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geekhack Projects => Making Stuff Together! => Topic started by: problemxyz on Wed, 01 September 2021, 07:57:05

Title: PE foam conductiveness - is testing with a multimeter good enough?
Post by: problemxyz on Wed, 01 September 2021, 07:57:05
Really what the topic title says.
Can you just rest the pins of a multimeter on the foam and decide its not conductive when there is no beep for continuity?

Asking because I have a bunch laying around from packing.
Title: Re: PE foam conductiveness - is testing with a multimeter good enough?
Post by: nevin on Wed, 01 September 2021, 09:17:49
PE = you mean, polyethylene?
typically, no, not conductive. commonly used as an insulator.

what do you want to use it for? (how do you want to use it?)

if you want to read into it more, do a google search for "polyethylene foam electrical conductivity"
Title: Re: PE foam conductiveness - is testing with a multimeter good enough?
Post by: problemxyz on Wed, 01 September 2021, 10:10:25
PE = you mean, polyethylene?
typically, no, not conductive. commonly used as an insulator.

what do you want to use it for? (how do you want to use it?)

if you want to read into it more, do a google search for "polyethylene foam electrical conductivity"


PE I mean the foam from the mod videos that say you can find it as packing foam but you need to see it's non conductive.
When I google PE foam it does say polyethylene so I guess that's what it is.

I want to use it for the PE foam mod that is becoming popular.


And I did try to read up on it more but I end up on ancient industrial webpages about materials that I don't understand because I don't have a degree in chemistry. Leave alone how it's going to tell me if the foam I have laying around is going to be dangerous or not, or how I could test it.

Of course I could order some more foam that says non-conductive/anti-static but if I can avoid ordering another little small thing plus shipping I would be very happy. It's been adding up quite a bit lately. As I can image many of us can relate.
Title: Re: PE foam conductiveness - is testing with a multimeter good enough?
Post by: nevin on Wed, 01 September 2021, 10:33:42
yes, should be fine.

"craft foam" is also often used. usually an EVA foam (ethylene-vinyl acetate copolymer foam).... pretty dense, small cell. what's typically used between the pcb and the plate to take up space.

watched the video.... if that's the profile you're going for thick PBT caps will also help push it that direction, if your pcb has relief cutouts, you can tape those (keep the flex, get back the better sound) and of course, add the foam.

plate material can also effect the sound. what plate material are you using? (for what you're going for, i'd suggest FR4, or plateless if your board supports it)
Title: Re: PE foam conductiveness - is testing with a multimeter good enough?
Post by: problemxyz on Fri, 03 September 2021, 02:15:45

"craft foam" is also often used. usually an EVA foam (ethylene-vinyl acetate copolymer foam).... pretty dense, small cell. what's typically used between the pcb and the plate to take up space.

watched the video.... if that's the profile you're going for thick PBT caps will also help push it that direction, if your pcb has relief cutouts, you can tape those (keep the flex, get back the better sound) and of course, add the foam.

plate material can also effect the sound. what plate material are you using? (for what you're going for, i'd suggest FR4, or plateless if your board supports it)

This is for a GMMK full size, a keyboard that is built quite different than what you are describing. The plate and the top case of the keyboard are just one piece so there is no fancy plate experimenting or anything. Its just the aluminum plate of this top case. All I want for that keyboard is to sound less like a box of wet cardboard. I did put PE foam in it now according to the mod directions of something like the video.
Currently I have thick PBT keycaps on it, which are cheap YMDK's but they have the lowest pitch of other keycaps which are ducky doubleshot and cherry profile double shots (all of them PBT)

The EVA foam could be a route yes, a more well known mod and maybe that is the answer.
Because by now I have have performed the mod and the keyboard sounds even more boxy, although a bit muted and and lower pitched.
Im also afraid the PE foam I put in is too thick, some switches have a hard time catching on to the plate.

This is my new model for what should be possible for my GMMK.

Title: Re: PE foam conductiveness - is testing with a multimeter good enough?
Post by: nevin on Fri, 03 September 2021, 07:52:00
noting wrong with cheap YMDK. i' ve been running blanks from them and NPKC for years and they are my favorite cheap, thick, pbt caps.

doesn't sound that bad.
- top mount doesn't help
- only thing i can think of (that you haven't tried or done already) is possibly a lighter spring, for a little less snap when returning...?
- have you tried dampened switches? aliaz (or dampened red's) have a smaller "bumper" than the boba u4's
Title: Re: PE foam conductiveness - is testing with a multimeter good enough?
Post by: SilitekModder on Wed, 08 September 2021, 18:27:07
As long as it's not antistatic you should be fine.
Antistatic packaging is slightly conductive I believe.