Goal:
Create a calculator with basic single digit addition on a breadboard.
Knowns:
There are various gates made of different transistor combinations. The most common are:
a. AND
b. NOT
c. OR
d. XOR
e. NAND
Please let me know if I have forgotten a common one.
A truth table is a table of inputs into a circuit and outputs after the corresponding inputs have been processed by the overarching logic path or set of gates the inputs go through. A circuit can have multiple combinations of inputs (consisting of either 0 or 1) and types of gates that those 0 or 1 inputs are modified by (AND, OR, NOR, etc...). For example a single NOT gate takes one input of 0 or 1. If input 1, but run it through a NOT gate, the output is NOT 1, but 0. Alternately if you input 0 into a NOT gate, then it will come out NOT as 0, but as 1. This is what the truth table for a NOT gate looks like.
NOT
Input (I) | Output (O)
1 0
0 1
Some gates take two input. Each of these gates handles each combination of input types differently. For example, if you take 1 AND 0, you get 0. However, if you take 1 OR 0, you get 1. There are truth tables to help lay out the full mathematical modification. This type of math is call boolean algebra. This isn't your normal adding, subtracting, multiplication and division -that is arithmetic. I have included the full truth tables for AND and OR as well. Now that you know what to search for online, you can learn more about digital logic -the language behind circuits and electronics. As a note before you research more, sometimes instead of saying "input" or "I", a truth table will use "p" and "q" for multiple inputs and use "z" or "r" or all kinds of other things for an output. The key for the output is that it'll always be the on the farther right and there'll always only be one.
AND
I.1 | I.2 | O
1 1 1
0 1 0
1 0 0
0 0 0
OR
I.1 | I.2 | O
1 1 1
1 0 1
0 1 1
0 0 0
A normal transistor is simply a physical device that either lets through a flow of something or not. Like a draw bridge that goes up and down. When it is lowered, flow of traffic between a castle and the outside can happen; when it is raised, the flow of traffic in and out stops. In circuits this is instead electrons (negatively charged particles normally found in an atom) flowing around the gold, silver or copper (metals -which are conductors).
I've been writing this post for a few days and finished the bulk so I'm gonna stop here for now and work on my next one.
Mindy R. Bowen
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