Day 15 04/16/2015 Passive RC Circuit Natural Response

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Some In class Practice Problem

These two are the one let us get used to use use inductor and capacitor

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Passive RC Circuit Natural Response

In this prelab, we were ask to write the differential equation relate to graph a and graph b

On graph a) the voltage change when switch is on we can calculate T by using Ta = R2*C

On graph b) the switch is off we can shortage the source so Tb can equal to to Rsum*C

After the Pre-Lab we set up the lab

This graph is graph b) output

In the graph b) above we pick 2 random point on the decreasing curve and know the delta t then we can calculate the RC(T) by v(t) = Voe^(-t/RC)

This is graph a) output

we using the same method as part b to calculate the T which is RC

Summary: the big T is RC

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Class Note

This graph is the voltage and current's relationship on inductor

the current for inductor is base on relation I(t) = Ioe^(-tR/L)

The graph of inductor will be like this 

Day 14 04/14/2015 Capacitor Intro

Class Note:

This one is about the relationship between power and energy 

To be able to solve energy we "open" the capacitor 

By knowing the relationship between power and energy we can easily solve the time 

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LAB : NAMEＵＮＫＮＯＷＮ

Pre-Lab for this experiment is to predict what would happen to the current when capacitor used.

This is our setup of experiment. We measured the voltage across resistor 100 ohm and 1 uf capacitor in the circuit. The resistor and capacitor are in series.

The first one we sent a signal by sine function with amplitude 2V and frequency 1kHz.

Second one we sent another sine function but the frequency be the 2kHz

Third time we send a triangular function with amplitude 4V and frequency of 500 H

As the result the

Capacitor is ideal add "inversely  in series and add "directly" in parallel.

Inductors (coils of wire) is not ideal add "directly" in series add "inversely" in parallel.

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Formula for Capacitor and Inductors

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Extra Lab From Mason

Umm ~ Don't remember Some kind to wave function of capacitor that reach the maximum which create these weird top.

Day 13 04/09/2015 Temperature Measurement system designed

Today we first talk about the cascaded op amp circuits

In the picture I know that understand that

Formula: Vout = -(Vf/Vi)*Vsource

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Lab

Temperature Measurement system designed

This lab is required us to use the preview's lab knowledge to make a overall temperature measurement system which require to make Thermistor connect with Wheatstone Bridge and difference amplifier.

And because real Wheatstone Bridge is expansive outside we build our own

This is circuit with thermistor and potential transistor 

To be able to make lab work we are required to test each system individually and on the Wheatstone Bridge we make Vab as close to zero as possible because we want to know what will Vout change when we increase the thermistor temperature.

On the different amplifier we first build the same circuit we built last lab which with 4 same resistors connect to amplifier and we suppose to get Vout = Vb - Va and by supply Vb with 2V and Va with 1V we got Vab = 0.996V

After all we connect two circuit together

And hold the thermistor to hope to see the Vab change by the ratio 

Formula Vout=R2/R1(Vb-Va)

Below is the video when we use R1=1k and R2=10k

The result end up

Even the ratio is not come out with Vf = 10times of Vi but the voltage did increase when the thermistor hold by our fingers.

Day 11 03/31/2015 Summing Amplifier & Difference Amplifier (Exam 1 End Here)

Class Note:

This one is buffer amplifier and it is important to know the amplifier has maximum gape so the output graph will not be smooth as input.

This one is inverting amplifier I'm still confuse on why its graph isn't inverse since the voltage is inversely

This one is exactly same as homework problem the key point for his is to find node a and b and understand  voltage a is equal to voltage s.

This one should be inverse amplifier since v1 and v2 is inversely

Formula reminder: V0=Vi(1+Rf/R1)

Key here is inverting amplitude makes output smaller than input and of course the non-inverting can only makes output bigger. (think about subtraction)

Summing Amplifier

This lab we mainly focus on what will happen on Voutput by summing two Vinput

As usual a simple setup...

In this lab we take a guess that R1 and R2 should be the same to make experiment work properly and R3 as the connection to the Vout should as small as possible but also not too small. 

From formula Vout = - R3/R1 (Va+Vb) 

I understand something that va and vb will add up together become the sum of voltage which is Vin, and Vout and Vin's ratio is all depend on R3/R1 so R2 may not affect the experiment.

But When we tried with R1 different to R2 we get the result that experimental value and theoretical value are way off each other.

So we understand the R3 and R1 ratio take place because R1 and R2 are the same, and even with more resistors involving in this summing amplifier it should be all the same as R1 and R2.

With proper resistance setup we got the experimental value is very closed to the theoretical value we calculated by formula above. 

Difference Amplifier

The main point for this lab is to understand the relationship between all resistors and voltage to be able to let difference amplifier happen. The difference amplifier means where there is need to amplify the difference between two input signals

SetUp the circuit

For the relationship between Vout, Va, and Vb is

Vout = Vb -Va

or

Vout = (R2/R1 + 1 )(R4/R3+R4)Vb - R2/R1 Va

To be able to amply relationship above resistor must be under below's condition

R1/R2 = R3/R4

After we successfully get the experimental data closed to theoretical data

We notice the amplifier can provide Vout exactly 5 V and also can't provide exactly -4V, and it must be the maximum of amplifier.