Home made Keypad PCB!

[rklm]

I have wanted to build a keypad companion for my Minimal Animal for a while now, but I was really compelled once I saw this video on home chemical etching:

https://www.youtube.com/watch?v=tWnfnt2rNO0

I started playing around with Eagle, but I am much more familiar with vector cad software... so I made this in Illustrator:



The bottom 6 rows are all Cherry MX switches, the row above are Matias Alps, and the two switches above that are Cherry M9 (or whatever 7bit is sending with his switch orders).

The smaller through holes (generally to the right of the switch mounts) are for the diodes.

I was hoping to get some help from workshop community for the pcb design. I think I have done a pretty good job, but I am very new to this.

Can anyone spot any egregious errors?

[rklm]

I just realized that the diodes won't be connected properly in that configuration... now I have to come up with a new way to wire them.

[pyrelink]

I have been very intrigued in the "home-made" PCB process, for a while now. The main thing holding me back, is learning CAD. Something that I plan to do but haven't yet. If you get the design working, then I will order up some switches and diodes and try my hand at a PCB as well.

Any reason for the 3 different switch types here? I have been wanting to do something with Matias switches, but I have heard that ALPS and Cherry MX, really don't fit well together on the same PCB in this sense. You will also now need to source different ALPS keycaps to fit along all the MX caps. While I wan't to try the PCB etching either way, I say you go all in on 1 switch type, rather then design for all 3.

[rklm]

Well, I was hoping to make this keypad also double as a switch tester. I wanted to use at least two of each available MX skew switch (except for locks), 2 tactile Matias, and 2 clicky Matias. The m9s are in there because 7bit sends them with his switch orders (or at least he did the last time I ordered switches).

I am pretty sure I have the switch spacing right (so that the keycaps will line up) and the mounting holes aligned properly for the switch pins. I had to get the Matias mounts from a single key pcb design that was made on the GH forums, and I had to measure my m9 to get the pins right. I also have a plate and case designed, which I will get laser cut soonish.

As far as keycaps go, I was going to ask SignaturePlastics if they had alps keycaps available, but I am expecting them to say no (or tell me the MOQ is ridiculously high).

I have access to three 3d printers and a laser cutter on campus, so maybe I will print keycap converters for those four alps switches. The m9 switches fit MX keycaps more or less though.

[pyrelink]

Oh wow okay. So you have some pretty big plans for this. I was thinking much smaller terms. Either way I will still be following closely. I loved the Minimal Animal!

[rklm]

Re did the wiring completely. I decided I would use a double sided PCB.

I could probably work out a way to wire the matrix properly on one layer, but it would be so cramped that the image transfer would not come out clean.

I will probably separate out the lines a bit, increase the stroke width, and fill the mounting holes so that the print comes out correctly.

Again, if anyone spots an error (or a game breaking wiring inconsistency) that I didn't catch, I would really appreciate a shout!




Also, I have been trying to come up with something neat to call this one. Maximal Keypad maybe?

[Vierax]

Mixing different switches is tricky.
Alps are designed to be plate mounted and you didn't add the PCB mounting holes for MX, so I guess you plan to add a mounting plate, am I right ?
The problem is that the space between plate and PCB is different between Alps and MX, I don't know if M9 are plate mounted or PCB mounted but it should be the same with them. That's why I personally stand with plate and handwired matrix.

Nevertheless, it's an interesting challenge

[rklm]

Interesting... I didn't take into consideration the space between the plate and the pcb...

If the difference is small enough, I guess I could extend the leads on the smaller switches... Shouldn't be too difficult... *knocks on wood*

Do you happen to know which are the smaller switches? I would imagine Alps, since they are more rectangular, but I haven't seen them in person.

Maybe I aught to just buy the switches and get to measuring!

[matt3o]

M9 PCB only I've been said.

alps are 13.8x12.2 but plate for them is 1mm (vs 1.5mm for MX)

[rklm]

Thanks for the measurements matt3o, the alps plate size matches what I found online, so I think the dimensions should work in that respect.

The plate thickness won't be too big of a deal. I am going to use 1/16th acrylic like I did for the Minimal Animal, so I will have to shave down the slots with my dremel anyways.

