Author Topic: Floating PCB?  (Read 599 times)

nolatone

Floating PCB?
« on: March 08, 2018, 12:14:29 AM »
Hi all,

I've been reading and pondering how to mount the PCB in a new pedal I'm working on. I've read various approaches and various objections/concerns to those various approaches. I've been thinking of a floating PCB with no hard mount. That may sound wacky, but hear me out...

My Nolatone amps use 20GA solid core Carol hookup wire which is very sturdy. Even though the turret boards are mounted using 4 screws, nylon standoffs and kep nuts, I'm quite sure I could omit those screws and it would be just *fine*. I can unbolt them, and with all that sturdy hookup wire and the short runs my layout uses, that board doesn't budge, and this is a 1/8" thick board, MUCH larger than what I'm working with on pedals.

I'm using the same wire in the pedal prototypes I've been working on. One of them uses the Alpha board mount pots, which is how the PCB is secured in that one, but I can imagine I could just let the board float and let the sturdy Carol wire leads hold it in place. They connect at various points around the board so there would be no one stress point to create a risk of a failing solder joint.

Plus, I could imagine if a pedal took a hit, having the board "suspended" by wires might help make it more resilient to damage from jarring than one that was hard mounted to the case via standoffs.

Is anyone aware of this being done, and if so, are there known issues?

diffeq

Re: Floating PCB?
« Reply #1 on: March 08, 2018, 01:35:32 AM »
Main issue is that sturdy wire strains the copper layer it is solder to when moved, even in through-hole way. It may be alright in itself, but it gets risky if the board was overheated slightly when soldered and bond between copper and laminate body got a little loose - it can get invisible cracks surrounding the solder joint. With standoffs, board won't move when chassis is "bumped",  so less stress on PCB layers.

DIY Bass

Re: Floating PCB?
« Reply #2 on: March 08, 2018, 04:38:42 AM »
If you suspend a board flexibly, you need to make absolutely sure that there is no way it can come in contact with a metal box and short out.  If there is a way that it might maybe happen in a 1 in a million chance, then it will happen within 5 minutes of the box being closed up.

merlinb

Re: Floating PCB?
« Reply #3 on: March 08, 2018, 05:44:45 AM »
20ga solid core wire in a vibrating/mobile environment will snap, eventually. Always.

antonis

Re: Floating PCB?
« Reply #4 on: March 08, 2018, 06:04:22 AM »
No Wellcome yet..??

@nolatone: You've got a remarkably low wellcoming factor..  :icon_frown:
Can't follow your signature changes, Stephen..!!

EBK

Re: Floating PCB?
« Reply #5 on: March 08, 2018, 06:36:16 AM »
Main issue is that sturdy wire strains the copper layer it is solder to when moved, even in through-hole way. It may be alright in itself, but it gets risky if the board was overheated slightly when soldered and bond between copper and laminate body got a little loose - it can get invisible cracks surrounding the solder joint. With standoffs, board won't move when chassis is "bumped",  so less stress on PCB layers.
Are you using cheap phenolic resin boards?  A solution to the stated problems would be a better substrate and thicker copper.
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

stallik

Re: Floating PCB?
« Reply #6 on: March 08, 2018, 07:05:44 AM »
I have, in the past, left pcbs and veroboard floating in this way as a temporary solution.
Where the board had to be floated above other things, it was easy to use wires attached to dummy pads on the board and fix the other end to something at the same level in the enclosure so the board could never move up or down too much.
Id never leave it like that though, for fear of a failure though Ive not had one yet. Self adhesive standoffs work well for me most of the time

Oh, and welcome
« Last Edit: March 08, 2018, 07:08:24 AM by stallik »
Insanity: doing the same thing over and over again and expecting different results. Albert Einstein

vigilante397

Re: Floating PCB?
« Reply #7 on: March 08, 2018, 10:15:14 AM »
WELCOME!!!

There we go, that feels better ;D

I have always used solid core wire because I liked the fact that it stayed where I put it, and on my first several (like honestly 50 or so) builds I left the PCB more or less floating and have had few issues. That being said I always make sure the board is pushed flat onto the backs of the pots (I always use pots with the plastic covers) so it has less directions to travel. Eventually I started using double-stick tape between the pots and the board. Less work than hard-mounting, more secure than floating, and still easily removable if needs be. All that being said, every amp I have built I use standoffs securely mounted to the chassis.

