## #3 Rectifier Diode Circuits [Post Homework Here]

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ThePyroElectro
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### #3 Rectifier Diode Circuits [Post Homework Here]

A new lesson was posted today:
http://www.pyroelectro.com/edu/analog/rectifying_diodes/

wr9h
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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

Got my oscillator working but I do not understanding the grounding in the bridge circuit. The 1meg resistor connected to the output of the bridge is also confusing. When I look at other bridge circuits in books etc. I do not see any that has the input and output arranged like this circuit. Finally, it is not clear how the 10u capacitor is connected with the 1 meg resistor. When I put it in parallel with the 1 meg I get no output. I have to admit that I like distinct ground and power rails. Having the double rails is confusing as to where ground actually is located!!!

Herb

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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

wr9h wrote:Got my oscillator working but I do not understanding the grounding in the bridge circuit. The 1meg resistor connected to the output of the bridge is also confusing. When I look at other bridge circuits in books etc. I do not see any that has the input and output arranged like this circuit. Finally, it is not clear how the 10u capacitor is connected with the 1 meg resistor. When I put it in parallel with the 1 meg I get no output. I have to admit that I like distinct ground and power rails. Having the double rails is confusing as to where ground actually is located!!!

Herb

Hello!

The 1 MΩ + 100kΩ part of the circuit is meant only as a protection measure for using a soundcard oscilloscope to see the rectified output, it is not part of the bridge circuit.

Connecting the 10u capacitor can be a little tricky. The best way is to take a close look at the schematic:
http://www.pyroelectro.com/edu/analog/rectifying_diodes/schematics/

I updated and corrected the probe connection points. Now in the schematic only the main ground is labelled. The 'new' ground created by the bridge is not labelled in any special way.

The capacitor does indeed go in parallel with the 1 MΩ resistor, however if you are looking at the soundcard oscilloscope for output, you won't see any because at that point the signal should be DC, which means a flat line and no more sine wave.

The lesson video demonstrates one way to see the fully rectified signal by using a digital multimeter and measuring the rectified voltage at about +3.5v. Then when the capacitor is added, the signal is fully rectified to DC and measures higher at about +4.75v

Unfortunately, seeing this occur on the oscilloscope is far less rewarding because once the capacitor is added the output on the soundcard oscilloscope is a flat line.

I hope this helps you out!

wr9h
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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

Thanks for the info.

HUMMMMM....perhaps I had a well filtered DC voltage but didn't believe it! I re-measure everything.

I have a nice full-wave waveform at twice the input frequency. It looks exactly like the one in the video except there is a little clipping on every other peak. Perhaps some diode distortion?

I have done some outside reading on the 741 as I had the most basic understanding of it.
1) operational amplifiers: linear IC that produces gain over a wide range of signal input frequencies
2) operational amplifiers: a product (originally) of Bell Systems (need for amplifier that would not be
sensitive to its environment.....)
3) 741 need for two power supplies: one supply is for emitters, the other for the collectors (multiple
internal transistors in IC)
4) External resistors determine gain but also if 741 will oscillate (inverting versus non-inverting
inp

Probably getting ahead here and I need to finish this lesson!!!
Herb/WR9H

ThePyroElectro
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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

wr9h wrote:Thanks for the info.

HUMMMMM....perhaps I had a well filtered DC voltage but didn't believe it! I re-measure everything.

I have a nice full-wave waveform at twice the input frequency. It looks exactly like the one in the video except there is a little clipping on every other peak. Perhaps some diode distortion?

Hello,

If you see the rectified full-wave measuring twice the input frequency, you have successfully built the bridge and the AC signal is being fully rectified!

Once you add the capacitor, it will charge up and any signal you see and the soundcard oscilloscope input signal will flat-line as you now have a stable DC electrical signal.

The clipping you see is likely because of the soundcard you are using. You can play with the microphone input volume setting and it might fix it so you can see the whole rectified wave.

Yea, op-amps come into play a little later on in this course!

wr9h
Newbie Pyro
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Joined: Sat Nov 09, 2013 7:49 pm

### Re: #3 Rectifier Diode Circuits [Post Homework Here]

Lesson 3 Questions

Q1) a) A half-wave rectifier only passes one half of an applied sine wave.
b) A full-wave rectifier uses both "halves" of an applied sine wave. The positive half
is passed as well as an inverted version of the negative half.

Q2) The DC produced by a bridge rectifier is composed of positive peaks of voltage at twice the input frequency! This type of DC is pulsating DC and the positive peaks are called ripple. This type of DC is generally considered unstable and not useable. A proper valued capacitor (10uF in our experiment) placed across the rectifier's output will smooth out the positive peaks and actually produced a higher more stable output voltage. In my circuit the rectifiers output ripple voltage was 5.25 volts. With the filter capacitor the voltage was ripple free and 6.76 volts.

Q3) Nearly all modern electronic devices require a steady stable DC voltage to operate, therefore, a need for AC rectification!!!

Q4) HUMMMM....How do I draw here???? I might find an image that I could put here....

Herb

wr9h
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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

Hello,

Just a quick note to let you know that I am enjoying the course!!!

Now, on to Zeners!

Herb

ThePyroElectro
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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

wr9h wrote:Lesson 3 Questions

Q1) a) A half-wave rectifier only passes one half of an applied sine wave.
b) A full-wave rectifier uses both "halves" of an applied sine wave. The positive half
is passed as well as an inverted version of the negative half.

Q2) The DC produced by a bridge rectifier is composed of positive peaks of voltage at twice the input frequency! This type of DC is pulsating DC and the positive peaks are called ripple. This type of DC is generally considered unstable and not useable. A proper valued capacitor (10uF in our experiment) placed across the rectifier's output will smooth out the positive peaks and actually produced a higher more stable output voltage. In my circuit the rectifiers output ripple voltage was 5.25 volts. With the filter capacitor the voltage was ripple free and 6.76 volts.

Q3) Nearly all modern electronic devices require a steady stable DC voltage to operate, therefore, a need for AC rectification!!!

Q4) HUMMMM....How do I draw here???? I might find an image that I could put here....

Herb

Hi! All correct answers. I was using rechargeable Nickel–metal hydride (NiMH) batteries, so the voltages measured in the video turn out to be a little lower than if you use alkaline batteries which have a higher voltage. I'm guessing you were using alkaline.

I admit the drawing portions of the homework are easier to do when teaching in class. Online people sometimes draw them using a schematic or paint program and upload them to an image host (like imgur.com) then post them in the forums. It's really up to you.

wr9h wrote:Hello,

Just a quick note to let you know that I am enjoying the course!!!

Now, on to Zeners!

Herb

Thanks, we are glad you're learning!

jessicapatel123
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### Re: #3 Rectifier Diode Circuits [Post Homework Here]

hi everyone i'm new here.
Dissertation Help

regards
jessica patel