Logic is used in the courtroom to structure sound arguments and can be used to deduce or induce a truth we’re grappling but in electronics and programming it’s the basis of how we put things together.

gates

In class I showed two circuits that would turn on a light using a battery and two switches.  The AND set of switches (AND Gate) requires that both of the switches be on in order for the light to turn on.  Then we built one using a breadboard and an LED with two switches

The OR gate only required that one of the switches was on but if both of them were on that would be O.K. too.

The other types of logic gates common in computing are NOR, XOR, NAND and NOT

These are NOT OR, EXCLUSIVE OR, NOT AND and the NEGATION.

OR

Evan and I went through the construction of truth tables for each of these gates and showed how they could be used in programming.  In programming another very important logic step was introduced called IF…THEN…ELSE.  Almost all computer programs and anytime our robot will be making a decision based on some input we’ll be using this logical argument.

The idea of using symbols was introduced as arbitrary but an important skill to master.  All subjects use some sort of shorthand or symbolism to represent the elements and systems of their discipline.  In the US, Logic gates are represented in a circuit diagram using the symbols shown below.

symbols

In your notebooks we constructed truth tables that showed TRUE if a switch was on and FALSE otherwise.  We showed the status of the switches and the status of the light (TRUE if “on”, FALSE otherwise) in a table.  If you placed an AND and an OR gate in series (the output of the AND gate formed the Ts and Fs of the OR gate’s input) what would the truth table look like?  Does it make any sense?  Why or why not?

Want to know more

http://www.youtube.com/watch?v=eJHmVlzH_9Q

http://www.youtube.com/watch?v=IwLExQbPlBU

http://www.doc.ic.ac.uk/~dfg/hardware/HardwareLecture01.pdf

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