Triac BT139 dimmer problem

hi all

Iam facing aproblem on firing triac , iam using pic16f84 to control the firing phase angl Via timing
attached the circuit
there is only problem that the triac cut off when itis loaded by 100 watt load

every thing is ok this include

1. zero crossing detectin
2 signals from/to pic16f84
3.opto coupler "IS623" and opto isolator 4n35

i check the phase control proccess by oscilloscope and phase controlled wave was OK

the only problem is the triac goes off when the 100watt load is loaded

any help will be appriciated

BR

At what phase angle are you trying to fire the triac? What voltage is driving the opto?

Try some resistance across the cross over iso-coupler diode. You may have poor rise and fall times without it.

Don't connect your lamp to the low side of the traic. Connect to the hight side.

hi all

thanks for replying

I try all what you all mentioned , unfortunally it doesn't work

actulay i have abeautiful phase controled ac 220 sine wave

But once i connect the 100 watt load it disappears i gues that opto coupler IS623 is the part which makes

the troubles

any ideas , hints will be appriciated

thanks alot

BR

I think this would happen if you have exchanged MT1 and MT2 on the triac. Be sure that MT2 is the center wire/tab.

Try using MOC 3021 -- see its data sheets you will find the application circuit in it.