D4 - Notes Nodal Analysis

We started the day with a quiz. It was important to use KCL and KVL to find I1,I1,R1,R2, and R3. I did not finish in time. There were a lot of equations to work through. After the quiz we started on the lab.

Temperature Measurement System:

We use a Thermistor rated at NTC 10K @ 25C for the lab. But first we must do some prelab, our goals were to make it usable with +5 input voltage, voltage varies 0.5V over 25C to 37C, and output voltage must increase as temperature increases.

White board work which describes the things out lined above on what our "resolution" is for this device.

We then measured and worked out the prelab like a regular voltage divider problem.

White board work with the design restrains in a voltage divider problem. Our preliminary design chosen R's are 1.3K and 5.6K ohms. We should get output voltages change of 0.5V. Did not work, later one we got one that did.

We re did some math with the Rth and tried again, this time we found R values that worked. We recorded real values of Rth@24C and Rth@37C which were: 9.6k and 6.75k, which was only 4% off the 10k rated ohms at 25C.

Another picture showing our percent error, our R's this time were 4.6k and 17.5k ohms. Our comparisons to expected results were 0%, our numbers did exactly what we wanted, a change of 0.5V with temperature.

The video below shows the voltage as we input heat into the resistor. It raises the 0.5V needed of the lab, 3.12V to 3.62V. We recorded the fix values actual resistance and did our percent error and the white board.

White page work of the real resistors numbers needed of the lab.

Hand work of the resistors used to get the 0.5V change in a lab.

After the lab we worked on Nodal Analysis, Node voltage method. We use the select a node with a voltage across it, and use KCL first and then sub the voltage laws into it. KVL is (v1-v2)/R1+... and so on for each voltage difference to ground.

White board work of the example gone over class, we found currents in and out and then used KVL and subbed the voltages across each element to the reference node. Used matrix math and got V1 = 13.33V

In summary:
We started the day with a quiz that was hard without the correct usage of KCL and KVL and good choosen nodes. We learn to implent design process with a NTC 10K @25C thermistors that sampled voltage with temperature. We found the whole design process takes iterations and recalculations of the required specifications needed of a design. Lastly we did another example and how useful voltage node analysis can be, for example it would of made the morning quiz doable.

D3 - Dusk-to-Dawn Light

We started our day with a pictures of wiener dogs and a bun with a wiener doing inside. Our thought exercise of the day in terms of Engr44 was what would happen to a hot dog if it was applied 120 Volts from an outlet. We wrote our prediction in terms of I vs T and in words in the white board below.

Graph of what we think would happen in I vs T and we choose it would burn out quickly. We were wrong, the hot dog took a long time to even began to fizzle and smoke.

We then moved onto another question where Prof. Mason decided it was a good idea to attach LED to the wiener dog and see if the LED would light and if so how bright.

Here is the picture of Prof. Mason brilliant wiener experiment.

White board work explaining  what we thought would happen.

We said that the LEDS parallel would light up. Those in series would not.

Another picture better explaining why parallel works and series doesn't longer R higher potential difference.

We then moved onto finding Dependent Source Examples.

Picture of the first one, 2 loops, one ideal and one dependent source. Used KCL at node.

White board work of the second, used loops and KCL at nodes.

We then moved onto the Voltage Divider. But spent some time on resistors in series for Req and resistors in parallel for Req. Which would be useful later on for using a voltage divider.

White board work for finding Vout.

White board work for values given in class for the voltage divider example. We used the formula earlier derived to get these values of R1 and R2.

Prof. Mason then told us in the real world resistor come in set values and then raise in cost by alot the more special the resistance is. Thus we found the cheap set values of resistors and got the same function out of voltage divider by using the voltage divider equation.

We then checked our resistors numbers into an example of finding if our numbers would provide enough wattage and current needed of a circuit.

Another example of resistors and how they would work in a problem with resistors in series and in parallel circuit.

After all the dirty white board work we moved onto the lab of the day which would use everything we learned thus far.
Dusk-to-Dawn Light:
The pre-lab was to draw the circuit and use KVL.

White board work for prelab and other stuff, we used KVL on the outer loop and found Rp.(Resistance of photocell), other pictures has Vb of the photocell.

Picture of proof of the BJT and LED working.

Picture of our circuit connected together on breadboard.

The video below plays showing the LED turning brighter and off with relationship to the hat covering up the light hitting the photocell.

Final picture of the voltage recorded of the photocell at .1V at 5k ohms and 1.4V at 20k ohms.

We finish up talking up how potentionmeters and DC meters work, just like a voltage divider. Similarly with current. The end of class had a link to EEblog which was very useful in understanding more how DMM read voltage, current and resistance of an element.

In summary:
We learned that wiener dog takes a log time to warm up even when it connected straight into a plug. The LED in series were shorted out and produced no light while the LED in parallel were bright. We talked about dependent sources and how useful KCL is when used properly at nodes. How resistors work in series, just add them; in parallel, R1R2/(R1+R2), resistors in parallel will never be higher than the smallest one. Voltage dividers follow the formula V1 = (R1/(R1+R2)V). In Dusk til dawn lab learned how to do prelab work and apply it usefully to actual circuit. BJT have a base, emitter, and collector, (CBE top to bottom) and LED's are polarized, which means the orientation is important and photocells are pretty fun things to work with in electronics.

