Switches, pots and switches mounted on PCB?

[add4]

After building my first projects, i find that the wiring part of the project is a part that takes a long time, is messy (when i do it!) and that it could very easily be improved if the pots, switches and jacks were directly wired to the pcb. The PCB would have roughly the size of the box, (A, B or BB) and include all the components on it (at least the pots, clean wires to the jacks, switches and DC is ok for me), more time planning, less time spent on routine details. This seems an obvious evolution to me, but most of the layouts i see out there do not include that.
Why is that?

- Does it make the PCB more fragile to mount the pots and switches on it? MXR and Proco do it, so i guess it should be ok, they couldn't afford having half of their pedals breaking after a few years i guess.
- My very limited experience in PCB layout seems to tell me that it's MUCH easier to layout a pcb without 'constraint' rather than having components fixed in some places and having to make the leads go in certain places. Would that be the reason?

A follow up to this question is : Is there a good resource on the net to learn how to design logical and neat PCBs? i used my university to get a cheap eagle copy, i can draw the schematic without problem, but the putting parts in places that allow an easy layout is much harder. I'd gladly take guidelines, resources, links, or videos to good tutorials on that.
I KNOW about RG Keen's book, but i have already spent a LOT of money lately on getting tools and basic material for pedal building and i would like to avoid spending the book AND the shipping to europe which doubles the book price...

Thanks in advance for your insight and ideas.
Arnaud

[defaced]

Mounting stuff on the board forces you to use a single layout for the controls and requires more accurate drilling.  Now obviously you can deviate from the layout, but then you have off board wiring to do.  Also board mounted controls take a little more planning and often won't let you get the smallest board size possible.  And last but not least, single sided board (which is what most DIY guys work with) can only be soldered from one side, so that means the parts and controls have to be on the same side.  This can cause mechanical interference problems with the components and the controls if you try to "layer" them (say put a resistor/cap/whatever under a pot for example).  I think these are the reasons you see professional boards with on board controls and DIY boards with off board controls.  Obviously you can do either, but there is a set of conditions you have to work in for each approach.  Your design goals will dictate which set is best for a given project. 

For layouts, I started with tube amps, which require you to know which wires are a noise source and susceptible to noise.  Also amps more or less require you to learn the importance of grounding and what the rules are.  All of these things come into play when you do a board layout to one extent or another.  But to get a neat layout, practice is the only way you're going to get good.  I did several revisions of my first projects until I was satisfied with the layout.  Tim Williams book The Circuit Design companion has a really good chapter on grounding.  You can read most of it on the Amazon preview.  Well worth the read and if you decide to buy the book, it covers alot of the real properties of components that can bite you in the rear if you don't know what they are and when they're important. 

[Scruffie]

Mounting stuff on the board forces you to use a single layout for the controls and requires more accurate drilling.

While this is true to some extent, i've always done it the lazy mans way (or may be not so) and used a circular file to adjust the holes to where they should be.

And last but not least, single sided board (which is what most DIY guys work with) can only be soldered from one side, so that means the parts and controls have to be on the same side.

Actually I regularly solder pots on to the back 'track' side, takes a steady hand but it can be done okay on single sided layouts, for switches though, it does become a pain which is why i've begun to add the physical holes for the switch so it mounts nicely with the pots and all but add pads so wires can be taken from each lug to connect it up.

This can cause mechanical interference problems with the components and the controls if you try to "layer" them (say put a resistor/cap/whatever under a pot for example).

You can use long pin board mounted pots, I haven't experimented with them but I was told they should fit the height of a 1590B with the circuit, it should help avoid mechanical interference, otherwise yes, this is why I mount the pots on the back of the board, far easier.

But to get a neat layout, practice is the only way you're going to get good.

This, while may be some people don't like my layouts or there style, they're what I like and I got there through practice and as I practice, the less mistakes I make and the better I can pack components.

After building my first projects, i find that the wiring part of the project is a part that takes a long time, is messy (when i do it!) and that it could very easily be improved if the pots, switches and jacks were directly wired to the pcb. The PCB would have roughly the size of the box, (A, B or BB) and include all the components on it (at least the pots, clean wires to the jacks, switches and DC is ok for me), more time planning, less time spent on routine details. This seems an obvious evolution to me, but most of the layouts i see out there do not include that.
Why is that?

I'm with you, I hate off board wiring, it's gotten to the point I wont start a project without it having on board pots at minimum, less mess, less time stripping 3 wires per pot.

I do skip adding the DC jack to the main board because i've read complaints of these breaking a lot (seems reasonable, step on a power cord by accident) easy enough to fix but i'd rather have them mounted along with the footswitch etc than the circuit itself.

