I am designing a prototype for a fuse blow buzzer and overcurrent protection circuit for 18VAC tranformer. Transformer has 2Amp fuse on the line. I am using AC optocoupler SFH628A-3 to sense current from the line and trigger an SCR that will operate relay. The buzzer is attached to NO of the 24VDC relay. My I need help in
1: I am unable to get short circuit conditions and use of proper resistors to limit the current.
2: I need guidance about how can i operate relay based on the current sensed from optocoupler and implement protection.
Your guidance will be highly appreciated.

I am new in circuit design and helping me in this will be great help.

Thanks

Regards,

Asif

 

I am designing a prototype for a fuse blow buzzer

Why? When the fuse blows the circuit will stop working, isn't that enough to tell you it's blown?

 

Why? When the fuse blows the circuit will stop working, isn't that enough to tell you it's blown?

We are making prototype for the student tranformer. Buzzer will indicate to the instructor that fuse has been blown.