The Steggo Rack Standard

Background

Steggo is a project to explore the use of LEGO™ blocks as experimental apparatus. Rather more accurately, it is a sub-project providing components to the FPath Project which, in turn, is an open ended investigation of the Feynman Path to nanotechnology.

FPath Experiment 007 demonstrated the use of modular electronic modules based on LEGO brick dimensions and which incorporate LEGO bricks as a cheap, effective and re-usable mounting apparatus. These modules are called Steggo Modules and this page defines an ad-hoc standard for their size and functional layout. This standard has been named the SteggoRack standard. For more information, please see the useful video associated with FPath Experiment 007 which details the purpose and utility of the Steggo modules.

The Origin of the Name: SteggoRack

You can find out about the origin of the name "Steggo" over on the Steggo home page.

The name "SteggoRack" is an homage to the Eurorack standard so beloved of the amateur music synthesizer community. If a defined standard for modular electronic components so useful to that community then it seems likely that people interested in developing electronics modules for the FPath project might benefit from a similar one suitable for their purposes.

The Basic Philosophy

In order to really understand what is going on here you should probably watch the video - it explains things pretty well.

It is important to remember that Steggo Modules are intended to address the problem of the endlessly mutating and changing electronics requirements when conducting experiments on the Feynman Path. This means the ability to add and remove modules and quickly create new ones is the primary focus. Such things as aesthetics take a very definite back seat to functionality.

Ultimately a Steggo module should be able to be placed horizontally side-by-side along with other modules. This chain of modules then forms a highly adaptable "rack-like" experimental apparatus and each module can be electrically connected to the others with standard connector wires in order to provide the required functionality. You can see this in the image above.

Since adaptability is the key here it is important that the modules can be easily mounted and dismounted. Accordingly, standard LEGO plates are used as the substrate for the rack and standard LEGO bricks are attached to the underside of each Steggo Module in order to mount it in position. The LEGO company has put a lot of R&D into getting the adhesion force in their bricks just right - and of course the bricks are designed for multiple attachment and detachment cycles. You can see some Steggo modules attached to a rack in the images below: (click on any image to enlarge it).

The rack itself is just a slab of 6mm MDF given a coat of varnish and with a cut up LEGO Plate (LEGO 11025 Classic Blue Baseplate) epoxied to it.

Note that in the above rack example, the center portion of the rack is 10 LEGO studs high and it is an indeterminate number of studs in length. It is the 10 stud height that is the critical dimension here. The strips of LEGO base plate along the top and bottom are just there as alternate fixing points for things like cable and wire guides. They have very carefully been positioned before gluing so that LEGO blocks placed on the central strip can reach across the gap and mate with them perfectly if required.

Note that in the interests of enabling horizontal placement, the attachment point for any necessary cabling is either on the top, bottom or face of the Steggo Module - never on the vertical sides.

The SteggoRack Standard

Ok, enough backstory and justification - here is the standard (such as it is). In order to meet the SteggoRack standard each Steggo Module should....

... be a 10 LEGO stud brick in height. This enables the modules to be mounted next to each other in a nice horizontal array.
... be an integral number of LEGO brick studs in width. The standard used is generally an 8 stud width with some of the smaller ones being 5 studs. Some 2 LEGO stud width versions have come in handy though and some wider ones have been built.
... use standard, commonly available, terminal block connectors for power.
... use commonly available spring terminal blocks (or similar) for signal connections.
... have all connectors placed on the top and bottom edges or placed on the central face of the module. No connectors should ever protrude over the 10 LEGO stud long vertical edge.
... have minimal functionality onboard each module. Obviously, the capabilities of each board are left up to the implementor but the general theme should be "separability" and "simplicity". Ideally, each Steggo Module should have minimal functionality and no more. For example, separating a switch to its own module means you can later re-use that component in another experimental apparatus, co-locating it on a stepper motor driver module means it can only ever be used when the stepper motor module is used. As another example, you could put two switches on one Steggo Module but, in general, it would be more useful to have two Steggo Modules each with one switch. You are not trying to save space here - you are looking for adaptability and re-usability. After all, connector wires are not expensive.
... attach two 10 stud LEGO bricks vertically along the edge of 10 stud length so the Steggo Module can be mounted on the rack. Technic, Brick 1 x 10 with Holes : Part 2730 are a pretty good choice for this. There are many vendors online selling these in small quantities. The method of attaching the bricks to the module is left up to the implementor - 2mm brass wood screws work well as does epoxy glue.
... not have the pcb material protrude past the edges of the two 10 stud LEGO bricks. In fact, the PCB should be slightly less wide on each side (0.5mm) than the edge of the bricks. This means the contact point between two adjacent Steggo Modules in the rack is the precision fit between the two LEGO blocks and that there is a very tiny gap between the PCBs. You can see this in the images above. This is also true for the height of the PCB - it should be slightly less (0.5mm) than the length of a 10 stud LEGO brick at each end.
... not mount any LEGO bricks horizontally on the underside of the Steggo Module. The two 1 x 10 vertical bricks are easily strong enough to attach the module to the rack. In general, the space under the Steggo Module should be kept free for ventilation and the running of wires.
... use standard 1.57mm FR4 PCB material for the circuit board so the mounted Steggo Modules appear to be level when placed side-by-side.
... not have any component protrude through the underside of the module so far as to prevent the 1 x 10 vertical bricks from making a solid connection. The faces of the Steggo modules must all be at the same level when rack mounted.

License

The intellectual property rights to all new and/or original ideas and technologies documented under the Steggo project and sub-projects are claimed in full by the author and are immediately released into the public domain under the terms of the MIT License. Any ideas, techniques, processes or methods of work documented in the Steggo project and sub-projects must be considered to be prior art and must be cited in any patent applications.

The contents of the Steggo project and sub-projects are provided "as is" without any warranty of any kind and without any claim to accuracy. Please be aware that the information provided may be out-of-date, incomplete, erroneous or simply unsuitable for your purposes. Any use you make of the information is entirely at your discretion and any consequences of that use are entirely your responsibility.