hi ,
just saw a circuit today and i wondered :

how to convert an ac transformer(12v) to a dc transformer,through diodes
do they come in built or we have to put some changes in the circuit?
how can we know the amount of turns in primary as well as secondary winding


thanks in advance

shankbond

 

I think you need to arrange 4 diodes to form a bridge, and connect them to one end of the transformer. I'm not sure of the actual circuit. Just look for an AC/DC converter on the net.

 

Post the circuit, or a link to it.

Right now I'm not sure if you're talking about an amplifier that's powered by AC, or one meant to amplify AC signals.

AC amplifiers (such as audio amplifiers) almost always have coupling capacitors between stages which block DC, but pass the effects of AC signals.

 

Wait, why would you want a bridge of diodes?

 

MusicTech,
We don't have enough info yet. Mik3ca was eager to help, but may have confused the issue.

We really need to hear back from the OP (original poster) before a helpful (and productive) direction can be taken.

But basically, if it's an amp designed to be powered by AC, then it already has an integral diode bridge rectifier. If it's an AC signal amplifier, they won't be able to use it to amplify DC levels due to the internal coupling caps.

 

MusicTech,

It's not a bridge of diodes, it's a diode bridge. It's an arrangement of diodes to rectify AC. This link to the Ebook explains - http://www.allaboutcircuits.com/vol_3/chpt_3/4.html.

Take some time and read up on basic theory.

 

ok , when you say dc transformer, do yo umean you want to rectifier an ac signal , or do you mean you want raise or reduce a dc voltge. To raise or reduce a dc voltage you need to make a dc to dc convetor,this can be done by taking the dc voltage of interest and chopping up, then feed this into a transformer, becuse you cant put pure, stable,flat line, dc into a transfomer due to fact there wont be any change in magnetic field, so by chopping it up you can step it up or down in the windings of the transformer, then just smooth the output using caps , is this what you meant., but if you just wanted rectifier an ac signal , then stick it into a full wave bridge rectifier,make sure the diodes are rated correclty and smoothing caps ect.

 

thanx man,but it would be nice of u to further elaborate it as i still don't understand the chopping mechanism .





shankbond

 

just saw a circuit today and i wondered

Like SgtWookie said ... can you post the circuit or a link to it? That way everyone can stop speculating on what you mean and everyone can be on the same page.

 

here ,it is ,it is a circuit of a stepper motor driven from PC through parallel port, here i need to make a dc voltage out of 220 v mains(50hz)

 

Oh, ok. You need a step-down transfomer.
One that will take 220VAC on the primary, and output somewhere between 14VAC to 18VAC, at about 1 Ampere. But there is no voltage regulator shown in the power supply section, and that is not a good thing. A simple 7812 linear regulator IC would work fine. It has three pins; in, out, and ground.