ELECTRONICS

LOGIC GATES - Identifying the Parts

• Integrated Circuit (IC), is a mix of hundreds of of other components, transistors,diodes,resistors etc. Our kit includes 7 kinds of IC's. These all require power to operate.
• The "notch" of the IC shows the 'direction' of the IC. The 1st pin to the LEFT of the notch is PIN1 , count down sequentially and go across and count UP.
  IC's are VERY SENSITIVE to static, so keep them inside the anti-static foam. Always touch a nearby grounded metal object to discharge static before you start any project

Seven Basic Logic Gates

Digital electronics relies on the actions of just 7 types of Logic Gates. In binary if voltage applied then it is "ON" or represented by a "1" or if no voltage then it is "OFF" or shown as a "0"
Logic gates process "INPUTS" to "OUTPUTS" and are the building blocks of circuits. They accept input and produce output according to a set of logical rules.

1. NOT GATE - A triangle with a 'o' at the end
2. AND GATE - A "D" shape
3. OR GATE - A "concave" bullet
4. NAND GATE - Opposite of the AND gate- A "D" shape with a 'o' at the end
5. NOR (NOT-OR) - Opposite of the OR gate - A concave bullet with a 'o' at the end
6. XOR (EXCLUSIVE OR)
7. XNOR (EXCLUSIVE NOR)

NOT GATE: One of the simplest logic gates is the "NOT" gate represented as shown below with the "triangle" . Here the NOT gate takes a single input (either a 0 or a 1) and INVERTS it. So if a 0 came through the input, the NOT gate would invert it and the output would then be a "1"

From the diagram above we can use a "TRUTH" table, which is just another way or=f writing down the rules for some logical formula. This table says:
* If the INPUT = 0 then the OUTPUT must = 1\ * If the INPUT = 1 then the OUTPUT must = 0

AND GATE: Circuits need to perform calculations based on multiple inputs as well, and not just a single bit as in the "NOT" gate , hence we also have the "AND" Gate\

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• The AND gate has 2 inputs A and B. As the name suggests, when the input on A is "1' AND the input of "B" is "1' THEN the output will be a "1"
  If we see the TRUTH table in the figure above

OR GATE: Is also a logic gate that takes 2 inputs. This gate will output a "1" if either A OR B is a "1"
If both A and B are "0" it will output a "0"

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  • Have a look at the TRUTH table in the above figure

These logic gates on their own follow fairly simple rules but they can COMBINE with each other to form more complex calculations. For example, we took 2 inputs, pass them into an AND gate and passed that output into a NOT gate, what would happen?

• If BOTH inputs are "0" the output of the AND gate would be a 0, which is the INPUT, then NOT gate output would = "1"
• If BOTH inputs are "1" the output of the AND gate would be a 1, which is the INPUT, then NOT gate output would = "0"

This appears to do the OPPOSITE of what an AND gate on its own would do and its called a NAND gate

NAND GATE: The NAND gate is exaclty as depicted above, an AND gate followed by a NOT gate and is OPPOSITE to an AND gate

• The TRUTH table OUTPUT of the NAND is the opposite of the AND table