BT138 Incandescent bulb dimmer

[jackylcw]

Hi, i am recently research on a dimming incandescent bulb using triac BT138. i refer to the circuit connection of microchip:
https://ww1.microchip.com/downloads/en/AppNotes/91094A.pdf
i follow their circuit fully except the triac i am using is different. As i read through their circuit connection, they say they input the gate with PWM and i not so sure it works o not. till now, i just using multisim to simulate and i are unable to get my result. i am doubt on its circuit design.

can anyone help me and explain in more detail hows the circuit work or did anyone have any recommended or suggestion on how to control a triac dimmer using bt138. This is my first time using triac, thanks in advance for the help.

 

[ericgibbs]

Hi, i am recently research on a dimming incandescent bulb using triac BT138. i refer to the circuit connection of microchip:
https://www.electro-tech-online.com/custompdfs/2010/06/91094A.pdf
i follow their circuit fully except the triac i am using is different. As i read through their circuit connection, they say they input the gate with PWM and i not so sure it works o not. till now, i just using multisim to simulate and i are unable to get my result. i am doubt on its circuit design.

can anyone help me and explain in more detail hows the circuit work or did anyone have any recommended or suggestion on how to control a triac dimmer using bt138. This is my first time using triac, thanks in advance for the help.

hi,
Using a Diac is an easy light dimmer.

 

[jackylcw]

thx ericqibbs... but i hope i can try to control it using PWM. can the diac can be control using PWM?

 

[ericgibbs]

thx ericqibbs... but i hope i can try to control it using PWM. can the diac can be control using PWM?

hi,
The Diac is not suitable for PWM, I thought you wanted some suggestions for other methods.
Look at Nigels tutorial link, near my signature on this post,,, for PWM

 

[jackylcw]

thanks for the suggestion and tutorial. i have the PIC PWM knowledge and thats why i hope to apply it into my research. Thus, i looking forward to control the dimmer using PWM. The circuit i i shown above failed to simulate. Thus, did any other way to control my dimmer using PWM or did other circuit other than Triac are able to do so?

 

[DirtyLude]

I'm not a PIC person, but the app note is more than clear on how this works and it does not mention PWM at all. Once zero crossing is detected, the microcontroller delays a selected amount of time before triggering the triac. The longer the delay, the more the dimming.

For more theory on how microcontroller/triac dimming works with zero crossing detection you can check this link which I think is pretty clear:
Andrew Kilpatrick