PCB mounting method

[stonerbox]

Here is a mechanical/mounting solution for others to try out, if they like.

I am aming for builds that will last, and relying on solderpoints for the coming 30 years, to handel major abuse, was not going to cut it.

I designed the PCB with several 4mm (0,157") mounting holes, got my hands on some long machine screws, nuts, washers and finally all-around steel strapping bands.
It turned out quite overkill, but I will sleep well at night.

The cheap pot is just for demo.

[crane]

it is hard to understand if this is to hold in place pcb or the pot.
a picture when mounted in enclosure would help.
what is wrong with mounting pot in enclosure hole and mounting pcb un plastic standoff?

[stonerbox]

Use your imagination, on all notes. 

[stonerbox]

Just mounted them (as a test) and it is rock solid but without any tensions. This will last 500 years, the PCB will probably rot before the mounts gives in.

[Fancy Lime]

If you're going to be secretive enough about your boards to bother with blurring them in a photo here, why not just fill the entire enclosure with black epoxy (the non conductive kind! Some of the black dies are conductive, so test first) after everything is mounted? Tank proof AND copy protected!

Andy

[stonerbox]

If you're going to be secretive enough about your boards to bother with blurring them in a photo here, why not just fill the entire enclosure with black epoxy (the non conductive kind! Some of the black dies are conductive, so test first) after everything is mounted? Tank proof AND copy protected!

Andy

I might just do that! The added weight will increase the Mojo-factor.

Anyways, I hope this gives people who are looking for a truly permanent mounting of PCBs some inspiration or just copy what I did.

[drdn0]

Solder joints on pots aren't going to crack if the pot is solidly mounted to an enclosure - the entire pot cannot move unless it is loosened.

A much easier (and less loony) solution would be just to tightly key your pots to the enclosure, and use star washers below the nut on top.

Pot can never rotate in the enclosure, and therefore the solder joints can never fail.

[stonerbox]

Listen, I see my way of going about this is somehow threatening to some, but you know what? You don't have to feel threatened or feed need to call me a loony. Ignore this post and just do things they way you like, after all, 99% of all builders/fabricators use the pot pins, and it works fine for a long while.

However, I did not want ugly screws on the front of the pedal or having the PCB swaying (ever so slightly) up and down, on thin solder points. I mean, have you seen how Noise, Industrial or Punk bands treat their equipment? Shit get tossed around, stepped on, beaten up, both on and off stage. So... my solution got rid of screws messing with the look of the artwork and makes it durable and highly reliable. All I need to do next is to omit clunky 3DPT stompswitches, and this thing will last through most abuse under a long god damned time. That's just my preference.

I like the idea of sharing with each other or even pointing out when people do wrongs, but please spare me from you ugly remarks and insults.


Here is a T-Rex that does heavy-duty PCB standoffs, which I personally appreciate a lot.

[Fancy Lime]

I'm pretty sure that drdn0 meant my epoxy suggestion by "loony", which I would agree with. I wasn't being entirely serious there and only had the idea because I saw that you blurred your boards in the image, which suggested a level of secrecy, which is quite unusual in this here forum. You of course have the right to not share stuff you don't want to share (which probably wasn't even the intention behind the blurring because you shared a picture of the unblurred board before). I just found the apparent dissonance between asking others to share their methods while hiding your own boards a bit funny. Again, that is everybody's right and I didn't want to school anyone or moralize about it. Just meant to make a harmless little joke.

Casting everything in epoxy would however indeed make for a very mechanically stable pedal and would probably look super rad with clear epoxy, if it's done right. Not easy to get the bubbles out unless you have a good vacuum chamber.

Edit: regular old standoffs mounted to the housing with screws and spacers are probably the most stable and easiest thing. Make sure to connect the pots with flexible wires in this case to make sure there is no stress on the solder joints. Or just make something with lots of pots in places that are chosen specifically to distribute the stress on the solder joints favorably. Or go with the super easy solution, which I have employed on my early pedals: all pots and other stuff connected by flexible wires, the board free floating in the housing and then wrap the board in so much isolating foam that it cannot really move anymore. Then quickly close the lid and never open it again, cause it ain't pretty.

[R.G.]

The steel strip is  new to me; creative solution I haven't seen before. Mechanical stress on solder joints can be a problem if you don't account for it.

The fundamental issue in pot (and switch and jack, etc.) is that the outside world interacts with the pot shaft (and switch actuator, and jack contacts,etc.) mechanically and the PCB interacts with the solder connections AND the mechanical mounting and PCB are not on the same plane, AND the relative plane of mounting of the actuators can be stressed by inaccuracies of holes and mounting, and/or mechanical stress on the chassis where the actuators are mounted.

The industry offers PCB mount pots with sheet metal supports built into the pots to take the mechanical stress. I've used this and it seems to work well. Often these have no bushing mounts at all, so the issue of mounting plane stresses is sidestepped; the stresses from actuator to PCB are resolved in the sheet-metal braces in the pots.

