Blog sheet Week 13: 

This week’s blog sheet will be both individual and group. 

Your blogsheet 13 tasks:

Daniel's Rube Goldberg

                  1.       Provide the updated computer drawing for your individual RG setup.  

                  2.       Explain your setup.

The circuit is triggered by knocking a ball down a ramp to push a small domino off of the photocell resistor. When the photocell receives more light the resistance is lower and is hooked up to a non inverting OPAMP. The photocell is R1 in the gain equation ( R2/R1 + 1 = gain). When the gain is increased the OPAMP outputs about 7 volts to the magnetic coil in a relay which switches the incoming 5 volts through pin 1 of the relay from pin 4 to pin 3. Pin 3 is connected as an input to the 555 timer which has its output connected to the 74192 BCD. Qa and Qd of the 74192 is connected to an AND gate and also a 7447 display driver and that is connected to a 7 segment display. So the display will count from 0 to 9. When the 74192 is 9 Qa and Qd are 1 and will output to another OPAMP which will power a transistor on. The transistor will provide power to a DC motor with a propeller connected to it. This propeller will blow air at a domino and the domino will fall on a cylinder which will roll down a ramp knocking a ball onto force sensing resistor which will trigger Moaad’s circuit.

                  3.       Provide photos of the circuit and setup.

Image 3.1 Rube Goldberg breadboard photo, ramp removed

Image 3.2 Rube Goldberg, white light indicates it is ready

Image 3.3 Rube Goldberg, finish to next Rube Goldberg

Image 3.4 Rube Goldberg, motor and fan

Image 3.5 Rube Goldberg, starting portion

                  4.       Provide at least 2 new videos of your setup in action, one being a failed attempt.

Video 4.1 Failed Attempt of Rube Goldberg

Video 4.2 Successful Attempt of Rube Goldberg

                  5.       What failures did you have? How did you overcome them?

My Rube Goldberg had a couple of physical reliability problems. The domino that sits on top of the photocell would not sit on top of the photocell very well, and also the ball that initially triggers my circuit was rolling and hitting the second ramp causing the cylinder to roll down prematurely. So I just bent the photocell wires to stand up straight and I moved the second ramp out of the way so the ball would not hit it, it has become very reliable at this point.

There were a couple of times the ball would not knock the domino off the photocell resistors. So I would have to reposition the ramp and the photocells to allow the domino the fall of the photocells easier.

Moaad's Rube Goldberg

      1.       Provide the updated computer drawing for your individual RG setup.  

1.1 computer drawing. 

2.       Explain your setup.

The circuit will start with a force sensing resistor that will get some load from my partner then the output is going to the 555 timer which gives the output to 74192 which send to the 7447. The 7 segment display will start counting. When it reach to 9 the motor will turn in by the AND gate which is prepared to. The motor will start the race by hitting a car and the car will be bombing a balloon at the end. The car will go through a racetrack. Another motor that will hit the car when the 7-segment display shows zero again. This car will take care of stopping the circuit by taking of the load of the force sensing resistor.

3.       Provide photos of the circuit and setup.

Image 3.1 the set up all together.

Image 3.2 the mechanical part set up.


Image 3.3 555-timer.


Image 3.4 Force sensing resistor.


Image 3.5 XOR gate, motor, and 7-segment display. 

4.       Provide at least 2 new videos of your setup in action, one being a failed attempt.

Video 4.1 fails attempt. 

For the video the racetrack slow down the car which does not make the car fast enough to bomb the balloon. 

Video 4.1 another attempt. 

5.       What failures did you have? How did you overcome them?

My biggest struggle in the class is when resistors touching each other. I take an hour trying to find the problem and then finally it was just two resistor touching each other. I overcome them by putting them away from each other, or put a small piece of paper between them as somebody in the class told me. 
Other two failures and I'm still trying to overcome them are make 7-segment display counts and get enough current to the motor. I overcome these problems by using a transistors to get enough current to the motor. 

6.       Group task: Explain your group RG setup. 

The group RG setup is started with Daniel's RG which is explained above. When the cylinder rolls down the ramp and knocks a wooden ball onto a force sensing resistor this lowers the resistance to Moaad's 555 timer. This begins Moaad's circuit which is explained above. Moaad's circuit finishes off with the car rolling down the cardboard tube which will provide a transition to the next group RG. It is also important to note that our power supply setup has two channels of DC voltage. One circuit provides 5 volts while the other provides 10.25 volts, we did notice that our circuits needed to be set precisely to these values for the circuit to work reliably.  

