06/23/2018 at 18:55 •
This latest pull request introduces a few modules (and 3D-printable files) designed to solve power-related issues. One of the main concerns I've had over the past several months was how readily-available power supplies & batteries might fit into the specification. One of the goals of the specification is to encourage adopters to use parts they already have in their shop. Power tool batteries, for instance.
Presently, most connectors noted in the spec at http://retrospec.cc have pins which can accommodate up to 20VDC. Most power tool batteries have a nominal voltage of around 18VDC, but can exceed 20VDC at full charge. For these types of batteries to be used, the average max power rating for connector pins needed to be higher. How high, though? An RC-industry 6S LiPo battery can exceed 25V at max-rated charge. Most golf cart batteries (and newer fancy RV batteries) have a 24VDC nominal voltage. In the end, I decided to go with 30VDC max voltage on most pins in the new proposal. Many inexpensive DC-DC buck voltage regulators are rated to work with voltages up to 30VDC. These regulators can easily fit into most modules, run efficient & run cool. This higher voltage allowance permits more power-hungry modules on the same relatively thin wires.
The new pull request (http://retrospec.cc/new) includes STL files for the two leading power tool manufacturers & reference information. Files for other leading power tool manufacturers will become available within the coming months. Support for LiPo batteries of varying form factors will follow. For lower-power projects, the good ol' 9V Battery module will certainly suffice.
The larger batteries presented a new opportunity for a standardized modular footprint. After messing around with a few different approaches I settled on the idea that one should be able to just print (or CNC/laser) thin plates... or full enclosures. The hole pattern accommodates up to 2X DA connectors, up to 2X DB connectors, up to 2X DC connectors & up to 4x DE connectors. These connectors, when mounted, should ideally be arranged in a palindromic fashion for greater ease of use.
All power-supplying modules using this footprint should have all female connectors. Each pin on a typical D-Sub connector can accommodate about 5A. As such, resistor-style fuses (or auto-resetting fuses) should be between each power pin and the actual power source. The connectors should ideally have all contacts properly connected so a small module plugged in on one side of the footprint can talk to a small module on the other side. If you're in a rush... just wire up the power contacts. You can always come back later & upgrade.
The footprint will allow for all sorts of small-form-factor computing devices to run atop a power tool battery. The new pull request includes STL files for Raspberry Pi devices & full-size Arduino devices... with support for more devices coming soon. Each of the holes in the STL file designs are compatible with M3 screws or Imperial #6 screws. Screws & standoffs can be purchased at many PC or RC part supply stores.
Since there are 2X 30VDC pins on DB-25 connectors & 1X 30VDC pins on DE-9 connectors, the configuration shown above can accommodate up to 30VDC at up to 30A. Please make sure to check the new PR (again at http://retrospec.cc/new) for new pin specs for high-current D-Sub connectors (with some accommodating up to 60VDC at up to 80A & some soon which will accommodate 60VDC at up to 160A).
This PR is a big bold step for this little free modular framework.
06/13/2018 at 04:49 •
Putting the finishing touches on a new pull request. This one is going to be fun. The dust is settling. Some of the big blockers are being resolved.
Stay tuned. New post next week.
05/18/2017 at 04:57 •
This pull request sums up several months of occasional planning & research work. The projects listed are projects that interest me; projects that I intend to build and/or contribute to in the future. Given present time constraints, I've simply chosen to compile notes about each project in the repo with the hope that others might find the reference material useful -- and that I can reference that material when I'm ready to do some serious building again.
The general idea of the repository is to provide a common electrical specification for maker-friendly projects. Adding known modular projects into the mix helps provide some extra inspiration. Modules & modular project reference materials are expected to be the complete scope of the repository.
More to come!
07/18/2016 at 04:52 •
Just finished up editing module ideas I've been dwelling on since February. Since the specification is now fairly stable, the focus now is: what can be built? Many big custom builds are just that: big & custom. Once demoed... they may be purposefully destroyed or fall into disrepair. With a basic open spec, modular parts of a big build can be salvaged & saved for later. Most of the ideas in this latest proposal are bigger ideas -- broken up. I'm looking forward to building a bunch of these. Since I do not (nor will ever have) the time to build all the things, I have included many references to other components & in some cases, other projects.
08/17/2015 at 06:57 •
After the Maker Fair 2015 revisions were adopted, I went back to work updating a bunch of Retro Modules which were no longer in compliance. This is one of the reasons I'm striving toward a stable pin specification in short order. It is not fun looking at a box full of no-longer-compliant modules. I've had to sift through existing modules to find the few which were not affected by the spec revisions. Thankfully, I am gaining momentum again.
When I built out the hardware for my 'Christmas Truck' project, I used the Retro Modules spec extensively. Those modules will need slight updates now, but even the basic modularity of the install proved useful. I recently traded my truck in for another, and the uninstall process was a breeze. That is -- everything except some of the oldest modifications I made to the truck. The 2012 Tacoma features a LCD screen in the rear-view mirror. It, at times, displays composite video from the stock rear-view camera. I wanted a way to send my own video to the mirror without making a big mess of the mirror housing. I was able to locate the video cable & make a splice quite some time ago. To undo this splice, I had to break out the soldering iron & solder the short segment of wire back together. If I decide to do a similar modification today, I would make it easy to remove any mods. How? I would add connectors (blade, etc) which allow the stock cable to be reconnected to itself with ease. This can increase the cost of the mod, but not by much.
