[Coco] new mylars

[Mark Marlette]

I'll add to this nearly irrelevant side-track as Ed put it... :)
I have no experience in Eagle as I spend all my time in Specctra and Orcad by Cadence. These are far from free or cheap tools, but they work and work well.
I place all components by hand then autoroute, review, adjust if needed and reroute. You can override the tool if needed but rarely is required. Specctra files are ASCII, so it is nice to go into the file and adjust, if you know the language, which I do.
Analog and digital fences, Manhattan length control, just to name a few ....
Just like in my shop.....power tools! :)
YMMV.
Regards,
 Mark Marlette
http://www.cloud9tech.com
mark at cloud9tech.com

      From: Zippster <zippster278 at gmail.com>
 To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
 Sent: Tuesday, August 11, 2015 10:44 AM
 Subject: Re: [Coco] new mylars
   
A side note to laying out circuits with Eagle or similar and using the autorouter.
If there was one piece of advice I’d give on autorouters, it would be to pretend they
don’t exist.

It does take a long time to lay things out manually, but it’s well worth it.
Even a well-designed circuit with good component placement on the board gets
very meh when the autorouter is applied to it.

Are autorouted boards functional?  Yes, usually.  They are also terribly inefficient in terms of
vias and proper power distribution (proper ground plane especially).  Also, they destroy layout
aesthetics, which might not matter to some, but I think is important.

Anyway, nearly irrelevant side-track over…  :)

- Ed




> On Aug 11, 2015, at 10:13 AM, Boisy G. Pitre <coco at toughmac.com> wrote:
> 
> At Cloud-9, we looked into this. There are really two options:
> 
> Option 1. A scan of the original mylar sheet, cleaning up in Photoshop, then having it duplicated on mylar with conductive ink.
> Option 2. Relayout the entire keyboard mylar with Eagle or a similar tool, let the autorouter figure out the placement of the traces, and then submit gerbers. This seems to be a more durable and flexible option.
> 
> In both cases, care must be taken to get the size exactly right. The additional gotchas are the screw holes which must exactly align in the proper places when the mylar is folded.
> 
> There’s also the plastic sheet insert that goes between the folded mylar. It also has specific holes for allowing the key contacts to go through as well as the screw holes.
> 
> Also there must be a rigid plastic piece glued onto the tail that is inserted into the 16 pin connector on the motherboard.
> 
> All in all, to get it right would be very tedious.
> 
> In the end, we came to the conclusion that the minimum order quantity that would be required along with the effort to properly duplicate the keyboard mylar (option 2 above) would be considerable when weighed against the availability of things like the PS/2 keyboard interface.
> —
> Boisy G. Pitre
> CoCo Projects Coordinator


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