha

[RnFR]

I'll start with in at the bottom or top left, power at bottom, pots along the top, and run a ground trace around the whole thing. that way, in Eagle, you dont have a bunch of confusing airwires running everywhere for your ground connections. I usually end up with the out coming off the volume pot on the top right of the board. that way the input is ready to go to the switch, and the wire for the LED is pretty close to where it should be. i try to keep the pots in their proper order, and make sure there is plenty of space between traces for easy etching.

here's a simple one I did recently.
http://apocalypseaudio.blogspot.com/201 ... ayout.html

[lolbou]

and run a ground trace around the whole thing.

here's a simple one I did recently.
http://apocalypseaudio.blogspot.com/201 ... ayout.html

\

Sorta ground loop, don't you think? Do you somehow open it after etching?

[ppluis0]

Hi there,

Is know that bigger components (huge electrolytics, transformers, inductors, heatsinks, etc) are prone to break up their connections due that the same pins used to connect them are generally also the mecanical support.

So, what is the problem about the use of stand up resistors ?

Its a matter of noise, crosstalk, erratic failures, etc., or its simply to avoid resemblances with any japanese unit ?

Back to the topic, I design pcb boards as freelance work since many years ago.

Usually the first thing to consider is the phisical dimension that a board must have, in order to fit inside the equipment that will use them or, in our case, inside a standard diecast box or a custom made enclosure.

Secondly, will see if the pots, jacks and switches will be mounted onboard or are wired separately.

After that, the components must be grouped by their relative function in the schematic: the first IC and their associated resistors and caps will be near the input jack, the last IC or buffer and their relatives near the output, the supply filters, polarity protection, bias divider near the DC jack, and so on.

Also its important avoid mix analog and digital subsections as, per example, the BBD delay lines or the LFO oscillators when draw boards of flangers, choruses or the like.

Once all the components are inside the shape of the board, the tracks can be draw according its longitude: first the short tracks then the longer ones, or first longer tracks (Vcc, Gnd, +4.5 v, etc) and then the rest. As you wish.

The final result may vary depending your skills, mood, and the way you place and move the components and tracks during the design.

If several people start to design a board starting from the same schematic, each of them arrives at different results.

cheers,
Jose

[RnFR]

I like to keep them lying down just because standing resistors are eventually prone to being bent. it just seems like good practice for the longevity of the PCB.

[Duckman]

Hi, bassist001

When you start a new PCB design always try to imagine how to get the external wiring as short as possible.
Try to start analyzing where you'll place your jacks, pots, leds and switches. Then you'll need to choice if those parts are external or onboard type. When you use onboard components, like jacks or pots, your wiring will be drastically reduced (good) but if you need to debug/change/repair, you'll hate them (bad)
On the other hand, if you cross too much wires internally, you'll get some extra noise for sure, not always if you're lucky, but most of the time.
After you make your decisions, try to keep your "in" close to your input jack and so on.
I must say all the previous tips are excellent and you need to read carefully. In fact, take some notes (I do )
Some time it's hard to get the right place for every component and you're mad about find a little more room, but sure you'll find it tomorrow with a fresh view.
By the way, Express PCB it's an amazing tool to me.

[snmavronis]

I start with the physical size I want the PCB to be so it fits in my enclosure of choice; in these examples below a Hammond 1590B. Most people don't do this but I had set another limitation on myself by having PCB mounted pots so their pads have to be in a specific location and knob spacing relative to each other. Then I have to figure out a way to fit the circuit in between. In the PCB layout screenshot on the left it was pretty easy since I have a lot of space to work with because the circuit was a pretty simple one. Yet I also tried to be authentic to the original PCB this was cloned from as far as the 'part order' connections. So I went through many versions adjusting things here and there to make it have an even distribution to get the layout artwork pleasing to my eye. On the PCB layout example on the right the circuit had 2 to 3 times as many parts to fit into the same physical space. This one was very frustrating and I almost gave up on it. You end up getting 75% of things connected and then run into an impossible roadblock - in this case even with using all stand-up resistors! But persistence pays off and finally you think outside the box so to speak and find a new way to re-connect things. Also I had to change the pot pads from circles to ovals and use thinner traces and pad sizes to make more room. This PCB is half the size of the original PCB it was cloned from! The layouts are mirrored because that's the way I print them to inkjet transparency sheets for UV exposure on the PCB material. You want the printed side to make contact with the surface by flipping the transsparency over so the edges etch crisply when UV light exposed.



Also to save space I like all non-circuit specific stuff like the LED and Footswitch to be off board plus I need to save room below the footswitch for a 9V battery.

Steve

[Dirk_Hendrik]

Step 1)
All predefined by location components. Pots, jacks, switches. These are fixed in place and all other circuitry will have to adapt to those requirements.
Step 2)
Choice of components. Dependent on complexity of build. If complex but not requiring SMD yet, resistors are the first to go vertical.
Step 3) Traces.
Power supply traces are the least concern. High impedance connections first and as short as possible. The're the most prone to noise and crosstalk. Supply lines gain the most when a jumper wire is required. Usually one jumper wire can reach multiple connections in a supply line but only one signal line.
Step4.
Sweat. If the components fit on the PCB, the layout can be made. Period.

No traces between IC pins? Gimme a break. That fully depend on the signal/impedance in that trace.

[mictester]

No traces between IC pins? Gimme a break. That fully depend on the signal/impedance in that trace.

Not really - it depends on the accuracy with which you can etch. Broader tracks, with plenty of space between them goes a long way to make easy-to-build, reliable boards.

[Hides-His-Eyes]

If you're down to 20mil interpin traces I had assumed we were talking about fabbed boards...

[RnFR]

and run a ground trace around the whole thing.

here's a simple one I did recently.
http://apocalypseaudio.blogspot.com/201 ... ayout.html

Sorta ground loop, don't you think? Do you somehow open it after etching?

is that bad practice? i haven't had any problems doing a ground pour around the whole board and running components out to it. honestly, i don't really understand the whole idea of ground loops on a pcb. the ground is running everywhere the pour is, it's not like it's running down wires. i haven't noticed any noise issues yet, either. i very well could be wrong though. as i've said many a time- i'm no expert.

[diemilchmann]

i dont usually bother with ground fills, i find that just case grounding everything in a star config works well

[ppluis0]

The use of ground planes filling the unused area inside the tracks with copper helps us in two things: reduce crosstalk and helps to extend the life of ferric chloride if the boards are etched by ourselves.

I agree with Dirk about the fact to keep signal tracks as short and direct as possible. The supply and ground lines are more simple to route after the audio connections.

Question: Wich size of pads and track width are you using normally...? I think that more copper is better but everyone have different preferences.

Cheers,
Jose

[snmavronis]

Question: Wich size of pads and track width are you using normally...? I think that more copper is better but everyone have different preferences.

Others will probably voice their ideas but for me make them as big as you can get away with based on the circuit and parts density. In my PCB layout illustrations above, the first simplier one uses 50 mill traces and 115 mill pads mostly. In my more dense second layout I used 40 mill traces and 80 mill pads.

BTW, all pad holes in my layouts are done at 20 mill because they are just used as a centerpunch so they are actually drilled slightly larger than the part lead diameter going through them, and for the insulated wire diameter of the four 'strain relief' holes at the bottom - those pads get almost completely drilled off for big enough holes.