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CH552-48-LPR: Low-Budget PCBA with Low Profile Redragon Switches
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@rgoulter rgoulter released this 22 Jan 09:25
· 48 commits to master since this release
ch552_48_lpr-rev2023.1
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CH552-48-LPR: Low-Budget PCBA with Low Profile Redragon Switches

Variation of the CH552-48 which uses Redragon low profile switches.

Redragon low profile switches are significantly cheaper than other low profile switches,
especially the popular Kailh Choc v1 switches.

Height varies depending on keycap profile. The distance between the top of the
PCB and the top of the keycap is around 11mm for Redragon low profile switches
with low profile keycaps. (In comparison, the same measurement is 10-11mm for
Kailh Choc v1, and about 20mm for MX).

Unlike MX switches (where switches from different manufacturers will have compatible pin positions),
different "low profile" switches have different pin positions from each other.
So, to use Redragon "low profile" switches, you need a PCB designed for Redragon low profile switches.

The KiCad footprint I used for this design can be found under pcb/ in this repository.

Redragon switches support keycaps with MX stems, unlike Kailh Choc v1.
Albeit, general MX keycap profiles (e.g. XDA) are NOT fully compatible with "low profile" switches,
since the bottom of the keycap bottoms-out below where a switch plate sits.
Instead, "low profile" switches with MX stems need 'slim' keycaps, such as NuPhy's or womier's, etc.

Since the Redragon low profile switches have 3-pins, it's best to assemble the keyboard using a switch plate
(e.g. a lasercut 1.0mm metal plate). Pictures below show what a build without a plate looks like.

Design goals:

  • A keyboard that uses Redragon low profile switches.

Pictures:

CH552-48-LPR in a JJ40 low profile aluminium case.

CH552-48-LPR in a sandwich style case.

Underside of the CH552-48-LPR in a sandwich style case.

Switches mounted to the PCB without a plate.

Unsoldered underside of the PCB, with switches mounted in a plate.

2D Renders of the PCB, revision rev2023.1

Firmware

Same as for the CH552-48.

Firmware: NCL files provided under ncl/ at https://github.com/rgoulter/fak

(NOTE: for flashing new firmware, on Windows, I recommend the official WCHISPTool. For flashing using open-source software, it's much easier to flash firmware onto the CH552 from Linux, e.g. docs/guide-liveiso-flashing-fak.md).

Plates and Cases

A bottom plate can be used to protect the components underneath the PCB.

Source files for plates to cut can be found under cad/ in this repository.

Assets 9
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