Essential Design Tips for Purchasing Pros

One of the most effective means of communication is by means of an illustration. If that illustration contains dimensional data and design characteristics that predict what a future product may look like, then the illustration can be referred to as a concept drawing. A concept drawing does not contain critical parametric or component values because at the time of the drawing’s creation, the product has not yet been designed.

However, in the early stages of the design effort, an engineer will “rough out” what the final product may look like. The engineer will consider all the features and interfaces, number of sub-assemblies, and prospective layout configurations. The interfaces, or I/O for inputs and outputs may include both signal and power interconnects along with a mechanical scheme for accessing the ingress and egress points on the proposed assembly.

Concept Design

It required less than an hour and a half for me to create this design concept using SolidWorks CAD. The product did not exists. I only knew that 2 daughter boards had to have 4 BNC RF connector type inputs and outputs, 2 boards required 2 BNCs, and the remaining 2 boards required 4 “F” Type connectors. I was also instructed to leave space for an add-on board as a configuration option. I asked if the boards were to be mounted vertical or horizontal, and if the motherboard would extend beyond the PCB’s PCI connector arrays.

The next thing I needed to conceptualize was the I/O for the motherboard. Here I was instructed to place 5 female SMA vertical mount connectors in two arrays. One array would have three connectors and the other would require two. The last instruction was that the overall width would have to fit in an enclosure designed to be mounted in a standard EIA 19” rack. I now had enough information to create a concept drawing for a proposal to a customer who was coming for a sales presentation in just two days.

Using the concept drawing as a basic reference, the following discussion points ensued in our meeting with the customer:

PCI Connector centerline spacing
Minimum footprint for Main Board sub-assembly
Board to board connector spacing
Enclosure height requirement
Component placement and count (best guess)
Airflow interference and cooling method
Panel design and I/O silkscreen nomenclature
The requirement to add a power good indicator LED
The requirement to add Alarm/fault indicator
Strategic connector board mount placements for cable spacing and finger access
Positive template for connector thru-hole locations on front panel of enclosure
Required board outline dimensions for daughter boards
Power budget for entire assembly

The meeting was more or less guided by the reference drawing and the customer could see that we had captured the essential requirements that would meet his needs. The changes proposed were quickly added and a modified concept drawing, along with a system block diagram was forwarded to the customer. Only a few days passed before we had our first order on the books.

The more sophisticated the illustration, the more the concept design review will be facilitated towards a successful end. This drawing took me less than two hours, including the final modifications. I had not spent a dime of R&D money in order to expedite a sale. When the company started, I used SolidWorks to design an entire CATV system that filled an 84” rack. The system only existed on paper, but we took orders at the next tradeshow based upon some pretty slick artwork and verbiage that would appeal to forward looking CATV operators.

The Concept drawing can be one of the first product illustrations in a company’s Product Requirements Document, PRD. As the product comes to life, it is always interesting to look back and review what the original concept looked like. The final product is never the same as the concept drawing because more feature and function details are added over time. To get started though, a concept drawing or a physical model really helps a company visualize the product and generate a sense of identification and ownership at the earliest stages of a product’s lifecycle.