Why no mounting holes?

[stallik]

Just wondering why so many pcb and vero layouts make no provision for mounting the board in an enclosure. Sure, pots can be utilised sometimes and it's not difficult to modify the layout to accommodate suitable holes but I'm curious why they are so often omitted

[GGBB]

Can't speak for all of course, but in my case I use board mounted pots. If anyone wanted to add mounting holes to one of my layouts, they could easily just cut the PCB larger and put holes around the edges - I'm sure that wouldn't be much different than if I had actually designed the board transfer with holes.

[stallik]

Yes Gord, I think a lot of people use the pots. My question was prompted after a trawl of loads of layouts trying to gauge how much support  was the norm. I'm putting a big board together and didn't want to rely on the pots and jacks. I'll probably end up with too much support to be on the safe side

[davent]

It would seem a very large contingent of builders are averse to stripping/running/soldering wires between pots and board so use board mounted pots to hold the boards.

dave

[R.G.]

Inexperience or lack of training. Leaving space for mounting and other mechanical provisions is the first step in laying out a board. PCB Design for Musical Effects teaches this as one of the first things to consider, before you ever lay down the first trace.

The days of laying out a PCB in the absence of knowledge of the enclosure it goes in are - or should be! - long gone.

[Cozybuilder]

Inexperience or lack of training. Leaving space for mounting and other mechanical provisions is the first step in laying out a board. PCB Design for Musical Effects teaches this as one of the first things to consider, before you ever lay down the first trace.

The days of laying out a PCB in the absence of knowledge of the enclosure it goes in are - or should be! - long gone.

+1
Thinking and planning ahead for proper circuit board mounting and wire routing when laying out pedals would eliminate a lot of the troubleshooting questions that are posted- which are frequently found to be misrouted wires or shorting  etc.

[GGBB]

It would seem a very large contingent of builders are averse to stripping/running/soldering wires between pots and board so use board mounted pots to hold the boards.

dave

I'm not sure aversion to wiring is the main reason behind the common use of board mounted pots. More likely that it just happens to be extremely effective and simplifies construction at the same time. In my case, I typically use lugged pots mounted with solid core wire, so I don't get to avoid dealing with wires. I will however confess to an aversion toward installing PCB mounts - why go to that trouble and add that potential fail point if you can use board mounted pots. It's probably more work to design the layout with properly placed pots than to include mounting holes.

[karbomusic]

why go to that trouble and add that potential fail point if you can use board mounted pots. It's probably more work to design the layout with properly placed pots than to include mounting holes.

I trust my standoffs which are JB Welded (properly) to the enclosure more than I do the potential stress points of the pot's tendency to flex the solder joint. IMHO, it tends to raise it's own risk. Meaning the nut on the pot will/may eventually loosen, and since it is attached to the PCB the user is going to either not know for awhile and/or manhandle it when tightening. That can't really occur when not attached to the board.

That doesn't mean I would never use board mounted pots (it would save me >1/2 hour on one particular build that I do a lot) but it has always felt like a failure waiting to happen although I see that many manufacturers seem to use it successfully making me a concerned, yet non-authority on the subject. 

To the main question, typically it isn't that hard to leave room for ~4mm diameter section on the PCB. Secondly, if I happen to use someone else's PCB and there is no mounting hole, I typically open it up in Photoshop and add them before etching provided the design isn't already so tight that that very small extension causes it to be impossible to fit into the enclosure.

[davent]

To the main question, typically it isn't that hard to leave room for ~4mm diameter section on the PCB. Secondly, if I happen to use someone else's PCB and there is no mounting hole, I typically open it up in Photoshop and add them before etching provided the design isn't already so tight that that very small extension causes it to be impossible to fit into the enclosure.

I use Inkscape to do the same, alter the layout to fit standoff holes.

dave

[GGBB]

provided the design isn't already so tight that that very small extension causes it to be impossible to fit into the enclosure.

That might be the case with many of my layouts. 

[KazooMan]

dave
[/quote]

I'm not sure aversion to wiring is the main reason behind the common use of board mounted pots. More likely that it just happens to be extremely effective and simplifies construction at the same time. In my case, I typically use lugged pots mounted with solid core wire, so I don't get to avoid dealing with wires. I will however confess to an aversion toward installing PCB mounts - why go to that trouble and add that potential fail point if you can use board mounted pots. It's probably more work to design the layout with properly placed pots than to include mounting holes.
[/quote]

I only do this for a hobby, but I have built at least fifty pedals.  I have never had one give me a problem due to the presence of mounting holes and the standoffs Smallbear sells or other home-brewed standoffs I have devised..  I have had an occasional failure with a board mounted pot flexing the board and breaking a trace.  Could just be my technique.  With board mounted pots the alignment of the of the holes in the enclosure needs to be pretty much spot on or there is some tension applied to the attachment to the board.  Wires soldered to the lugs of pots are never a problem, but I agree that the attachment point to the board can be a weak spot if the board is moved around a lot.  When there is room, I like to run the wire up through a second hole in the board and then down into the proper hole for soldering.  Pretty much bullet proof that way.An issue for me with board mounted pots has always been that you need to remove all of the knobs and mounting nuts to get the board out for any repairs or mods.  PITA.

