[WTT] Have first prototype replica Space Cadet keyboard PCB, want switches for it.

[MathematicalJ]

I have for trade my first prototype replica Space Cadet keyboard PCBs. This is the first anyone has attempted to replicate this famous keyboard electronically as far as I know.

Spoiler:

https://imgur.com/gallery/tWKQyBx

This first prototype isn't perfect, but the issues I have found are not by any means show stoppers. I can go into more detail if anyone is interested.

I will need 122 Micro Switch (Honeywell) SD Series Hall effect keyboard switches:

Code: Select all

Model	Count	Activation	
4B3E	84	2.5 oz	This is a very common switch, relatively speaking.
6B1D	22	1.3 oz	Dummy support switch with Pom pom on top.
4B1E	12	1.3 oz	
5B3E	4	2.5 oz	Alternate action (latching)

This switches are hard to come by, but if I can get my hands on a few of them then I can evaluate the feasibility of fabricating my own. Another possibility is to cannibalize some other Micro Switch hall effect keyboard. (I wouldn't actually destroy another vintage device, just move the problem of fabricating switches to it from this project.) So, of course, if you have one of those I would certainly be open to trade.

For other ways of supporting this project or acquiring one of my prototypes, please PM me.

[XMIT]

I remember you from viewtopic.php?f=7&t=27283&p=504512 . You asked for "review" and I asked what specifically you wanted reviewed. I never heard back.

Yes, this is the forum where people would be interested if you have more detail. Can you tell us what you're trying to do?

[MathematicalJ]

Oh, you're right. When I didn't get a response after a couple of days, I stopped checking the post itself, but I guess I didn't have it set to notify me on replies. Apparently that option is turned off by default. Sorry about that. Thanks for responding anyway.

I am having trouble understanding the confusion about my posts. The idea is to accurately represent the Space Cadet keyboard's schematic and PCB in KiCAD. The peer review I requested is very explicit:

• The mounting holes are approximations at best. These need to be verified.
• The Space Cadet has multiple models of switches, but I have assigned each switch the value SD Series 4B3E. I'd like to know which switches were at which spots. [I was subsequently able to find this information in my reference material, but it wouldn't hurt to have someone check my work anyway.]
• The values of the capacitors need to be verified.

I can understand if no one is able to or interested in verifying the above. But is there anything about it that needs more explanation?

Recently someone from PCBWay discovered my KiCAD project on GitHub somehow and offered to produce them for me in exchange for a review or promotion (not here—on GitHub or YouTube). At the time I did not have plans to get them made, but it was my intent to have design files that could be manufactured if one wanted. Of course I am only too happy to have PCBWay sponsor the project! (Thanks!)

Now that the project has entered meat space, I think the only thing to do is to try to accurately replicate a Space Cadet keyboard. What constitutes "accurate" is still pretty fluid. I know I can make the key caps accurate. The switches and the enclosure are the big question marks. The ideal situation would be to somehow source genuine switches, but that's a challenge at best. Barring that, if I can get a few real switches to use as reference, I have two or three ideas of how to fabricate replicas. I have actually done this before on a small scale with SN series switches. The original keyboard was made in at least two different styles of enclosure, so I don't feel a need to spend a lot of energy reproducing something really specific. I don't have an interest in replicating the daughter/controller board or internal speaker, although it wouldn't take much peer pressure to get me to add it to the KiCAD project. I've been making progress on a switch plate in FreeCAD, which I have already started fabricating out of a nice piece of found steel sheet.

I now have resources with which to obtain the remaining things I'll need to complete the project, namely almost $200 in replica PCBs courtesy of PCBWay. It'd be nice if I could trade the four extra PCBs for some switches and whatever other materials I need.

[Muirium]

That's better! When you're up to an interesting project, tell us about the project. Your PCB design makes a lot more sense now we know what you're trying to do with it. Curious minds seek context.

As it happens, I've a related Micro Switch keyboard I'm due to photograph again (it's been years) and map out for a potential controller upgrade. If there's useful data to be found there for you, I can try to find it. I'm no engineer, however, so all I've really got is rulers and tape measures, not callipers or micrometers!

[John Doe]

About the 3-terminal OG sensors, as they're basically smth hard to get or get enough to complete the project, you may want some replacers. I tested few types before and I can sure you the modern sensors like A3144 could take over this part flawlessly, pad is bit thick so you need sand one side carefully to make it fit in the hall effect switches houses, I have taobao link if someone interested in:https://m.tb.cn/h.fCg9yu6?tk=Ssva2Kqmii ... 3144/Y3144。

Different pins order from the OG so have to tune pcb tho, hope help bit. Your passion about this is impressive, appreciate sharing with us.

[MathematicalJ]

About the 3-terminal OG sensors, as they're basically smth hard to get or get enough to complete the project, you may want some replacers. I tested few types before and I can sure you the modern sensors like A3144 could take over this part flawlessly, pad is bit thick so you need sand one side carefully to make it fit in the hall effect switches houses, I have taobao link if someone interested in…

Indeed, I have 20 NOS Honeywell sensors of the 4-pin variety, and I have already ordered a 50 pack of that very sensor you linked to in order to see if they'll work. Glad to know they will!

I am surprised they require sanding, though. The technical drawings I have for the SN series switches show that the slot is 0.104±0.012", while the drawings for the A3144 claim a thickness of 0.058"—0.062". The difference might be that the SN series drawing assumes a plastic clad sensor, and the SD switches used a naked sensor... but what do I know?

