Mosfet stable Volt out

[mister_e]

here's something to play with

' PIC18F2220 
DEFINE OSC 20

TRISC = 0 ' PORTC as output
TRISA = 3 ' RA0 & RA1 as input

PR2=$FF ' load frequency period (PWM freq=1.2 KHZ)

ADCON1 = %00001101 ' Set RA0 & RA1 as analog
ADCON2 = %10000110 ' Right justified result
                   ' Fosc/64
                   ' Tad = 0
                   
ADCON0.0 = 1       ' enable a/d

TMR2DutyVar     var word
AdResult        var word
Voltage         var word
Source          var word
SelectedVoltage var word
Quanta          con 125 ' (5Volt/1024)*256=0.125 = 125

SelectedVoltage = 110 ' mean 1.1 volt
tmr2dutyvar = 156 ' according duty to get 1.1Volt = (1.1/7.2)*1024

Start:
    gosub InitPWM
    
    ' Read Motor voltage supply line
    ' ------------------------------
    '
    ADCON0 = %00000101 'select channel 1 
    pauseus 100
    ADCON0.1 = 1 'start conversion
    while ADCON0.1 ' wait for end of conversion
    wend   
    Adresult.highbyte = ADRESH
    adresult.lowbyte = ADRESL
    Source = (adresult */ quanta )
    Source = source * 288 ' to have a range of 7.2volt
    Source = div32 100 

    ' Read feedback motor voltage
    ' ---------------------------
    '
    ADCON0 = %00000001 ' select channel 0
    pauseus 100
    ADCON0.1 = 1
    while ADCON0.1 ' wait for end of conversion
    wend   
    Adresult.highbyte = ADRESH
    adresult.lowbyte = ADRESL
    voltage = (adresult */ quanta )
    voltage = voltage * 144 ' to have 7.2V range
    voltage = div32 100     
    voltage = source - voltage 

    ' Voltage regulation
    ' ------------------
    '
    if voltage < selectedvoltage then 
       if tmr2dutyvar < 1023 then TMR2DutyVar=TMR2DutyVar+1
       gosub initpwm
    endif

    if voltage>Selectedvoltage then
       if tmr2dutyvar then TMR2DutyVar=TMR2DutyVar-1
       gosub initpwm
    endif
    goto start


InitPWM:
    'set Duty cycle
    CCP1CON.5=Tmr2dutyvar.1
    CCP1CON.4=Tmr2dutyvar.0
    CCPR1L =(tmr2dutyvar>>2)
    
    T2CON=%00000110 ' start timer 2
                    ' set prescaler = 16

    CCP1CON = %00001100 ' pwm mode for CCP1
    return

[jetpr]

Hi thanks for the help...

Hi what type of software do you use for draw the Schematics ...

[mister_e]

Hi jetpr, I use P-CAD. I heard also some good comment on something called EAGLE.