Not that it isn't a PITA, but the 1/16th from my local maker space is cheap.

Also, here is the revised PCB:



And the case parts (in case you guys are interested)

[skrsh3r]

aren't alps 15.5x12.8 mateo? and if you are doing this for the first time rklm i think it's better to go with one sided pcb.

[matt3o]

aren't alps 15.5x12.8 mateo? and if you are doing this for the first time rklm i think it's better to go with one sided pcb.

I don't know which are the specs, but I just measured them and they are indeed 13.8x12.2 (at the top aka plate hole size)

[skrsh3r]

I don't know where are you getting those measurements from but i just measured hole on one of my plates and it's indeed 15.5x12.8

[matt3o]

I'm a very practical guy

[rklm]

Couldn't I make it a few tenths of a mm tighter without warping the switch case?

That might be a decent alternative to having the proper plate thickness if they are also mounted to the PCB

[skrsh3r]

You will never get switch on plate with a hole that size, as you can see here hole on a plate is a little wider.

and here you go these are the spec matias uses

[rklm]

This is why I love the Keyboard enthusiast community!

I really appreciate the measurement help!

I have redesigned the case a little bit to accommodate the m9 switches (I haven't messed with the alps sizes yet). Since they are low profile, if I mounted them to the plate directly, they would stick down more than 3mm farther than a cherry switch

So I made a smaller hole in the plate for the bottom of the switch to fit into snugly, and a normally sized mounting hole in a separate layer that will sit on top.

I have never seen anyone use two plates before, this is turning out to be an awesome project!

Here's an export of the new case design:

[rklm]

Hot glue is a good idea! I wish I had seen this earlier!

I wish I had access to a laser cutter that could do metal, but alas.

http://imgur.com/a/7XnJX

[Vierax]

You doing well, but you really should have some alps to perform some preliminary tests.
Hot glue is a bit too permanent to me, but it's good to know the trick.

Thanks matt3o and skrsh3r, this is really helpful for me too

[rklm]

I am going to order the switches from 7bit tonight, and hopefully be able to measure them and figure out proper dimensions soon.

Another thought that I had was to get a bunch of .5mm acrylic and layer it so that each switch has a mount that fits it properly (similarly to what I did above).

If all else fails, this unit will be small enough for me to 3d print custom mounts for it.... Which might be the easiest solution after all.

[matt3o]

PS: if you need to laser cut metal, ping me

[rklm]

If you have .5mm aluminium/steel available, I might have to take you up on that offer...

Also, I just noticed this on the DT banner. Am I missing a switch?

[matt3o]

you mean 0.5mm?!

the yellow switch is a Kailh (MX clone). It's linear and stiff like an MX Black.

[rklm]

Yes, .5mm. My idea is to use 3 layers of .5mm to accommodate for each type of switch.

I want to attach the alps switches to two of the layers (leaving one of them open on that spot) and the mx switches to all 3.

You said in one of your build logs that the steel's thickness was more consistent overall? That might be important for what I am trying to accomplish.

The thinnest acrylic I can find is 1/32" (almost exactly .75mm) which I don't think will work for this plan.

[Vierax]

that's not a bad idea at all, I hope the differences of high are small enough

[matt3o]

you could have 1.5mm and have the service engrave as much as they can on the alps spots

[Vierax]

you could have 1.5mm and have the service engrave as much as they can on the alps spots

Maybe a tool like this Dremel accessory can be precise enough, isn't it ? Done in the non visible side of the plate to keep the aesthetic
We talk about 0.5mm, it's really a few.

[rklm]

I found some .5mm acrylic here:
http://www.ebay.com/itm/RJ-Speed-Lexan- ... 58aefbae62

I have worked out most of the layer design for the case and the plate (the plate has like 6 layers not counting duplicates )

Here is an export, for those who are interested:

[Vierax]

are you sure that's acrylic ? because Lexan, as Makrolon, is a brand for polycarbonate and you don't want to lasercut it because of dangerous vapours. But if you drill/mill it there's no issue to concern.

[rklm]

Yeah, I just talked to the guy who runs the laser cutter, and he said it wouldn't work.

I could put all the layers together and 3d print the plate, or I could figure out a way to do it with the sizes available in acrylic.