Omron B3G series
Omron B3G series is a mechanical switch series that preceded its well-known successor, B3G-S series. Discontinued in December 1987 (with production ending in February 1988), it is not known to have ever been observed. The design of the switch is similar in some ways to SMK J-M0404 series, with a vertical contact that rests against a crossbar when the switch is closed. Existence of the switch was made possibly solely by Omron’s published discontinuation notices on their site, although the alternate action type has a known patent.
The keycap mount is the same as that of B2A, B2H, B2C and B2R switches, and they are used with B2HK series keycaps.
Having put in a request to David Luna at Quest Components in the US, he was able to obtain an Omron catalogue page documenting the B3G series, with a cutaway diagram of the switch (from “1984/7”):
- B3G series specification (1984)
|Total travel||4±0.5 mm|
|Electrical rating||5–24 V DC at 1–10 mA resistive load|
|Contact resistance||100 mΩ at 5 V DC, 1 mA|
|Bounce time||5 ms maximum|
|Lifetime||10 million (momentary)|
|1 million (alternate action)|
The following models were listed in the 1984 catalogue entry. No additional subseries were listed when B3G was discontinued.
|Model||Action||LED||Operating force||Total travel force||Product code|
|B3G-1000||Momentary||None||40±10 gf||60±10 gf||B3G-1000M|
|B3G-2000||None||55±10 gf||80±10 gf||B3G-2000F|
The 1984 catalogue page notes that yellow LEDs are also available, and to contact Omron for this option: no yellow LED part numbers are given.
No explanation appears to be given for the strange product codes.
The only patents located to date are for the alternate action design, which is very similar to that of Cherry M6 and MX.
|US 4495391 A||Alternate on-off switch mechanism||1982-12-29||1985-01-22|
|EP 0083508 B1||Contact structure for an alternate switch mechanism||1982-12-30||1987-05-06|
|US 4647742 A||Alternate on-off switch mechanism||1984-07-16||1987-03-03|
All three patents were given a priority date of 1982-12-29, giving a rough indication of the age of the switch. Between the specification and the patents, it is possible to get a fairly good idea of what the switch looks like.
What is not know is how far into the lifetime of B3G series the alternate action switch was introduced.
B3G series was discontinued in favour of B3G-S on 1987-12-01 (PDF document).
Many thanks of course to David for the catalogue page, and to Sandy with help with translation (all Omron PDFs are in Japanese).
PRDN 387 compares the specifications of the discontinued B3G and then-current B3G-S. No direct model replacements are given.
|Date of notice:||1987-12-01|
|Date of discontinuation:||1988-02-29|
|Discontinued types:||B3G series|