1.0 Super Capacitor Lab
2.0 Flywheel Lab
3.0 Introduction to Labview

1.0 SUPER CAPACITOR LAB

The aim of this task is to observe charge and discharge characteristics of a super capacitor, after that to compare achieved and theoretical characteristics.

1. 1: Recording the Supercapacitors Charge Characteristic

PANASONIC - EECHW0D306 - CAPACITOR, RADIAL, 30F, 2.3V Farnell 1305076

Using the battery discharge test PCB setup the charging experiment as shown below but DO NOT connect the capacitor. The current may exceed 500 mA so SET THE AMMETER TO THE 10A RANGE (using the correct terminal). Turn on the 5V supply and check the voltmeter reading is between 2.0V & 2.3V, record this value. If the voltage is correct switch off the supply and connect the capacitor observing the correct polarity.

Now Turn on the 5V supply, this will immediately start charging the capacitor. Record in your logbook the voltage and current at 30 second intervals for ten minutes. Continue to record the voltage and current at one minute intervals until the capacitor reaches the voltage recorded above. It is important to record the time from the moment of connecting the current meter whenever recording values, rather than the interval.

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Time, min | Voltage , V | Current , A | 0.5 | 0.53 | 0.45 | 1 | 0.82 | 0.43 | 1.5 | 1.08 | 0.4 | 2 | 1.26 | 0.38 | 2.5 | 1.37 | 0.37 | 3 | 1.48 | 0.36 | 3.5 | 1.59 | 0.35 | 4 | 1.66 | 0.35 | 4.5 | 1.7 | 0.34 | 5 | 1.75 | 0.33 | 5.5 | 1.79 | 0.32 | 6 | 1.83 | 0.32 | 6.5 | 1.86 | 0.31 | 7 | 1.88 | 0.31 | 7.5 | 1.91 | 0.31 | 8 | 1.93 | 0.3 | 8.5 | 1.94 | 0.3 | 9 | 1.95 | 0.29 | 9.5 | 1.96 | 0.29 | 10 | 1.97 | 0.29 |

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1.2 Charge Characteristic

************************************************************************ By using Excel have been drawn capacitor charging characteristic (voltage and current) against time. Figure 1.1 - Capacitor characteristic voltage against time

Figure 1.2 - Capacitor characteristic current against time

Figure 1.3 - Capacitor characteristic voltage, current against time

Over first 4 min period the voltage has risen considerably, after that has been gradually growing till 10min or 5, where began remain stable. According to the teoretical knowledge, during chargering of the capacitor, voltage has grown until 5, after that stay at the same level. To compare voltage charge curve, that has been reached in labaratory and theoretical curve of chargering capacitor, both curves are almost the same.
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1.3 Discharging Characteristic of the Supercapacitors Rearrange the test setup as shown below but DO NOT CONNECT THE AMMETER.
(DO NOT ALLOW THE CAPACITOR TO BE DISCHARGED!)

When ready connect ammeter, this will immediately start discharging the capacitor. Record in your logbook the voltage immediately before and after connecting the ammeter, and then voltage and current at 30 second intervals until the capacitor is discharged.

************************************************************************ According to the circuit diagram that has been provided, new circuit has been built for recording the supercapacitors discharge characteristic, reached results is illustrated in Table1.3

Table 1.3 Obtained results from capacitor discharging experiment

Time, min | Voltage , V | Current , A | 0.5 | 1.89 | 0.26 | 1 | 1.7 | 0.24 | 1.5 | 1.53 | 0.21 | 2 | 1.39 | 0.19 | 2.5 | 1.25 | 0.17 | 3 | 1.12 | 0.16 | 3.5 | 1.02 | 0.15 | 4 | 0.9 | 0.13 | 4.5 | 0.84 | 0.12 | 5 | 0.79 | 0.11 | 5.5 | 0.73 | 0.1 | 6 | 0.67 | 0.08 | 6.5 | 0.61 | 0.08 | 7 | 0.55 | 0.07 | 7.5 | 0.53 | 0.06 | 8 | 0.51 | 0.05 | 8.5 | 0.49 | 0.04 | 9 | 0.46 | 0.03 | 9.5 | 0.43 | 0.02 | 10 | 0.39 | 0.02 |

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1.4 Plotting the Discharge Characteristic
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By using Excel and obtained experimentally results of capacitor voltage and current supplied to the load, against time, has been drawn capacitor discharge characteristic.

Results:

Figure 1.4 – Voltage against time over discharging of the capacitor

Figure 1.4 – Current against time over discharging of the capacitor

Figure 1.4 – Voltage, Current against time over discharging of the capacitor

Voltage discharge characteristic of the capacitor obtained experimentally in laboratory is slightly different from theoretical curve. Comparing two curves there some difference, because theoretical curve declining dramatically at the beginning, then more gradually. Graph that presented in Figure1.3, decreases gradually almost over all period of the time.
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1.5 Processing of Results

1.5.1 From the measurements above, or using additional measurements, calculate the capacitance and internal resistance of the Supercapacitor and compare to the manufacturer’s datasheet.
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According to the manufacturer’s datasheet, the capacitance is 30F.

According to the manufacturer’s datasheet, internal resistance has not exceed 0.1 for capacitor 30F.

