Micro Switch SN Series
- See also
SN Series is the standalone equivalent to SW Series. SN Series comprises the self-contained switches with sealed bases. These switches could be snapped into a panel, or affixed to the PCB by adhesive pads prior to soldering. A base is fitted to the switch to contain the internal parts. The base notwithstanding, SN Series switches are externally identical to SW Series switches, and they use many of the same components.
The base for SN Series makes use of cutouts in the shell that provide clearance around the securing rails of SW Series keyboards. From this, it is not clear if SW and SN were conceived together, or whether SN was added shortly afterwards, taking advantage of the cutouts in SW switches as a way to attach the base. The base is noted in 201SN Chart 2 to be ultrasonically welded to the shell. The base is primarily attached by two internal clips, and then welded. With sufficient force, the base can be prised off.
Switches in SN Series fall into numerous subseries:
|1SN Series||Snap-in panel mount||Non-illuminated confirmed||Special terminal layout|
|11SN Series||Snap-in panel mount||Illuminated and non-illuminated||Quick connect|
|20SN Series||Not observed|
|101SN Series||Self-adhesive PCB mount||Non-illuminated||PCB solder terminal|
|105SN Series||Not observed|
|108SN Series||Self-adhesive PCB mount||Non-illuminated||PCB solder terminal|
|115SN Series||Not observed|
|201SN Series||Self-adhesive PCB mount||Illuminated, with optional lamp||PCB solder terminal|
|205SN Series||Not observed|
A 1SN product sheet was advertised in 1970, but not seen; 1SN is described as “developed for keyboards.” The two 1SN examples observed to date (1SN1 and 1SN31) each have a PCB riveted to an SW-style securing frame, that provides a completely different terminal layout, with each terminal relocated to one of the four corners of the switch. The terminals are the style found on miniature snap-action switches, not the more conventional PCB solder terminals. 1SN switches still have the snap-in panel mount.
In Computerworld, May 10, 1972 on page 28, Micro Switch announced that they would be demonstrating (amongst other things) their solid state keyboards and general-purpose solid state switches at the Spring Joint Computer Conference in Atlantic City, New Jersey (15th to 19th of May 1972). This is the earliest mention to date of 101SN and 201SN switches. A single keyboard model, 75SW12, is also mentioned in the magazine, as well as SS series general purpose solid-state switches including the then-new 15SS current sink type.
101SN is non-illuminated and 201SN is illuminated, and these are the series of which the PCB-mount switches are normally found. The only known instance of 108SN, specifically 108SN11, outwardly appears to be the same as 101SN, with the differences to 101SN being a mystery. Honeywell’s charts for 101SN and 201SN suggest that at least some models used quick connect terminals (although no such switches have been seen yet); the specifics of each of the various subseries remain very unclear.
11SN illuminated and 201SN switches are centre-lit within a cylindrical plunger, and thus require special keycaps. Lamps were optional: there were separate part numbers based on whether or not a lamp was included.
Switches use either an SW packaged sensor unit (as widely observed in SW Series) or an SD sensor PCB, shared with SD Series. The types with packaged sensor units have two magnets, one on either side of the sensor. The types with a sensor PCB use taller magnets; the charts only show the one magnet, but nonetheless indicate that two are present.
In 2020, Honeywell located charts for the following additional SN subseries, but never had time to make them available: 20SN Series, 105SN Series, 108SN Series, 115SN Series, 125SN Series, 150SN Series, 151SN Series, 155SN Series, 160SN Series, 205SN Series, 211SN Series, 225SN Series, 250SN Series, 260SN Series and 501SN Series.
SN series uses two separate schemas; the reason for this split is not known.
Non-illuminated SN models use a numeric model number arrangement very similar to that of SW Series. It appears that odd-numbered switches are sloped and even-numbered switches are stepped, as with SW Series.
- Prefix for snap-in panel mount non-illuminated subseries
- Prefix for PCB-mount non-illuminated subseries
- Series name
- Model number
Illuminated SN models use a structured model number arrangement similar to that of SD Series. The sensor type codes appear to be the same as for SD series, while the switch type codes are different.
- Prefix for snap-in panel mount illuminated subseries
- Prefix for PCB-mount illuminated subseries
- Series name
- Type: 1 = momentary standard force, 2 = alternate action, 3 = uncertain, 4 = low force momentary, 5 through 9 uncertain
- Output: A = sink level, B = sink pulse, C = source level, D = none (dummy), S = logic scan
- Lamp: 1 = no lamp fitted, 2 = lamp fitted
The nature of types 3, 5, 6, 7 and 9 is not clear, as the bill of materials for each type does not indicate the spring weights or sensor types. Once this information is obtained, these types will be better understood.
