Topic: Electrical Engineering
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A Pragmatic Introduction to the Art of Electrical Engineering
This is a class in electrical engineering, not programming. But it is very difficult to talk about building modern circuits without doing some programming. And, as we implied earlier, programming a micro can be tedious.
The hope is that this approach will not only yield a solid understanding of electrical engineering fundamentals, but will also promote actual skill at designing and building functional electronic systems.
The same is true of voltage - it is always measured between two points. But like the original weight example, sometimes the reference point is not specifically mentioned, but is nevertheless presumed to be the ground. In fact, electrical engineers use this exact same word, ground, to refer to a reference level to which all voltages are compared. So when we say that the Stamp has 0 volts or 5 volts on a pin, that is measured with respect to ground. Which, in the case of the BASIC Stamp 2, happens to be on pin 23, and is labeled "GND". In more generic terms, voltage is an across variable - it is always measured across two points.
In case you should ever find yourself wanting a Ph.D. in Electrical Engineering, you should be warned that a favorite qualifying exam question involves these equivalent circuits. You are given two identical looking boxes with two terminals sticking out. One box contains the Thevenin circuit with a one volt source and a one ohm resistor. The other box contains the Norton circuit, made with a one amp current source, and a one ohm resistor. How can you tell which is which? The answer: you can't tell electrically. However, the Norton box has power dissipating in the resistor. So you feel the boxes, and the one that is getting hot is the Norton circuit.
Source: www.parallax.com
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