[KazooMan]

A while back I submitted a post on home-made standoffs for boards with no allowance for mounting holes.  Here is a link.  This actually works very well.

http://www.diystompboxes.com/smfforum/index.php?topic=106882.msg968508#msg968508

[GGBB]

An issue for me with board mounted pots has always been that you need to remove all of the knobs and mounting nuts to get the board out for any repairs or mods.  PITA.

On the other hand, probably close to 50% (well at least 25%) of the time I open a pedal that has the pots wired and I work on the board without removing the pots, one or more of the wires break at the board. Even bigger PITA IMO. You can avoid that with strain relief holes (or even goop of some sort), but that gets to be a lot of extra holes if you've got 2, 3, 4 or more pots. Oh the humanity! Board mounted pots makes it so simple - with 2 pots you have six mount points, 3=9, 4=12. But it does make the layout design a fair bit more complicated especially if single sided.

But I digress. I agree that pcb mounts probably are a little better, but board mounted pots done well aren't likely to be a true problem. Back to the original topic - why people don't include one or the other probably is due to inexperience/lack of education as RG said.

A while back I submitted a post on home-made standoffs for boards with no allowance for mounting holes.  Here is a link.  This actually works very well.

http://www.diystompboxes.com/smfforum/index.php?topic=106882.msg968508#msg968508

I remember that post - very clever!

[bloxstompboxes]

I did buy, read, reread, and still own R.G.'s book mentioned above. I do try to include mounting holes on all my boards except when they just won't fit in the layout. But, I have to admit, I have never actually used them.  Though I have drilled them out every time. My problem is just finding a way to have them so perfectly placed on the board as to be able to use a stand-off without it hitting the back of a pot or whatever. I typically use the triangular 3 knob drilling pattern with side mounted jacks except on the most recent build I did which was a return to the first pedal I built, everyone's favorite, the TS808, lol. I put them straight across in a 125B enclosure but it was such a tight fit between the LED, lugs of the pots and the board on one end, and the board and switch on the other end. I included the space to offer the use of a battery, even though I don't use them. Because of the tightness top to bottom, I still only had room for a bit of 3M adhesive tape since the board was basically stuck under the switch. Normally, I use that or velcro and mount the board to the back of the pots. The pot condoms prevent shorts. This layout is very similar to Tonepad's in that it allows the build of a TS808 or an SD-1. I had planned maybe to sell a few.

I tend to draw my layouts so that I can either etch or order them professionally made using the same layout. Of course, drawing up a double-sided board would allow for the use of board mounted pots due to the added flexibility in doing the layout. This is something I may tackle in the near future.

The image below is the above mentioned build. It was a board I made up over a year ago and then never used until now. It was originally drawn in DIYLC but has since been redrawn in diptrace with a ground pour and so on.

The only way I could see myself using the mounts I put on my boards would be to omit the battery or use an oversized enclosure like you see on the old fuzzcentral builds. I like having the option of a battery though as it is an added selling point.



I had so many issues with this damn build too.

[karbomusic]

The standoffs I use are 1/2 inch (I think) or rather just tall enough to leave ample room for the pot + pot condom and enough room on top to allow ~11mm tall caps etc., that's just enough clearance that it doesn't touch the bottom plate of the enclosure. Since I know that always works, I can now trust it.

The general fit problem I always solve by laying out the internals in Photoshop/Inkskape etc, to scale so that I can be 100% sure what fits where. Once I have a couple of templates, I just move parts around until I find what works best so it isn't very much work. Since it is to scale, I can print it out and use as the drill template.

[deadastronaut]

add a toggle..or 3....holds it in place...

[bloxstompboxes]

I need to work on learning inkscape or something similar to be able to better plan my enclosure fitting of all the components.

[R.G.]

Putting everything inside a stompbox is an exercise in 3-D thinking, a kind of 3-D puzzle. I actually watered down the advice in "PCB Layout for Musical Effects" so as to not run off timid beginners. In my opinion, a layout starts with a 3-D representation of the whole box and all its parts.

The reality is that if a PCB is intended for an enclosure, then the entirety of the enclosure, all the controls and even wire routing need to be decided on before the PCB is started. Positions of controls and such may be moved later if a complete incompatibility is found, but you have to start with the mechanical design. The PCB itself is the most-flexible part of the design, easiest to change.

I use Corel Draw. I used to do several 2-D views of parts in boxes before starting a PCB, but these days I use FreeCAD to do a 3-D design. It's completely free, if a true bear to learn.

[karbomusic]

I use Corel Draw. I used to do several 2-D views of parts in boxes before starting a PCB, but these days I use FreeCAD to do a 3-D design. It's completely free, if a true bear to learn.

I use Blender for all my 3-D printed designs, which after a $50 online course I can get around in pretty well. I'm dying to create the basic enclosure/parts for pedals so I can really check them in 3-D there. So if any of you guys have such parts and can export them in .STL format,  I'll buy them a virtual beer or virtual steak, or the real thing if you are close by. Otherwise, I can just use stickmen equivalents which would also work.