11SN switches have used both the old sequential numbering system as well as the later schematic numbering system. Just as with 1SW, some models were made obsolete within the lifetime of the series, and the model numbers were deleted from the charts. The encircled letters are verbatim from Honeywell’s charts and indicate the revision of the chart in which that model was removed, with some removals being great enough that the removed types were not listed out, causing the model numbers to be lost.
|Catalogue listing||Action||Mount||Lamp||Force||Sensor||Circuit function||Plunger style||NSN||Notes|
|1SN1||Snap-in||—||Sloped||Black plunger; eBay (7147)|
|11SN31||Snap-in||—||Sloped||Black plunger; eBay (7251)|
|Ⓑ||Momentary||Snap-in||Not supplied||SD-10023||Sink pulse|
|11SN2A1||Alternate action||Snap-in||Not supplied||SW-11920|
|11SN2C1||Alternate action||Snap-in||Not supplied||SW-11921||7025-01-359-9992|
|11SN3D1||Indicator (sprung)||Snap-in||Not supplied||—||—|
|101SN11||PCB||Sloped||5930-01-035-0807||Black plunger; eBay|
|101SN12||PCB||Stepped||Black plunger; eBay (7449)|
|101SN25||PCB||Black plunger; eBay (7449)|
|101SN51||PCB||Sloped||Black plunger, slot type for wide keys; eBay|
|201SN1A1||Momentary||PCB||Not supplied||Sink level||5930-01-013-3788|
|201SN1B1||Momentary||PCB||Not supplied||SD-10023||Sink pulse||5930-01-025-9323|
|Ⓓ||Momentary||PCB||Not supplied||Sink pulse|
|Ⓑ||Momentary||PCB||Not supplied||Source level|
|201SN3D1||Momentary||PCB||Not supplied||ca. 1 N||Indicator|
|201SN3D2||Momentary||PCB||Supplied||ca. 1 N||Indicator||6210-01-092-1366|
|201SN4A1||Momentary||PCB||Not supplied||Low force||Sink level|
|201SN4A2||Momentary||PCB||Supplied||Low force||Sink level|
|Ⓑ||Momentary||PCB||Not supplied||Low force||Sink pulse|
|Ⓑ||Momentary||PCB||Not supplied||Low force||Source level|
|Ⓑ||Momentary||PCB||Supplied||Low force||Source level|
|201SN5D1||Momentary||PCB||Not supplied||Low force||—||Dummy|
|Ⓑ||Momentary||PCB||Not supplied||Low force||Sink level|
|Ⓑ||Momentary||PCB||Supplied||Low force||Sink level|
|Ⓑ||Momentary||PCB||Not supplied||—||Indicator||Plunger permanently positioned in free position|
|Ⓑ||Momentary||PCB||Not supplied||—||Indicator||Plunger permanently positioned in alternate action actuated position|
|Ⓑ||Momentary||PCB||Not supplied||High force||Sink [sic]|
|Ⓒ||Alternate||PCB||Not supplied||Sink level|
|Ⓒ||Alternate||PCB||Not supplied||Source level|
At present there is no “M” chart for 101SN.
Equipment using SN series switches is rarely encountered. So far, the following have been discovered:
|Kenway E3 1901 F||69-station MC-8 Terminal keyboard||101SN7, 201SN2A1, dummy|
|Kenway 2-9907||27-station MC-8 control panel||Illuminated and non-illuminated|
|Eaton Kenway D3-5828||36-station control panel||Illuminated and non-illuminated|
|CDC 9427H cartridge disk drive||Front panel controls||201SN1A2, 201SN2A2, 201SN3D2 (parts information from Ramon Cases Jové)|
Honeywell have kindly provided a collection of SN Series switch charts. The charts themselves were extensively redacted by Honeywell as switches went end-of-life, but they do have some older versions of the charts, and with luck, they may find some more older revisions with more switch details.
- Micro Switch 1SN product sheet advertisement, Electronics, Vol. 43 No. 7, March 30 1970 (scanned by Bitsavers)
- Soldering and Installation Instructions for 11SN Series Switches (PK 8513 0)
- Micro Switch 201SN Series Chart 1, created 1995-09-11, last revised 1999-04-14
- Micro Switch 201SN Series Chart 2 (A), created 1995-09-11, last revised 1996-08
- Micro Switch 11SN, 101SN and 201SN switch charts (surviving charts for individual switch types)
- SW Series, the keyboard version of this switch