Zener diode connections

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Homework Statement

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I don't know how to do connections.I just know how to do it in specific type of zener diode because i have learn this.I don't understand these connections.Within 30 minutes i have to leave for my exams please help.


Homework Equations


zener-diode-characteristic-apparatus-500x500.jpg
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The Attempt at a Solution

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I really don't have any idea.I think it should be like this
upload_2015-1-23_9-32-10.png

Please give me general idea how to do connections so that i can do in any kind of zener diode.Please it's urgent.
 
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Answers and Replies

  • #2
berkeman
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Well, I'd love to help, but the pics of the instrument don't help much.

Basically you will want to plot the I versus V characteristic, for both positive and negative bias of the diode. Use Google Images to see what that IV curve looks like to help you with your lab prep.
 
  • #3
NascentOxygen
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Please give me general idea how to do connections so that i can do in any kind of zener diode.
You have the wrong polarity connection for measuring the zener effect. You also seem to have the wrong connection for the voltmeter. The voltmeter should be connected parallel to the diode, but you show both meters in series with the diode. There needs to be a double-adapter available so that you can plug two wires into the one socket to get this right.
 
  • #4
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You have the wrong polarity connection for measuring the zener effect. You also seem to have the wrong connection for the voltmeter. The voltmeter should be connected parallel to the diode, but you show both meters in series with the diode. There needs to be a double-adapter available so that you can plug two wires into the one socket to get this right.
Can you further elaborate this?
 
  • #5
NascentOxygen
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The easiest way to get this right would be to connect up the voltage source, the zener diode, and the ammeter. Then, without changing or unplugging any of these wires, add 2 new wires to connect the voltmeter directly across the diode.

Gingerly adjust the voltage source until the zener current is a few mA. (I say gingerly because there seems no resistance is present to limit the current, so beware that current may increase suddenly with ony a tiny change in voltage source level.)
 
  • #7
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but the pics of the instrument don't help much.
But it is really helpful to me.Can you please correct my connections in the diagram? .
 
  • #8
NascentOxygen
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How?In series?
Yes, these all in series, except not the voltmeter. A voltmeter always connects in parallel to the voltage it is to measure.
 
  • #10
NascentOxygen
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Means battery ,right?
Yes, that's close enough. Though on your apparatus it is called "voltage control".

The designer has introduced some ambiguity (presumably with the best of intentions) by including a switch labelled forward & reverse, but failing to indicate whether the switch function applies to the voltage control, or maybe the voltmeter. Groan. :(

You can't be sure until you try it.
 
  • #11
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Does the lab include any sort of instructions with the "box?"
 
  • #13
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The box with the meters, and power supply.
 
  • #14
NascentOxygen
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It might be a virtual apparatus.
 
  • #15
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virtual apparatus.
That switch --- range for voltmeter? Range for PS output? Commutator for zener socket?
 
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  • #16
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Observe this video from time 2:19 to 2:44

In forward bias why positive of battery is not connected with positive of diode?
 
  • #17
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This demonstration is for normal diodes. Current flow through normal diodes is in the same direction as the arrow in the schematic symbol. Zeners will work the same way. When reverse biased, zeners will "break down" without burning up at whatever the rated voltage is for the given zener (provided current is limited to whatever the zener is rated to handle). A "normal" diode when reverse biased at a voltage that exceeds its rating will also break down, but the breakdown is "fatal" for the diode (the "magic smoke" escapes) and it doesn't work at all as a diode after burning up.
 
  • #18
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This demonstration is for normal diodes. Current flow through normal diodes is in the same direction as the arrow in the schematic symbol.
I am concern with normal diodes.
 
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  • #19
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Where are battery terminals in the apparatus taken in this video.
 
  • #20
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battery terminals in the apparatus
The red and black terminals (pos. and neg.) in the lower left hand corner ---- it's an adjustable power supply, but same thing for this purpose.
normal diodes.
For normal diodes to have a flow of current in the circuit, you will have to connect them in series ( + to - and - to +) rather than parallel since they do have a polarity.
 
  • #21
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you will have to connect them in series
What 'them' indicates?diodes?
 
  • #22
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The battery/power supply and the diode.
 
  • #23
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Is the connection in video right?
 
  • #24
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Yes.
 
  • #26
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This is describing series connection of a normal diode and a battery/power source with the diode being forward biased. Positive terminal/polarity of one to the negative of the other, and negative to positive to complete the circuit so that current can flow. The other way of connecting (parallel) positive to positive and negative to negative gives you a reverse bias on the diode, and no current will flow.
 
  • #27
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The red and black terminals (pos. and neg.) in the lower left hand corner
The positive terminal of the battery is the red terminal which is just left to where forward bias is written.And negative terminal of the battery is the black terminal which is just right to where forward bias is written.Right?
 
  • #28
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Yes.
 
  • #29
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But in video,negative terminal of diode is connected with negative of battery and positive terminal of diode is connected with negative terminal of Milliammeter.Just look at the video at time 2:40.
 
  • #30
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We've just run into another "convention" problem, haven't we?

The way I've always kept myself sorted out on diode polarities is to look at the arrow printed on the diode, and think, "Okay the arrow points the direction that current will flow, and that is from positive to negative (yeah, electron transport is in the opposite direction, but we don't care). So we're back to that "cathode inside the cell as source of electrons for cell contents is also anode outside the cell as a sink for electrons moving in the circuit outside the cell game."

The way to think of it for this exercise is that if we're going to assign polarities to the terminals of a regular diode, is that the arrow points to the "negative" terminal of the diode, and the other end is the positive. At least that will agree with what's in the video.
 
  • #31
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But my question is still alive.

in video,negative terminal of diode is connected with negative of battery and positive terminal of diode is connected with negative terminal of Milliammeter.Just look at the video at time 2:40.
 
  • #32
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I think I have caught my mistake .Positive terminal of diode is connected with positive of battery in forward bias that doesn't mean it (Positive terminal of diode)should be directly/immediately connected with it(positive of battery).Even though positive terminal of diode is connected with negative terminal of Milliammeter, if we follow this it is eventually connected with positive terminal of battery.Right?
 
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  • #33
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But my question is still alive.
In forward bias why positive of battery is not connected with positive of diode?
Okay. Just went back to a couple handbooks to sort my brains out --- there is no fixed polarity convention to terminals of diodes. Each terminal can be, and is, described as having either polarity. Bottom line here is that the video should have been using some other color terminals for connecting the diodes (white at either end to indicate the ambiguity of their use of positive and negative terminals when describing the diode connections).

A diode will pass current only one direction. That direction is indicated by the arrow, and you can think of positive charge passing in that same direction, or electrons moving the opposite direction. Hooking a positive source to the pointed end of the arrow is the same as an open circuit, no current flows. Hooking a positive source to the blunt end of the arrow and completing the circuit with some other components (plain wire, meters, resistors, whatever) allows current to flow.
 
  • #34
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Is my post 32 correct?
 
  • #35
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It works. My suggestion for the long run is to remember the "arrow is direction of current."
 

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