Diode and Zeners

Diode
The function of a diode is to let electrical current flow only in one direction, in a circuit is to stop electrical current from flowing in the wrong direction. Thus diode can be put in place to protect other component from back emf happening.



IMPORTANT: As you can see in the graph below, too much forward current and the diode may be damaged and conduct in both directions. Too much reverse voltage will damage the diode and cause it to conduct in the wrong direction.

If you look closely at VF the diode doesn't start conducting until 0.6-0.7v this is known as the knee voltage, so when calculating voltage after the diode, voltage suplied(vs) - (vd) voltage diode 12-0.7=11.3v

Data Sheet infomation
what to look for so you dont blow the diode
Peak Inverse Voltage: This represents the maximum reverse voltage that can be
applied before the diode breaks down.
Maximum DC forward Current:This is the maximum recommend forward current, if the current exceed the rating it will destroy the diode.

What is a Zener diode
A zener diode is  a  special kind of diode that if voltage is apply in the reverse bias it acts as a voltage regulator, so input might be 12v but the output of the end result would be eg 9.1v if you use 9v1


zener diodes are typically available in the following voltages: 2.4, 2.7, 3, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1, 10, 11, 12, 13, 15, 18, 20, 22..., and in 300mW, 500mW, 1.3W, 2W, 3.25W, and 5W rated packages.

How to use
To use the zener diode, the diode has to be in parallel with the zener as above in the picture



To work out Zener diode resistor

If Vs=10, Vz=5v1, Iz max= 0.06, RL=470
I=V/R
Rs=Vs min-Vz/Iz min

I=5/470=0.01063A
Rs=(10-5)/0.01063=470



Breakdown voltage
 Breakdown voltage of a zener is  the maximum reverse voltage the zener can handle until it stops working like it should. eg 9.1v  but only a small amount of current can be pass through it eg 1A a resistor is put in series to prevent this.
This is why we use a zener diode for, so that no more than eg 9.1v can be pass through in the reverse bias to protect components 

Forward bias region
This is the region voltage is passing through the zener diode in forward bias anode to cathode.this work just like a normal diode.

Knee voltage

This is the region in the forward bias before it reaches the working voltage of 0.7V.

power circuit

     Circuit diagram 

           A component list

     2x1n4007 Diode

     2x capasitor 33mF  

     1xZener diode 

     1x voltage regulator LM317

     1xR1

     1xR2

     1xR3

     1xLED
1x PC Boards Vero Type Strip

Calculations

           Calculate the values of R3,R2

           Vref=1.25 

           Vout=5v

           Use Vout=Vref (1+R3/R2)

               5 = 1.25(1+R3/R2)

       5/1.25 = 1+R3/R2

               4 = 1+R3/R2

          4 - 1 = R3/R2

               3 =  R3/R2

             R3 = 3 x R2

This mean that R3 is 3 times bigger than R2, So we were given 330R for R2 and 1K resistor for R3.

For R1: LED resistor

    R1 =   (V_S - V_L) / I

    R1 =  (5-2.1)/30

    R1 = 100 R

Lockmaster

      A Technical Explanation 
     This is a normal voltage regulation circuit. As the raw 12V is presented into the circuit, it goes through the diode (These diodes 1N4001 is to  prevent back EMF) using  0.7V so 11.3V goes into the regulator  (The regulator is a LM317T) which is then stepped down to 5V. C1 and C2 are 33 mF , the capacitors job is to  provide stability in the output voltage .The 2 zener is a 2V2 zener. . The R1 100R with the LED is a indicator to tell if there is voltage going through the circuit. R2 is 330 R and R3 is 1 K, R2 and R3 are used to determine how much voltage output will be. 

      Test Procedure 
 12V to the input  and out put should be 12v on the red wire and 5v on the yellow wire and black to ground (negative)

      Reflection 
I wouldn't do anything different if i was to build the circuit again. as my circuit worked  first time, so i dont see how i could make a different. 

   

      Finish result

oscilloscope

how to set up a oscilloscope

DC=button in 

AC=button out

set up where you want the y axis and x axis. im using dc so my y axis is all the way down there.right now the reading is 0v dc.

 power supply 5.7v dc

5.7v dc going through it

to tune the y axis to go up by 1 or 2.......

to tune the time/div

1sec dev per square on x-axis 

ch1 and ch 2 together by pressing the ALT  button

Injector circuit

 Circuit diagram

A component list 

2 X 330R

2 X 1K3

2 X LED http://www.kpsec.freeuk.com/components/led.htm

2 X BC547 Transistor. http://pdf1.alldatasheet.com/datasheet-pdf/view/11551/ONSEMI/BC547.html

Calculations 

To work out what resistor to use with LED

Rs=(Vs-Vled)/IIed

Rs=(12v-2v)/0.035A (35mA)

Rs=285ohm closes to E12 group resistor is 330R

To work out what resistor to use with transistor

Beta=IC/IB

IB=0.035/110

IB=0.000318  (0.3mA)

Rb= (V-Vtrans)/I base trans

Rb=(5v-0.7v)/0.000318

Rb=13,314 ohm closes to E12 group resistor is 15K

Lochmaster

 A Technical Explanation of how the circuit works.

What this circuit does is convert a 5v E.C.U signal to 12v to power a 12v component eg injector.In other words  it uses the 5v to switch to 12v

In more details 12v is the main power supply (red + and black -lead) this 12 volt passes through the resistor ,led and onto the collector.

Negative is hooked up to black and 5v is then hooked up to the yellow or white lead this connects to the transistor base  which in turn when 5v is pass through the transistor acts like a switch and enable 12v to pass through to the emitter.

 Test Procedure

Both led should be off when hooking it up to 12v but when 5v is pass through one of the signal leads one of the led should light up.

The avalible voltage to collector

Same as Vce.

This is a good result, ideal should be 0v but this is very near. datasheet says 0.5 saturated Vce

 The avalible voltage to base

voltage at emitter

Problems

The circuit did not work the first time. This was trace to a faulty transistors. when test with a diode tester base and emitter displayed O.L both ways this indicates that there is a open circuit in the transistor.

Reflection  

If i was to do it again i would test all the components first .

Also made sure i was drilling the right spot before drilling, i auctily drilled a row across and when i went to put all my components in one of the legs had no copper connection to solder to. i solve this by bending the legs across.

Finish result

 

Emission test

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