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

#### Halim.Akiki

Joined Dec 29, 2014
44
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

#### djsfantasi

Joined Apr 11, 2010
9,160
Can't see your images. If you are having problems, take a look at my blog entry here.

#### WBahn

Joined Mar 31, 2012
30,028

#### Halim.Akiki

Joined Dec 29, 2014
44

#### Halim.Akiki

Joined Dec 29, 2014
44
Are they clear now?

#### MrChips

Joined Oct 2, 2009
30,789
Of course you will get negative voltages. Turn your rectifiers around.

#### Halim.Akiki

Joined Dec 29, 2014
44
Are they clear now?

#### Halim.Akiki

Joined Dec 29, 2014
44
Of course you will get negative voltages. Turn your rectifiers around.
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?

#### MrChips

Joined Oct 2, 2009
30,789
Then increase the value of C1 to 1000μF.

BTW, use a thread title better than Urgent!!

#### Halim.Akiki

Joined Dec 29, 2014
44
Then increase the value of C1 to 1000μF.

BTW, use a thread title better than Urgent!!
Thank you! I will use better titles.

#### WBahn

Joined Mar 31, 2012
30,028
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.

#### Halim.Akiki

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

#### WBahn

Joined Mar 31, 2012
30,028
Man you're a genius!
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?

#### Halim.Akiki

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

#### WBahn

Joined Mar 31, 2012
30,028
I was u sing a 1K resistor. increasing the capacitor's size to 10mF made the result perfect.
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.

#### MrChips

Joined Oct 2, 2009
30,789
Please note that 1mF is 1000μF.

#### WBahn

Joined Mar 31, 2012
30,028
Please note that 1mF is 1000μF.
Yes. So an increase from 0.83uF to 10mF is an increase by a factor of over 12,000.