Image 6.1 Daniel's setup. 

Image 6.2 Moaad's setup. 

Image 6.3 the whole setup. 

7.       Group task: Video of a test run of your group RG. 

Video 7.1 testing our RG. 

Blog sheet Week 12: 

This week’s blog sheet will be individual but you will post it on your group blog.  

Your individual Rube Goldberg (RG) setup should satisfy the following:

Moaad's Rube Goldberg

1.       Provide the computer drawing for your individual RG setup.  

Photo 1.1 Circuit set up

2.       Explain your setup.
The circuit will start with a force sensing resistor that will get some load from my partner then the output is going to the Amplifier that is connected to the 555 timer which gives the output to 74192 which send to the 7447. The 7 segment display will start counting. When it reach to 9 the motor will turn in by the AND gate which is prepared to. The motor will start the race by hitting a car after bombing a balloon. The car will go through a racetrack. I am ready to change the end if it doesn't help the next person. 

3.       Provide photos of the circuit and setup.

Photo 3.1 Force sensing resistor. 

Photo 3.2 amplifier.

Photo 3.3 555-Timer and 74192.

Photo 3.4 The 7-segment display, the AND gate, and the motor.

4.       Provide at least 2 videos of your setup in action (parts or whole), at least one being a failed attempt.

Video 4.1 The first failed attempt.

5.       What failures did you have? How did you overcome them?  

My biggest struggle in the class is when resistors touching each other. I take an hour trying to find the problem and then finally it was just two resistor touching each other. 
Other two failures and I'm still trying to overcome them are make 7-segment display counts and get enough current to the motor. 

Daniel's Rube Goldberg

  

2.       Explain your setup.

The photocell will be used in the rube goldberg circuit to switch on the 555 timer using a transistor. When the photocell is covered the voltage at the base of the transistor is about .2 V and when uncovered it is about 1V. The transistor powers the 555 timer to start counting and will count up to 9. When the 7 segment display shows 5 an and gate will switch on for pins A and C which is the binary number 0101. The and gate will power a small motor that knocks the domino off of the other photocell.
Another photocell resistor limits voltage to the op amp to about .8V when the photocell is covered. When uncovered the op amp puts out about 6.6V, which should be enough to switch the relay, the relay is hooked up to a motor that swings a wire around to knock a ball over to knock over some dominoes.

3.       Provide photos of the circuit and setup.

Image 3.1 Op Amp and photocell resistor

Image 3.2 Relay and transistor with Op Amp

Image 3.3 7 Segment Display and BCD(7447)

4.       Provide at least 2 videos of your setup in action (parts or whole), at least one being a failed attempt.

Video 4.1 Showing a failure of Rube Goldberg

Video 4.2 A Part of the Rube Goldberg circuit

5.       What failures did you have? How did you overcome them?  

I had a faulty Op Amp and also a faulty portion of my breadboard at the same time in the same location. This consumed a lot of time attempting to change out Op Amp with good ones with no success. I then put the original Op Amp back in on another spot on the breadboard and with trial and error I found that both the Op Amp and a portion of the breadboard was malfunctioning.

I Also had troubles with the 7 segment display resistors touching each other, but with some careful bending they were not touching anymore. 

The relay proved troublesome in that the voltage had to be around 6-7 volts for the coil to energize and switch the relay. This was achieved by setting the gain on the op amp to about 4. (R2 =330) (R1=100)(3+1=4).

Blog sheet Week 11: Strain Gauges

Part A: Strain Gauges:

Strain gauges are used to measure the strain or stress levels on the materials. Alternatively, pressure on the strain gauge causes a generated voltage and it can be used as an energy harvester. You will be given either the flapping or tapping type gauge. When you test the circle buzzer type gauge, you will lay it flat on the table and tap on it. If it is the long rectangle one, you will flap the piece to generate voltage.

