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48G Re-creation Project (fantasy)
10-31-2019, 01:27 AM
Post: #31
RE: 48G Re-creation Project (fantasy)
(10-30-2019 10:48 PM)lemontea Wrote:  Anyway, I have been brainstorming this keypad thing for days. Still nothing substantial.

I even tried to look for mechanical keyboard switches that are small enough for our purposes. Nope. Doesn't even look like we can just take the switch component out of the whole chassis, at least not with ALPS or Cherry switches.

The following is based upon my hands-on controls development which includes sourcing keypads.

There are companies out there that make tactile keypads. As an example Nelson-Miller, CSI Keyboards, GM Nameplate, Almax, and others. The keypad usually falls under the generic name of membrane keypad. Most of these are manufactured in Taiwan or China however final assembly for the above suppliers may be done in the US - especially in the case of Nelson-Miller. These places are one-stop shops for final product.

The PCBs are not rocket science and can be made using 1 or 2-layer styles. These PCBs can be made for cheap at JLCPCB - hard substrate using

The PCBs can also be the flexible kind (FPC) which can have a built in pigtail that uses a low profile ZIF socket for connection to. This is seen on many laptop internals.

The keypad domes, which are the switch making and spring portions of the keypad, are stamped in different diameters and shapes with round being common and either gold or carbon plated or a combo of the two with gold being favored in low current applications like this.

The layers of the keypad with domes are literally taped together with double-sided tape including the overlay which is the portion with the print on it.

Plastic keys can be made as with the DM42 of which require additional hardware to attach and seal or one can make an overlay out of silicone rubber, painted with undercoating of white, as an example, and then painted with black and then laser etched with the names of the keys. The rubber overlay is more cost effective than using hard keys as in the 48 however one will get the HP 49 rubber keypad feel.

Overlays can also be made of polyester and can be printed on, preformed with key shapes, and then taped down. I think this is the case with some of the Swissmicro calcs. Polyester keypads can be sealed from the environment very well and can be spill-proof and UV resistant.

Quality wise, one may get better mileage / cycles out of dome switch designs versus very small mechanical switches, but dome switches can have growing pains until the manufacture works out the assembly process.

Oh, and there are also piezo-electric keypads which make electrical impact based upon impact and not mechanical contact. Also, the Microchip CPUs will work with either mechanical or piezo inputs through programming.

Anyway, see if membrane keypad technology answers some of your questions about keypad switches.
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RE: 48G Re-creation Project (fantasy) - maxrk - 10-31-2019 01:27 AM

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