Different pins order from the OG so have to tune pcb tho…

Actually, I don't think I will (fingers crossed). I just need to reverse the polarity of the what would otherwise be the signals from the SN74154 decoder and connect one or two jumpers to ground instead of +5V. In other words, I don't think I will need to modify the PCB itself, only a few components that get soldered onto it, in order to swap +5V and GND for the switch matrix. Convenient!

Your passion about this is impressive, appreciate sharing with us.

Thank you so much for your kind words!

[MathematicalJ]

As it happens, I've a related Micro Switch keyboard I'm due to photograph again (it's been years) and map out for a potential controller upgrade.

I have a pair of Maxi-Switch keyboard modules numbered 630107-02 that are similar in design to other Maxi-Switch keyboard PCBs. They use vintage linear switches, though. Maxi-Switch PCBs are mostly very similarly designed: they use an 8048 microprocessor connected to an SN74154 to drive the rows, while the columns are directly sensed by the 8048. Even the component arrangements are very similar.

What's useful, though, are measurements that don't generalize. For example, I took the switch spacing from the recommended measurements found in Micro Switch's technical documents, not from direct measurement. I don't trust that the switch spacing for my boards, which use Maxi Switch vintage linear switches, matches the spacing used for Micro Switch SD series switches. The spacing I used seems to match up with my reference photos, but there is only so much you can get from a photograph. The same goes for mounting holes and other dimensions of the switch plate. I can make reasonable guesses, and maybe that's good enough, but it would be nice to have a little more confidence in the dimensions.

[I will almost certainly accidentally say Micro Switch when I mean Maxi-Switch or vice versa at some point. Gah!]

If there's useful data to be found there for you, I can try to find it. I'm no engineer, however, so all I've really got is rulers and tape measures, not callipers or micrometers!

Thanks, dude! I appreciate it.

[MathematicalJ]

A bit off topic, but since I have your attention: Do you think there would be interest in other vintage keyboard PCBs I have reproduced? Except for the TARDIS keyboard, none of them are particularly famous, but they also have never been digitally reverse engineered as far as I am aware. Reverse engineering old PCBs is therapeutic for me, like how some people do adult coloring books. I have a lot I have not bothered putting out publicly, because I assumed nobody would really be interested.

[John Doe]

At least some ppl would be interested in Consul 262.3 keyboard PCB, also 3 terminal sensors, VCC, input and output legs, hold type so very friendly to use. Question is pcb has no matrix so impossible to make it beyond 1 key rollover, desperate to deserve a new one to go NKRO. No idea if will interest you tho.

How it looks: viewtopic.php?f=55&t=27243&p=503968&hilit=tesla#p503968

[MathematicalJ]

At least some ppl would be interested in Consul 262.3 keyboard PCB…

See also the 262.12 and 259.6. There are presumably others using these Czech clones.

My knowledge of the Tesla Consul keyboards comes from the following:

1. the Tesla Consul 259.6 keyboard was recently featured on KBD News, and
2. Telcontar.net has an article about the hall effect sensors in the Tesla 262.3 and 262.12 models.

According to Telcontar.net:

Four hall sensor models are known. MH1SS1 is known from central European keyboards, and is a copy of the Micro Switch SW Series sensors, which are found in switches that are themselves a copy of SW Series switches. There was also a central European copy of Micro Switch SD Series…. … All four models are four-terminal with dual outputs.

So no three-terminal clones. (Telcontar does not mention the MS1SS1 model.) The four-terminal sensors do appear to be easily attainable in large numbers. I have not seen a source for the switches, however.

I'd love to acquire a Tesla Consul keyboard. They are lovely devices. If I had a scan of the PCB or some reference photos with a few measurements, it would not be difficult to create a compatible PCB, a drop-in replacement, that uses a modern microcontroller and key matrix for NKRO and USB or Blutooth connectivity.

[John Doe]

So no three-terminal clones. (Telcontar does not mention the MS1SS1 model.)

Apologise, I have it in hands very limited time and let it go quickly, memory messed. I shared sth here one year before:viewtopic.php?f=2&t=25902&p=488830&hilit=262#p488830

[MathematicalJ]

I shared sth here one year before:viewtopic.php?f=2&t=25902&p=488830&hilit=262#p488830

Ah, yes, I understand what you are saying now. Do you have a better picture of the entire PCB? I can take a look and get back to you on your original post.

[TNT]

Out of curiosity, what is your solution for the keycaps and the case?

[MathematicalJ]

Out of curiosity, what is your solution for the keycaps and the case?

The key cap profiles are common Micro Switch key caps from the era, which happen to also be on a couple of other keyboards I have. I can resin cast the key caps.

The Space Cadet was manufactured with at least three different enclosures during its lifetime. I don't feel the need to exactly replicate any of them. Right now I'm thinking I'll make something that's a cross between the black enclosure and the earlier simpler white enclosure, probably out of metal sheet.

[TNT]

Out of curiosity, what is your solution for the keycaps and the case?

The key cap profiles are common Micro Switch key caps from the era, which happen to also be on a couple of other keyboards I have. I can resin cast the key caps.

The Space Cadet was manufactured with at least three different enclosures during its lifetime. I don't feel the need to exactly replicate any of them. Right now I'm thinking I'll make something that's a cross between the black enclosure and the earlier simpler white enclosure, probably out of metal sheet.

Eager to see the end result!