All my layouts include on board pots, some people don't care, some people don't want to buy special pots, some people think they add mechanical weakness etc, etc, etc.

- Does it make the PCB more fragile to mount the pots and switches on it? MXR and Proco do it, so i guess it should be ok, they couldn't afford having half of their pedals breaking after a few years i guess.

It is another point of mechanical strain, say the nut comes loose and turning the pot turns the PCB & weakens the solder joint or pressing the footswitch flexes the board however, it's a price i'm personally willing to pay on my own boards, it's yet to happen to me, I think with care it can be avoided and as it's my pedal, if I plan it and make it right, it'll be an easy enough fix any way, i'd rather fix it up then spend a long time with a load of wires that could come off/short as well for all I know.

- My very limited experience in PCB layout seems to tell me that it's MUCH easier to layout a pcb without 'constraint' rather than having components fixed in some places and having to make the leads go in certain places. Would that be the reason?

There might be some truth to this, a lot of times people aim for the smallest board size possible, I aim for neatest layout, no stand up components (the odd jumper instead really doesn't bother me, if I used a 0ohm resistor, what's the difference?) and least off board wiring but I will always have an enclosure size/ the build itself in mind, so there's really no need to aim for the smallest, I know what my constraints are to get the PCB, Footswitch, Jacks, Battery, DC Jack, LED Holder all in to a 1590B so I can size accordingly and use the PCB space to my advantage.

That's my opinions and experiences any way.

[defaced]

Actually I regularly solder pots on to the back 'track' side, takes a steady hand but it can be done okay on single sided layouts, for switches though, it does become a pain which is why i've begun to add the physical holes for the switch so it mounts nicely with the pots and all but add pads so wires can be taken from each lug to connect it up.

The rest of my thought was that if you do this, one wrong pull and you have a lifted pad/trace.  There's no hard stop to keep the pot from moving in the wrong direction like there is if the pot and trace are on opposite sides of the board. 

[Scruffie]

Actually I regularly solder pots on to the back 'track' side, takes a steady hand but it can be done okay on single sided layouts, for switches though, it does become a pain which is why i've begun to add the physical holes for the switch so it mounts nicely with the pots and all but add pads so wires can be taken from each lug to connect it up.

The rest of my thought was that if you do this, one wrong pull and you have a lifted pad/trace.  There's no hard stop to keep the pot from moving in the wrong direction like there is if the pot and trace are on opposite sides of the board. 

I've only had issues with this when lifting/bending the Pot up and down repeatedly when debugging new layouts, as long as you stick it straight through the board and don't mess about with them, they seem pretty stable, i've had some like this in pedals for quite some time now.

I can see the concern though, but if you wanted to avoid it, you could drill the pots tab hole, should remove the danger of it moving.

[.Mike]

Is there a good resource on the net to learn how to design logical and neat PCBs?

I don't remember how in-depth it goes, but I had this site in my bookmarks.


I pretty much design all my own layouts. I really enjoy it. It's like a big puzzle with an almost infinite number of solutions, each with their own benefits and drawbacks. I have setup a few rules that I follow, like most of us seem to do. None of what I like to do is unique or original. It's all a product of seeing what other people have done (the Pictures topic is an idea goldmine), and finding what I like.

I do board mounted pots if possible, since I find it to be more fun to work a layout in software than to create neat wiring. If necessary, I will do a board just for the pots, and connect it to the main board with neat, short wires. This means being absolutely sure that you have your pots wired the right way, and so for me, that means I only build what I have breadboarded.

I don't mount anything that will have direct mechanical stress on the board. My logic is that jacks and footswitches undergo enough physical stress to possibly cause problems over time. I run wires for them, but I make sure the wires are as short and direct as possible. I also try to use strain relief for the wires.

Here is an example of a big muff that I made that demonstrates what I mean: Link. The pots and tone control parts are on their own board, connected with jumper wires. The jack wiring isn't particularly short, but it is shielded. The LED is mounted to the main board, and sits perfectly in its mount. The wires that connect the switch to the board are short and direct. The board is held in place by 4 standoffs. So much planning, and I still managed to screw up every single transistor pinout! 

All of this adds up to a very slow process for me, but that is fine. This isn't a race. A few pedals a year and I am happy. I prefer quality over quantity, and I've slowly improved my quality.

Good luck!

Mike

[therecordingart]

Part of me likes the idea of onboard pots and switches. The other part of me likes the idea of being able to beat the sh&t out of a stompbox with a hammer and not have a sunken pot take out the whole PCB. I may be wrong, but I thought being "Milspec" means no PCB mounted stuff that makes it through the panel.