Help with Power source device

[Sonia1234]

Hello there folks,

I a supposed to design a power source device. And this is what has been done in multisim so far, am falling short of time but I really want to know valuable suggestions of the experts over here since I really want to make this design final and robust. Also sine am a beginner in electronics, please can someone direct me on the attachment of oscilloscope and voltmeter to test.
Waiting or your replies.
Thank you

 

[errakeshpillai]

Use a single Ground point and connect all the components to the same ground.
Now for oscilloscope, just connect the A-port across the load.
Same with the voltmeter.

You just have to connect the two terminals of the meter across the load(component) where you need measurements.

 

[Sonia1234]

Alright, but now I have one more problem. I need a voltage outlet of 220Vac which is capable of supplying fixed or variable DC voltage. I am confused as to how would I make this happen. Thanks alot for your response.

 

[errakeshpillai]

I'm not clear with your problem.
You need a 220V ac source or need a 220V ac output...???

 

[Sonia1234]

I'm not clear with your problem.
You need a 220V ac source or need a 220V ac output...???

I actually need a 220V ac source since the local main in the country is 220V ac.
And this is what I am getting on the voltmeter. Am not getting why is it showing this value instead of 12V.

 

[errakeshpillai]

The connection of the capacitor C1 is shorting both the output of the transformer. I think there a mistake there.
And if you need a 12V dc at the output you can use a LM7812 IC with the transformer to get a constant 12V dc.

 

[Sonia1234]

Okay what do you think about this one? I will get a positive voltage supply unless I want a negative one. But the problem is that the voltmeter should show 20Vac and its not. Am really frustrated with this problem. I think there's something wrong with the transformer. What do you think here?
P.S. This is just part of a circuit

 

[errakeshpillai]

Thats after stepping down..
You have to rectify the voltage to your required 12V..
Try this circuit using LM 7812.