D2 - Resistors and Ohms Law, Dependent sources and MOSFETs

We started the class again with another light switch electrical problem, picture below with our tables response.

Picture of our answer to the light switch problem, we were wrong. The correct answer was C which was both the top and bottom bulb stayed the same.

We then moved on to the subject of resistance and Ohm's law. V = IR. G = 1/R. A couple of picture of examples worked out in class, describing power and resistance.

P = VI and also P = I^2R.

White Board work of an example done in class manipulating P = VI and P = I^2R

Resistors are passive elements, incapable of producing energy. We then moved onto our second lab.
Resistors and Ohms Law, Dependent sources and MOSFETs:
We set up the Resistors and Ohms Law lab first. Pictures below. Required of lab picture of schematic, data, and graphs.

Picture of recording resistance of our resistor.

Data of Vs Vr ir with our R = 101.3.

Another picture of our resistor lab.

Picture of data and schematic of Resistor lab.

Post lab work for Resistor lab.We did a poly-fit both linear and quadratic. Our r value was close to one, which means it was solid data, the further from one the less sense a fit makes.

Voltage Vs Current of a resistor, higher voltage more current in the resistor.

We then moved on in class and talked about nodes branches and loops. A branch is something that connects elements together, a wire connected two resistor. A node is connection between branches. A loop is any closed path in a circuit. b = L + N - 1

An example in class to find the b, L and N of the circuit. b = L + N - 1

We then talked about KCL and KVL. Pictures below of an example following current through a circuit.

Finding current and voltage through circuit using KCL and KVL, I = 4A V = 28V

We then moved onto the second lab of the day:
Dependent sources and MOSFETs
The second lab required: pictures of the set up, schematic, data, and graphs.

Picture of our setup of the MOSFET lab. We used the same resistor as the last class with R = 101.3 ohms

A more far away picture of the same setup with a laptop.

Picture of the data and schematic required of lab. We note the Voltage threshold.

Data and plot of MOSFET Lab, r value is not close to one so the liner fit is not the best, however this makes sense sense the MOSFET does not act linear like the resistor. The slope is the G value the 1/r of a resistor. So resistor is 101.3, G = 1/101.3 = 0.009 or G = I/V = 2.5E-3/2.5 = 0.01

The transistor acts like VCCS - Voltage Controlled Current Source. It needs a certain amount of voltage to "turn on" like a transistor, or diode. (0.7V) The gap between P-N or N-P.

Data and plot of MOSFET Lab, r value is not close to one so the liner fit is not the best, however this makes sense sense the MOSFET does not act linear like the resistor. The slope is the G value the 1/r of a resistor. So resistor is 101.3, G = 1/101.3 = 0.009 or G = I/V = 2.5E-3/2.5 = 0.01 (Edit ver 2)

In summary:
We learned about resistance and Ohm's Law. V = IR, G = I/V or 1/R. What branches, nodes and loops are, b = L+N-1. Learned about KCL and KVL to diagnosed a circuit. How resistors act linearly with voltage and current. How MOSFETS don't act linearly and have a threshold voltage like transistors and have a cap after a set amount of voltage. Used Matlab to find and plot relevant data.

D1 - Solderless Breadboards, Open-circuits and Short-circuits

Engineering 44 being taught by Professor Martin Mason.

Our class started with a question about two lights connected with a switch in the middle. Our table guessed that the Upper and lower light would become dimmer and the middle light would go on. We were wrong. We then talked about charge and current. I  is a derivative of charge per time and measured in Amps. There is AC and DC current. To find i(t) of a sine wave  take the derivative. We have pictures of the following work done in class relating to current, voltage, and power.

An example in class of i(t).

An example of current and power signals.

Worked out example of power and work. P = VI, W = Pt

After some examples we worked on our first lab:
Solderless Breadboards, Open-circuits and Short-circuits
Below are some pictures required of the lab.

Picture referring to question 1 on lab. We found very low resistance. "Short circuit"

Pic. referring question 2 on lab, we found infinite resistance. "Open Circuit"

The other lab questions were 3 and 4 pictures could not be found but they were "Open circuit" for 3 and "Short circuit" for 4.

Picture of the last question in lab. We recorded the resistance.

For the blog lab: 1) closed circuit 2) open circuit 3) open circuit 4) closed circuit.
We then moved on to talk about each circuit has power abosirbed and power supplied. We talked about passive sign convection. We then moved on to some class examples. Pictures below.

Picture of an example to be worked on for Power.

Continued example of Power. We broke up the area into triangle and square and integrated the parts together.

Another example of P in = P out. We used P = VI to find the answer of 20V

We closed the first class talking about using Matlab and Waveforms programs for later classes.

In summary:
We learned our common sense of electronics and our intuition of electrical flow is usually wrong with the light bulb example. We learned current is the change of charge per time. Power is Voltage times current. Work is Power times time. We worked out examples to solidify our understand of physics equations. Our first lab introduced how a solder-less breadboards are connected in the inside and what a short and open circuit is. P in is equal to P out, and then we were out.