HIGH and LOW...


OK, Fans, it's ELECTRICITY Time ! And, the weird thing about electricity is it's INVISIBLE! So we need to learn how to make it visible to us.


Our theme music: "Watch Closely Now"... You've probably seen this diagram above before, but we have added a dose of reality: Arduino is powered (usually) by +5.0 Volts of DC (Direct Current).

We show the +5.0 Volts connected HIGH on the top. Look at your Arduino (or a photo).. find the PIN marked "5V". that's the one +5.0V power is connected to. Where does it come from?? To start, from the USB cable from your computer to Arduino.

We show GND (Ground) connected LOW down on the bottom of Arduino. Look at your Arduino (or a photo).. find the PIN marked "GND". ("Watch Closely Now" - There are actually 3 "GND" PINS).


Often the parallel lines of +5V HIGH on the diagram, and GND - LOW on the diagram are called "RAILS". Kind of like railroad RAILS across the top and bottom. Almost everything that happens on Arduino is between the +5V HIGH RAIL and the GND-LOW (0.0V) RAIL.


When a PIN (or wire or connection) changes from 0 to 1, or 1 to 0, we say it is a SIGNAL. Kind of like someone raising up a flag or lowering it.

OUTPUT SIGNALS: An LED or Buzzer connected to to an Arduino OUTPUT can "signal" you that something has happened.

INPUT SIGNALS: If you push a button that changes an INPUT, you "signal" Arduino that something should be done.


Oh, um.. what's a BIT anyway? It is a Binary InTeger which is a number which has only two possible values: 0 and 1. Each Arduino Input or Output PIN is one BIT inside Arduino. (A GROUP of 8 BITS is called a BYTE. Bet you knew that!).

OK, Look again at the diagram above:

The pushbutton switch causes the INPUT to change from LOW to HIGH, which is a "signal" to Arduino.

Arduino can change the OUTPUT from LOW to HIGH, causing electricity to flow through the LED and "signal" you.

OK, another one of those tekkie words:

DIGITAL: This means Arduino will use these Pins only as ON or OFF.

You will hear "Digital" things described three or four ways: but "0" and "OFF" and "LOW" mean the same thing. And "1" and "ON" and "HIGH" mean the same thing.

"DIGITAL" values
0 1
0.0 Volts(GND) 5.0 Volts(5V)

SO, when SOFTWARE inside the Arduino sets an OUTPUT PIN to a "1" it is "ON" and "HIGH" . Arduino connects the PIN to 5.0V (5V).

AND, when SOFTWARE inside the Arduino sets an OUTPUT PIN to a "0" it is "OFF" and "LOW". Arduino connects the PIN to 0.0V (GND).

Sorry for the multiple names for the same things, but those names are widely used, and it's TIME for you to KNOW them...

PINS, BITS, ONES and ZEROS, HIGH and LOW... (Make Sense??)

OK, time to look at how to hook things up to those INPUTS and OUTPUTS. Look at the Arduino again for a minute. You'll get to know it well. And next you should be powering YOUR Arduino up... (PIN 13!)


Let's look at those PINS in more detail. After that we'll hook up your Arduino and make it really work!


OK, "Watch closely now" ...

The PINS (Places you can connect wires and devices to) are numbered 0 to 13 from right to left. You can push wires into those "Black Holes" and connect them to many different devices.

We'll be looking at many of the different INPUT DEVICES and OUTPUT DEVICES you can connect to Arduino. [LIST] But about now, you should be actually connecting your Arduino to your computer (Can be a PC or MAC or run Linux).

Here's how to get your Arduino running (CLICK NEXT)



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