  1.     Connect the oscilloscope probes to the strain gauge. Record the peak voltage values (positive and negative) by flipping/tapping the gauge with low and high pressure. Make sure to set the oscilloscope horizontal and vertical scales appropriately so you can read the values. DO NOT USE the measure tool of the oscilloscope. Adjust your oscilloscope so you can read the values from the screen. Fill out Table 1 and provide photos of the oscilloscope.

Table 1.1: Strain gauge characteristics

Flipping strength	Minimum Voltage	Maximum Voltage
Low	- 1.36 V	3.52V
High	-1.44 V	5.92 V

Photo 1.1 Low Flipping strength graph. 

Photo 1.2 High Flipping strength graph.

Table 1.2: Strain gauge characteristics

Tapping  strength	Minimum Voltage	Maximum Voltage
Low	-4 V	29.6 V
High	-12.2 V	56.8 V

Photo 1.1 Low Tapping strength graph.


Photo 1.2 High Tapping strength graph.

  2.     Press the “Single” button below the Autoscale button on the oscilloscope. This mode will allow you to capture a single change at the output. Adjust your time and amplitude scales so you have the best resolution for your signal when you flip/tap your strain gauge. Provide a photo of the oscilloscope graph.

Table 2.1: Strain gauge characteristics

Flipping strength	Minimum Voltage	Maximum Voltage
Low	- 1.28 V	10.4 V
High	-1.4 V	16.4 V

Photo 2.1 Low Flipping strength graph.

Photo 2.2 High Flipping strength graph.

Table 2.2: Strain gauge characteristics

Tapping  strength	Minimum Voltage	Maximum Voltage
Low	-2.8 V	1.8 V
High	-12 V	8 V

Photo 2.3 Low Tapping strength graph.

Photo 2.4 High Tapping strength graph.

Part B: Half-Wave Rectifiers

  1.     Construct the following half-wave rectifier. Measure the input and the output using the oscilloscope and provide a snapshot of the outputs.

Photo 1.1 Outputs Reading. 

  2.     Calculate the effective voltage of the input and output and compare the values with the measured ones by completing the following table.

Effective (rms) values	Calculated	Measured
Input	3.54 V	3.689 V
Output	2.5 V	2.6 V

  3.     Explain how you calculated the rms values. Do calculated and measured values match?

(Peak to Peak Voltage)/(2*sqrt(2))

  4.     Construct the following circuit and record the output voltage using both DMM and the oscilloscope.

	Oscilloscope	DMM
Output Voltage (p-p)	2.16 V	1.78 V
Output Voltage (mean)	3.01 V	0.63 V

  5.     Replace the 1 µF capacitor with 100 µF and repeat the previous step. What has changed?

	Oscilloscope	DMM
Output Voltage (p-p)	.08 V	.028 V
Output Voltage (mean)	3.38 V	.011 V

Part C: Energy Harvesters

  1.     Construct the half-wave rectifier circuit without the resistor but with the 1 µF capacitor. Instead of the function generator, use the strain gauge. Discharge the capacitor every time you start a new measurement. Flip/tap your strain gauge and observe the output voltage. Fill out the table below:

Tap frequency	Duration	Output voltage
1 flip/second	10 seconds	.65 V
1 flip/second	20 seconds	1.44 V
1 flip /second	30 seconds	3.46 V
4 flips/second	10 seconds	5.4   V
4 flips/second	20 seconds	6.5   V
4 flips/second	30 seconds	8.6  V

  2.     Briefly explain your results.
As we tapped at 1time/sec the voltage would climb very slowly, but as we tapped 4times/sec the voltage would climb very rapidly and partially though the 30 second cycle it started to drop and then climbed rapidly through the rest of the cycle up to a much higher voltage than the 1 tap/second.

  3.     If we do not use the diode in the circuit (i.e. using only strain gauge to charge the capacitor), what would you observe at the output? Why?

If we leave the diode out of the circuit the output of the circuit would look more like a sine wave because you would see the negative and positive values from the capacitor. So the voltage would oscillate between negative and positive.

  4.     Write a MATLAB code to plot the date in table of Part C1.

clear all;
close all;

x = [10 10 20 20 30 30];
y1 = [.65 5.4 1.44 6.4 3.46 8.6];

plot (x, y1) 
grid on

xlabel('Time (s)')

ylabel('Vout (v)')

Graph 4.1 Voltage output of tapping strain gauge