D13 - 1st Order Circuits

We started the class with what questions would be on the day of celebrations.

The Six question type to be on the day of celebrations.

We then move onto finishing our talk of inductors. Inductors in parallel L1*L2/(L1+L2), in series L1+L2. We did a example below.

White Board work of inductors in series and parallel, in series they just add, while in parallel they L1L2/(L1+l2).

We then further discussed the difference in capacitors and inductors.

White Board knowledge, inductor for i integrate, while i for capacitors take derivative.

We then did some first order derivations to show that inductors behave first order like.

White board work for finding Vo using first order.

More White Boar work for finding Tao of the capacitor. We took Tao = RC and found after 5 Tao there is nothing left in capacitor.

We continued to explore the current by using V = IR. Power = I^2R

White Board work using Tao of a capacitor, note that 2*tao and everything else is the same for power.

We then move onto  source free examples.

White board work for V. We used source free and then Tao for RC and got Vc of cap and Ic of cap.

More white board work and we figured the time constants of Tao range form nanoseconds to hundred seconds.

We then move onto the first lab of the day:
Passive RC circuit Natural Response.
Prelab:
R1 = 971 ohms, R2 = 2.16 k ohms, C = 22uF. After 5 tao's Vc should be near zero. Tao is 15.

Picture of the Passive Capacitor circuit.

Picture of capacitor discharging by hand feeding in and out, after 5 Tao's its close to zero. 1 Tao = 15ms.

Another picture showing Tao and voltage at those points, starts at 3.4 V, after 15ms (1 Tao) drops to 2.67 V, and after 5 Tao (75ms) V drops to 0.891 V

Another picture of the capacitor discharging with hand feeding and pulling out.

Picture of waveform feeding the capacitor. Note the drops look the same as the disconnect above.

Another picture showing the amplitude 1.75 V and maximum of 3.45 V.

Picture below with trigger of one of the humps shown above.

Close up picture of one of the humps, same as the disconnect discharge.

Picture of the hump data, same amp and max as before, since it the same trigger data.

Picture of more data, however note the Tao is the same of 15ms and after 5 Taos (75ms) V is near zero. Just like the previous example.

We then move onto a source free inductor example with inductors with a switch component added to it.

White Board work, inductors act like a short in DC settings. Tao = L/R.

We then move onto the second lab of the day:
Passive RL circuit Natural Respond
Prelab:
Same resistance values of before, r1 = 971 ohms, r2 = 2.16 k ohms however L = 1mH. Tao is 1.7us.

Picture of the inductor circuit.

Picture of the fast disconnect and reconnect on the inductor.

Picture of the data from the quick disconnect reconnect. Amp = 1.2V max = 2.4 V.

Second part we assigned square wave to the inductor.

Picture of square wave feeding into inductor. Amp at 2.5 V offset at 2.5 V we changed to frequency to making feeble to see with diligent.

Another picture of data from the squarewave max and amp the same.

White board work showing how we got Tao to equal 1.7us. We noted we need to change the frequency higher then the lab requested since our time constant was so small, we ended up using 1k hz.

In summary we talked about inductors and how they behave in series and parallel. And then did first order problems with capacitors and inductors. We then did two labs showing how reliable our Tao constants calculated are close to in actual circuits. The first being in a capacitors which match our time constant perfectly, 15 ms and after 5 Taos zero Volts which matched the 75ms. For the inductor lab we found tao to be 1.7us which very small so we had the option to change R or change frequency in the circuit to get reliable data out of the oscilloscopes, we chose the frequency change to 1k hz. We found our Tao matched the one observed in the oscilloscope, however the picture can't be found :(
Lastly we talked about source free problems on which capacitors are open, and inductors are shorts.

Day April 7 stuff! Temperature Measurement System Design (Weatstone Bridge)

I am not sure where in the class of word files we did the lab of: Temperature Measurement System Design. None of the word files document it but I have pictures and video of the Weatstone bridge working so here they are.

Prelab:
We followed the derivation of the appendix A. We used R1 = R2*Rnorm/R3. The Rnorm is the Thermistor at normal value of 10.7 k ohms at 27 degree C. We decided to use a pot system to cover the range of the Thermistor from 10.7 k ohms to 7.5k ohms.

At the beginning of class we were asked to tell which Op amp was what, the first was a inverting amp since it had a source to negative node, b was inverting same as the first, and C was summing since it had many V's and R's going into the negative node.

 We then started the class with the lab of the day:
Temperature Measurement System Design

White Board work of the prelab, we found V2 = 350mV and Io in terms of Vs. We also drew the circuit schematic for the lab.

