Urgent!! (i want to create a full wave rectifier}

Discussion in 'Homework Help' started by Halim.Akiki, Dec 29, 2014.

Dec 29, 2014
44
1
Hello
I have a small project and i want to create a full wave rectifier. I drew the following circuit
But i am having a negative result
Can anyone help me?
The sine wave is :
DC = 0 V
AC = 16 V
VOFF = 0 V
VAMPL = 16 V
FREQ = 60 Hz

2. djsfantasi AAC Fanatic!

Apr 11, 2010
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Can't see your images. If you are having problems, take a look at my blog entry here.

Halim.Akiki likes this.
3. WBahn Moderator

Mar 31, 2012
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Halim.Akiki likes this.

Dec 29, 2014
44
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Dec 29, 2014
44
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Are they clear now?

6. MrChips Moderator

Oct 2, 2009
12,442
3,361
Of course you will get negative voltages. Turn your rectifiers around.

Dec 29, 2014
44
1
Are they clear now?

Dec 29, 2014
44
1
Thank you very much. I turned the rectifiers and the output turned out right. But when i added a resistor on the output i had the following result.
Any suggestions?

9. MrChips Moderator

Oct 2, 2009
12,442
3,361
Then increase the value of C1 to 1000μF.

BTW, use a thread title better than Urgent!!

Dec 29, 2014
44
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Thank you! I will use better titles.

11. WBahn Moderator

Mar 31, 2012
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What size resistor did you use? How can we give good feedback if you don't give us the information?

Since your output appears to be drooping from 14V down to 1V and that is being pulled from a 0.83uF cap, that means that you are pulling about 11uC of charge from it. Since that is being pulled out in 1/120th of a second, that's an average current of about 1.3mA. Since the average voltage is about 6.5V, I'm going to guess that you are using something like a 5kΩ resistor. Is that close?

If you follow how I did that, then see if you can work backwards to find a good capacitor value to use to keep the droop (also known as ripple) below a desired value.

Dec 29, 2014
44
1
Man you're a genius!

13. WBahn Moderator

Mar 31, 2012
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Wouldn't go anywhere near that far, that's for sure. But thanks anyway.

What size resistor were you using?

What was the final result?

Dec 29, 2014
44
1
I was u sing a 1K resistor. increasing the capacitor's size to 10mF made the result perfect.

15. WBahn Moderator

Mar 31, 2012
17,747
4,795
Yeah, in increase by a factor of 10,000 probably reduced your ripple voltage for that size load down to a millivolt or two. It will give you a pretty high inrush current, though.

16. MrChips Moderator

Oct 2, 2009
12,442
3,361
Please note that 1mF is 1000μF.

17. WBahn Moderator

Mar 31, 2012
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4,795
Yes. So an increase from 0.83uF to 10mF is an increase by a factor of over 12,000.