Omron B2H

Contents

• Overview
• Characteristics
• Pinout
• Models
• Specifications
• Features
  • Low noise
  • Tactility
  • Keycap mount
  • Illumination
  • Profile
• Disassembly
• Space bar assemblies
• Keyboards
  • Documented
  • Examples
• Discontinuations
  • PRDN 389
  • PRDN 651
• Documentation
• References

Overview

B2H was a Hall effect keyboard series from Omron. The date of introduction is not known; a Japanese patent S55-105916A “Contactless Keyboard Switch” was filed for it in February 1979, but it was described in detail in an August 1978 JEE (Journal of Electronic Engineering) article Hall IC Keyboard Switches Become the Leading Type by Yoshikazu Kitao (pages 27–31). The series was discontinued in March 1990, with B2A-□□2 named as the alternative. B2H switches use Matsushita/Panasonic miniature Hall IC.

All indications are that B2H was only produced in a PCB-mounted low-profile style, although the patent for the switches does also depict a switch outwardly identical to the larger B2R reed switches but with a Hall sensor fitted.

B2H is exceptionally rare. The series was discovered through a single model, B2H-F7W, after it became apparent from reading Omron patents that the Hall effect equivalent of the B2R reed switches would likely be called either B2C (“contactless”) or B2H (“Hall effect”). Both series exist, but B2C is a foam pad capacitive type. No other switches have been found, nor have any B2H keyboards or keypads.

B2H switches can be identified by the series name “B2H” moulded into the top of the switch. The complete model number, or the remainder of the model number following “B2H-” can be found affixed to the side of the switch on a label.

The catalogue entry provides the following description; English translations have been added:

• 高さわずか29mmの無接点キーボード・スイッチ
  29 mm tall contactless keyboard switch
• ホールICを使用した無接点方式のため、高精度、長寿命を実現しています。
  The switch offers high precision and long life due to Hall effect contactless sensing.
• 高さ、わずか29mmという薄形です。
  The switch is low profile at only 29 mm tall.
• モーメンタリ、オルタネイト、感触つき、照光など、オプションも豊富です。
  The many options include mometary and alternate action, tactile feedback and illumination.
• 照光には、LED（発光ダイオード）とランプ（白熱電球）の2種があります。
  There are two types of illumination: LED (light emitting diode) and lamp (incandescent bulb).
• チャタリング、バウンシングが皆無で、遅延回路が不要です。
  Because there is no contact bounce or chatter, no delay circuit is required.
• 出力は、DTL、TTL、CMOSコンパチブル
  The output is DTL, TTL and CMOS compatible.
• 充実した2色成形キートップ群に汎用即応性をもたせたトップ・カバー方式もあります。
  ?
• 出力形態には、出力なし、コレクタ抵抗つき、オープン・コレクタの3種があります。
  There are three types of output: no output, collector resistance, and open collector. (“Collector resistance” refers to the use of internal pull-up resistors within the Hall IC for each output.)
• 分岐ダイオードつきもあります。
  “There is also a branch diode.”
• 取りつけ形態は、スロープ形とステップ形の2種があります。
  There are two mounting arrangements: sloped and stepped.

Characteristics

The total switch height is given by Omron as 29 mm, which includes a type A, E or F B2HK series keycap. The switch housing is 12 mm tall and 18.8 mm square, and the total height of the switch from the plunger tip to the stand-offs is around 25.5 mm. At this size, it is fairly large (taller than Cherry M9 for example) but it is over 3 mm shorter than B2R.

The following characteristics are common to the series:

• Matsushita/Panasonic miniature Hall sensor, with a choice of open collector and 6 kΩ internal pull-up resistor outputs
• Patented dual-magnet tactile and click feedback system
• 4 mm travel (momentary models only)
• Support for centre illumination via LED or lamp
• Capacity for an internal diode (presented via terminals rather than internally connected)
• Upstroke and downstroke damping

The switch uses exceptionally long terminals: those of the Hall IC are 8–9 mm, and those of the diode are 11 mm in length. The securing leg is around 6.2 mm long.

Just as with RAFI RS 76 C, the Hall sensor uses a tiny magnet, far smaller than that of the late 1960s Micro Switch SW Series. The magnet is 2.5 mm long and 2.2 mm in cross section and is made from samarium cobalt. A thin wash of white substance marks the face that points towards the Hall sensor. The magnet rests against a yoke within the plunger.