Picture of our circuit with Thermistor and potentiometer circuit.

Another picture of our weatstone bridge temperature measuring circuit.

Video below with the range of 2V with the potentiometer range relating to the thermistor. Note the voltage range as the temperature of the thermistor raises thanks to my hand.

 

Video of the range of the voltage working from the Weatstone Bridge.

More white board work below for the lab with R values.

White board work of the weatstone bridge, Rf = 10 M ohms, Rf2 = 1 M ohms, R2 = 10 k ohms.

More white board work, our regular Vout at room temperature is 0.46 V, and Vout when the thermistor is human temperature at -3.54 V.

 For the lab we found our design worked, the Vout had a range of 2V with it dependencies of the thermistor temperature. We had difficulty understand why we couldn't get our Vout regular to be 0 V but got close to it. Overall we happy we got the range desired and change dependent on thermistor temperature aka resistance of Rnorm.


In summary I do not know where this goes in the time line of stuff but here it is and working, we learned on this unknown day that weatstone bridges are hard to design but are rewarding to get working.

D 12 - Capacitors and Inductors

We started the day with a discussion of why sometimes there is a spark when we plug stuff in, turns out to be because of capacitors and having mechanical engineers design electric circuits.

White Board work of why and how Capcitors charge. It is a function of A and d. Area and distance.

We then were asked to design our own version of a variable capacitor.

White Board work of our variable capacitors. Mine is on top with a triangle screw to close d, and Jon's is on the right with a squeezer on top to change d.

We then move onto solving for the energy in a capacitor, with P = VI and taking the integral. E = 1/2CV^2

White Board work for finding E. E = 1/2CV^2

We then drew the change of current over time. It is important to understand that the slope is what define the integral. Constants turn into linear and linear turns into parabolic.

White Board work of I versus t and we use the slope for the V versus t graph.

White Board work of V versus t took integrals of I.

We move onto an example of a DC capacitor circuit.

White Board work of the DC circuit, we turn capacitors to "open" and find Req.

More White Board work,  we found Va = 4 , Vb = 8V, then found E1 = 0.016 J and E2 = 0.128 J.

We then moved onto the lab of the day:
Capacitors Voltage-current Relations
Prelab:
We then sketch the "phase" shift the capacitors causes.

White Board work of the sketches of graphs for the capacitors. Sine wave. The shift is pi/2.

More White board work of the sketches with square waves and saw tooth wave. This also has the pi/2 shift. from I to V.

Picture of the capacitor circuit below.

Picture of our capacitor circuit.

More white board work with the equations used for Ir and Ic.

Picture of the signals before capacitor and after on the resistor.

Picture of the sine-wave going through the capacitor.

Picture of the freq 1khz period of 1ms and amp of 114 mV the M1 math value is 77uV,  C2 amp is 2 V freq of 1khz and period of 1ms.

Picture of the second sinewave input at 2 khz.

Picture of  C1 freq 2khz period 200us amplitude 218mV, and C2 amp 1.98V freq 2khz period 500us with M1 math value being 76uV.

Picture of the square wave being fed into capacitor.

Picutre of square wave, C1 amp 18 V freq 100 hz period 10ms, C2 amp 2.7 V freq 100 Hz period 9.99 ms M1 math value of 75 uV.

More sketch for the prelab for the sine wave, triangle wave and square wave expected outputs.

White board for prelab expectations of the output across the resistor. Our expected results matched the output graphs from the oscilloscopes taken for each one.

We then move onto how capacitors work in series and parallel. We did an example with capacitors below.

White Board work of capacitors in series and parallel, series you C1C2/(C1+C2), parallel add C1+C2.

More White Board work, with talked about how finding C and finding L.

Lastly we talked about how Inductor are like everything like a capacitor but different. Like for adding in series and parallel they the opposite. After 10 minuets of inductor knowledge can be summed on the white board picture below.

White Board knowledge of summarizing Capacitors and Inductors, same thing but different.

In summary we learned how capacitors charge up and how find the energy stored in a capacitor by using E = 1/2CV^2. Learned that capacitors in a DC setting act like an open. Did a lab on capacitors and found the phase shift of pi/2. Talked about inductors how they relate to capacitors. We found our expected graphs matched the output on the oscilloscopes. We then finished the class with an example of capacitors in series and parallel. In series C1C2/(C1+C2) and parallel C1+C2. Lastly we said inductors behave opposite of capacitors and made a white board with all the difference on it.