If you are willing to put in the time/money/labor for flying leads, and don't like screwheads through the box, you might try something like this:
https://www.mouser.com/datasheet/2/184/7-27_115-909012.pdf
These are still going strong in some boxes from 20+years ago - not all adhesives are weak, and these were designed for the purpose.
Also you could try cleaning the inside of the box with acetone and gluing threaded standoffs in with JB Weld or similar.
There are industrial grades of velcro that are not weak, and don't use weak, heat sensitive adhesives as well.
A middle ground is to make a snap-off section of PCB that carries just the pots and has jumper wires to the main PCB, as this gives both lower labor costs and decoupling the PCB from the pots and enclosure. It looks like you might be thinking about mounting the steel strip under the PCB mounting screws. If so, it makes the number of pots and steel screws now a consideration.

On epoxy copy protection - it doesn't work. This was a popular thing back in the 1990s and 2000s when people thought their new design (often a variant of a Tube Screamer 8-)  ) needed protection. Usually, epoxy covering attracted the very people who the epoxier didn't want to look - the ones who knew their materials and how to soften and remove epoxy. Potting and gooping are good for environmental protection, but they make service and repair nearly impossible, and attract copiers.

[stonerbox]

Thank you, RG.

We have several more tricks up our slevens than just gooping, I have read on a certain page by "someone" but also found other ways.. We will also be able to repair any devices that need service down the line.


This thread keeps going off topic! I hope someone finds the steel strapping band useful, if they are looking for similar results as me. I have never seen it been done before and wanted people to know it is possible.

[amptramp]

Epoxy copy protection wasn't usually used to conceal a great new design - it was usually used to hide the fact that the manufacturer was infringing on someone else's design.

There was a plastic material to the steel strapping with smaller holes that turned out to be a great way to space LED's for when you had to line them up with equal spacing.  This plastic was usually used to hold children's plush toys into the box they came in.

[Baran Ismen]

Okay, so I'm trying to figure out what's good or how beneficial this solution would be.

Theoretically, you're binding the pots to the PCB (or vice versa, doesn't matter much), so that the PCB won't float inside the enclosure, that's what I get from it. Personally, I liked the idea, it not only gives some space for the parts on the other side and the cables between the PCB and the pots but also holds the PCB steadily. The only thing that matters is the shaft/screw distance, which should be pre-considered and well-calculated beforehand. Also just came to my mind that one can also use metal spacers for this as well, distance separation might be narrower on them (2mm's), in case one can't find a specific length of screw.

What about those metal stuff, or straps as you address them? Are they something special, CNC-cut stuff, or something regular that everyone can find in any hardware store? Once said in a Vine video; "what are those?"

[davent]

Pipe strapping, hardware store.

[PRR]

Pipe strapping, hardware store.

Yeahbut....  The "common" pipe strapping is not 3/8" (pot) holes. 0.25" and 0.18".

https://www.amazon.com/Fixirons-Galvanized-4-Inch-100-Feet-Strapping/dp/B0CWLCC8CY

The strap in this thread *seems* to be the new-for-2022 Gardner-Bender GHS-32. Only one of the local home-stores stocks it. (I would use it more if the local Depot had it, but no.) There was a similar strap in the 1970s but has not been on shelves in a while?
https://www.gardnerbender.com/p/GHS-32/0-67-in-x-32-ft-20-Gauge-Pered
https://www.gardnerbender.com/-/media/inriver/GHS-32_Hanger%20Strap%20%20NPA_0422.pdf?modified=20220405160933

[davent]

My 'walk to' neighbourhood hardware store.

https://www.homehardware.ca/en/34-x-25-steel-pipe-strapping/p/3210634

[marcelomd]

Hi,

Someone with more experience in manufacturing please correct me.

I see 2 sources of mechanical stress between PCB and PCB mounted potentiometers:

1- tension and torque generated by misalignment between PCB+soldered potentiometers and the enclosure holes when fitting it all together;

2- torque when tightening the potentiometer nut and/or turning the potentiometer shaft.

Case 1 can be prevented by soldering the pots after everything is fitted and mounted on the enclosure.

Case 2 can be prevented by using that little metal tab that everyone breaks off and/or by using wires.

Again, someone please correct me, but the way I see it, the proposed solution, screws + straps, is cool, but addresses neither. It just creates a "virtual" enclosure, like a roll cage, or skeleton, inside the enclosure proper.

Mounting the PCB on screws does offer some shock resistance, though.

[stonerbox]

You will find these in all hardware stores. These are metal strips that is fastend with nails or screws, to hang up or steady stuff with. Cheap and super reliable.

USA
plain-steel-all-round-strapping

dahl-all-round-3-4-in-x-25-ft-steel-strapping

UK
Colored "fixing" bands

Forgefix Galvanised Band 12mm x

What about those metal stuff, or straps as you address them? Are they something special, CNC-cut stuff, or something regular that everyone can find in any hardware store? Once said in a Vine video; "what are those?"

[Phend]

The ultimate in pedal box design

[stonerbox]

I believe you have misunderstood the design, the pots are not inserted into the PCB, they are only connected with stranded wires, so no strain will ever be present at these connections.

Again, someone please correct me, but the way I see it, the proposed solution, screws + straps, is cool, but addresses neither. It just creates a "virtual" enclosure, like a roll cage, or skeleton, inside the enclosure proper.

Dang it, I'm going to have to step up my game!

The ultimate in pedal box design