Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Direct Drive Triac from ATtiny Processor

Status
Not open for further replies.

manishb

Newbie level 4
Joined
Mar 16, 2020
Messages
5
Helped
1
Reputation
2
Reaction score
1
Trophy points
3
Activity points
39
Hi Everyone, this is my first post here.



I am trying to drive a triac BT134 directly from the ATTiny816 processor. The goal is to drive the triac in Quadtrant 2 and 3. I have referred to the note by ST for negative power supply. Please see attached images of the power supply section and the drive section. The speed control pin is connecte to an ATTiny816.



When I switch the pcb on, I get a spark on the triac, or the resistor or transistor connecting to the triac gate blows up. Can anyone see what I am doing wrong here?



(ST note for reference - https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00266635.pdf )



I need to use non-isolated power supply and drive for cost reasons.
 

Attachments

  • Power.PNG
    Power.PNG
    46.1 KB · Views: 148
  • Triac.PNG
    Triac.PNG
    38.2 KB · Views: 144

When I switch the pcb on, I get a spark on the triac, or the resistor or transistor connecting to the triac gate blows up.
Just expectable.

Your circuit misses the bridge between +5V and AC input, as shown in Figure 8 of the application note.

triac.PNG

It's not possible with the presently used capacitive voltage dropper. But you can redesign the power supply with flipped polarity, using positive common and tie it to triac A1 terminal.
 

Thank you for your reply Fvm. If I keep the same circuit and move the capacitive drops to neutral, will that work?
 
  • Like
Reactions: FvM

    FvM

    Points: 2
    Helpful Answer Positive Rating
I have modified the circuit and attached the full circuit. Does this look fine to you?
complete.PNG
 

A half-wave capacitive dropper will work, as long as it is wired to provide a negative voltage.

But as FvM mentions, show your complete schematic. We can't read minds.
 

Hi FvM, so far the triac is no longer blowing up, so it looks promising. However, I have a new challenge to see the waveforms on the oscilloscope. Earlier, since the ground and neutral were common, I could connect the oscilloscope ground to circuit gnd / neutral, and could measure any waveform in the circuit. But now since the neutral and ground are no longer common, if I connect the oscilloscope ground to circuit ground and try to measure, the zener immediately shorts. How can I measure the waveforms on the oscilloscope? I need to see zero crossing and trigger timing on the scope.

Thanks for your help.

- - - Updated - - -

Also, the zero crossing detector circuit no longer works. Is this because 5V is tied to power? I had connected a pin from power through 1M resisistor to zero crossing pin. Now since power and 5V are tied, its not working. Should I take a connector from neutral through 1M to zero crossing pin?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top