Side, showing the model number (B2H-)F7W and what appears to be the lot number

Base, showing the six terminals and dummy post; the Hall IC terminals are very thin and often bent

Although the catalogue indicates that there are stepped and sloped arrangements, nothing is indicated as to how this is made possible: there are no indications of either angled keycaps or plungers. The JEE article appears to give more information but this data cannot be accessed. Likewise, the catalogue indicates that a dummy type exists (“出力なし”: “no output”), but does not mention such a model. There are definitely more models than the catalogue lists, as can be seen by the existence of model B2H-F7W.

Pinout

The base of the switch has nine holes, eight of them numbered. The purpose of some terminals (where fitted) depends on the type of switch. The assignments are as follows:

This can be seen in the following diagram:

The internal diode, where fitted, uses terminals 7 and 8 on one side. Lamp-illuminated switches use terminals 5 and 7 at the two sides, in the same manner as B2H-ME/-ME1; these switches presumably do not allow for a diode. LED-illuminated switches do not, however, use the same terminals as the lamp: they include an internal 510 Ω resistor in line with the LED, and expose the LED on terminals 5 (side) and 6 (front), where 6 appears to double up as the solder anchor. Since the diode is not securely held and the Hall IC legs are flimsy, terminal 6, a T-shaped metal piece, may be intended primarily to secure the switch in place.

There are two illuminated modes indicated for LED switches:

1. 自照式として使用の場合。
2. 他照式として使用の場合。

The indication seems to be that the first option illuminates the LED while the key is held: the LED is expected to be connected into the second output from the Hall sensor, presumably externally to the switch. The second option expects an external circuit to drive the LED; here, the circuit diagram in the catalogue omits the diode across terminals 7 and 8. No explanation appears to be given for why the self-actuating illumination would expect a diode in parallel with the LED, also connected to output 2 of the Hall IC.

The switch is also highly unusual in not providing stand-offs to hold it away from the PCB. Terminals 5 and 7 have tubes around the holes that could keep the switch away from the PCB (depending on the size hole drilled into the PCB) but at best the switch would perch precariously on these shafts. B2R has similar shafts for the LED spring legs, but it also has dedicated stand-offs.

Models

Model numbers took the following pattern:

B2H-S(I)O(W)

S

Sub-type: M = momentary linear, S = space bar, F = tactile (“feeling”), A = alternate action

I

Illumination option: E = LED, L = incandescent lamp

O

Hall sensor output: 4 = 6 kΩ internal pull-up resistor per output, 7 = open collector

W

W = unknown, H = unknown

The output digit appears to correspond to the model of Hall sensor used.

It seems likely that the corresponding B2R-ML, B2R-S and B2R-A reed switches would have existed.

Model B2H-F7W has a “W” suffix that is explained neither by the Omron catalogue or the 1978 journal article. The journal article depicts two types, B2H-M7H and B2H-ML7, giving us a second unexplained suffix of “H”. There is nothing about the photograph of B2H-M7H to indicate what may be different about it compared to a regular B2H-M7.

Specifications

Subseries-specific data

The Matsushita/Panasonic DN837 four-terminal redundant-output Hall IC was introduced in 1976. It was superseded in 1979 by DN6837, an improved model with only three terminals. DN837 has since been discontinued, with DN6837 being listed as a replacement in the Hall IC Series Application Notes from Panasonic published in 2002. The terminals are (from left to right) V_CC, Output O₁, Output O₂ and Ground (the Hall IC faces the front of the switch). The Hall element is 1 mm² and is located in the centre of the plastic SIL package.

Features

B2H switches provide the following features:

• Momentary and alternate action
• Linear and tactile (where the tactile type has louder click feedback than many clicky switches)
• LED and incandescent illumination, centre position
• Low-noise operation
• Sloped and stepped profiles

Low noise

B2H uses internal rubber dampers for quiet operation. The following is noted in the JEE article:

Low Noise . . . . . The design philosophy behind the B2H was to reduce operating noise to as low a value as possible. The plunger impact sound was reduced to the absolute minimum by utilizing noise-cancelling rubber for key depression and return.

The rubber dampers were also included in the click-tactile models. It’s not clear whether this was done for manufacturing simplicity or to give a cleaner noise profile, as the tactile models use a mechanism that generates a very loud click sound.

