The A500 mini - Working Keyboard Mod

Everybody, press the key to start. Okay, keyboard and mouse, I believe, is how you... [Music] After receiving my A500 Mini from Amazon (link in the description), there was one thing I really thought was missing. It really does make sense why the keyboard is non-functional. The scale is not conducive to any real usefulness. I still thought it would be a cool project to create a working keyboard for the A500 Mini. At the very least, I can always learn from these types of projects.

keyboard is non-functional the scale is not conducive to any real usefulness I still thought it would be a cool project to create a working keyboard for the A500 Mini at the very least I can always learn from these types of projects

The truth is, I never had very high expectations for this build. Once I opened up the case and looked at the clearances, unfortunately, I lost the footage of opening up the case and examining the keyboard, but here is a pretty good representation of the key assembly that I made as part of the design process. The injection molded key assembly is actually three parts separated by color. Unlike the outer case, the key assemblies are painted. The underlying color of the plastic is black, as you will see later. The base of this assembly is a scant 1.6 millimeters thick. There is not enough room for any type of plunger or otherwise ergonomic key switches, at least not if I wanted to keep the case looking normal from the outside and have minimal modifications on the inside. So that means I need to use micro switches. There was a bit of room in the upper part of the case, so I looked online for the smallest keyboard controller I could find. I thought about taking the time and effort to make my own controller, but I quickly found a small controller designed just for this kind of DIY project. The 104-key version should suffice for the A500's 94 keys. It comes with a goofy key matrix, which I will undoubtedly replace with my own custom one for the A500 Mini. The dimensions of the controller board are not listed, but fortunately, someone answered my question on the subject.

representation of the key assembly that I made as part of the design process the injection molded key assembly is actually three parts separated by color unlike the outer case the key assemblies are painted the underlying color of the

Wait, 152 millimeters? That's the keyboard matrix, not the controller board. It's probably because I misspelled "please write." Using the pictures as a reference, I compared the dimensions given, and it seemed small enough. I plan to remove the USB port, which will save a lot of room. So I rolled the dice and ordered it. Here's to hoping. This picture was taken in perspective. While I wait for the controller board to come in, I went in search of the right micro switches. I bought a ton of them.

keep the case looking normal from the outside and having minimal modifications on the inside so that means I need to use micro switches there was a bit of room in the upper part of the case so I looked online for

If you know anything about prototyping, you can look at the data sheet for dimensions all you want, but you will never know for sure until you have one in hand. The two types of micro switches that would work are snap dome and button type. The only other way in such a thin application was to use a custom membrane, but that would either take longer to design, be more expensive, or both. Regardless, once I had received my plethora of switches, I decided to use this button switch, which seemed to have the right balance of tactile feel and ease of installing on a PCB. I then received my keyboard controller kit and made sure it worked with the A500 Mini. It seemed to work fine, so then I had to go about reverse engineering the matrix so I could replicate it with the needed modifications for the A500. Of great help was the fact the backside of the matrix was labeled with the keys and also with what seemed to be numbered row and column designations on the connector. Then it was simply the tedious task of creating a schematic with all the information gathered. I decided to lay the schematic out roughly the way the keyboard is laid out to help in revising and troubleshooting mistakes I may make. By the way, I do not know who designed that keyboard matrix that came with the kit, but they certainly do not suffer from OCD. Look at how these row and column paths jump around.

suffice for the a500s 94 keys it comes with a goofy key Matrix which I will undoubtedly replace with my own custom one for the A500 Mini the dimensions of the controller board are not listed but fortunately someone answered my question on the subject

