# Trying to understand voltage on rectifier

Discussion in 'General Electronics Chat' started by sebastianpatten, Nov 28, 2010.

1. ### sebastianpatten Thread Starter New Member

Nov 28, 2010
18
0
Hi there,

Im trying to get into electronics and the first thing I want to build is an AC to DC converter. I am using Tina to model the circuit first so I can fully understand it. However I am having trouble understanding two things.

I built the circuit at the top, basically a simple AC source that is a sine wave, Amplitute of 10 (I think this is volts) and Frequency of 50. I also have a diode.

When i measure what the voltage is on the circuit it reads as -1.54e -18v. Why is this voltage so low? I can only think of that because of the diode, one cycle of voltage is not being allowed past the diode. But i dont get the huge difference of 10v in and reading the low reading.

Also when I look at the oscilloscope, I would expect to see half of the full sine wave when looking at the circuit with a diode as the diode. But when I look at it, it looks like i see the full sine wave. Why is that?

The diagram on the top of the allaboutcircuits page looks like it only shows half of the sine wave.

Thanks!

2. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
It would help a great deal if you posted an image of your Tina-TI schematic, and/or uploaded the simulation file.

What value did you assign to the load resistor?

What diode did you use?

So many questions can be answered by posting a schematic. It eliminates ambiguities, and will get you answers much more quickly.

.PNG format is preferred; the files are of small size, not "blurry" like .jpg files, and no additional software is required to view them other than a browser.

3. ### sebastianpatten Thread Starter New Member

Nov 28, 2010
18
0

Thanks and here you go:

I dont understand why the oscilloscope's wave doesn't look like the one on the top of this page:

It looks like it goes to +3 ish volts to -3 ish volts.

Also why when i run the app does the dc voltage look so tiny?

Many thanks!

4. ### sebastianpatten Thread Starter New Member

Nov 28, 2010
18
0
Any input on this? I'm new to electronics but don't understand why the waveform goes to negative voltage and why the voltage when measured in DC is so small.

5. ### retched AAC Fanatic!

Dec 5, 2009
5,201
312
Try reversing the diode to see if tina responds to that.

Try measuring it with no diode and show results.

Add a ground to the circuit also. It may just be a simulation error because there is no assigned ground.

Many spice packages will not run without a defined ground.

6. ### sebastianpatten Thread Starter New Member

Nov 28, 2010
18
0
The signal is a 10V sine wave.

Does what I am expecting sound reasonable? I don't want to get the wrong end of the stick regarding the ac waveform.

Also the ground point is interesting. Is Tina crappy software?

It seems like a lot of the circuits I have seen recently have had ground. Why would you need ground when you have a closed circuit?

7. ### mik3 Senior Member

Feb 4, 2008
4,846
63
I don't know if Tina is not good but using PSpice or LTSpice will give you good results.

The ground may be needed as a reference point for the measurements.

Try to put a ground and a resistor for a load.