In my last post, I talked briefly about the Arduino Project and how you only need to know about 5 Volt logic driven electronics. Most likely any Professor or Engineer would shoot me down in flames for saying this but in practice – there is a lot of truth in this statement! To explain myself, the roll of a micro-controller is to act as the brains for a given piece of hardware. Software determines the state of pins on the controller (the inputs and outputs on the chip). These pins can be connected to all sorts of devices to test temperature or light levels etc They can also be connected to devices such as motors, LED’s and LCD screens. In other words they can “Listen” to a sensor to determine a course of action and then output a result. The way they do this is by converting analog signals into digital. They sample a moment in time, record a value which is then sent on for further processing by the software you design. After a course of action is determined, the software will enable or disable an output pin on the micro-controller. Essentially, the role of the micro-controller is really simply a “Switching” controller. It turns the light off with a switch or turns the motor on with a switch etc. Obviously, the input pins can also be other switches as well and not just analog signals. So for instance, a switch connected to the micro-controller, when pressed might trigger a new result by the chip.
So for anyone starting in electronics – and I guess I’m really talking about myself, this basic concept of “off” and “on” or HIGH and LOW or “1″ and “0″ is easier to understand. It reduces what you immediately need to learn – to get started. Most of the circuits I have built so far have required only a minimal understanding of “Passive” and “Linear” components – things like Capacitors and Resistors, Regulators and Diodes for example. Really it’s about how to use them so they won’t burn up on you as some are polarised and can’t be connected the wrong way around! The nice thing about learning this way, you find yourself acquiring the knowledge about these “analog” devices and there associated mathematics anyway!
For us as micro-controller based designers, the most important thing we need to concentrate on is how to acquire a digital value. If this means we need to interface with a circuit built from Passive/Linear devices, feeding the input pin of our controller with an analog signal then our job will be to determine how best to turn that signal into something Digital. I won’t confuse the issue here, but many micro-controllers (including the AVR) have the ability to do this conversion for you but this statement is mostly true.
Finally, 5 Volts you say. It doesn’t have to be 5 Volts it could be 3 Volts but the controllers I am using at the moment have two states that represent “On” and “Off”. 5 Volts for “On” and 0 Volts for “Off”. In practice, it’s more like 2 volts for “Off” and 4.7 Volts for “ON” but this is the general idea. In a later post I will explain the two “Families” of digital logic that are most common – TTL and CMOS
