mounting keypad to acrylic faceplate - suggestions?

  • Finally getting around to putting the finishing touches on my kit, so it's time to move on from rubber bands and attach the keypad to the faceplate more permanently.

    I'm using a 6mm acrylic faceplate (from big blue saw) and wondering how others who were in that group buy have gone about mounting the keypad. I'm concerned that just screwing bolts directly into the acrylic from underneath (after drilling guide holes) may result in the bolt eventually stripping out , so I'm looking at going for countersunk bolts going all the way through the faceplate.

    I grabbed some bolts that looked the right size from Jaycar today - but I think I've got a metric versus imperial problem - I've got M3 metric sized bolts, but they're just slightly too big to fit through the holes in the PCB of the keypad - which I guess is sized for an imperial #43 size drill bit.

    Is there any risk of damaging the PCB if I use the metric sized bolts? They'll tap into the holes just slightly, but I might be able to find some imperial sized bolts if I dig around the right hardware stores....

    thanks for any advice - would love to hear how other acrylic faceplate folks have approached this task....

  • i don't think you'll have any problems. i put space around the holes to avoid bridging any traces. one thing though is if you put a nut on the other side of the pcb it might be large and overlap traces, which may rub away the soldermask over time and create bridges. add a plastic washer or something in between the nut and pcb.

    you could even drill out the pcb holes a second time, make them a bit larger.

    i'm all for completely switching over to metric. america just can't handle it, though.

  • @ Frogstar can you take a pic of the acrylic top..A bunch of us are looking into a 128 style top for two 40h kits. I would love to see it with the LEDs on and off to get an idea of light bleed. Thanks.

    @ Tehn. I'm with you on Metric. Americans need to just suck it up and switch to what the rest of the world is using. It would save tons on printing and we would lose less satallites!

  • @tehn:
    >i'm all for completely switching over to metric. america just can't handle it, >though.

    I always use metric when I write, and put the conversion in parentheses. Makes it accessible to US citizens while making the point it's not the world's system. It needs to be deprecated!

    There are only three nations on the globe who have not adopted metric. Maybe if enough of us pave the way, then Myanmar and Liberia will officially switch and the United States will finally make its move. ;)

  • thanks all - I'll post an update (and some pics) once I've finished putting the enclosure together.

    c1t1zen - I'll also try to take some pics so you can see the light bleed - but to be honest, the existing photos of some of the kits (e.g. bolig's http://www.flickr.com/photos/boligrafoe/sets/72157600946452355/ ) give you a good idea of how little bleed there is. if you're thinking about having a clear acrylic faceplate, then I think the main aesthetic consideration is whether you want to see the whole of the rubber moulding of the keypad (and a tiny bit of green pcb) or just the keys. Light bleed from the LEDs is not really an issue, IMHO. I'm still considering either painting or putting a tint underneath my acrylic faceplate, but there's also a lot of appeal in the combination of clear acrylic and wood.

    If I could, I'd actually go for a 100% enclosure (vacuum formed perhaps) but I haven't had time to really explore that option.

  • You could make templates of different colors and designs, keep the top plate removable, and slip the templates between the clear acrylic and the buttons. Essentially re-skin your monome for different apps.

  • seems like making transparencies would be the best way to go. i have thought of doing this for molar and monochrome if i printed some type on there at 10pt it would fit in the "margins" between the pads. i think it could be useful for the 40h but probably even more so for the 256 or 128.

  • Are there any examples of the PCB board being supported from underneath? If this was easy, then I'd consider going acrylic.

  • >> ...i'm all for completely switching over to metric. america just can't handle it, though.

    Yeah, but you gotta wonder, I mean 10 cm SOUNDS bigger than 4", but... ;)

    As for supporting the button pcb I haven't tried it but it looks like standoffs could support it pretty well from underneath. You could use add a stiffening layer of plastic or something between 2 standoffs to make it even stronger.

    I have these kind of metal standoffs that are male on one end female on the other, you could attach them from the top with very thin bolts this might also provide an opportunity to attach the acrylic in some clever way.

  • back OT,

    > I'm concerned that just screwing bolts directly into the acrylic from underneath
    > (after drilling guide holes) may result in the bolt eventually stripping out ,

    i'm a bit worried about this as well. is there any other way besides drilling all the way through? i'd like to avoid having screw caps on top, but i guess if it can't be avoided...

  • you should be able to use a wider threaded screw directly into the plexi without worry of stripping. 4-40 (what we use for the aluminum) probably won't do the trick though.