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In last month’s article we discussed the “magic” of the electromagnetic (“EM”) spectrum. This month we begin discussing the impact of EM waves on computing.

We have had mechanical “computing” devices for centuries, but our present computers depend on the movement of electrons and the storage of electromagnetic data. We need to start this journey with the power grid, for without that we would have no moving electrons and no modern computers.

Transformers are the foundation of our electric grid. Transformers use EM waves to raise or lower voltage in a circuit. Transformers enabled the creation of the electric grid and are instrumental to computing devices. Ironically, while computers and most technology use direct current (“DC”) our power infrastructure is based on alternating current (“AC”). This was an economic decision as the

higher the voltage transmitted, the lower the line

loss. Our electric grid uses AC because, at the time of creation, no DC transformers existed.

Additionally, with no transformers to alter voltages [in a DC world], all devices had to be connected to a power source creating the specific voltage needed for a device. To run devices of various voltages would necessitate being connected to multiple power sources [each producing different voltages].

The electric grid is generally separated into three segments: high voltage running from power production to cities, medium voltage running from a transmission station at the edge of town to the pole in front of your home, and the low voltage section from the transformer into your home [and all other houses on your side of the transformer].

You have surely seen a few types of transformers. In neighborhoods with overhead wires, they appear to be small trash cans at the top of poles. In neighborhoods with underground utilities, the transformer is a steel rectangle on the front lawn. Inside, they operate in the same fashion.

Utility transformers contain two coils of wire that run parallel to each other in a bath of insulating oil. One coiled wire is energized which, through EM waves, induces a voltage in the other coil. The “magic” is in the number of turns of the coils. If both coils have the same number of turns, the output voltage is the same as the input voltage. But if the output coil has half the turns of the input coil, the voltage coming out would be half of that going in.

As an aside, one of the conceptual differences between AC and DC circuits is that while electrons do “flow” in a direct current circuit, the movement of electrons in an AC circuit move back and forth like a saw blade.

Back to computing devices. All our electronics are powered by direct current and use a built in “wall wart”. This enclosure houses a transformer and rectifier circuit. Unlike the utility transformers, there are no oil insulated coils inside these wall warts. Instead, the transformation is provided via microelectronics. Our homes are full of AC transformers connected to rectification circuits. The transformer decreases the AC voltage to match the needed voltage of the target device and the rectification circuit converts the AC voltage to DC voltage.

Becoming more common are inductive chargers for electronics. With these, you place your device on a surface generating an electromagnetic field. Your device has an antenna on which the EM field induces a charge. New technology will create room-wide EM clouds that can simultaneously charge all your devices. While some worry about exposure to EM waves, “despite extensive

research, to date there is no evidence to conclude that exposure to low level electromagnetic fields is harmful to human health.”

Think About IT!

get IT done

Tony Keefe, COO, Entre Computer Services www.entrecs.com

SEPTEMBER 2022 The ROCHESTER ENGINEER | 15