Ideas on how to mount FSR to enclosure

[patrick398]

Will be soldering and boxing up my SVF envelope filter tomorrow (basically the sabro SVF with a few changes and an FSR; schematic to follow shortly) but wondering if you guys had any ideas how best to mount the FSR to the front of the enclosure.

http://www.interlinkelectronics.com/FSR406.php

It has self adhesive backing so obviously i could just stick it on but i'm worried about peeling over time. Could do with some kind of border around the edges but just thought i'd throw it out to you wizz kids for any suggestions

Peace

[Mark Hammer]

First, thanks for kickstarting this.  FSRs are an underexploited resource for us stompbox types.

One possibility is the use of an adhesive-backed cork or other overlay.  You'll want some sort of impact-absorbing material over top anyway, or else the FSR resistance will tend to lose any nuance, and only give you min and max values.  One can buy cheap packages of those beige thick felt pads that go under furniture legs.  They come in a variety of shapes and sizes, and have an adhesive backing.  The challenge would be that, once the perimeter of the felt pad starts to lose its grip, accumulate dirt, and need replacing, the central part of that adhesive-backed pad will still stick to the FSR and potentially damage it during replacement.  So maybe a simple barrier between the adhesive on the back of the pad that would be in direct contact with the FSR is a good move.

[EBK]

The challenge would be that, once the perimeter of the felt pad starts to lose its grip, accumulate dirt, and need replacing, the central part of that adhesive-backed pad will still stick to the FSR and potentially damage it during replacement.  So maybe a simple barrier between the adhesive on the back of the pad that would be in direct contact with the FSR is a good move.

You could stick the felt pad to another surface, like a hinged flap over the FSR.  A thin sheet of plastic over the FSR, but not adhered directly to it, would protect the FSR from abrasion.

Top to bottom:
Hinged flap
Adhesive felt (attached to underside of flap)

Protective plastic film
FSR
Substrate (enclosure, etc.)

[EBK]

I also have an FSR on my workbench, by the way (I have the smaller, round kind).  My plan was to create a linear actuator by using a spring to press down on a metal coin, which will sit on the FSR.  I suppose my spring is the functional equivalent of Mark's impact-absorbing material.

[duck_arse]

mousepad.

[patrick398]

Yeah i was thinking something alone those lines. I'm not overly fussed how it looks but saying that i don't want something that looks totally naff. Mousepad is definitely a good shout for the actuating/protective element. I'm thinking something like this could be really cool: https://img0.etsystatic.com/109/0/7751466/il_570xN.912709776_doyu.jpg
That's totally naff in a cool way though right? 

If that was screwed onto the enclosure with mousepad foam underneath and then the FSR under that it could look pretty snazzy. Could even have a picture of my choosing in the frame haha. The only difficulty would be ensuring that zero (or minimal) pressure was being applied to the FSR when i'm not using it.

I just did the schematic on KiCad, never used it before so it took forever but i think it's right. It's been on the breadboard for a while and i've been throwing components in and out so what i've ended up with may be a little strange in places but i've arrived at a sound i really like so i've just going to leave it as is.

[patrick398]

Also, using the 'photo frame' style border around the FSR would allow for a small hole underneath one of the edges which i could feed the wire through

[Mark Hammer]

I find the ones I bought from Smallbear quite responsive.  Like I say, not that it is a weakness of any sort, but I find the challenge to be providing some impact buffering such that gradations of pressure can be easily applied.  In that spirit perhaps some sort of material underneath the FSR might be useful in addition to some sort of impact-diffusing material above it.  Of course, if a person is intending to use it as a sort of on/off device, then those concerns are moot.

Now that I think of it, and prompted by the thread I started regarding expression pedals, a person could stick one of these atop one of those small square Hammond boxes that Henretta uses (I think it is the 1590LB size) and use that for an expression-pedal of sorts.

[Kipper4]

Actually the break out box office s a good idea. Easy to replace and repair. Experiment with.

I've got some white 3mm thick foam if you want to try that.

Was going to suggest putting the fsr under the labelling with a big "Force Here" target.
But a breakout sounds good.
I'm not an enclosure salesman.

Can't wait to see this.

[patrick398]

https://www.youtube.com/watch?v=0maYbn8ED-A

[patrick398]

I think i'm going to try and use one of these, or at least part of it. It's basically the perfect size...45mm by 45mm. Just about fits over the fsr and doesn't take up much more room on the enclosure than necessary. I shall return (probably covered in superglue and with a broken fsr)

http://www.ebay.co.uk/itm/Blank-Photo-Keyring-1-5-10-25-50-100-Jumbo-Passport-Square-Round-Heart-Shape-/110836007300?var=&hash=item19ce574184:m:mNukosunKLqQjZmx6ORhoeA

Seems like they're only available in packs of 5 so if anyone is thinking of doing something similar, you know where to come.

[Processaurus]

Contact cement is good for glueing non metal things to metal. You put it on both sides and it is a formidable/permanent bond.

I see it in production music gear, like a drumkat I took apart. They used it to glue down the rubber drum pad that protects the FSR. They just glued the edges, rather than glueing the pad to the fsr, but that might have been to make replacing one of the pieces easier, since the fsr sheet and the rubber are expensive. Here it might not be worth it to bother.

[patrick398]

Thanks for the suggestion, i'll hit the hardware shop tomorrow

[Mark Hammer]

What is that white-ish goop I used to see used to adhere cover CDs to magazines all the time?.  It is thick enough to provide some useful cushioning, and appears to have sufficient adhesive properties, without being potentially destructive if the FSR is being removed.

[Kipper4]

In my experience working with paper and glue for the last 20+ years I'd suggest the glue is a low melt point hot melt glue we often refer to as nappy glue.
It's sticky enough to hold light items under pressure but will form a ball in the fingers and remove almost all traces.
Pressure sensitive hot melt
Maybe Mark.

[Mark Hammer]

Maybe, Rich.  But it feels more like silicon caulking than anything else, particularly since it stretches.

[patrick398]

I always referred to that as 'bogey' glue or 'booger' glue for those of you across the pond. Starts out kinda sitcky but then you can roll it up into a ball and flick it at a family member...the glue i mean of course.

[duck_arse]

I wuz thinking that "a" person Mark talks about might stick the fsr thing to the underside of the box, then glue mousepad over that, so the box sits on the neoprene-y stuff as a foot. and you might put in a thin card spacer or something, to unload the sensor from the box weight. then person can go absolutely mad with the box-top decorations.

and yes, boogey glue. not sure how we spelt it.