Im having 230v to 12v transformer ,i have to supply it for different devices which works with different input voltages like 2v and 3.5v like that for some hardware testing purpose.
Near our home the supply is not constant it will go some time like 250v, so can anybody tell me how to make ac voltage regulator

 

Is the 2V and 3.5V DC or AC?

 

its Ac so only i'm worrying much

 

How much current for there 2v and 3.5v hardware and what are the hardware?

 

That may be take in mili amps

 

How much mA?
10mA, 100mA?

If you have another transformer as AC230V to 16~24Vac then you can in series the secondary side with the primary side of 230v to 12v transformer.

In series with two transformers as:
AC230V city power → 0.5A Fuse → 230Vac(230Vac to 12Vac transformer) → 16~24Vac(transformer AC230V to 16~24Vac) → AC 0V