First working keyboard keycaps are off the printer! Only this bit to show as most of the print failed 😛
Well,, 3 prints failed, I’m trying to learn how to use my Photon Mono-X, so far mostly unsuccessfully, these were printed using a known good combination of Photon Mono and Commodore Brown resin 🙂 ….and still it partly failed!!
Next, I have to optimise the design for printing. I’d added some features to make them work better, but, those features don’t translate to printing very well, D’oh! (That’s called not doing Design For Manufacture!).
Resin printing can be a hard beast to tame, especially when printing 94/98 individual items (98 if I can two keyboard types!!)
This first print is literally an ‘auto supports, Jab a few extras on, hope for the best’ quick test to prove the mechanics. When the design is finished, I’ll need to spend a couple of solid DAYS (maybe a weeks worth of evenings) adding thousands of supports MANUALLY to ensure every keycap comes off the print perfect!
That sounds a lot, but printing a single item is different than printing the same item hundreds of times, so it’s really worth the up front investment in time.
And, speaking of time, I’ve just clocked about 600 hours evenings and weekends, on this project now 😛
I’m rather happy otherwise, next week, I should have a full working keybaord to demonstrate 🙂
Quite a lot of progress, but it doesn’t look like a lot of progress.
Firstly, I’ve had to re-do most of the keyboard CAD – I simply didn’t like the ‘blocky’ effect of the wider topped keycaps I’d created – as you can see below they look a lot more square in real life than they did in CAD…
I’ve now clocked well over 200 hours developing this set of keycaps, likley there’s going to be tens more tweaking / optimising!
So, along with the less blocky (more slopey) keys, I’d discovered my workflow in CAD had created tapered keys – the tops when viewed from above look like parallelograms, wheras the original Amiga had more square keys – it was quite a lot of work to alter this – see the parts below by the red arrows – the bottom bit is in towards the middle more than the top bit.
Progress to date has been surprisingly quick – most of the ‘easy’ stuff is now done and I’ve added some extra functionality. Most of the research is now done – have spent waaaaay too long googling connectors, Pogo pins and component types / dimensions.
My workflow generally is to eyeball, sketch, measure, adjust….Then when it’s close enough, i’ll print on paper, adjust in CAD, print again then………3D print
I’m quite chuffed – the first 3D print seems to fit reasonably well! – there’s some adjustments needed, mainly the top of the keycaps are a little too wide, but overall for a first run, not bad.
To work out a PCB outline, I’ve scanned the A500 Mini on a flatbed scanner and trace around the important parts, measuring many with calipers
Before I 3D printed the sample, I put the A500Mini on a flatbed scanner to match up the holes – as you can see, it’s pretty darn close! – you’re seeing a canvas underneath the actual CAD model of the keycaps in Fusion. The Enter key is black as i’d discovered a slight profile error, so spent half hour correcting a 0.2mm height error 😛
During the design phase, there’s a process of discovery. My main discovery for the A500Mini keyboard was that….I’d possibly need TWO PCB’s!!
If you look above at the underside of the keyboard you’ll see that there’s no space on the top for electronic components! The PCB needs to mount entirely flush to the case of the Mini. This means I’d need a PCB assembly service that can handle double sided boards (a possibility) – And to also consider a two PCB solution. There’s cost and ease of install considerations for both ways.
The A500Mini has a number of test points on the back, I think using Pogo Pins I can maybe make a clip-on PCB that can securely tap off the USB test points, meaning, a solderless install! – hence the upper white PCB that sits in place of the A500 PCB above
And, now I believe I’m going to go with a THREE PCB solution…….because…
the one with the holes in sits above the stock PCB
I figured I’d go one better and make a REAL fake floppy disc. and, the best thing, after several solid days of research and CAD testing, I believe it can work 🙂 – it’ll only need two small cuts inside the A500 case and be totally stock outside. there’s a little more tweaking needed for the floppy disc design to make the MicroSD slot more elegant . I’ve ordered a whole bunch of parts to physically trial this and see if it’s viable.
So, Summary. Still a long way to go, the Keyboard itself is the priority here, the ‘floppy disc’ is just a whimsy on my part for the time being, its development is secondary and may not even make it to a real release if it’s not robust enough.
Keycap CAD – Cosmetics finished, Just needs the ‘switch’ solution figured out
Main PCB – Outline finished, needs routing, quick job to finish
Not much of an update, just a couple of pictures to show i’m still slowly tinkering.
The keys do seem much easier to model as they’re less curvy. there’s only a top ‘dip’ in one plane which is easily extruded into the keys using circles that are varying radius’s to give a 0.9mm ‘dip’ in the top of the key. that dip will be much less prominent when the whole thing is shrunk 50%, but I like to try to be reasonably accurate.
First Proper scale PCB layout for the A500 Mini. it mostly looks like it’ll work – BUT, there’s some problems.
I’ve highlighted the problematic switches with white blocks
The Problem – Having switches at 0 degrees or 90 degrees means at some point, due to the staggered keyboard, some will overlap. I’ve spent a few hours optimising the rotation of the switches to reduce the number of overlaps to a minimum, AND, to give all those overlaps a common ‘thing’ that possibly provides one way of easily fixing this.