If it was me, this schematic would have traces that look like a grid rather than a rat's nest. Perhaps it would look better if this was a Chinese language keyboard matrix. Pretty likely this was designed and produced in China. So then it is the equally tedious task of creating a PCB layout. This is what happens when you convert the schematic to a PCB. You still have to do all the placement and labeling work, but at least all the components are here. It starts with the dimensions of the PCB. I'm going to replicate the original keyboard base for the A500 Mini, including this cutout. Foreign s here is our final product, and you can see more of the rat's nest as I highlight signal paths. Not ideal. And here you can see I built in a caps lock LED, the wire connections for which are located on the back of the PCB in a convenient spot. I have a lot of experience modding projects for LEDs, and at this stage, I have a rough idea of how I will be showing it on the actual caps lock key. So we have a PCB figured out and the components sorted. So what am I going to do about actual keys on the keyboard? I thought of 3D printing keycaps, but really, I already have some on the A500 Mini. The path of least resistance would clearly be to cut these out and use them. That decided, I know I can't just glue them on top of the micro switches with such a small contact point on the top. That would never last. I came up with the idea of making a flexible support membrane to glue the keycaps to. I can do this with my 3D printer using TPU filament. I rarely use this flexible filament as the parts I usually print need to be rigid, but I'll be damned if this wasn't a good use of it. For those unfamiliar, the major drawback of using TPU is it is hygroscopic. It absorbs moisture from the air. I live in a moderately humid area, which means my prints come out stringy unless I keep the filament dry or use a dehydrator on it. As it turns out, this is not really an issue because, remember, this will be a substrate for the keys rather than a visible part. I will just have to yank off the stringy bits. I just need to be able to glue the keycaps to it, and I see that there is a cavity under each key. I will design a membrane that has nubs to go into those cavities, and I will make them slightly smaller to give myself some wiggle room, literally, in order to tweak the alignment and position of the keycaps. I will also create a very thin spacer out of regular ABS plastic to go between the PCB and the membrane to lift the membrane off the PCB and help mitigate accidental key presses. [Music] Foreign [Music] Okay, so I got a system down. Actually, when you keep doing this, you got to do this 96 times or whatever it is, and, uh, you know, basically I can cut just enough with enough experience doing a dozen of them or so by now, cutting just enough to make it super loose and pretty much where I need it, and then the thing kind of basically just pulls off. And then from there, I can just finish it off just rubbing on the sandpaper, and this way it only takes me one to two minutes to do each one, whereas the first few, you know, is up to like five minutes a key or something ridiculous like that. Still have to cut out the part that got melted on the inside. You got to cut it out good because it will hang up on the TPU posts. And also, I didn't, uh, probably I'm going to mention this before, but I didn't properly have my TPU dry when I started printing it, and these posts are kind of ugly, but, you know what, for the purposes of this, they actually kind of work. So [Music] [Applause] [Music] As I said, I had four iterations of the PCB. I had issues like needing to change the micro switch pad placements, ribbon connector poor placement, and of course the addition of the caps lock LED. Okay, so this is the latest version, um, version zero point four. Okay, so obviously we went through four versions of this. It didn't take too long to get it correct. Um, a couple things I did is I shrunk down the labels here so that they would fit in the corner instead of having them spread out over this area. And a very disappointing thing I did was I took the caps lock LED on version zero point three and I put it underneath this where this switch needs to go here for the caps lock, which was really dumb. I don't know why I did that. So here it is off to the side, and hopefully a LED...

so I rolled the dice and ordered it here's to hoping this picture was taken in perspective while I wait for the controller board to come in I went in search of the right micro switches I bought a ton of them

if you know anything about prototyping you can look at the data sheet for Dimensions all you want but you will never know for sure until you have one in hand the two types of micro switches that would work are snap Dome and button type

the only other way in such a thin application was to use a custom membrane but that would either take longer to design be more expensive or both regardless once I had received my plethora of switches I decided to use

this button switch which seemed to have the right balance of tactile feel and ease of installing on a PCB I then received my keyboard controller kit and made sure it worked with the A500 mini it seemed to work fine so then

