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RAFI magnetoresistive

Contents

Overview

As with other contemporary contactless switches, RAFI’s magnetoresistive keyboard switches were mostly likely created to be able to directly drive logic circuitry without the problem of contact bounce. These switches are described in German patent 7024643U filed in July 1970, and US patent 3668596 filed in October 1970.

The design as described in the patents uses a magnet (with ALNICO 450 given as a successful magnetic material) to control the resistance of a semiconductor junction, whose resistance increases when the magnetic flux passes through it. A separate logic element is placed within the switch to interpret the resistance and provide suitable output. The resistance is said to increase by a factor of five when the switch is actuated. The principle of magnetically-controlled resistance pre-dates switching, and was previously described in RAFI patents from 1966 for non-keyboard switches.

The series offered a choice of positive and negative logic, and three different operating voltages (5 V, 12 V and 24 V). Momentary and alternate action were offered, as was illumination. Mechanical switches were also included in the range, although these are not depicted.

Non-illuminated types have a square section keystem. Illuminated types have a central lamp surrounded by a large, hollow, square section plunger.

These switches were only current for around three years, before RAFI introduced RC 72 Hall effect switches.

Specifications

Force and travel are given as “Operating stroke” and “Operating force”, so the forces given appear to be the total travel force.

Property Non-illuminated Illuminated Mechanical
Travel 4 mm
Total travel force 70 cN max (momentary) 150 cN max 180 cN max
100 cN (alternate action)
Lifetime (momentary) More than 100 million More than 10 million 50 thousand
Lifetime (alternate action) 50 thousand

Product range

Contactless switches

The part numbers take the following format:

The following parts were given in the 1972 catalogue:

Part number Type Action Keystem Operating voltage Output Logic
3.11705.001 Non-illuminated Momentary 5 V 50 mA Transistor Negative
3.11705.011 Positive
3.11706.001 Schmitt trigger Negative
3.11706.011 Positive
3.11712.001 12 V 50 mA Transistor Negative
3.11712.011 Positive
3.11713.001 Schmitt trigger Negative
3.11713.011 Positive
3.11724.001 24 V 40 mA Transistor Negative
3.11724.011 Positive
3.11725.001 Schmitt trigger Negative
3.11725.011 Positive
3.11805.001 Alternate action 5 V 50 mA Transistor Negative
3.11805.011 Positive
3.11806.001 Schmitt trigger Negative
3.11806.011 Positive
3.11812.001 12 V 50 mA Transistor Negative
3.11812.011 Positive
3.11813.001 Schmitt trigger Negative
3.11813.011 Positive
3.11824.001 24 V 40 mA Transistor Negative
3.11824.011 Positive
3.11825.001 Schmitt trigger Negative
3.11825.011 Positive
3.11705.101 Momentary 13° 5 V 50 mA Transistor Negative
3.11705.111 Positive
3.11706.101 Schmitt trigger Negative
3.11706.111 Positive
3.11712.101 12 V 50 mA Transistor Negative
3.11712.111 Positive
3.11713.101 Schmitt trigger Negative
3.11713.111 Positive
3.11724.101 24 V 40 mA Transistor Negative
3.11724.111 Positive
3.11725.101 Schmitt trigger Negative
3.11725.111 Positive
3.11805.101 Alternate action 5 V 50 mA Transistor Negative
3.11805.111 Positive
3.11806.101 Schmitt trigger Negative
3.11806.111 Positive
3.11812.101 12 V 50 mA Transistor Negative
3.11812.111 Positive
3.11813.101 Schmitt trigger Negative
3.11813.111 Positive
3.11824.101 24 V 40 mA Transistor Negative
3.11824.111 Positive
3.11825.101 Schmitt trigger Negative
3.11825.111 Positive
3.16705.001 Illuminated Momentary 5 V 50 mA Transistor Negative
3.16705.011 Positive
3.16706.001 Schmitt trigger Negative
3.16706.011 Positive
3.16712.001 12 V 50 mA Transistor Negative
3.16712.011 Positive
3.16713.001 Schmitt trigger Negative
3.16713.011 Positive
3.16724.001 24 V 40 mA Transistor Negative
3.16724.011 Positive
3.16725.001 Schmitt trigger Negative
3.16725.011 Positive
3.16805.001 Alternate action 5 V 50 mA Transistor Negative
3.16805.011 Positive
3.16806.001 Schmitt trigger Negative
3.16806.011 Positive
3.16812.001 12 V 50 mA Transistor Negative
3.16812.011 Positive
3.16813.001 Schmitt trigger Negative
3.16813.011 Positive
3.16824.001 24 V 40 mA Transistor Negative
3.16824.011 Positive
3.16825.001 Schmitt trigger Negative
3.16825.011 Positive

Mechanical switches

The mechanical switches use illustrated as having an illuminated plunger in all versions.

Part number Type Action
3.11700.001 Non-illuminated Momentary
3.11800.001 Alternate action
3.16700.001 Illuminated Momentary
3.16800.001 Alternate action

Dummy switches

The dummy switches use standard (non-illuminated) plungers.

Part number Keystem
5.00010.104
5.00010.105 13°

Documentation