I hope some part of that is helpful :P
"I'm not sure what "serious design flaws" you see. Does it explode or poison your dog?" - PRR

"Tayda's Whipping Boy" "Most Detestable Forum Member 2018"

http://www.sushiboxfx.com

samhay

Re: Floating PCB?
« Reply #8 on: March 08, 2018, 10:47:54 AM »
^
what they said, including the welcome.

If you are building something to kick around your bedroom floor, it will probably survive for quite a while with the PCB 'floating'. The world is full of such boxes, and many of them still work.


But why not do it properly? Pete Cornish can charge silly money for guitar effects because he built his reputation on building gig-worthy kit. Below is what it looks like in the box. All it takes to do something similar is a little planning so:
1. the PCB/board has room for standoffs and
2. there is enough room for the standoffs to actually fit in the box.


(from: http://coldcrafteffects.net/blog/tag/cornish/)
« Last Edit: March 08, 2018, 10:52:04 AM by samhay »
I'm a refugee of the great dropbox purge of '17.
Project details (schematics, layouts, etc) are slowly being added here: http://samdump.wordpress.com

nolatone

Re: Floating PCB?
« Reply #9 on: March 08, 2018, 12:22:46 PM »
No Wellcome yet..??

@nolatone: You've got a remarkably low wellcoming factor..  :icon_frown:

Sorry, I don't know what a wellcoming factor is. Was I supposed to do something before posting?

nolatone

Re: Floating PCB?
« Reply #10 on: March 08, 2018, 12:26:49 PM »
Main issue is that sturdy wire strains the copper layer it is solder to when moved, even in through-hole way. It may be alright in itself, but it gets risky if the board was overheated slightly when soldered and bond between copper and laminate body got a little loose - it can get invisible cracks surrounding the solder joint. With standoffs, board won't move when chassis is "bumped",  so less stress on PCB layers.
Are you using cheap phenolic resin boards?  A solution to the stated problems would be a better substrate and thicker copper.

I've not yet had boards fabricated. I'm a noob when it comes to PCB material. All my experience so far has been with G10 glass epoxy drilled for turrets, but since I don't think many people will want a sheet cake pan sized pedal on their board, I'll need to learn the PCB ropes.

A lot of good input here. I'll be digesting it further when I have a bit more time.

Thanks to all!

Paul

vigilante397

Re: Floating PCB?
« Reply #11 on: March 08, 2018, 12:39:17 PM »
@nolatone: You've got a remarkably low wellcoming factor..  :icon_frown:

Sorry, I don't know what a wellcoming factor is. Was I supposed to do something before posting?

It's kind of a tradition that before anything else on a new member's first post we formally welcome them to the forum, and I think he was commenting on the fact that nobody had really done that before jumping into the question you posed. Everyone here is really cool and remarkably helpful, I think everyone just got excited to answer your question :P
"I'm not sure what "serious design flaws" you see. Does it explode or poison your dog?" - PRR

"Tayda's Whipping Boy" "Most Detestable Forum Member 2018"

http://www.sushiboxfx.com

nolatone

Re: Floating PCB?
« Reply #12 on: March 08, 2018, 12:46:11 PM »
^
what they said, including the welcome.

If you are building something to kick around your bedroom floor, it will probably survive for quite a while with the PCB 'floating'. The world is full of such boxes, and many of them still work.


But why not do it properly? Pete Cornish can charge silly money for guitar effects because he built his reputation on building gig-worthy kit. Below is what it looks like in the box. All it takes to do something similar is a little planning so:
1. the PCB/board has room for standoffs and
2. there is enough room for the standoffs to actually fit in the box.


(from: http://coldcrafteffects.net/blog/tag/cornish/)

I wonder if something new to market could get away with the larger footprint required for the beautiful internal layout of the Cornish pedals.

vigilante397

Re: Floating PCB?
« Reply #13 on: March 08, 2018, 12:55:10 PM »
I wonder if something new to market could get away with the larger footprint required for the beautiful internal layout of the Cornish pedals.

Only one way to find out ;) If it's cool enough people will make room on their board to fit it, but if it takes the same space as 3 normal pedals and is mediocre then it will obviously not do well. Also in my experience guitarists are more understanding of more complicated pedals (modulation, anything with 4 or more knobs) being larger, but if you have a 2-knob fuzz in a huge box chances are people won't be thrilled about it.

Side note: took a look at some of your amps, you do excellent work. Good luck with your pedal endeavors ;D
"I'm not sure what "serious design flaws" you see. Does it explode or poison your dog?" - PRR

"Tayda's Whipping Boy" "Most Detestable Forum Member 2018"

http://www.sushiboxfx.com