I have created a light computer that generates an effect like the scanner
of the car KITT in the TV series Knight Rider. You can see a visualization
of the effect in the image below:
of the car KITT in the TV series Knight Rider. You can see a visualization
of the effect in the image below:
Schematic design with the PIC16F84A microcontroller
Many circuits on the Internet are built with a CD4017 counter IC. I myself
chose to use a microcontroller for this job: the PIC16F84A. A microcontroller increases
the complexity but it allows you to build a very flexible light computer. The circuit
can be kept very small, this was a requirement for this circuit.
chose to use a microcontroller for this job: the PIC16F84A. A microcontroller increases
the complexity but it allows you to build a very flexible light computer. The circuit
can be kept very small, this was a requirement for this circuit.
The circuit can be powered by a DC voltage between 7 ... 12 V. I used a
7805 regulator to create a stable 5 VDC voltage. It you want to keep the circuit very
small you could use a zenerdiode for the stabilization.
7805 regulator to create a stable 5 VDC voltage. It you want to keep the circuit very
small you could use a zenerdiode for the stabilization.
The microcontroller is oscillated by an external RC oscillator. The capacitor
was left away. This can be done but it decreases the stability of the frequency.
The resistor has a value of 10k.
was left away. This can be done but it decreases the stability of the frequency.
The resistor has a value of 10k.
The microcontroller drives LEDs through output ports RB0 ... RB7.. During
the execution of a knightrider effect there are always 2 LEDs active at a time.
the execution of a knightrider effect there are always 2 LEDs active at a time.
I did some measurements on the circuit and the LEDs are active for a period of 0.14 seconds. To change the speed you can simply change the value of resistor R1.
You could also add a capacitor between OSC1 and the GND.
You could also add a capacitor between OSC1 and the GND.
Software Design
Over time I wrote two different versions of the software for this light computer.
A basic version in the assembler language. It runs the knight-rider light effect with only two possible output states: ON or OFF. Download the assembler source code.
An extended version in the C Language. This software generates a little trail before and after the active LEDs. The intensity of the LEDs in the trail is lower. This is done by implementing some sort of PWM (pulse width modulation). Download the High-TECH C source code.
basic Why should I use a microcontroller?
A question you might ask yourself is why this circuit should be made with a PIC microcontroller. You get a 555 and a 4017 counter IC for less money.
With them the same effect can be achieved.
With them the same effect can be achieved.
I have to admit the microcontroller is overkill for this kind of application. But one big advantage about microcontrollers is they are very flexible: the complete light effect
can be changed without having to change the electronic circuit. To demonstrate
this I have written the extended version of the software (see previous topic - extended version with PWM control).
can be changed without having to change the electronic circuit. To demonstrate
this I have written the extended version of the software (see previous topic - extended version with PWM control).
I also designed a second hardware version of this circuit, with the PIC12F629.
This is a DIL-8 microcontroller that uses very little place. You don't need any
external parts other than LEDs and resistors.
This is a DIL-8 microcontroller that uses very little place. You don't need any
external parts other than LEDs and resistors.
Pictures of the circuit
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