I have spent some more time fleshing out pin header specs & documentation. The very common 26 pin header is hardware compatible with a 25 pin DB-25 connector. The 10 pin header is compatible with the DE-9 connector. This allows the use of old-fashioned header-to-connector ribbon cables. You may have had some of these cables in an older desktop tower.
Another common staple of desktop computing is the "AC'97"/"HD Audio" header & breakout modules. Many modern single-board computers feature analog & digital audio, but are often broken out via consumer audio jacks. These small computers could leverage the AC'97 header with great ease -- reducing circuit-board complexity & increasing design flexibility. A source of confusion for many, however, is S/PDIF headers on motherboards. Legacy graphics cards often shipped with a tiny cable for routing digital audio. S/PDIF headers are not well standardized & may consist of two to eight pins. Given this problem, I opted to append five pins to the end of the "AC'97"/"HD Audio" header. This keeps compatibility with off-the-shelf desktop audio modules yet allows S/PDIF in/out on a custom header if so desired.
Pro audio is also an important area to focus on.
Since part of this spec features analog audio next to other digital signals, there is a greater risk of noise. Many environments do not require pristine audio conditions. Some do. This is why I have included support -- in certain connectors -- for AES Digital Audio. S/PDIF is the consumer version of AES. AES42 has some really great features that quite a few sound engineers enjoy. These signals are generally sent on a standard 3-pin XLR connector. There is risk, though, in sending digital signals on a connector primarily used for analog audio. Audio mixers may get damaged if a AES signal is connected to an analog input. I have proposed a spec for 6-pin IEC XLR connectors to hopefully address this issue -- and add a feature or two. The 3-pin connector only allows for one-way transmission of digital audio signals (generally). A 6-pin connector allows for power & bi-directional AES transmission. This opens up doors for chainable digital effects processors, digital audio pedals, mics & remote monitoring. For instance, an artist performing on stage generally needs a mic, guitar input & monitor mix. This could be accomplished via this single XLR cable. The monitor mix would arrive on the `digital-audio-aes-host-out-client-in` pins, and the audio source(s) on-stage would be sent back to the mixer via the `digital-audio-aes-client-out-host-in` pins. These on-stage modules could be powered via the `fourty-eight-volts-max` pin.
This latest work can be seen on the incoming branch of retrospec.cc.
08/17/2015 at 05:35 •
Maker Faire Bay Area 2015 and the events leading up to it really helped refine the specification in a few very important ways. First, I found many of the features packed into the DB-25 spec should be moved to DA-15. This was in an effort to make the spec more accessible as one gets started. The DA-15 spec is not the best candidate for a plethora of chained modules. If chainability is your main focus, shift over to DB-25 and/or DE-9.
The old version of the spec featured USB and lacked CAN. USB is difficult to support when chaining is considered. USB is also a riskier thing to mess around with, since it probably has an expensive computer connected to it. CAN, on the other hand, chains easily and can be run over long distances. It is not as fast, but is sufficient for many electronics experiments. It is used extensively in automotive, automation & robotics environments.
Finally, after taking a look at some other multi-pin connectors, I found it wouldn't be to difficult to support 1080i HD video. While not the cleanest means of transmitting video, it is an ideal transmission method for those who like to tinker. The other connectors I mentiond combined composite, 'super' video & component video onto three pins. This pattern has been followed with the DB-25 connector pin spec.
When I decided to make an appearance at Maker Faire, I knew I would need a set of modules to help attract interest. I chose to embed a number of modules into an old flatbed scanner -- along with an Arduino Uno to run everything. The control surface featured all sorts of buttons & fiber-optic-backlit DE-9 & DB-25 connectors. The buttons & LEDs were driven by I2C port expanders & the NeoPixels via the `pixel-bus`. When one (or a few) of the buttons were pressed, the pin holes corresponding to the button label(s) would illuminate. Since I already had a 16x8 I2C LED display, I programmed the Arduino to display button label text there as well. The LED display was behind the scanner glass, while the control surface was mounted on a board well below. The scanner 'display case' and other parts of the display were linked by a single 25 connector ribbon cable. There were other means of input & output as well. Important to the design: I needed certain modules to protected, while others could be messed with. Those goals were well achieved.
08/17/2015 at 02:09 •
Here are a number of the Retro Modules I've been working on as I've been fleshing out the spec. This video demonstrates some of the possibilities provided via this framework. In building the modules, I discovered pros & cons of varying connector specifications. As things became more stable, I found I was able to deploy quite a few modules around the house, shop & truck. Just the beginning...
06/23/2015 at 07:57 •
Hey! So I've been working to make a few revisions to the existing specification (http://retrospec.cc), while adding a few connectors to the fray. I aim to make as few revisions to the spec as possible. People should be able to expect a rigid specification as they build. These revisions are directly related to feedback from fellow engineers.
I realized one thing in particular: there needed to be a connector geared toward those first trying out the spec. I decided on the DA-15 connector, since it is familiar yet slightly rare. The more 'pro' pins, in the new proposal, are found on DE-9 & DB-25.
Others communicated their desire for a longer-distance communication protocol present on these connectors. While generic RS-232, RS-422 & RS-485 were in the running, I decided on CAN bus. The bus will ideally provide the communication backbone for each group of modules. Consider CAN for both flexibility & long cable runs, and SPI/I2C for the simplicity & shorter cable runs.
There was another suggestion related to higher-current applications (i.e. motor controllers). There are connectors in the DB-25 form factor that feature a few large pins. These connectors are usually available via an online order and a slow boat. The connectors are a variant of older connectors which featured one or more coaxial connectors amongst the D-Sub pins.