I had to go about reverse engineering The Matrix so I could replicate it with the needed modifications for the A500 of great help was the fact the back side of the Matrix was labeled with the keys and also with what seemed to be numbered

row and column designations on the connector then it was simply the tedious task of creating a schematic with all the information gathered I decided to lay the schematic out roughly the way the keyboard is laid out to help in revising

and troubleshooting mistakes I may make by the way I do not know who designed that keyboard Matrix that came with the kit but they certainly do not suffer from OCD look at how these row and column paths Jump Around

if it was me this schematic would have traces that look like a grid rather than A Rat's Nest perhaps it would look better if this was a Chinese language keyboard Matrix pretty likely this was designed and produced in China

so then it is the equally tedious task of creating a PCB layout this is what happens when you convert the schematic to a PCB you still have to do all the placement and labeling work but at least all the

components are here it starts with the dimensions of the PCB I'm going to replicate the original keyboard base for the A500 mini including this cutout foreign s here is our final product and you can see more of The Rat's Nest

as I highlight signal paths not ideal and here you can see I built in a caps lock led the wire connections for which are located on the back of the PCB in a convenient spot I have a lot of experience modding

projects for LEDs and at this stage I have a rough idea of how I will be showing it on the actual cap slot key so we have a PCB figured out and the components sorted so what am I going to

do about actual keys on the keyboard I thought of 3D printing keycaps but really I already have some on the A500 mini the path of least resistance would clearly be to cut these out and use them that decided I know I can't just glue

them on top of the micro switches with such a small contact point on the top that would never last I came up with the idea of making a flexible support membrane to glue the keycaps too I can do this with my 3D

printer using TPU filament I rarely use this flexible filament as the parts I usually print need to be rigid but I'll be damned if this wasn't a good use of it for those unfamiliar with the major drawback of using TPU it is hydroscopic

it absorbs moisture from the air I live in a moderately humid area which means my prints come out stringy unless I keep the filament dry or use a dehydrator on it as it turns out this is not really an

issue because remember this will be a substrate for the keys rather than a visible part I will just have to yank off the stringy bits I just need to be able to glue the keycaps to it and I see that there is a

cavity under each key I will design a membrane that has Nubs to go into those cavities and I will make them slightly smaller to give myself some wiggle room literally in order to tweak the alignment and position of the keycaps

I will also create a very thin spacer out of regular ABS plastic to go between the PCB and the membrane to lift the membrane off the PCB and help mitigate accidental key presses [Music] foreign [Music] Okay so I got a system down actually when you

keep doing this you got to do this 96 times or whatever it is and uh you know basically I can cut just enough with enough experience doing a dozen of them or so by now cutting just enough to make it super loose and

pretty much where I need it and then the thing kind of basically just pulls off and then from there I can just finish it off just rubbing on the Sandpaper and this way it only takes me one to two minutes

to do each one whereas the first few you know is up to like five minutes a key or something ridiculous like that still have to cut out the uh part that got melted on the inside you got to cut it out good because

it will hang up on the on the TPU posts and also I didn't uh probably I'm going to mention this before but it's I didn't properly have my TPU dry when I started printing it and these posts are kind of ugly but you

know what for the purposes of this they actually kind of work so [Music] [Applause] [Music] as I said I had four iterations of the PCB I had issues like needing to change the micro switch pad placements ribbon connector poor placement and of course

the addition of the caps lock LED okay so this is the latest version um version zero dot four okay so obviously we went through four versions of this it didn't take too long to get it correct um and

couple things I did is I'm shrunk down the labels here so that they would fit in the corner instead of having them spread out over this area and a very disappointing thing I did was I took the caps lock

LED on the version zero point three and I put it underneath this where this switch needs to go here for the caps lock which is was really dumb I don't know why I did that so here it is

off to the side and hopefully a LED will fit there it's a standard 1206 um LED and hopefully the switch and and the LED can co-exist in fact that's probably the first thing I'm gonna I'm gonna try so the switches that I'm using for this

are from digikey um they're made by mitsumi this is probably the mitsumi part number here r-667843 or maybe that's I mean that does seem to match the others okay anyway so that's what I designed this circuit board with I it's you know they're just

