Based on stories I've heard from fellow engineers and my own experiences, we easily could have avoided quite a few problems by building a model of the system to scale. Take connectors. If you've ever been on a team engineering a system, chances are you or someone on your team had some issue with one or more of the connectors.
I once was on a design team responsible for building a system with several proprietary high-speed busses connected by complex connectors. I had a kit with the connectors we planned on using and even some ribbon cable. Also, our team held no less than three meetings on just the connectors, and we still got it wrong. Heck, I even heard of a project that had a connector with only two pins, and guess what? It was designed so the pins were opposite of what they should have been.
Why do connectors cause headaches? Why don't things always line up correctly? Why is the fan hitting the heat sync? It isn't because we don't spend enough time thinking about things, drawing them in 3D, and so on. The answer is quite simple.
Once we get our system back from the factory and start putting it together, do we realize that our drawing was off or we weren't thinking about something correctly? Or, maybe we forgot that the IC was soldered to the bottom of the pc board. As for connectors, the pin ordering alone is simple enough to screw up. So what should we do about it?
Model, model, model. Just make sure everything is built to the same scale. Get yourself some wood, paperboard, string, and whatever else it takes to model the pc boards, heat syncs, wires, cables, and so on. Next, find someone who is good with woodworking to help you out. Finally, the same team that is designing the product should help build the model.
The process of building a scaled-down version of a system may not only help you understand how all the parts will fit together, it also may expose any potential design flaws and even help you realize a better way to re-engineer something. The obvious drawback is that it will take time. But can you really afford to get your alpha system back from the factory only to discover your connector pinout is totally wrong?
Oh, and don't forget to measure twice and cut once. Send your design tips to dharris@penton.com
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