I’ve made it so that Every ‘overlapping’ switch has the bottom left pad causing the overlap. This means, with the right switch type, I can simply cut off this leg for each of the 8 problematic switches and have the keyboard work just fine!
In Most SMT switches this size, there’s 4 legs, but often only 2 are used, (single pole) or sometimes there’s 2 separate switches inside (double pole). provided I use the correct two pins, they should just work fine with 3 legs soldered in. This isn’t exactly an industrially abused keyboard, so 3 legs is plenty of mechanical support.
BUT – I’m unsure if I could ever convince a PCB assembly house to cut a leg off the switches and solder them at a reasonable price, meaning that I may need to solder these 8 manually myself.
There’s a potential other fix also – Rotating the switches at ‘odd’ angles!
If you squint closely, there’s now no overlapping pads on the switches, However, this comes with potential issues
1 – Manufacturing, companies may not want, or be able to put switches on the PCB at arbitary angles like this
2 -Available space within the A500 Mini is currently unknown, which may not give me enough height to be able to do this.
Physically, a 6mm switch, placed at 45 degrees ‘just’ fits within the available 9mm envelope for each 50% scale switch
What this means –
If I rotate the switch, I will not be able to have a recess on the keycaps. On the C64Mini, to keep the keyboard profile height correct, the switches sit about 1.5mm into the keycaps when pressed down. Without this recess, the new keys may need to sit higher than they should. But, this depends on how much space is available underneath the fake keyboard in the mini – it should be possible to add some spacers in to bring the height back down.
So, The big summary is, Right now, there’s no roadblocks to making this work. a Fully automated production is preferable to bring costs down, so i’ll keep working down that route.
Things to do –
Contact PCB manufacturers to figure out manufacturability
Minor update! – Slowly working on the PCB design for the Amiga Mini – I’m tempted to actually produce a few of these as a Beta run so I can get ahead on the keyboard matrix programming.
I’ve priced up on https://jlcpcb.com/parts/ a BOM to build a minimalist Pi pico so that I can place one directly on the keyboard – and surprise, just like the Arduino Pro Micro device – The sum of the components is more expensive than the price of a full Pi Pico ! BUT, and key point, it’s not all that much more. building Arduinos out of components were typically around DOUBLE the cost. The Pi Pico isn’t!.
However, adding a RP2040 discreet chip to my PCB adds a small level of additional complexity to the board and puts me at risk of parts going out of stock so it’ll be a weigh up when the real Amiga mini is released – If there’s enough space on-board to make a 2 layer board, I may well do this. If not – well, that’s what the TWO circuit boards above are.
Early days yet, but first look suggests that the above would be only marginally cheaper (almost not worth it) than putting a discreet pi pico on-board
oh, and of course, these will be fully populated boards! just add keycaps and ‘go’
Had a little play, using some SMT buttons i’m using in another project. These switches aren’t quite correct for this project – I need ‘square’ button-y bits and preferably ones with a small sticky-outy or inny bit that’ll let it capture a keycap straight.
Assuming the A500 Mini is 1/2 scale, like the C64Mini was then it’s looking good for keyboardification.
Half that gives about 235 x 162. take a bit off the 235 for the case thickness bit – gives 225. then height is set roughly by the number of keys ‘down’ and eyeballing the various membranes i’ve found!
However – I don’t know the internal space availability of the A500 yet – so plan going forward for now is to prototype as a 2 part PCB.
One design part of the C64 Mini keyboard kit I never really liked is the standalone Arduino Pro Micro mounted on the rear due to being no space. Adding it to the main PCB was also out of the question as the separate components would have been at least double that of a ‘cheap’ arduino.
I’ll keep a 31 way (ish) connector on the main keyboard part, so it essentially acts like a traditional Amiga Keyboard. I’ll then have a ‘special’ RP2040 based PCB that converts the Amiga matrix into USB for the A500.
I’m currently working on a design assuming I can use the same again. There’s very few switches on the market with a ‘square’ style centre part that can capture keycaps. I have leads on a few others, but plan this time is to find surface mount versions and try to get a batch ‘mass produced’ – i.e. little to no soldering needed for you lot!
Early days yet, it’s been quite hard to ‘get back into the grove’ . here’s hoping I get this finished in 2022!
Switches will be here in a day or two!, i’ll email everyone about kits shortly.
Purchased some ‘old gold’ pigment from https://www.resin8.co.uk/ and tried it with the keycaps for something different. Came out ‘ok’ – nice and gold on the top, but lacking in gold on the sides. I suspect the particles weren’t being agitated sufficiently and sank to the bottom.
I’ll try again soon with a higher concentration of pigment and see how that goes before considering offering these as a product!
The final hurdle for ‘good enough’ for me now is the space bar.
Every key prints lovely, except the largest one……Take a look
I’ve gotten all the ‘hard stuff’ over and done with first, or so I thought. Life’s taught me to generally avoid going for the low hanging fruit first, save the easy stuff for later when you need a boost.
