Tahmid's blog

Embedded Systems and Power Electronics

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I am currently a PhD student at UC Berkeley, following a 6-year journey working at Apple after my undergrad years at Cornell University. I am a 2025 Paul & Daisy Soros fellow. I grew up in Dhaka, Bangladesh where my interest in electronics was cultivated, resulting in the creation of this blog.

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Jun 18, 2011

Temperature sensor with PIC18 and MCP9700

  June 18, 2011    

 This can be a complete project on its own - a simple DIY digital thermometer with LCD display and only a handful of parts - the PIC18F45K20, LM35 and a small number of resistors and capacitors running off a regulated 5v supply.

Display type - LCD (can be 16x1, 16x2 or anything larger)
Controller: PIC18F45K20
Programming Language: BASIC
Compiler: mikroBASIC PRO for PIC v3.20

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'Programmer: Syed Tahmid Mahbub
'Compiler: mikroBASIC PRO for PIC v3.20
'Target PIC: 18F45K20
'Configuration: Check the project in the download link for the configuration bits


program MC9700_Temp

dim LCD_RS as sbit at RC4_bit
    LCD_EN as sbit at RC5_bit
    LCD_D4 as sbit at RC0_bit
    LCD_D5 as sbit at RC1_bit
    LCD_D6 as sbit at RC2_bit
    LCD_D7 as sbit at RC3_bit

    LCD_RS_Direction as sbit at TRISC4_bit
    LCD_EN_Direction as sbit at TRISC5_bit
    LCD_D4_Direction as sbit at TRISC0_bit
    LCD_D5_Direction as sbit at TRISC1_bit
    LCD_D6_Direction as sbit at TRISC2_bit
    LCD_D7_Direction as sbit at TRISC3_bit

dim ADRead as word
dim Temp as longword
dim vDisp as word[3]
dim Display as string[7]

main:
     TRISA = $FF
     TRISC = 0
     PORTC = 0
     LCD_Init()
     LCD_Cmd(_LCD_CURSOR_OFF)
     LCD_Cmd(_LCD_CLEAR)
     LCD_Out(1, 1, "Temp:")
     Display = "+125 'C"
     while true
           ADRead = ADC_Read(0)
           if (ADRead > 102) then 'If temperature is positive
              Temp = (100 * ( (10 * ADRead) - 1024 ) ) >> 11 'Get temperature
              Display[0] = "+"
           else 'If temperature is negative
              Temp = ( (1024 - (10 * ADRead) ) * 100 ) >> 11 'Get temperature
              Display[0] = "-"
           end if
           vDisp[0] = Temp div 100
           vDisp[1] = (Temp div 10) mod 10
           vDisp[2] = Temp mod 10
           Display[1] = vDisp[0] + 48
           Display[2] = vDisp[1] + 48
           Display[3] = vDisp[2] + 48
           LCD_Out(1, 8, Display) 'Show temperature
     wend
end.

 

Hex file + Schematic + Code freely available for download:
http://www.4shared.com/file/b8bT5a9e/MC9700_temperature_sensor.html

The code can be freely used and there is no copyright restrictions or anything as such. Only credit the author (me) where necessary.

  1 Comment

Example of how to generate PWM in mikroC using the CCP module

  June 18, 2011    

//Program to generate 40kHz output at RC2(CCP1) pin
//Microcontroller: Microchip PIC18452
//Language: C
//Compiler: mikroC v8.20
//Programmer: Tahmid

void main (void){
     TRISC = 0;
     PORTC = 0;
     ADCON1 = 7;
     T2CON = 0;
     TMR2 = 0;
     PWM1_Init(40000); //40kHz
     PWM1_Change_Duty(128); //50% duty cycle
// Choose Duty cycle as such:
// PWM_Change_Duty(x);
// x = ( (Duty Cycle in %) / 100) * 255
     PWM1_Start(); //Start PWM
     while (1){ //Loop forever
// Whatever else might be needed to be done while PWM is running
     }
}

In mikroC, you set the duty cycle by using the function PWM1_Change_duty(x). The value you put within the parentheses (x) has to be between 0 and 255. 0 means 0 duty cycle, 255 means 100% duty cycle, so 128 means 50%.

You get PWM output at RC2 (pin 17).

  8 Comments

Jan 14, 2011

Software "Sine Wave"

  January 14, 2011    

Here I present my software "Sine Wave" for free use.

Here are some screenshots of my software "Sine Wave":





Download link for software:
http://ifile.it/bgnmj34


Prerequisite:
For Vista and 7, nothing required, just install
For XP, download and install the latest version of Microsoft .NET Framework 3.0

Max number of variables: 1000
Peak max: 65536
Peak value can be increased and software modified if required. If you notice any bugs, please let me know.

Use the new, improved software "Smart Sine": http://tahmidmc.blogspot.com/2012/10/smart-sine-software-to-generate-sine.html

  3 Comments

Jan 6, 2011

PCB for ATMEGA Inverter

  January 06, 2011    

Hi everyone,

Here I give the PCB for my design:

Top and bottom:



Bottom Copper:



Top Silk:



The PCBs were then modified by a professional. I hope to upload those soon as well. These are the ones I designed myself. As I am not a professional at PCB designing, the boards became slightly large.

Tahmid.

  17 Comments

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