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 ... :D )

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.