(Zener diodes) For Engineers.

Hi Guys and Girls ,Sorry for the Delayed Post.
We are using Zener Diodes to make Somewhat Stable Voltages Somewhere in a Circuit.Zener Diodes are not Good for High Current Applications.most of them are using for few hundred mA Loads.
this is the Symbol Of Zener Diode.

Zener Diode Works only when it Is Reverse Bias.
But How is this Thing Works.Eazy.
Lets Look at the VI Curve of a Zener Diode.
Graph is in the -X and -Y Side, Because it is Reverse Biased.
The Zener Voltage of the Zener Diode Is the its's Braking Voltage.As You can see in the Graph ,When the Zener Current Increases (-Y),Zener Volatage Remains Roughly Constant(Vx).

 Here is A Zener Regulator Circuit.We use A Risistor Because ,To Limit the Maximum Zener Current.(Because Zener Diode can't Handle High Current Than Its Maximum Zener Current.)

Now Lets Select a Zener Diode For Our Application.Lets Say We need 1.8V Somewhere in Our Circuit.We can Just Use a 1.8V Zener Diode.

Is It Finish,Not yet!

Next thing We want to Select is Power Ratings of Our Diode.To calculate that We need to decide Maximum  Zener Current.Maximum Current will Flow When Nothing is attached To the Output(Uout).So,To limit Our Maximum Current We Use Ohm's Law.

Lets Say We need 1.8V From 10V Supply.

Uin =10V so The Voltage Drop Across R is   R = Uin-Vzd = (10v-1.8v=8.2v)

where Vzd=Uout

lets choose Maximum Zener Current = 50mA .Use Ohm's Law  V=IR
8.2V/0.05A=R=164Ohm


R must be small enough that the current through ZD keeps ZD in reverse breakdown. The value of this current is given in the data sheet for ZD. For example, 5.6 V 0.5 W zener diode, has a recommended reverse current of 5 mA. If insufficient current exists through ZD, then U_OUT will be unregulated, When calculating R, allowance must be made for any current through the external load, not shown in this diagram, connected across U_OUT.
Now we can Calculate Zener Power Consumption
To Do that  we need Dynamic Impedance of the Zener Diode at 50mA ,you can find this on the data sheet of Zener Diode
Dynamic Impedance Measure in (Ohms).Now Think Zener Diode as a Risistor ,Then use W=I^2R (Where R is the Dynamic Impedance).Thats the Power Disipation in Our ZD,When We are designing a Circuit,Use a bigger Diode than calculated.so we can Improve Lifetime of the Zener Diode.

Also We can Calculate the Ripple of the Output Voltage.Lets think our Uin Veriest from 10V- 5V So when Uin=5V Zener Current =(5V-1.8V)/164Ohm=0.0195A=19mA
When its 10V its 50mA(Calculated Earlier)
Current Change is=50mA-19mA=31mA
Use ΔV=ΔI X Rdyn Equation to calculate OutPut Voltage Change
( Δ (delta) Means Very Small amount)
( Rdyn  means Dynamic Impedance or dynamic Resistance)

ΔV=? ΔI=19mA Rdyn =7Ohm
ΔV=(19x7)/1000 =0.133V

as you can see Zener Diodes are Quit Handy.

Also You need to Worry about Temperature Coefficient Of the Diode.It doesn't matter If you are using this For Low Power Applications.and using in Room Temperature.
Thats Enough About Zener Diodes

Good Bye!!
If you like My Blog Please  Fallow.Ask me If you Don't Know Something,by comment .

Voltage Divider's For Engineers.

Hi Guys/Girls Electronics One of the Impotent Lessons . This is the easiest way to get a Lover Voltage From Higher Voltage.
Main Charastaristics!

• Output Voltage Is Lover Than Input Voltage.
• Output Voltage Changes with the Load.
  In That Case This Is Non Stable.This Thing Happens Because,When we attach a Load ,The load will be parallel with One of the divider Resistor.Causing OutPut Voltage to Drop.

• What is the Output Voltage ?

When nothing Attach to the Vout,Current is Same every Where. We will get an Answer like in Picture 2.

After that Use Ohms law to Find the Voltage Across R2.That's Our Vout!






Lets Look at an Example.Lets Think We need 6V from 10V

OK.now We know Vin and Vout ,But we can't find R1 and R2 from one Equation.So lets Choos R1 For Our maximum current Need.
  According  toVoltage Divider Law ,Voltage Should Divide to Ratio R1:R2     4V:6V.In That case R1 will get 4V.Lets Think Maximum Current = 50mA From Ohms Law ,We will get 80Ohm for R1 .Picture 4



Now We can find R2 from Voltage Divider Equation  Picture4
Weget R2 as 12Ohm.. Simple, Isn't it?

But,When We are drawing maximum current from Our divider ,what is the power dissipation in 80 Ohm Resistor (R1), to do that ,use W=I^2R Now you can see its 0.20W in our R1,So that,s a waste,not good for the 1/4W resistor..In that case we cant draw that much current from a divider,so use large values as much as you can,this is not the Best solution ,when its comes to Impedance ,im not going to talk about that right now,

its good to use lower value resistors for a divider,but it needs much more power ,and large Power Risistors.So rule of thumb use 1K-100k

Lets calculate Power dissipation without a load, ,Total Resistance  80+12 =92ohm ,so according to  W=V^2/R  see Picture 5

This thing is pissing away about 1W !
So use Large values for R1 and R2












Another Example
Think we need to divide 12v to 6v, so just use 2 Equal Resistor For R1and R2.Now i need 2mA from my divider , Picture 6

I can't do the calculations in typing,so see the Picture



Now you can see the power consumption of the divider.
as a conclusion use Voltage Dividers for Low Current  Applications.
But you can Experiment With It.

