### Waveforms in 8051 Microcontroller

Square Wave
To create a square wave generation using Delay.
let us say we want to construct a 1khz square waveform
the processor instruction cycle of 8051 is 1.085microseconds
so for 1khz (1milli seconds =1/1khz), is 1ms/1.085microseconds = 921.6 (this value is set to the for loop)

#include <reg51.h>
void delay()
{
int i=0;
for(i=0;i<922;i++)
}
void main()
{
P0=0xff;
delay();
P0=0x00;
delay();
}
Sine Wave generation
Since sine wave is plotted in a digital device the number of samples determines the smoothness, hence in this case, more the samples, smoother is the waveform. so a lookup table is been created to get the samples. in the following examples, there are totally 36 samples are taken, starting from 0 degrees to 360 degrees with a step of 10 degrees
 Degrees A = 5 (1+Sin theta) Where 5 is the full scale voltage DAC = 25.6 * A 0 5 128 30 7.5 192 60 9.3 239 90 10 256 etc…like this we need to calculate for 13 samples  with a step of 30degree
// SINE WAVE
#include<reg51.h>
int main()
{
int j;
int c[37]={128,150,172,192,210,226,239,248,254,255,254,248,239,226,210,192,172,150,128,106,84,64,46,30,17,8,2,0,2,8,17,30,46,64,84,106,128};
while(1)
{
for(j=0;j<36;j++)
{
P1=c[j];
}
P1=128;
}}

Triangular Waveform
//Triangular wave
#include<reg51.h>
void main()
{
int j;
while(1)
{
for(j=0;j<256;j++)
{
P0=j;
}
for(j=255;j>0;j=j-2)
{
P0=j;
}
}
}

Saw tooth or Ramp Waveform
// SAWTOOTH WAVE
#include<reg51.h>
void main()
{
int j;
while(1)
{
for(j=0;j<256;j++)
{
P1=j;
}}}

Pulse Width Modulation (PWM) Generation in 8051
#include <reg51.h>
sbit pinpwm = P2^0;
unsigned char PWM = 0;//PWM is the variable to alter the pulse width from 0 to 255
unsigned int temp = 0;
int main(void)
{
P2=0x00;
PWM = 0; //0% duty cycle
//Initialize the timer
TMOD &= 0xF0;
TMOD |= 0x01;

TH0 = 0x00;
TL0 = 0x00;

ET0 = 1;         //enable timer interrupt
EA  = 1;         //enable all interrupts

TR0 = 1;         // Start Timer 0
PWM = 220;       //a duty cycle of 220/256
while(1)
{}
}
// Timer0 ISR
void Timer0_ISR (void) interrupt 1
{
TR0 = 0;    // Stop Timer 0
if(pinpwm)    // if high
{
pinpwm= 0;
temp = (255-PWM); //this is in decimal
TH0  = 0xFF;
TL0  = 0xFF - temp&0xFF;    //to handle in hex
}
else         // else if low
{
pinpwm = 1;
temp = PWM;
TH0  = 0xFF;
TL0  = 0xFF - temp&0xFF;
}
TF0 = 0;     // Clear the interrupt flag
TR0 = 1;     // Start Timer 0
}

Here the PWM Waveform is generated with a duty cycle of 220/256(86%) duty cycle. PWM are advantageous in controlling the power to machines be reducing the supply voltage by altering the pulse width.
Duty Cycle means, the time percentage for which the duty is done. in the image show above, the high waveform for 86% and low waveform (0) for 14%.

### Installing TexLive 2019 in Ubuntu 18.04

Installation of TexLive 2019 in Linux (Ubuntu 18.04 LTS)
TeX (Tech)

Installation of TexLive 2019

Please watch the video for full installation

I used .iso file to download, the Total size is 3.3GB for Linux,

Extract the .iso file to a folder and open a terminal

\$] sudo ./install-tl
(it goes into a terminal mode, which is faster compared to the GUI Mode)

\$] sudo ./install-tl -gui
after the installation, set the PATH, MANPATH and INFOPATH as suggested by LATEX

export PATH=\$PATH:/usr/local/texlive/2019/bin/x86_64-linux
export MANPATH=/usr/local/texlive/2019/texmf-dist/doc/man
export INFOPATH=/usr/local/texlive/2019/texmf-dist/doc/info

put these lines in to the /home/pradeepkumar/.bashrc

We have installed TexLive 2019 and texstudio.

To install texstudio

\$] sudo apt install texstudio
The look and feel of TexStudio looks like this image.

texlive, it install everyt…

### Implementing a new system call in Kernel version 2.6.32

A system call is used by application or user programs to request service from the operating systems. Since the user programs does not have direct access to the kernel whereas the OS has the direct access. OS can access the hardware through system calls only.The following files has to be modified for implementing a system call/usr/src/linux-2.6.32.5/arch/x86/kernel/syscall_table_32.S/usr/src/linux-2.6.32.5/arch/x86/include/asm/unistd_32.h/usr/src/linux-2.6.32.5/include/linux/syscalls.h/usr/src/linux-2.6.32.5/MakefileNew set of files to be createdCreate a new directory newcall/ inside the path “/usr/src/linux-2.6.32.5/” Create new files Makefile, newcall.c and put them in the /usr/src/linux-2.6.32.5/newcall/ folder Create new user files (in any folder of Linux) to test the system call
testnewcall.c, testnewcall.h (created in /home/pradeepkumar) syscall_table_32.S Find the file /usr/src/linux-2.6.32.5/arch/x86/kernel/syscall_table_32.S and add the following line at the end
"…

### Electrical Machine Design (equations)

FactorsDC Machine Transformers Induction Machines Synchronous MachinesOutput EquationPa=CoD2Ln, where Pa=P/h for generators, Pa=P for motorsFor Single Phase
Q=2.22 f Bm Ai Kw Aw d10-3
For Three Phase
Q=3.33 f Bm Ai Kw Aw d 10-3Q=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * hQ=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * h
For Turbo alternators
Q=1.11Bavac KwsVa2 L 10-3/nsOutput CoefficientCo=Bav ac* 10-3where Bav-magnetic loading and ac - electric loadingDNACo=11 Kws Bav ac 10-3Co=11 Kws Bav ac 10-3 Choice of Magnetic LoadingFlux Density in Teeth Frequency of Flux Reversals Size of machineDNAMagnetizing current, Flux Density, Iron lossIron loss, Stability, Voltage Rating, Parallel Operation, Transient ShortCircuit current Choice of Electric LoadingTemperature rise,
speed of machine, Voltage, Armature reaction, CommutationDNAOverload Capacity, Copper losses, Temperature rise, Leakage ReactanceCopper loss, Synchronous reactance, Temperature rise, Stray Load losses,
Voltage rating Flux …