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EVERYTHING FOR ELECTRONICS
Well, first, expect the circuit to change. This means installing IC sockets for ICs
instead of soldering them directly to a printed circuit board. It also means avoiding
epoxy and other semi-permanent mounting schemes that could impede physical
changes to the device later on. It also means that — given a choice — you should
probably avoid soldering connections until you've made at least one improvement
in the circuit. Breadboards and jumpers are a great way to explore the limits of a
prototype. Wire wrapping provides a more stable/more compact circuit design
than friction-fit jumpers — which is especially useful with mobile/portable
Finally, how do you know you're "there?" That is, how do you know when your
device is v1.0? That's where the art of prototyping is replaced by solid engineering
principles. The engineering community has standards such as the common "mil
spec" that define factors ranging from circuit operating conditions (such as
ambient temperature range) to maximum electromagnetic interference (EMI)
levels, and the ability to withstand G forces from rough handling or dropping.
(Refer to the three-axis hockey-puck accelerometer data logger project we featured
last month that will provide you with a device you can use to monitor how your
packages are treated.)
Not surprisingly, many of the inexpensive devices on eBay are fancy looking
prototypes. They're often not UL listed, and the "specifications" are at best taken
with significant skepticism. For example, I've seen power supply specifications for
unbelievably inexpensive units from China with specifications rivaling high-end
power supplies from established suppliers such as HP, Kenwood, and others. Given
the price, these inexpensive eBay units can be a bargain — especially if you
recognize them as prototypes and are willing to invest some time in improving the
circuitry so that it fits your needs. Perhaps replacing a flimsy heatsink with a more
substantial one is all that's needed to create a workable power supply, for example.
Whatever changes are required, you'll certainly learn more about the
underlying circuit than you would if you simply purchased a name brand
commercial unit — and you'll save some money, as well. Enjoy prototyping. NV
December 2014 9