Well, no matter what i’ve done (so far) in 12 iterations, have I been able to get a good looking space bar.
Now this has become my sole focus and roadblock for a successful print
Turns out that this is a combination of quite a few variables, I’ll list a few and probably follow up another time with clicky links and research
Exposure times are wrong –
They could be , I’ve really just gone and shoved stuff in to print and hoped for the best with standard settings. I Have now tweaked up the settings a little bit to 2.2s per layer due to mixing pigment in, and have had no real failures. I’ve also increased the first layers exposure times to 30s, still seeing minor issues there
FEP tension is wrong
Not really, This is a brand new printer, i’ve had zero catastrophic failures and have been overly cautious monitoring (and catching) early delamination from the print bed issues – Three times now
Possibly. I’ve 3 types (all anycubic) and seeing the same on all 3
Possibly, lots of people have been reporting issues in cold climates, I use the printer in the conservatory and it’s sub 10 degrees C in there regularly
Low temperatures cause increased viscosity and warpage issues with fine features from the FEP pulling them through the thicker resin
Too low exposure times on fine edges cause resin to cure, but not as hard as it should. So, when the layer sets on the bed, when it’s pulled off the FEP, it warps as it’s soft. This, I believe is causing the sagging issues i’m seeing on that space bar – it’s printed upside down, so the supports hold the points up, and between the walls sag, like an electric line held between two pylons
Probaly waaay too many supports, but this way, each ‘sag’ will be between supports that are just 1mm apart.
I’ve also nearly doubled the wall thickness to about 1.8mm – from 1mm
Hopefully now, this is the last step, Colour’s good, CAD is good, Supports are good.
I’ve ordered 2 Litres of clear resin ready to go and have a colour that’s not exact, but close and, importantly , very easy to re-create
Resin8 Earthy Brown, 3 ‘blobs’ of the end of a lollypop stick to 100ml of resin. and Black, 1 blob.
– The Rich brown used previously was too red. I’ll experiment a little with more black when running off the final tests
They’re a “100Pcs A28 Tactile Push Button Switch Cap 6*5.1mm Applies to 5.8*5.8 7*7 8*8 8.5*8.5 Self-Locking Switch Button Cap”
And, judge for yourself……
Well, it’s more comfortable than nothing, and certainly opens up some options for unusual keyboards in the future 😛
yes, it’s not perfect, BUT for £1.68 you can have non painful pokey bits and actually do a reasonable job of typing on basic
or, splash out £3.36 and go for a dual colour like I did 😛
BONUS PRIZE TIME………………..[edit, grabbed by someone! ]
THE first person to order a kit and mention that they want these keycaps, I’ll chuck in a set of grey/black ones as pictured for nothing – I purchased enough to do properly do 2.5 keyboards, or 3 if you don’t mind a mix / match of black and grey!
Note, if you’re ordering your own keycaps off aliexpress, the internal dimension is key here, they fit, you can go a little smaller
the absolute maximum external dimension is 9mm, this leaves about 0.48mm clearance between keycaps.
Most people would say this was caused by an over excited person, whom, upon waking early and discovering the complete print decided to not follow the correct drying / washing procedures in order to get it finished quickly!
I, err, disagree…
Either way, I now have a firm grasp of changes needed to the CAD model and also the supports needed in the slicer.
Those changes are fairly substantial, so I expect it’ll be a little while for my next update, happy to document them also if anyone’s interested.
It’s going to be a while yet, but I’ve finally fixed some long standing issues with the keyboard model i’ve been building in Fusion360
The main issue was a badly created model!. I’ve junked quite a lot and started back prior to when some odd dependencies crept in and really put some roadblocks on scaling things correctly and adding finishing touches.
But, it’s been worth it
That previous picture is the underside of the Keyboard – Those holes in the keys are 2.2 x 2.8 holes. it’s a first run at fitting the key switches into the keycaps. a lot more iteration needed to hollow it out a little and create some form of inbuilt snap-fit with stress relief, but…it’s a start!
The silver / grey keys over on the left are the ‘parent’ keys
If I make an update to the curves or size of a parent key – it rolls out to all the same sized keys in its row
if I need to iterate the hole size for the key switches, I simply change a few parameters for the hole size and it rolls out to all the keys in one go.
I’ve taken so long to develop it parametrically as it’ll now be so much quicker to iterate
and, here’s a new render!……..going to spend the next few weeks iterating, and hopefully over Christmas , fire up the resin 3D printer for the first time!
After a few days, I’ve now got something workable – The switches being Thru-hole allow ease of routing on both the top and the bottom layers. I’ve named each switch and diode with the keyboard’s actual Symbol to make placing them on the PCB much easier. you’re seeing the results of a few days work (maybe about 4 hours all up) of starting from scratch on the design.
Next step will be aligning the PCB layout and spacing with the plastic buttons
I’ve done what I can based upon rough assumptions above – the top row of switches for example – its row of buttons ‘just’ fits within my calipers – so it’s about 151mm wide