The no defunct DataHand keyboard is a very interesting input device but with a few serious limitations the greatest of which is that it is no longer in production and there is no indication that production will ever resume. However, there is sufficient interest in this form of keyboard that the excellent DodoHand project has been setup to create an open-source version of the DataHand using state of the art 3D-printing methods to create the opto/magnetic switches. While this is very promising it relies on very high quality and expensive 3D-printing methods and cheap filament-based techniques are not suitable.
The aim of this project is to create a DataHand equivalent from scratch using readily available switches and components and avoiding the need for 3D-printing. A benefit of using spring/contact switches over the optical/magnetic switches in the DataHand is that they have better tactile feel and are more consistent but arranging them close enough is tricky.
Once a basic prototype is operational it is planned to add a laser trackball in the same arrangement as the TrackHand option for the DataHand DH200 and proposed for inclusion in the DodoHand.
Here is the first prototype for the right-hand unit:
Low force Cherry MX, either the linear “red” or tactile “brown”. One switch is required for each finger and thumb. Obtaining Cherry MX switches in the UK from The Keyboard Company:
Need keycaps with long stems, ideally with a spherical rather than cylindrical finger shape. One possibility is row 3 of the Signature Plastics SA range but these do not seem to be available anymore. Only the DCS and DSA are readily available but the DSA are two low, only row 5 of the DCS family are tall enough. These shape of keycaps are readily available from many sources, in particular the Keyboard Company, from which the top row of the Filco keypad set are suitable.
One option is to use the double length DSA keycap from Signature Plastics:
- Thumbs: 2x 4INHEAKS78 DSA Extra Blank Keys 2 Space Deep Dish-Black (NDY)
but if the Filco keypad set are used for the finger keys the DCS “enter” keycap could be used.
There is not enough space to use Cherry MX for the side switches and small tactile switches generally require too much force and do not have a good feel. Having tried a Microwriter which uses Cherry micro-switches it is clear that these would be a very good choice if they will fit in the space available. In the DecaKeyer I played with both Cherry and Panasonic micro-switches and found that the Panasonics to have a slightly better feel and are more readily available in the UK. RS-Components stock a large range of Panasonic micro-switches, the AVT and AVL types being most suitable as the leaver is more robust and has less lateral play. The “L” versions are longer-life (at least mechanical) but the actuation force on the plunger is 1.47N compared with 0.98N for the standard “T” versions (lower force versions are also available, 0.49N and 0.25N). The long-leaver AVT323461 has an actuation force of 0.25N whereas the long-life long-leaver AVL3835613 has an actuation force of 0.44N which is may be too high for finger switches but maybe good for thumb switches.
The DB3 range of Cherry switches might be suitable alternative and are cheaper than the equivalent Panasonic. Rapid Electronics stock the full range of DB3 micro-switches for £1.04:
- Cherry DB3C-A1LD Microswitch, Long Lever, product code 50-2582 £1.04
However, after playing with these switches for a while it is clear that they do not feel as positive as the Panasonic switches, have a higher force than even the longer-life version and the leaver is too flexible.
The micro-switch leavers are a bit too narrow for comfort and it would be better if pads, plates or some other extension were added. Currently small pads of Polymorph are used, created by rolling-out a thin sheet, cutting small rectangles, heating them and folding over the end of the leavers, flattening and trimming with scissors. This process is a bit tedious but quite effective and the result has a good feel and durability without the need for 3D-printing.
Finger-cluster prototypes with the standard and long-lifetime Panasonic swtiches operate well and although the lower force standard switches feel better in some respects the long-lifetime switches require the same force as the Cherry MX down switch and this consistency feels good. Also the click is even more positive on the long-lifetime switches so the first complete prototype has these switches to see if the force is acceptable for typing.
The switches are mounted (glued) on to cross-shaped ABS plates glued to the heads of M6 bolts and bolted to the ABS base-plate to allow changes in height and orientation. The hand-rest it hand-carved out of a piece of laminated EPE packing-foam which is quite easy to work with a modeling saw and coarse glasspaper and has a very nice warm comfortable feel. It is so good that I am not planning to change the material in subsequent versions as this is easy to replace when it gets dirty and also washable and different shapes can easily be made for other hand shapes and sizes.