There’s lots of interest and even substantive action on getting students interested in STEM (science, technology, engineering, math) via hands-on activities. I have seen some basic-level teardown STEM groups, where young teen gars do teardowns of products such as PCs, DVD players, keyboards and mice, small appliances, and more. That’s all well and good, but due to the high level of integration in many of today’s consumer products, there’s often not much to see: a few ICs, some connectors, perhaps a few discrete wires, some passives, and a few other odds and ends.
Actually, the most interesting products are the ones which are not mostly filled with electronics, since they have moving parts such as motors, solenoids, gears, and more. Even if they no longer work (or are left unpowered for reasons of teardown safety), they also tend to have lots of switches, indicator lights, and fasteners (screws and other types) to hold everything in place, and these can be disassembled and examined. That’s much better than a smartphone, crammed to the max with barely visible components and very few tangible, hands-friendly pieces.
But these teardowns by themselves are only part of a good hands-on STEM program. What can really make a difference when exploring the item being dissected are its “maps”: block diagram, schematic, or interconnect diagram. A mechanical interconnect or assembly drawing showing all the nuts, bolts, and washer is also very good, as it shows the deeper complexity of the complete product, Figure 1.
This exploded assembly drawing of the Pro-Form GR 75 exercise machine shows the hidden world of nuts, bolts, washers, and specialized parts within this mostly mechanical product. (Image source: ICON Health & Fitness, Inc.)
That makes the teardown not only more informative but also more interesting, as it become a journey rather than merely an observation teardown session. The problem is that schematics, block diagram, and interconnection figures can be hard to find.
That’s why I was fascinated by a site I stumbled on: readingrat.net, subtitled “Free wiring diagram for your inspirations.” It compiles hundreds of overall wiring diagrams, schematics, circuit diagrams, block diagrams and more. Although it is a bare-bones, no-frills site without any clear indication of who runs it, it’s a real gem. Many of the drawings it has are for appliances or larger items such as engines, pumps, and even house wiring, but there are also some for audio equipment and small household products and appliances, Figure 2 and Figure 3. Even if these products have some ICs and processors (meaning invisible firmware embedded within), they also have external components which are good for STEM interest.
The wiring diagram (Figure 2) and interconnect diagram (Figure 3) for a simple home appliance such as the Panasonic WhisperFit Bathroom Fan and Light can be a very useful educational adjunct to a STEM teardown. (Image sources: National Trade Supply, LLC; HandymanHowTo.com)
I’ve always felt that showing STEM students the trio of a good system-level block diagram, an interconnect wiring diagram, and perhaps even the detailed internal schematic are the markers of a properly documented product. It implies that its designers are truly proud of their product and want to show off its place in the world, even if this documentation is not required for the user. This documentation also serves as a teaching tool for students by making it clear that there is more to a high-tech product than a sealed magic box with a PC board inside, plus a user interface and some connectors.
Have there been times when you saw one of more pieces of product documentation, and it gave you a greater appreciation for the design, and respect for the design team – even if you did not need those diagrams? Have you ever had to make your own in order to understand or even fix a product?
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