Hello dear all

I'm Irfan and I have searched alot to find the the circuit that can adjust stepdownd 12V AC with 1Amp or 0.5Amp current like variac device(vary the AC voltages by using winding tapings),but i havnt found yet.Let me tel u all, mostly every where I have DC adjustable circuit with LM317 etc., 1 thing more I dont wana use transformer secondry tapings to vary the AC voltages on diffrent secondry positions I just want 12vac from 240 v main, using step down transformer and wanna make it vary...plz plz help me........

Thanking u all in anticipation....

 

1 milliamp or less? What are you going to do with so little current?

If you don't want to use a transformer, then you'll need to use batteries, and build an oscillator circuit.

It is very dangerous to attempt to power circuits directly from the mains without a transformer.

 

Use something like this: http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1322 and put a current limiter after it.

 

sorry dear I did spell mistake its ampere(amp) and let me tll u I used the word stepdownd its mean im using 240vac to 12 vac stepdown trasformer....thanks for reply

1 milliamp or less? What are you going to do with so little current?

If you don't want to use a transformer, then you'll need to use batteries, and build an oscillator circuit.

It is very dangerous to attempt to power circuits directly from the mains without a transformer.

 

Hello,

Take a look at this page from Bill Bowden.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm

Greetings,
Bertus

 

Elektroman,

What you probably need is an buck converter. As far as I know, this forum will not give you assistance for a circuit that connects directly to the power line without a transformer of some kind for isolation. I think this is a safety concern. Circuits that connect directly to the power lines should only be designed and tested by people with a lot of experience in the design of this kind of circuit, a thorough understanding of the dangers and safety practices, and only when properly trained medical help is available (never work on line powered equipment when alone.)

You can step down and regulate AC. I once hired a consulting company to do that. It was complicated and it was very difficult to make it reliable. If you really need to do that (simulate a Variac with AC in and AC out), I suggest you hire a consultant who has experience in this). Even better would be to use a transformer or a Variac.

 

Choice A) Variac.

Choice B) Non Sinusoidal adjustable RMS AC. A Triac with some support components could accomplish the task. If a closer representation to a sinewave is required, adding a multiple pole low pass filter could help, though unsure about the current levels.

Choice C) Sinewave generator IC feeding a variable gain power amplifier having a stout DC Power supply. This option keeps you away from line voltages completely, outside of the power supply for the amplifier.