a couple millimeters I think it's four including the contacts it's four you know width wise and like something close to three Heights but then you take the switches and you mount them at 90 degree orientation so that the longer

the longer length with the contacts is is up and down on the top and the bottom as you can see you can kind of tell that these aren't exactly Square you know because of where the contacts are it's

it this switch is taller than it is wide you can see the white line delineates the edge of the switch or just outside the edge of the switch technically so a couple of decisions I made which seemed to have panned out pretty well is

the fact that on the larger Keys such as space bar shift enter uh I I decided to put more than one switch so that if you push in a on one side or one Edge closer to one edge of the of the key it's still

going to register a key press if I for example put the space bar and I only had a micro switch in the middle when you pushed over here on the edge it probably wouldn't register so I did on the space

bar with three and then the others such as shift and enter I did two and then there's the enter key on the numpad I did two as well so basically as with most SMD assembly you want to use flux

it has two purposes actually you'd think it would only have one where it lets the solder flow but it actually will hold your part in place so every single one of these I'm gonna use with some extra chip quick

SMD 291 SMD 291 obviously tweezers are a requirement here looks like our components are going to fit next to each other Get the Led Out so the LED um did I not put the um polarity on the board

covered up a flux and I can't see it now okay so the top one's on the top and it says negative so negative is on top the bottom one goes to a via that's on the bottom and that says positive so

okay so the green side with the little cut out is negative cathode an anode is is over on that side all right we have our soldering iron set to a logical SMD Heat 350 there we go so I'm actually using

a tip that is too big normally for this application because these switches are you know a little more bulky and larger it's helping me to take the wedge the flat part of this and go up against the switch

so getting a little solder on the tip first and then going like this seems to be helping me so that's a common so I'm just going to test to make sure my polarity is right and that I have a good

connection pieces are there see so I'm going to have to yeah all right so I'm just going on the back of the board and I'm just going to go like this and light it up and there you go

all right so yeah so we have a nice set of pads here for soldering a wire two and we're going to use some really thin wire I recommend it at the very largest 30 gauge 30 gauge or something smaller a

lot of those a lot of people have 24 22 26 that that'll probably interfere with the fitment of this board and it's always a good idea if you work on stuff like this to have 28 gauge or a

30 gauge anyway I'm going to get to work um installing the rest of these on here [Music] [Music] foreign [Music] [Music] [Music] so that doesn't look perfect to you right doesn't look perfect to me either but you know what I got a lot of these

to do I'm getting sick and tired of this job and they're going to work and they're going to be hidden and as long as I make sure that we don't short against the top plate and that we don't have solder like

sticking up past the button or the assembly or whatever then um I think we're good to go I'm getting the flux is actually flowing everywhere even inside the switch one thing I did learn on the last revision of the board is

that uh it does affect the ability for the switch to to recognize a keystroke so I found a good way I mean I use my normal technique actually of of spraying it off with alcohol but when I do it on

this one I put the bird bird put the board vertically squirt it just keep squirting it and squirting it and then and then use compressed air to kind of get what's in there to come out and then do it again do it like three times and

it it really uh fixed the uh the connection issue that I was having so foreign [Music] [Music] foreign [Music] and now for the most important part the part that a lot of people forget or skip over to do a

close visual inspection with some magnification to make sure that it looks good and now for the 26 pin connector now the first time I did this I didn't get it quite right basically what we wanted to do is we want it to lean

toward the back of the board down so with the board and it's facing normal facing up orientation we are simply going to solder this the connector is actually tilted down a little bit because I guess the connector is about 1.5

uh millimeters of space between the pins it's a two millimeter pitch thing and this is a 1.2 millimeter thick board and the only the next size up is 1.6 at least for a normal standard production size [Music] foreign

[Music] now we just need to test actually it is a bit messy I'm going to go ahead and do that alcohol bath give it an alcohol bath just compressed air blowing it out and then we'll test by the way the A500 mini has only three

