Circuit 3

My third and final circuit to be made was to work in conjunction with a vehicles oxygen sensor, and should give readings via LED's to interpret the state of the vehicles air/fuel ratio.

To achieve the necessary outputs to engage each LED i would need a semi-complicated circuit involving a triple Op Amp chip.

Other than the chip itself, me circuit consisted of:

3 x 1K Resistors

1 x 10K Resistor

1 x 410ohm Resistor

1 x 470ohm Resistor

1 x 270ohm Resistor

1 x 9.1v Zener Diode

3 x 1N4001 Diodes

2 x 0.1 uF Capacitors

3 x 5mm LED's (Red, Yellow, Green)

This circuit was much more difficult to map out than the previous circuits, as not only was it alot more complex, but we also had a restricted amount of space to fit it into, and also the pin-outs on the chip were not always in the easiest place to tap into. 

This meant that alot of trial and error on the computer screen was necessary. 

Once I had completed this seemingly possible task, i set to acquiring my components and creating my circuit.

This required alot more skill than the last two, as the whole circuit was alot more compacted in design. After a couple of hiccups in the build process, the circuit seemed to come together nicely. 

When i went to test it however, i found that the potentiometer setup that we have been supplied for the testing of our circuits, was faulty, and a short circuit somewhere inside the potentiometer had caused it to have a steady output of 5v, which is the input voltage it had been given in the first place. This is also far too high for our circuits to be tested on, as they are designed for fluctuations between .1v and 1v. 

This meant i had no correct way to test my circuit. From what i did see though, i found i had a loose connection in one of my Op Amp pin-outs, which caused one of my LED's to flicker when touched.

Transistors

First thing i learned with transistors if how to determine an NPN type or a PNP type by use of a Multimeter. By using the diode function on the multimeter, i found it simple enough to find this, as a transistor is basically two diodes back to back. The first transistor i tried was an NPN type, i found this out by putting the probes of the multimeter on the three pinouts on the transistor. After finding the collector, base, and emitter pin, a then put the positive probe on the base and the negative lead on the emitter. The multimeter showed continuity. By trying the same thing with opposite leads, the meter showed an open circuit. Trying this same test with a PNP type transistor, i had the opposite results.

I continued to use the Diode test mode to test voltage drops across the transistor. On a NPN type, Vbe(Voltage from Base to Emitter) showed .726v, Veb(Voltage from Emitter to Base) showed an open circuit, Vbc(Voltage from Base to Collector) showed .721v, Vcb(Voltage from Collector to Base) showed an open circuit, Vce(Voltage from Collector to Emitter) showed an open ciruit, and Vec(Voltage from Emitter to Collector) showed an open circuit also. On the PNP type, Vbe showed an open circuit, Veb showed .725v, Vbc showed an open circuit, Vcb showed ,721v, Vce showed an open circuit, and Vec showed the same. By doing these tests, and seeing that reversing the polarity of the tester showed open ciruits, i could see the diode-like characteristics of the transistors. The tested also showed that the device needed switching before there would be any continuity through the Vce or Vec circuit.

Circuit 2

For my second circuit, I was making a voltage regulator to turn a 12v input into a 5v output.

To achieve this, i used a LM317T, among other components. 

In this circuit, other than the voltage regulator itself, i used: 

2 x Capacitors

1 x 5mm LED

2 x 1n4007 Diodes

1 x Zener Diode

1 x 150ohm Resistor

1 x 220ohm resistor

1 x 680ohm resistor

After completing this circuit and testing, i found that it was working correctly without modification.

My readings across the circuit were as follows:

Vs=12v

Vs@LM317=5.17v

Vd@R1=1.24v

Vd@R2=1.25v

Vd@R3=3.92v

Vd@LED=3.94v

From this circuit, i now have a stable 5v supply output, plus another 12v RAW output.

Circuit 1

My first circuit was a simple circuit containing transistors to switch an LED circuit on.

After given our circuit diagrams, our first task was to calculate the correct components to use in order to make the circuit function correctly.
We had 1x12v supply and 1x5v supply.
We used 2x npn type c547 transistors for switching our circuit.
We used 2x1k resistors, one each for our two base circuits. These were to control the 5v supply to switch the circuit on. If not correct, these would either have made the light not turn on correctly, or would have had too much voltage for the transistor to handle and destroyed it.
We used 2x560ohm resistors, one each for our two load circuits. If these weren't correct, we may have had too much current flowing through the circuit, resulting in an open circuit in either the LED or the transistor, dependent on the maximum specification of each component.
We used two 5mm LEDs, one of which was a high intensity bulb, which I would find out after powering the ciruits up. I found that the high intensity bulb, instead of having the normal 1.7-1.8v drop, it had over 3v drop across it. This may have been dangerous to the functionality of the circuit, but after testing, and leaving the circuit turned on for a considerable length of time, i found that the circuit would function correctly still with the different bulb without an early breakdown.
After finding the required components for the circuit, we then mapped out a circuit on LochMaster, a computer program designed for mocking up circuits.
Once the circuit was planned, we acquired all of our components and began to build our circuits. Once they were built, we powered them up and tested them. My results were as followed.

My circuit was faulty, so i checked my soldering
I found that i had placed one of the LED pins in the wrong place, connecting it straight to the other of the two LED circuits
Once that was repaired, I tested once again and circuit functioned correctly
My voltage drops were as follows

Vd@LED1=3.09v
Vd@LED2=2.2v
Vd@R14=9.14v
Vd@R15=10.01v
Vd@R13=4.6v
Vd@R16=4.6v
Vce@T1=45.5mV
Vce@T2=44.6mV
Vbe@T1=.77v
Vbe@T2=.82v

These voltage drops were desirable in the sense that they fell between specification for each component.