ELECTRONICS - [Knight Rider Lightcomputer]
For a friend, a created a small lightcomputer. The computer generates the same effect as the lights of the car in the TV serie 'knight rider'. In the image below, you can see a visualisation of the effect:
To keep the circuit as small as possible, I chose to use a microprocessor for the job. I only have a programmer for the PIC16F84 processors, so I made the circuit with this microprocessor. The processor has more than enough I/O channels. You can see my designed circuit below:
The circuit must be powered by a DC voltage between 6 and 12 V DC. I used a 7805 voltage regulator so the microprocessor get a stable 5 Volts DC. On the processor, outputs RB0 - RB7 are used to drive the LEDs. I used regular red LEDs. For bigger output currents, you might need to use transistors. The microprocessor is oscillated by an external RC oscillator. I chose a value of 10 kiloOhms for this resistor. Changing this value will change the speed of the lightcomputer. But I think 10 kiloOhms is a perfect value here.
The software for the microprocessor is written in Assembler. I did not do assembler in a while, so the program is quite messy. Download the assembler source code.
I designed this circuit when I started working with microprocessors. Using a 16F84 microprocessor is a little bit overkill for this application. The same effect can be achieved with standard logical ICs. This circuit is a good alternative when you have very little place on your circuit board.