Tactility

B2H uses a click mechanism invented by Ashikaga Norihiko and Seiyama Shinkichi and described in Japanese patent S53136680 filed in May 1977. Although designated “F” for “feeling” in the model numbers, this mechanism generates a loud click and soft tactility. A pair of identical magnets provide the both the tactile feedback and click sound without any mechanical interaction with the plunger that could cause undue friction. One magnet is inserted into the plunger, and does not move (relative to the plunger, that is). The other magnet is inserted into the shell, and is free to move vertically within a slot. The magnet in the plunger moves past the magnet in the shell as the switch is operated. The magnets are placed such that (according to the patent) their north poles face each other. The magnets repel each other, and this holds the movable magnet in its down position, preventing it from rattling around within the switch.

The force curve of B2H-F is comparatively shallow, and only reaches around 40–45 cN at its highest. A combination of low force gradient and precise tactile drop (of 10 cN) gives it a smooth, clean feel and distinct tactile sensation. The diagram below shows the official force graph as published by Omron in JEE, and Jacob Alexander’s measured B2H-F7W force graph taken from a new old stock surplus part from Japan.

As with various other graphs from Jacob, the readings in proximity of the zero travel region are strange; here, that portion is shown with dashed lines to indicate uncertainty.

The operation of this mechanism is depicted in the following sequence of diagrams:

As the plunger is depressed, the magnets get closer together. Although you would expect a sharp rise in tactile force as a result, this does not occur.

As the magnets cross over each other, the plunger magnet’s north pole passes over the movable magnet’s north pole and approaches its south pole. At this point, the magnets start to attract instead of repel:

The attraction between the magnets pulls the plunger downward, providing a drop of over 10 cN in force. The movable magnet is pulled upwards towards the plunger magnet, and is driven into the end of its track, causing a sharp impact sound:

As the movable magnet has slid upwards, the plunger will have to be released some distance before the two north poles come into contact, giving physical hysteresis. As this switch is Hall effect, this hysteresis has no effect on the actual electrical actuation, which would have to be implemented in the keyboard controller.

The click system has a high level of hysteresis. The tactile event occurs at around 2.7–2.9 mm, while the release click occurs around 1.2–1.3 mm. Being Hall effect, the click sound and feel do not physically correspond with actuation, and the keyboard is required to define these points.

Keycap mount

Most models are Micro Switch mount and accept Micro Switch’s SW Series keycaps. The incandescent illuminated models use a separate keycap mount that bears a strong resemblance to the corresponding keycap mount of illuminated Micro Switch SW and SN Series keycaps. Compatibility between the two series’ incandescent illuminated mounts has yet to be tested.

Illumination

B2H switches can be illuminated with either an LED or an incandescent bulb. Switch models that use an incandescent bulb use a separate keycap mount, as noted above.

Profile

B2H can be used in both sloped and stepped profile. Stepped profile was achieved by angling the switches relative to the PCB, as shown in the following diagram from the 1978 JEE article:

The article did not detail the means by which the switches are propped up within the stepped profile, and the illustration did not clarify this either. The slope angle in their illustration is 12.5°, which is the midpoint of their typical tilt range of 10–15°.

Disassembly

The switches obtained from Yahoo! Auctions in Japan have stiff, fragile plastic. As such, attempting to open a switch is liable to at least weaken one of the four retaining prongs, if not completely snap it off. Casual disassembly is not advised.

Space bar assemblies

Space bar assemblies fall under B2HS. The following space bar assemblies were listed in the JEE article:

“□” denotes the keycap colour code from B2HK, which if omitted indicates a standard grey keycap.

Keyboards

Documented

A number of B2H keyboard models are known from Omron’s discontinuation notes (see further down). The following items were included in the catalogue entry:

• B2H-11F: 11-key decimal keypad, unencoded (“0”–“9”, “.”)
• B2H-11EF: as above, but encoded
• B2H-16F: 16-key hexadecimal keypad, unencoded (“0”–“F”)
• B2H-16EF: as above, but encoded

B2H-11(E)F and B2H-16(E)F were supplied by default with Type F B2HK keycaps as standard.

Based on the discontinuation data, actual keypads were likely to have more complex model numbers.

Examples

No B2H keyboard has ever been found.

Discontinuations

PRDN 389

PRDN 651

Documentation

• B2H catalogue entry (Japanese), unknown document title or date; obtained from Omron by “Lukas” (scanned from hard copy 21/01/2022)

References

• Kitao, Yoshikazu: Hall IC Keyboard Switches Become the Leading Type; JEE (Journal of Electronic Engineering), August 1987, pp. 27–31