Problem With 220 VAC Halogen Lamp Dimming

[mehmetOzdemir]

I was using Pic based Zero Cross Detect dimmer Incandescent lamps with no problem.
However; when i use halogen lamps instead of incandescent lamps, The dimmer circuit isn't working properly.

So, what seems to be the problem? Any sudgestions?

Regards..

[longpole001]

i would check the rating of the switching mosfet , as some halogen can have a higher load current at startup than incandescent lamps

[mehmetOzdemir]

I have used Opto-Triac and triac for dimming A.C halogen lamp.

[aratti]

You need to post the schematic and the code, if you want some real help.

Cheers

Al.

[EarlyBird2]

Having looked into Halogen lamps I noticed that there are Dimmable versions and was wondering what can be the difference between standard Halogen lamps and dimmable Halogen lamps?

[mehmetOzdemir]

You need to post the schematic and the code, if you want some real help.

Cheers

Al.

Hi aratti,

This is the test code that i have used always for many projects. The microcontroller is PIC16F876A. PORTB.0 is Zero Cross Detect Input. PORTB.7 is fire triac output.

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System

    
    TRIAC       VAR PORTB.7
    
    TIMEX       VAR WORD
    TIMEX_L     VAR TIMEX.LOWBYTE
    TIMEX_H     VAR TIMEX.HIGHBYTE

    OUTPUT  TRIAC
    INPUT   PORTB.0
    
    TRISC   = 255
    TRISA   = %111111
    
    
    ADCON1  = 7
    
    T1CON = 0
    CCP1CON = %00001010
    TMR1L   = 0
    TMR1H   = 0
    OPTION_REG  = %11000000
    
    
    FLAG  = 0
    TIMEX = 9000
    
    CCPR1L      = TIMEX.LOWBYTE
    CCPR1H      = TIMEX.HIGHBYTE
    
    
    LOW TRIAC
    
    
    PAUSE 100
    
    ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
    INT_Handler   INT_INT  ,  INT_GEL_1,   ASM,  yes
    INT_Handler   CCP1_INT   ,  INT_GEL_2,   ASM,  yes
        ;INT_Handler   TMR0_INT  ,  TMR0INT,   ASM,  yes
    endm
    INT_CREATE               
    ENDASM

@ INT_ENABLE  INT_INT
@ INT_ENABLE  CCP1_INT

   MAIN :
    
    
    
    TIMEX = TIMEX + 1
    
    
    IF TIMEX >= 9600 THEN
        FLAG = 0
        low TRIAC
    ELSE
        FLAG = 1
    ENDIF
    
    PAUSE 1


    
    GOTO MAIN
    
    ASM
INT_GEL_1
    
    BCF _TRIAC
    BSF T1CON,0
    
    INT_RETURN 
    ENDASM
    
    ASM
INT_GEL_2
    
    BTFSC _FLAG , 0
    BSF _TRIAC
    BCF T1CON , 0
    CLRF TMR1H
    CLRF TMR1L
    
    
    
    MOVF    _TIMEX_H , W
    MOVWF   CCPR1H
    
    MOVF    _TIMEX_L , W
    MOVWF   CCPR1L
    
     
    
    INT_RETURN 
    ENDASM

END

[Acetronics2]

Hi,

I noticed a little funny thing while building a dimmer ...

take care to the input port behaviour vs input ( TTL or ST ? ) AND the applied rectified voltage ...
the zero detection can occur very, very late from what is expected ...

scoping what happens is very interessing.

I solved it using the falling edge detection and applying a small delay leading precisely to the very beginning of the rising edge - 'scope used here -.

so, the zero detection is very precise.
( application is a 250W IR Lamp for heating my hens home ... )

Alain

[mehmetOzdemir]

Thanks Alain and other friends for your replies..

The problem was solved with a small R-C snubber. Connected to A1 and A2 pins of Triac.