Cherry miniature open
|This article requires photographic illustration|
|Sense method||Metal contact|
|Patents||US 3056002 (1959)|
Series S30 standard miniature open switches are mains power switches rated for 10 A at 125 VAC, and 5 A at 250 VAC; as such, they cannot use gold crosspoint contacts, and instead use flat contacts. Series S31 comprises gold crosspoint variants intended for low-energy circuits.
Being lever action switches, both basic open and miniature open switches do not accept keycaps.
Multiple S30 types exist, including standard and narrow panel, multiple terminal types and multiple configurations. The part numbers according to the Cherry Switches & Keyboards Catalog C-73 are as follows:
- Series: S30 — mains, S31 — low energy
- Unknown (can be 0, 2 or 5)
- Poles and throws: 0 — SPDT (changeover), 1 — SPST NO, 2 — SPST NC
- Terminals: P — "PCB" (tubes, narrow type only), W — integral solder, T — flat solder, Z — quick connect
The codes above do not differentiate between wide and narrow base switches. "Integral solder" terminals are vertical with notches cut into either side; "quick connect" terminals have diagonal corners and no notches. "Flat solder" terminals protrude horizontally, with holes punched through them.
The default form of all miniature open switches is SPDT.
The only gold crosspoint type listed in the C-73 catalogue is S31-20P, is specified as follows:
|Operating force||7.5 oz (213 g) max|
|Rest position||0.533″ (13.5 mm) max|
|Operating point||0.378″ (9.6 mm)|
|Overtravel||0.045″ (1.14 mm) min|
|Movement differential||0.850″ (21.6 mm)|
No confirmed examples exist. The Computer Communications 303 keyboard has switches virtually identical to catalogue depictions of Cherry Series S31 (with the only visible difference being a steeper actuator arm). Unlike S31-20P, the switches in this keyboard are simple SPST NO; one possible part number could be S31-21P.
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