I received some great feedback that turned this post into a series. I put too many internal details on the BDD and broke the diagram out in this post. I'm keeping the old content up so that everyone can follow along. Diagrams marked "obsolete" are revised in later posts.
START ORIGINAL POST
In most rock and jazz performances, electronic instruments like electric bass guitars are enhanced using digital or analog effects. Effects make electric guitars buzz, shimmer, warble, or echo. Often, these effects are packaged as pedals so that they can be turned on an off during a performance without requiring the musician to take his or her hands off the instruments.
What's Being Modeled
This picture shows the bass guitar effects pedals that I use during performances. There is also a tuner that is a pedal so that I can check my tuning between songs.
|Bass Guitar Effects Plus a Tuner and Direct Box|
If there is an incorrect voltage, the pedal won't work. If there is an incorrect current, the pedal (like the digital tuner) will work intermittently. If you use a cable of the wrong polarity, you'll damage the pedal. In the following picture, plugging the red-tipped cable instead of the black one destroyed this bass distortion pedal.
|A Ruined MXR Blowtorch|
|SysML BDD of Bass Guitar Effects (Too Many Internals Details)|
At the top of the diagram, there is a block "Carl's Bass Effects" which is the item that we're modeling. All other blocks on this diagram are linked to "Carl's Bass Effects" by a composition connector (black diamond). These relationships define the system boundary by telling the viewer what is in "Carl's Bass Effects". Anything not in this BDD can be considered outside of the power system boundary.
EA's Project Brower also supports composition by making each related block a property of the parent block. In this case, a "Boss TU-1000 Stage Tuner" is a part of "Carl's Bass Effects".
|Project Explorer Showing Properties of Carl's Bass Effects|
|Properties Aren't Needed Since BDD Shows Composition|
There can be other BDDs involving these blocks. For example, a signal processing BDD would leave off the power details and focus on the inter-pedal connection. For that diagram, I'd use the same core blocks (the effects pedals), leave off those devoted solely to power like the Power Strip, and add in the direct box which is not powered by an external source.
Ports are the small squares drawn over the edge of a block (ex "Isolated 18V" on the "Voodo Labls Pedal Power" block). This particular diagram is using SysML 1.2 standard ports which are still supported; they could be changed to full ports. The purpose this power system BDD is to prevent accidents like the one that happened to my Blowtorch. So, each block has one or more ports indicating the connection and power interface.
Ports hook up to other ports using connectors. I'm using the name of the connector to describe a cable.
Reading the Diagram
Here are a few statements that you can make based on the diagram.
The Pedal Power is plugged into one of the outlets on the Power Strip. Three of the effects are in turn plugged into the three Pedal Power's isolated 9V port using center negative cables. All of the effects require 9V. Their current requirements vary, but none needs a lot (>=300ma) of current.
In this electronics application, a SysML Block Definition Diagram was used to define the power requirements and to describe connections between collaborating parts.
UPDATE FROM COMMENTS
From Stephan's suggestion...This version uses aggregation since the parts of Carl's Bass Effects are easily transfered. (They're velcro-ed on to a metal frame so they're not totally loosely coupled. Hopefully.)
|Effects and Part References BDD|