Problem With 220 VAC Halogen Lamp Dimming

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..

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

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

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

Cheers

Al.

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?

Quote:

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Originally Posted by aratti

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

Cheers

Al.

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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.

Code:

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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

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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 ... :D )

Alain

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.