The new Beta has arrived and if fits *Perfectly*
and here’s some glory shots from the front and back.
Next step, soldering and, that’s a wrap for the Arduino based controller 🙂
There’s a few very minor tweaks needed for a production version of this, but there’s nothing I can think of now that needs changing. Any future design changes will need to come from feedback from the Beta testers.
One tiny thing i’ve picked up, that’s really a non-issue, but i’m going to change it anyway – the clearance between the PCB and the next case is very tight. I need to allow just a little more to really make things feel good when assembling
An example – the picture below shows the case, upside down from the joystick side – the original screw looks slightly silver
I’ve exaggerated the true distance here, but it shows the clearance i’m on about – realistically, there’s a lot less than this.
The tallest protrusions on the Next PCB are the joystick and VGA ports – both of which stick out just over 2.5mm from underneath the PCB, lets say 2.6mm
In theory, this suggests that, provided I keep any ‘add-on’ to the case < 2.6mm, it will fit perfectly!
Here’s a quick CAD rendering of the screw into my PCB –
That screw head has a roughly 0.5mm rim and tapers down to the 3mm width over about 1.5mm.
Here’s a cutaway view – with the original hole in my PCB at 5mm, which gives a nice 0.3mm overlap to hold my PCB down in
As you can see above – the top of the screw head should sit about 0.714mm above my PCB
in practice, it’s actually closer to 0.6mm with the 5mm hole.
What this means.
Next PCB + 1.6mm (my PCB) + 0.714mm = 2.314mm height above the Next PCB total.
Actual measurements – it’s a bit less! what’s important is that the 2.3mm is << the 2.54mm height of the highest protrusion on the next PCB
BUT…experimenting putting the case back together, re-assembling to test for clearance shows that it doesn’t feel right re-assembling the case.
I think that it’s so tight in there that when re-assembling, there needs to be a bit more clearance to allow for flex and to allow a bit of a push in – if it hits the bottom when pushing, it doesnt feel ok.
I need to make the hole in my PCB just a tiny bit larger to allow the screw to sit just a tiny bit lower – note the slight gap below. I’ve changed the hole from 5mm to 5.2mm. The screws i’m using are supposed to be 5.3mm, so this gives just 0.1mm clearance! BUT….
it gains the extra depth I need to allow the case to flex imperceptibly when closing so it just feels right. – I’ve gone from 0.714mm protruding to just 0.574, a 0.14mm reduction.
The 5.3mm screw sitting inside the 5.2mm hole.
Now, why this generated a blog post –
I’ve assumed that everything I do needs to ensure t hat I don’t use more than 2.5mm below the board – My PCB, if it’s 1.6mm thick can only have protrusions 0.9mm high.
That assumption wasn’t true. There seems to be some form of taper, lengthways inside the next case, meaning that the Next circuit board actually sits a fraction higher on its standoffs at the coloured insert sides than it does on the SD card side.
This means the clearance between the PCB and the case is less on the inserts side than the SD card side!
I’d speculate that it’s likely to be some sort of drafting angle to allow release from the injection moulding machines.
it’s 10’ths of a mm, but has thrown out some careful calculations
The summary of all that waffle – I’m making the 5mm screw holes a bit bigger in the production PCB to give a better feel for installation.