Relay circuit for AC switching

[rabhishek91]

Hi everyone.
Below is the relay driver circuit for MCU. It works good for DC voltages (ignition coil). I myself tested it.
If i use AC voltage as a supply for ignition coil then i am sure the same driver circuit does not work.
Please help me with the changes which have to be made for AC supply voltages.

 

[alec_t]

Are you using the relay to switch the DC supply voltage for the ignition coil? If it works well with DC why do you want to drive the coil with AC?

 

[be80be]

You get rid of the diode and Q1 get you a logic level triac and your done.

Hook the bottom of the relay coil to gnd and feed the coil with the triac. You fire the triac on with the 1k resistor from the mC.

 

[rabhishek91]

You get rid of the diode and Q1 get you a logic level triac and your done.

Hook the bottom of the relay coil to gnd and feed the coil with the triac. You fire the triac on with the 1k resistor from the mC.

Thank you sir. I have modified the circuit and attached below. Is it right ?

 

[be80be]

No that's shorting the triac look at this one

 

[rabhishek91]

Are you using the relay to switch the DC supply voltage for the ignition coil? If it works well with DC why do you want to drive the coil with AC?

Sir i am using a ignition coil circuit where i need to control it. Initially i thought of controlling it in below manner.

But later by trying out in lab i got to know that voltage at input crosses more than 400V due to overload. So i decided to control the circuit by switching AC (before the conversion of AC to DC i.e. before transformer). In this way,the transformer acts as an isolator and protects the relay.

 

[rabhishek91]

No that's shorting the triac look at this one
View attachment 73395

Thanks for the correction sir. I'll try it and keep you posted

 

[Jibby]

Rectify it