Last Question Why is this Voltage Divider Isn't Stable?.

When We attach a Load Resistor (Load Circuit) to the Vout , Load Resistor  become parellel with R2 in that case Vout drops ,due to the reduce of total resistance of the R2 and Load,Lets take the Second Example,lets See what will happen when we attach a 1Kohm  to the Vout.

According to the picture ,now you can see what is the total resistance Across the Load.it reduce 3Kohm to 0.75Kohm

 Lets apply Our Voltage Divider Equation Ok now theVout Reduce to 6V to 4V, Thats the Diss advantage of the Voltage Divider.

FAINISH!
 Voltage Divider's are finish.
,Good Bye!!
If you like My Blog Please  Fallow.Ask me If you Don't Know Something,by comment .

Welcome to Electronic Engineering, Fellows!

Hi Guys /Girls Today I'm gonna start a new Blog  about Electronic Engineering,So Stick with me Guys.I'll Show you how to design a Product From Start to Finish.

I'm Chamli Priyashan Abeysingha ,and I'm Electronic Engineering Student (Year 1)at SLIIT
and a Crazy Fellow About Engineering .I Think That's  Enough About Me!(Have to Later)

Before We Start You all must Have Curiosity about Engineering and Must Have Basic Electronic and Basic Mathematics.

I'll Teach you Everything about

• Zener Diodes 
• Capacitors
• Transistors
• FETs(MOSFET,JFETs)
• OPAmps
• Inductors
• Filters(LowPass,HighPass)
• Microcontrollers
• FPGA,
• PCB Designing
• Etc.......Including Hacking,Tear-downs ,Developments.

Enough Talk Lets START!

First Of all  You must have a Basic Electronic Workshop.

I'll Guide you through to Have a Reasonably good Quality Lab.
To do that.You have to Pay About (12000LKR or more)
Its OK That You don't Have That Much,But Stick With me!It Will be Much Less

For a Good Lab you Should Have

•  At least 2 Multimeter s Or more (2100LKR Minimum)

Auto-Ranging Multimeter (35$ at eBay)

(because we should be able to measure Voltage and Current at the Same time.I Recommend you to have Auto-Ranging  Multimeter s but they are about 35$ for each(Chinese )

Normal Multimeter (1050LKR at Peta/Sri Lanka)

So you can Have 10$ Cheap Normal Multimeter.

• You Should Have Good Power Supply (8500 LKR for Commercial Lab-PS)

You Will Defiantly want a Variable Power Supply,It Should Have Voltage Adjustment Pot and Current Limiting Pot .Because we need to Generate various voltages and need to limit Current  Flow in Some Times.So You can straightly Buy a Power supply from eBay or From a Electronic Shop (Electronic Shak)

Or You Can Built One for Your Self    (1500LKR)

It is Very Easy to Make a Good Power Supply by your Self.Lets Design a Lab Power Supply as Our First Project In next Blog.

• You Should Have Oscilloscope (45000 LKR )

You Defiantly need a Oscilloscope in electronics,but these are very expensive,you must buy as much as high band width one,because the higher the bandwidth the more frequencies you can measure.buy 2 Chanel or more one ,so you can measure many signals at once.

or you can buy  USB Oscilloscope they are cheap but not that much precision.but that is more than enough for us.USB Oscilloscope is about 13000 LKR

BUY A  Oscilloscope above 20Mhz bandwidth.Even i Still don't have one.  

• You Should Have 2 Good Soldering Iron s Or More (1000LKR For Cheap 2)

This One is Also Important. I Recommend You to Buy  Temperature Variable Soldering Station

This thing Is About 85$ In eBay and Excellent Quality One.

But you Can Buy 2 Normal 25W Soldering Irons

And You Should Have a 60W Iron Also(because some times you will have To De-solder Some Components From Old Circuits) these ones Are 200LKR In SriLanka .

• You Should Have a Bread Board

  This is very Use-full Thing to Build Test Circuits Without Soldering.

You can just Plug your All  Component and in to places and connect all of them as you wish by Wires.

•  You Should Have a PC (Computer,I think You all Have one so that's Free)

Your PC Should Have Serial Port(For Programing)If You Have USB Programmer, Serial  Port Is Not Essential.Programmer is not that much necessary for our Basic electronic lab.And Also I'll Show you How to build One In Future Blog.

• You Should Have Various types of Screw Drivers

To take things Apart ! And to Assemble Them.

also include Alan-keys 

•  Should Have.

Proper Engineering Ruler.~

                                        Normal Ruler Will Not Work Because There Measurements Very With Temperature Range.

Paper Cutters. ~ 

To Cut Tracers in Some Circuits

Scientific Calculator ~ 

You can't do all The Calculations By Hand ,Because That's Silly 

Component Storage ~ 

            Because You can't Go to Shop Always.in your Storage you should Have all flavors Resistors,Transistors,FETs,Zeners,Diodes,LEDs,Opamps,Capasitors.etc

            

Dust Bin ~ 
To Put All Your Fail Projects! That's How We Learn Electronics,All Buy Mistakes

Junk Circuit Box ~ 

Collect as much as Circuits To Take Parts. I Have About 60 Kg  Of Junk Bin.

I Think That's It ,Now you've got basic Electronic lab Equipments., Its 10.25PM Now,So Have to say Good Bye . Hope To Update Soon .Have a Good Day Guys.