The Scanner - called Kitt Scanner

KITT SCANNER
Kitt Scanner is produced on the smallest board in this project with a 6-LED display to produce a scanner very similar to  David Hasselhoff's K.I.T.T Car from 'Knight Rider.'
To remind you here are some of the photos of the car and similar cars:

HOW THE 555 WORKS
The way the 555 works is very hard to understand.
Here are the first 10 facts:
Pin 8 connects to the supply.
Pin 1 connects to 0v.
Pin 4 connects to the supply rail and the chip will work. When it is taken to 0v, the chip will stop working. The chip will start working when pin 4 is 0.7v or higher.
Pin 3 is the output pin.
It will deliver (source) 200mA to a LOAD and sink 200mA. But the chip will get very HOT when doing this and so the output pin normally drives a buffer transistor and the transistor drives the LOAD.
Pin 7 goes LOW when pin 3 goes LOW and pin 7 goes "open" when pin 3 goes HIGH.
In other words, pin 7 will sink about 20mA but it will not SOURCE.
Pin 5 has 2/3 of the supply voltage on it and by changing the voltage on this pin, the frequency of an oscillator can adjusted slightly.
An oscillator works by charging and discharging a capacitor via a resistor.
When the frequency of an oscillator is higher than one cycle per second, it is called an oscillator and the frequency is measured in cycles per second (called Hertz).
When the frequency is less than one cycle per second, the oscillator is called a TIMER  or DELAY circuit. And the timing is measures in seconds.
The  555 can be used as an OSCILLATOR or TIMER (Delay circuit).
It contains all the components to detect when the capacitor is charged and when it is discharged.
It also charges and discharges the capacitor via one of the pins.
This pin is normally pin 7, but because pin 7 and pin 3 are LOW at the same time, you have a choice of which pin to use.
The only pins left are pins 2 and 6.
A capacitor is added to the circuit with a series resistor.
These two components are called a TIMING CIRCUIT.
If we connect pins 2 and 6 to the join of these two components, the chip will be able to detect when the capacitor is charged and when it is discharged.
Pins 2 and 6 do not have any effect on the charging and discharging.
They are called HIGH IMPEDANCE pins or lines.
If we connect the TIMING CIRCUIT between the 0v rail and the supply rail, the capacitor will charge.
To make it discharge we have to remove it from the supply rail and connect the timing resistor to 0v.
That's what pin 7 does.
In one of the states, pin 7 effectively disappears and the capacitor charges. In the other state, pin7 takes the charging resistor to 0v.
We need to add a resistor between pin 7 and the supply to allow Pin 7 to do this.
The designer of the 555 chip allowed the capacitor to charge to 2/3 of the voltage on the supply rail and pin 6 detects this level. He allowed the capacitor to discharge to 1/3 of the voltage on the supply and pin 2 detects this level.
This has been done because the charging of a capacitor is not linear but between 0 and 66% it is very linear.
This has been the simple explanation of how the 555 works.
It gets more complicated when you have a circuit that can have a high or low voltage on pin 6 and at the same time a high or low voltage on pin 2.


PINS 2 AND 6
Now we come to the "first-in best-dressed" situation with pins 2 and 6.  Is there is an "over-ride" situation for these two pins?   NO.  That's why you have to be very careful.
Pin 2 must be LOW to make the output HIGH
Pin 6 must be HIGH to make the output LOW.
Pin 2 has control over pin 6.
If neither pin is "controlling the chip" at start-up, what is the output?
There are some circuits where Pin 6 is LOW and Pin 3 is HIGH, waiting for an input to make it LOW.
In this situation no pin is sending a "set" or "reset" message and the output can be either HIGH or LOW, depending on the imbalances within the chip.
But for all the other cases, the output is known.
 
SET OR RESET?
If pin 6 is HIGH and pin 2 is LOW - the output will be HIGH - pin 2 is sending a "set" message
If pin 6 is HIGH and pin 2 is HIGH - the output will be LOW - pin 6 is sending a "reset" message
If pin 6 is LOW and pin 2 is LOW - the output will be HIGH - pin 2 is sending a "set" message
If pin 6 is LOW and pin 2 is HIGH - the output will be HIGH or LOW - this is because no pin is sending a "set" or "reset" message.

THE CIRCUIT
The

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board can be wired to produce all sorts of 555 circuits, including these: