Experiment 11: A Modular Project:

Introduction, Through out the previous practicals, I have gained such a knowledge in building circuits and

becoming more familiar with every days life components. That I was able to build such a complex circuits that makes a siren noise which can be used in an intrusion alarm.

To accomplish such a complex circuit, there was four main steps or processes involved!

Step 1: Slow-speed oscillation, Plan, This step or process involved a circuit with a flashing LED which seemed to be easy and

reasonable to me. In this part I used a 2N6027 PUT (Programmable unijunction transistor) to make a solid-state or

a proper version of the oscillating circuit that I built in experiment 8: A Relay Oscillator. To accomplish this circuit, the components that I used are: 3 resistors (470k, 15k and a 27k), a

2.2UF electrolytic capacitor, an LED, and finally but most importantly a breadboard! I then measured the peak to peak voltage and frequency and lastly the time for the voltage

across the LED to return to zero of the whole circuit. These measurement were calculated using a Digital Oscilloscope.

Background, As I mentioned earlier, this process seems to easy and required a simple circuit. Yet, there was

a lots of theories and knowledge behind it that needs to be known in order to accomplish such a circuit.

For example, you might ask yourself why didnt I just do what I did in experiment 8 instead of this (using a transistor)?

- Firstly, I will define what is a transistor. A reference from make electronics by Charles Platt states that A transistor can switch the flow of electricity, just like a relay. A unijunction transistor was first manufactured during the 1950s.

- Secondly, I used a transistor rather than a relay because the way a relay works is so complected that its to hard to understand it.

Also you need to be familiar with resistors and how to know them using the colours band to know their values.

More importantly, make sure you pick out the right capacitor ( 2.2UF capacitor), otherwise the circuit wont work and the LED will not flash.

I also must be familiar with how each component should be placed in the breadboard, otherwise the circuit wont work.

Lastly, the most important part, is to become familiar with a digital oscilloscope and how to use it. An oscilloscope is used to measure peak to peak volt, frequency and time.

Development and test,

1. Firstly I got a breadboard then attached the three resistors (470k, 15k and 27k) then attached the 2N6027 PUT between the first two resistors (470k and 15k) and the last resistor (27k). Then finally attached the LED and a 2.2UF electrolytic capacitor.

I then connected the breadboard to a 6 volts using an AC Adapter. I believe this was a successful part as the LED kept flashing.

2. To measure peak to peak voltage, frequency and time using a digital oscilloscope. But before measuring these concepts, firstly I had to train and familiarise myself of how to use a digital oscilloscope.

- Station number: 13

Firstly, I turned the oscilloscope on. I then pressed the save/recall button. I then noticed that a column appeared on the right hand

side of the screen. In the right column, I ensured that the setups are highlighted and to see Recall factory on the

second window on the right column. The reason for this step is to delete or eliminate any setting that a previous user have made.

I then pressed the CH1 menu button. I then changed the probe setting to 1x.- NOTE: The above steps were just to set the oscilloscope. I connected the oscilloscope lead BNC into CH1. As for the other side of the lead, the black wire

to ground and red to top of the 5v. I then pressed Auto set button, I then observed a waveform on the screen. The reading shows

that for every division on the y-axis equates to 2v and every division on the x-axis equates 500 micro second.

I then calculated the frequency,

F= 1/Time of period

F= 1/1.000ms

F=1/1ms = 1/1x10^-30 = 1000hz = 1khz

I then pressed Measure button. where a column will appear on the right, I then highlighted or chose source and made sure that the next two windows show CH1 .

Then, I changed the top window from source to type and for the next two windows to pk-pk and frequency. I was able to see the peak to peak voltage and frequency which I have calculated above.

I then adjusted the Volts/Div on CH1 by turning the knob to the left. Then adjust the time by turning Sec/Div knob to the right. I observed a different waveform from the previous one.

Now, its time to test what I have learned from the previous steps, where I test my circuit that I made earlier. By connecting the oscilloscope lead to the circuit and replace the 2.2UF capacitor with a 47NF.

I then pressed the Auto Set to show the new waveform. Then run/stop so that the waveform stops at a certain instant to allow me to take a frequency and voltage.

I then wanted to measure the time it takes for the voltage across the LED to return to zero. To do this I pressed the cursor button. A column appeared on the right. I set the first window to time. Then use the two vertical position knob to move the two lines to position them on the waveform. I got the reading of the Delta time.

I then used the cursor to measure the voltage.

Conclusion, Although, this was the first step of the practical, yet it was pretty tough and interesting both at

the same time. I learned the following:1. How to use an oscilloscope to measure peak to peak voltage, frequency and time of a circuit.2. I also learned how to create a circuit which involves a flashing LED.

If I was to do this part again, maybe I would chose a different values for the resistors to see what will happen. Also try to measure the peak to peak voltage, frequency and time of a more complex circuit.

Step 2: Beyond the persistence of vision,

Plan, In this part of the practical, I added more complex and interesting components to the circuit that I

made earlier in step one (Slow speed oscillation) resulting in an interesting complex circuit that can have a function in every days life.

The new components that I used during this step apart from the previous step are as follows: four resistors (470k, 33k, 27k and 100 ohms), a 0.0047UF capacitor, a 2N6027 transistor and finally a 8 ohms 1-inch loudspeaker.

What I am trying to do in this step is to add a 0.0047UF capacitor along with the 2.2UF capacitor from the previous step resulting in the LED to flash faster. But I wouldnt be able to see that due to the rapid pulses. Yet my ears can if I attach an 8 ohms 1-inch loudspeaker to the circuit.

Background, This step perhaps seems easy the fact I have to follow the instructions from the schematics

drawing of the circuit. Yet mistakes can be made easily. This is why its important to be familiar with every component in aspect of its function and its location in the breadboard. Therefore, the schematic drawings of the circuit must be studied in advance.

To accomplish this circuit, I firstly had to be familiar with where should each component be positioned in the circuit and also of its on the positive or negative side of the breadboard. For example, the transistor, the fact it have three sections (collector, base and emitter), if it is placed in the wrong order in aspect of its three sections, then the circuit will not work. I cant describe the importance of placing the components in their right position. Its like the foundation of the circuit!

Theres also a quite unusual notice about our new component, the 0.0047UF capacitor. Its really small in size that it cant be spreader across the breadboard. Some people just force it in. Yet theres a high probability of damaging the capacitor itself, also current may not travel as theres a break in the circuit. An easier and safer approach is to try to attach one side of the capacitor into the breadboard then connect the other side by a small wire to the breadboard. This seems to be an ideal and safe method.

Lastly and most importantly, our new component, the 8 ohms 1-inch loudspeaker. For the circuit to work, its important to connect the loudspeaker in an ideal way so that current can travel through it.

For the loudspeaker, its connected to the breadboard by using wires. Also it doesnt matter where should each side of the loudspeaker be connected to which terminal (positive or negative) of the breadboard. I would also recommend that the wires connected to the loudspeaker must be connected gently, otherwise this may damage the speaker and not allowing the current to travel through.

Development and test, Firstly I picked the resistors using their colours band table. The resistors that I used were the

following including the ones for the previous step: 470k, 15k, 27k, 470k, 33k, 27k and 100 ohms. I then attached them to the breadboard according to the schematic. Secondly, I attached the two following capacitors: 2.2UF (from step 1) and 0.0047UF capacitors. Again, the reason I am using a 0.0047UF capacitor is to make the LED to flash more. So you can imagine the compactor as a booster! I also kept the LED from the previous part. I then attached a two 2N6027 programmable unijunction transistor. Lastly I attached the most important part, the 8 ohms 1-inch loudspeaker. Again, make sure you

connect the loudspeaker in gentle way so that the loudspeaker doesnt get damaged. A reference from make electronics by Charles Platt states that you should hear a faint buzz like

a mosquito and that convinced me that my circuit was successful!

One of the problems I have faced during this step is that I didnt connect the wires to the loudspeaker properly and so the circuit didnt work. The solution for this problem was to connect the wires to the loudspeaker using Alligator clips.

Conclusion, The things I have learned and accomplished during this step is:1. I now became familiar with a 0.0047UF capacitor.2. I also got introduced to our new friend, the 8 ohms 1-inch loudspeaker! I learned how to use it

and connect it to my circuit.3. A human eye wont be able to see the LED flashing 1000 times per second, yet our ears can

hear it!

If I was to do this step again, maybe I would add more LEDs or change the values of capacitors to see what will happen.

Also I would maybe pick a different value or quality of a loudspeaker.

Step 3: Amplification,

Plan, This step seems to be an upgrade to my circuit, making it to have a useful function. This step was broken down into two mini steps, mini step no (i) and mini step no (ii). These two

mini steps shows how I can play with resistors and transistors to change or increase the amplification of the 8 ohms 1-inch loudspeaker.

In mini step (i) I will be changing the place of one of the resistors from the previous step (Beyond the persistence of vision) and also add an extra resistor with a 2N2222 transistor. A louder amplification of the sound should be observed at the end of this mini step.

The amplification of the sound that I observed in mini step (i) wasnt really high and have no use to me and this is why in mini step (ii) I will try to create such a louder or higher amplification of sound by adding an extra 2N2222 transistor

Background, Theres a lot of things you are probably wondering about by now. For example, Why did I put a

2N2222 transistor in general and how it make the loudspeaker to be louder?- Well, first let me give you the reasons for using the 2N2222 transistor. A reference from make

electronics by Charles Platt states The emitter of the 2N2222 is connected to ground and the collector is supplied through the loudspeaker and its 100 ohms series resistor. This way small fluctuations in the output from the PUT (Programmable unijunction transistor) are sensed by the base of the 2N2222 which converts them into bigger fluctuations between the collector and the emitter which draws current through the loudspeaker. To sum up the following reference, you can imagine the 2N2222 transistor as booster which converts small portion of fluctuations into larger portion which can creates such a huge amount of current through the loudspeaker.

Note: The above passage describes mini step (i).

In mini step (ii) I added a second 2N2222 transistor. You probably by now think I am in love with 2N2222 transistors! But sadly this is not the case! Theres a simple reference from make electronics by Charles Platt really describes whats happening, The 240:1 amplification of the first transistor is multiplied by another 240:1 giving a total amplification of more than 50000:1. This gives rise to a higher amplification from the Loudspeaker.

These two above points really needed to be known in advance as it sounds interesting, yet complicated to understand!

Development and test, Firstly, I started by attaching the following resistors to the breadboard: 470k, 15k, 27k, 470k,

33k, 27k, 100 ohms and 1k.

- Note: The first seven resistors were attached form the previous two steps: slow-speed oscillation and Beyond the persistence of vision.

I then attached the following three transistors: 2N6027, 2N6027 and 2N2222.- Note: The first two transistors were attached already from the circuit made in the previous

steps.

I then kept the following capacitors from the previous two steps: 2.2UF and 0.0047UF capacitor. I also kept the LED from earlier. Then lastly I connected the 8 ohms 1-inch loudspeaker to the circuit. I was then convinced that this circuit was working successfully as the amplification of the

loudspeaker became louder.

Note: The above few procedures were all for mini step (i).

Note: Now, the following procedures are the procedures for mini step (ii)

I then wanted my circuit to have a much louder amplification. To do this I added an extra resistor (2k). I was suppose to use a 2.2K but a 2.2K resistor wasnt available so I used a nearer value i.e 2K.

I also added an extra 2N2222 transistor with the previous three transistor from the previous steps.

I then convinced myself that this was a successful step as the loudspeaker gave rise to a louder amplification.

Conclusion,

What I have accomplished and learned during this step was:1. I saw how I was able to play around with two components in my circuit making a louder

amplification.2. I also now know the proper idea or function of a 2N2222 transistor.3. Thirdly and lastly I was able to build such an interesting and complex circuit with such an

unusual and interesting components at the same time.

If I was to do this step again, I would have probably attached more than one loudspeaker to see what will occurs?

Also I would add an extra 2N2222 transistor to what could occurs.

Step 4: Pulsed Output,

Plan, Thinking about what I have accomplished during the previous steps I havent really constructed

a circuit that can be a useful product, i.e It doesnt really have a function. Its like a boat on a dry land! What I have really created was circuits that can create a buzzing sound. But what about if I wanted to create a useful circuit that can produce an alarm ringtone?

To do such a circuit with such a product function, I used the circuit I have created during the previous steps with a few changes. For example, removing the LED, adding an extra resistor (10k) and finally an 2.2UF capacitor.

Background, This really seems to be an easy step, the fact I had to add two extra component, yet you might

ask yourself why am I doing this and how can just two simple component makes the circuit to makes an alarm ringtone? How did it really happened?

- Now I shall describe to you why did I use an extra two Programmable Unijunction Transistor. A reference from make electronics by Charles Platt states that The first section of the circuit you have made, created a pulse signal about twice per second, how about if you remove the LED and feed the output from the Q1 to Q2 by removing the LED and substitute a 10K resistor.

But then I wanted to make a pulsing output that can be so smooth and so I needed an extra 2.2 UF capacitor.

Therefore you can imagine the whole reason for adding the 10K resistor was to change the direction of the output i.e from Q1 to Q2. This will be resulting in the Q2 to emit a two-tone signal. Where as for the 2.2UF capacitor, it was to smooth the pulsing output resulting in the circuit to make an alarm ringtone.

Development and test, Firstly, I removed the LED from the circuit I made in the previous steps. Secondly, I attached the following 10 resistors: 470k, 15k, 27k, 470k, 27k, 33k, 2.2k (2k), 1k and

100 ohms. I added the following 4 transistors: 2N6027, 2M6027, 2N2222 and 2N2222. I then added the following three capacitors: 2.2UF, 0.0047UF and 2.2UF. Lastly and most importantly I connected the 8 ohms 1-inch loudspeaker.

Note: Some of the components mentioned above are already have been placed on the breadboard from the previous steps.

I convinced myself that my circuit was working perfectly as I observed an alarm ringtone from the circuit I have made.

Conclusion, What I have learned and accomplished during this step is:

1. I was able to learn how to change the fluctuating output direction from Q1 to Q2 using a resistor.

2. Also I was able to see how I can use a 2.2UF capacitor to smooth a pulsing output.

If I was to do this experiment again, maybe I would have:1. Changed the values of the resistors.2. Change the position of some of the components.

Overall conclusion,

In my point of view, I though that this was such an interesting practical showing me the complexity of such a components and how I can play around with them forming an alarm ringtone.

It was also a fun practical where I felt I have accomplished something that can have such a function.