What is rapid prototyping?
Rapid prototyping is an umbrella term that encompasses microcontroller hardware, development software, and services. It refers to the tools and techniques to quickly move from initial idea to production. The term continually evolves to match the sophistication of modern embedded products. Today, the rapid prototyping ecosystem encompasses the physical hardware, wireless networking, and cloud services that enable highly interconnected and easy-to-use products. At the same time, we include energy-efficient battery-powered devices.
Figure 1 presents the relationship between rapid prototyping and production. It is divided into three stages:
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Initial Demonstration: This is a critical stage where an idea is converted to a working prototype. There is a natural overlap with the maker community. The maker is driven by curiosity and passion while the rapid prototyping community emphasizes production.
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Design for Manufacturing: In this stage, the working prototypes are prepared for manufacturing. There are several crossover points based on the total number of units to be produced. For our purposes, these points are defined as tiny (<10 units) and small (1000 units). For the smallest production runs the designer may simply use the prototype hardware. For a small production run under 1000 units, the designer may modify the prototype hardware. For a large production run, the design team will seek custom hardware optimized for low cost and ease of manufacturing.
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Production: For the final production stage the design team selects the best available options for the given production run.
Figure 1: Diagram showing the relationship between prototyping and production.
Tech tip: The distinction between tiny, small, and average production runs reflects the time required to recoup engineering effort. When the production run is large, there is a good Return On Investment (ROI) associated with cost optimizing the product. For instance, expending a month of engineering time to shave $100 from each unit is a reasonable return on investment. The larger the production run, the more emphasis and development time is dedicated to cost reduction. By contrast, there is little to no ROI in cost optimizing a tiny production run.
Note that the design for production stage has room for growth. With small successes, the design team may optimize subsequent production runs. A good example is the evolution of 3D printers which continue to evolve with each generation.
What is an example of a rapid prototype?
The Arduino Portenta Proto Kit VE represents rapid prototyping for embedded systems. The kit’s foundation is shown in Figure 2 where we see the Portenta H7 installed on a Mid carrier board with provision for 4G, GNSS, environmental sensors, and vision.
Figure 2: Arduino Portenta H7 installed on the mid carrier board options for 4G and vision.
The Arduino kit includes additional equipment not shown in Figure 2 such as a 4G GNSS module, environmental sensing board, IMU, and even a vision module. Just as important, the board allows expansion to Ethernet-connected devices. There are thousands of ways to use this Swiss army knife in your embedded projects.
Tech Tip: The System on Module (SOM) is closely related to rapid prototyping. The Arduino H7 as shown in Figure 2 is a representative example. It contains a dual-core processor, Wi-Fi, Bluetooth, Ethernet PHY, and all the peripherals we expect from the top-tier STM32H7 series processor. The carrier board provides additional support for the SOM.
With regard to production runs, tiny production may use the SOM and carrier board directly. Small production runs may use the SOM with an application-specific board. Large production runs focused on shaving every penny may dispense with the SOM but keep the STM32H7. The distinction is always a function of ROI.
What are the advantages and disadvantages of rapid prototyping?
In my opinion, this is a false dichotomy. Given the need to produce new products in a short amount of time, there is no choice but to leverage the best available tools. Today that includes the SOM and hardened carrier boards. Just as importantly, we need to leverage the software. For example, can you remember a time before git? It wasn’t nearly as pleasant.
We also need to consider the cyclical nature of the design. There are times when developing a working prototype is the prime consideration. I would argue this is an essential task required to develop the system specification. Yes, we should clearly define what the project should and should not do prior to coding.
Always remember Fred Brooks’ essays from the Mythical Man-Month:
Plan to throw one away: you will, anyhow.
While I’m a generalist in the field of electronics, I’ve seen it too many times. People struggle with system specification. We lock in specification before we truly understand the landscape. With rapid prototyping, we can quickly climb the knowledge ladder. We gain valuable knowledge with feedback from real-world systems.
Tech Tip: Embedded projects range from playful applications—like fuzzy teddy bears—to quadruple-redundant automotive safety hardware. Your design team must carefully consider the application and choose the appropriate tools and techniques.
Returning back to Figure 1, it’s helpful to expand the Venn diagram to show the overlap between rapid prototyping and safety-critical and compliance-driven fields. Then again, we may be able to use “maker” equipment to build the prototype but need to add a safety and compliance layer to the design for production stage.
Parting thoughts
It’s difficult to precisely define rapid prototyping. Instead of a single definition we find overlap with the maker as well and hardened safety-critical fields. However, our simplest explanation holds as we define the rapid prototype ecosystem in terms of production run size. The hardware, software, and web services support fast, frictionless transition from prototype to production for tiny production runs.
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Best wishes,
APDahlen
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About this author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.