SMK Discrete Dome
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This article requires photographic illustration |
| Manufacturer | SMK |
|---|---|
| Switch type | Clicky, Tactile |
| Sense method | Conductive dome, Membrane |
| Keycap mount | SMK two-prong , |
| Switch mount | Plate mount |
SMK discrete dome is a name given to a line of switches produced by SMK. It appears to be similar in concept to Alps integrated dome, except the contacts are either on the PCB or on a membrane sheet, rather than being contained within the switch module. A miniaturized version exists for use with small keys.[1]
Description
All observed examples of the clicky variety have a pair of conductive traces on the PCB for each key, above which the switch is clipped into the metal switchplate. The bottom housing of the switch sits flush with the PCB and there is a circular opening in the middle of the bottom housing. Inside the switch there is a rubber dome with a conductive pad on the underside that presses through the opening in the housing and onto the PCB to bridge the traces. Over the dome there is a spring and click jacket and over that there is a slider clipped into the bottom housing. The tactile version of the switch deviates from the clicky version in that it is situated above a membrane instead of a PCB, it does not have a conductive pad on the underside of the dome and instead has a non-conductive nub that presses on the membrane, and there is no spring between the dome and the slider.[2] There is no functional reason that the clicky and tactile versions use different contact types but no clicky membrane or tactile PCB have presently been identified.
The slider is notably large, covering most of the area of the switch. The switch bears a passing visual resemblance to Omron B3K series switches, and to a lesser extent, Alps SKCP series.
Like other spring-over-dome switches, such as Fujitsu Peerless, the switch is linear until a distinct tactile/actuation event near the bottom. Unlike the Peerless, however, it is very smooth and wider keys are fully stabilised. The switches have been noted to be more tactile, and in the case of the clicky version, louder in a disassembled keyboard.[3]
Variants
Two-prong mount
The keycap mount consists of a pair of holes: north and south on the slider, for two prongs on the inside of the keycap.
Related switches
There is also a miniaturised switch for use with smaller-sized keys. This appears to be similar in design to the full-sized version, but uses a different mount, with a cruciform shape.
Another switch which appears to be related to this and may be an additional variant has also been observed.[4] This features a grey-coloured slider with a different pattern. The keycap mount is the same as the normal full-size version.
Keyboards
- Various Canon typewriters, including the S-51[1], Typestar 5[5] and Typestar 6[6] (Keys with lock lights have a round window in the top left of the cap.)
- DataDesk PC 8700 JR/XT[7]
- Sony KI-9700P keyboard contains the tactile variant[2]
References
- ↑ 1.0 1.1 Deskthority - Canon S-51 typewriter (SMK "peerless"?)
- ↑ 2.0 2.1 YouTube - Sony KI-9700 review (SMK spring-over-dome)
- ↑ YouTube - Hjalfi opens a Canon TypeStar 4 thermal typewriter
- ↑ Deskthority - IDENTIFY THE KEYSWITCH thread (page 3)
- ↑ Imgur - What switch is this? Canon Typestar 5
- ↑ Reddit - So I just found this machine and I'm not sure what switch is it. Is it just a rubber dome?
- ↑ Geekhack — DataDesk International PC 8700 (for IBM PCjr). Postged 2016-03-29. Retrieved 2019-05-05
