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TESLA Hall sensors



TESLA manufactured a range of keyboard Hall effect sensors, modelled after Micro Switch products. These Hall sensors are best known from Zbrojovka Brno keyboards, in switches also modelled after those of Micro Switch.

MH1SS1 was also used in RFT TSH 19. TSH 19 was followed by TSH 19 F which replaced the TESLA chip with an HFO B 461 G chip with enable input. Enable input is more suitable for matrix scanning, although matrix scanning was also achieved with TESLA sensors by cycling power to the sensor chips.

View full-size image TESLA MH1SS1 (left) compared to a Micro Switch SW Series sensor (right); these are the front and rear views respectively, where the inscription is placed


Catalogue details on TESLA’s Hall effect sensors do not contain any descriptive text. The heading for the specifications is “Pro bezkontaktní spínače ovládané magnetickým polem”: “For proximity switches controlled by magnetic field”. The presence of a square containing the letters “HG” is the only written indication that a Hall sensor is used (sometimes—especially in German—referred to as a “Hall generator”).

Four Hall sensor models are known. MH1SS1 is known from central European keyboards, and is a copy of the Micro Switch SW Series sensors, which are found in switches that are themselves a copy of SW Series switches. There was also a central European copy of Micro Switch SD Series; in keyboard Zbrojovka Brno 262.12 these can be observed to have a slot for a sensor of the same cross-section as MH3SS2/MH3SD2. These sensors are reported to be MH3SS2. The Consul 262.3 keyboard is confirmed to use MH3SS2. Zbrojovka Brno schematics indicate that the “D” pulse types were also used in keyboards—presumably for N-key rollover purposes—although such an example has yet to be observed.

All four models are four-terminal with dual outputs. From the circuit diagrams they all appear to be current sourcing.

TESLA Hall sensor models
Model Type Package Illustration Schematics
MH1SS1 Source level IO-51, IO-52 MH1SS1 at Hadex 1983 parts catalogue entry
MH1SD1 Source pulse IO-52 MH1SD1 at Hadex
MH3SS2 Source level IO-53 (low profile) MH3SS2 at Hadex 1983 parts catalogue entry
MH3SD2 Source pulse MH3SD2 at Hadex

There is not even a written description of the output modes in the catalogue. The only clue is that the “D” models have a defined value for “Šířka výstupního impulsu” or “Šířka impulsu”, the output pulse width, given as being in the range 20–1000 µs.

The SW-style sensors can be found in two packages: IO-51 and IO-52. (IO denotes “integrované obvody”, meaning “integrated circuit”). The dimensions are virtually identical; the difference is that parts of the internal structure of the package are exposed in the IO-51 package, as they are with the Micro Switch sensors, while IO-52 is fully-enclosed with no visible indications of what is inside. The front aperture of IO-51 is large and rectangular and is typically filled with a piece of opaque white material, although on some examples this is material appears to be transparent and the integrated circuit die is visible as it is with all SW sensors. MH1SS1 can be found with either package, while MH1SD1 seems to have only come in the fully-enclosed IO-52 package, which seems to be the newer format.

Form factor IO-51 has a case around 13 mm tall, while IO-53 is greatly reduced to only 7.2 mm. The widths and depths are similar. IO-53 is the reduced-size package designed to fit into switches copied from Micro Switch SD, although the sensor is a full package instead of the bare board with glop-top that Micro Switch used. See image pouzdra IO 6 at Integrované obvody for dimensions of the different packages used with the Hall sensors.