USB ports so with a keyboard a mouse a joystick and a USB thumb drive you are going to need a USB hub I use this one Link in the description so after a successful test we need to proceed with the task of fitting

everything into the case foreign the first order of business is to remove the USB port from the controller board and hardwire the board to the A500 Mini and that was a simple matter of doing some continuity tests making a diagram

and then doing some desoldering and re-soldering the connections for the caps lock LED and our two connectors for it to match our connection on our keyboard controller board the controller board has four LEDs on it one is for USB power the other three are

for caps scroll and num lock functions the second from the left is the caps lock and I desolded the LED and replaced it with a dual pin header starting with the ribbon cable connector because clearances are tight I have to

cut off the top stress relief portion don't attempt to take it apart just cut it and when you cut it use the Dremel I went right through and sliced the ribbon cable when I used a knife here's a better look at the top part

removed and also I needed to cut off the indexing tab when fitting the whole thing together a few of the support Parts on the bottom of the case were just a little bit too long and of course there is the clearancing

for the keyboard connector here is the inside of the case fully assembled pay no mind to the folded cardboard spacer so enough tweaking and fiddling resulted in a case that is very close to original foreign something was bothering me however I

felt I should block off the last USB port since I had made it useless with my internal connection so I went on thingiverse and found something that I could use [Music] so the caps lock light how am I going to get the LED on the PCB

to shine up through the key itself the idea I have is to transmit the light to the top of the key using what they call end glow fiber optic filament despite the name the material that this filament is made of is not truly fiber

optic I actually sell this in my eBay store Link in the description mostly to model railroad enthusiasts but I think it's the perfect application here you can shine a light on one end and it will transmit to the other with very

little attenuation and you can blossom the end with heat to create a lens on the end to further the effect wind blossomed the filament will be about the right diameter to fill the caps lock light spot on the key

I just need to make a small hole there carefully increasing the size until it fits just right [Music] [Music] now it's time to remove the key from the assembly and line things up for drilling through our membrane once the job is done you can see that

even the ambient light from my work table shines through nicely I think this is going to work [Music] now comes the extremely arduous task of removing the remainder of the keys and gluing them to the membrane this will take me many tedious hours to

complete so let's skip to the end shall we [Music] [Music] so before we get to the actual demonstration there's one small item I would like to tweak the caps lock LED bleeds over a bit and I think the fix for that is simple

so I just used a little bit of acrylic paint which is not usually nice and flexible when applied thinly to coat around the caps lock key but not to but stay away from that little piece of filament go around it just to mask off that uh

the caps lock indicator LED bleed it bleeds over into the gaps between the keys and since it was an easy fix I went ahead and did this and I can tell that it's going to work because if I go like this

you can see that you can't see around the cap slot key within the gaps although you can see all the other keys through the gaps so that should take care of that well I knew this was going to happen

because basically the keys well you always you'll always get a couple of keys falling off because it's hard to judge exactly where the contact patch is these Nubs on the membrane are smaller than the inside of the keys

so it might grab it on the top it might grab it on the bottom I've tried to do my best to guess where it would grab it but undoubtedly you were gonna experience a couple you know two or three in my case I

believe it was three keys that's the third one that fell off but quite expected actually so anyway [Music] foreign [Music] okay we're gonna play Dark Side again to test the keyboard for those who watched my last video this

is a sneaky sneak preview of what was going to happen in this video okay as we can see I can move us around the mouse controls your gun I guess in conclusion this build was definitely a challenge perhaps the largest of which

was the tedious repetition involved with 94 keys I had to repeat several of the processes 94 times think of it as the equivalent of one of those challenging jigsaw puzzles I give this a lukewarm rating of 7 out

of 10 for usefulness but a 10 out of 10 is a learning experience I would only recommend this project to those very familiar with working with plastic and for those with good soldering skills so if you're interested in this project

please check the description of this video for a complete bill of materials I will be selling the pcbs in my eBay store as well as putting them up on PCB way there we go anyway thanks for joining me again

friends and we'll see you on the next one [Music] foreign [Music] thanks for watching [Music] foreign [Music]