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2.0 FLYWHEEL LAB

Introduction

The aim of this activity is to measure the power-storage and subsequent power-release characteristics of a simple flywheel electromechanical energy storage system and then to use these characteristics to develop a simple equivalent circuit model.
2. 1: Calibrating the Flywheel
A small DC motor has been connected to a flywheel comprised of an ordinary computer CD-ROM disk. An optical speed sensor has been implemented that measures the angular velocity of the disks by providing one pulse per revolution. It is available on one of the four BNC connections on the PCB, see figure 1. This signal is also connected to a frequency to voltage converter connected to another one of the BNC connectors and provides a DC voltage proportional to the speed of the disks. A third BNC connector provides direct access to the motor terminals and the final BNC connector allows an external input signal. The external input will normally not be used for these experiments so the selector switch should be set to Internal. A current meter is needed between the two Imotor connectors for this part of the experiment.

N.B. The Flywheel will fracture if spun too fast. Before connecting the PSU to the flywheel assembly ensure that the current limit is set below 1.5A. Do not exceed +10V.

2.1.1 The output from the frequency to voltage converter is to be calibrated by applying a varying range of conditions to the DC motor and recording the sensor readings. The motor supply will be adjusted by turning the speed control. The speed of the motor should be allowed to settle to a stable value before taking any measurements. The DC motor supply can be measured using an ammeter on Imotor and a voltmeter on the Vmotor BNC connector. Increase the current in approximate steps of 100 mA up to maximum (<1.5A) and record the actual motor current, motor voltage, frequency of the Flywheel and the Voltage from the Frequency to voltage converter. (Frequency can be measured using the DSO). (For convenience a form is provided table 1).

Speed Pulses
Vin
(Not used)
Vmotor
F - Vout

Ext
Int
Speed
Imotor
Speed Pulses
Vin
(Not used)
Vmotor
F - Vout

Ext
Int
Speed
Imotor

Figure 1: Flywheel connections

Results: Calibration Data

Table 1: Calibration – increasing speed

I Motor(mA) | V Motor(Volts) | ‘F to V’(Volts) | F out (Speed Pulse)Hz | 175 | 0.98 | 1.17 | 22.2 | 260 | 1.34 | 1.91 | 37.4 | 370 | 1.72 | 2.68 | 51.0 | 450 | 1.99 | 3.17 | 62.9 | 540 | 2.28 | 3.76 | 73.6 | 610 | 2.49 | 4.13 | 80.7 | 690 | 2.73 | 4.54 | 89.3 | 740 | 2.89 | 4.89 | 92.6 | 790 | 3.03 | 5.09 | 100.5 | 840 | 3.16 | 5.29 | 104.9 | 890 | 3.32 | 5.59 | 108.5 | 940 | 3.44 | 5.77 | 113.9 | 990 | 3.56 | 5.95 | 119.2 | 1040 | 3.73 | 6.02 | 124.5 | 1190 | 4.12 | 6.05 | 131.9 |

Figure 2.1 – F speed against frequency to voltage

Figure 2.2 – Motor current against motor voltage over speed increasing

Table 2: Calibration – decreasing speed

I Motor, mA | V Motor, V | ‘ F to V’, V | F out (Speed Pulse), Hz | 1175 | 4.12 | 6.06 | 115.1 | 1080 | 3.75 | 6.03 | 114.9 | 965 | 3.46 | 5.89 | 114.4 | 875 | 3.25 | 5.48 | 108.9 | 775 | 2.9 | 5.02 | 97.15 | 675 | 2.69 | 4.55 | 88.3 | 545 | 2.26 | 3.86 | 76.77 | 485 | 2.0 | 3.58 | 68.16 | 365 | 1.64 | 2.76 | 52.2 | 285 | 1.35 | 2.24 | 43.36 | 205 | 1.0 | 1.68 | 32.25 | 155 | 0.8 | 1.16 | 21.47 | |

Figure 2.3 – Motor current against motor voltage over speed decreasing

Figure 2.4 – F speed against frequency to voltage over speed decreasing

2.2: Speed-up and Slow-down Characteristics

2.2.1 Connect up the flywheel system and connect the DSO. Confirm that the pulse signal and the ‘FtoV’ signals are working correctly. Now set the DSO into the Roll time-base mode so that it will sample the F to V signal over the start-up period of the flywheel. This is several seconds long. Turn the speed potentiometer to maximum and then turn off the DC motor using the ‘External’ switch on the right hand side. Wait until the flywheel is stationary. Now change the switch to Internal and allow the motor to accelerate to the maximum speed. Display the ‘FtoV’ signal on the DSO (stopping the sweep to capture the waveform). Download the DSO trace to the PC:

Screenshot which is represented below presents speed –up characteristic, when have been reached maximum velocity (DC motor has been turned off) then can be observed slow-down characteristic. Figure 2.9 – Screenshot from DSO of Speed-up and Slow-down Characteristics

Figure 2.10 - Speed-up and Slow-down Characteristics from Excel 2.2.1.2 Capture the speed-up characteristic as ‘data’. Plot the data in EXCEL – ensure you scale the axes.

Figure 2.11- Graph of speed-up characteristics from Excel

2.2.2 After the DC motor has reached its maximum velocity, repeat 2.2.1 but this time turn off the motor signal rapidly, to obtain the slow-down characteristic.

Screenshot from DSO presented slow-down characteristic is illustrated in Figure 2.9

2.2.2.2 Capture the slow-down characteristic as ‘data’. Plot the data in EXCEL – ensure you scale the axes.

Figure 2.12 - Slow-down characteristics from Excel

2. 3: Adding a load to the Output – Energy Delivery

Repeat the slow-down characteristic of Task 3 but this time with a resistive load connected to the Vmotor output terminals. (The speed up characteristic is not required). Now connect a resistance box to the Vmotor output and set it to 50 Ohms. Repeat the slow-down characteristic. Try different values of load resistance and measure the change in slow-down characteristic. Capture the slow-down waveforms from the DSO.

Results:

Resistance box with 50 Ohms has been connected to Vmotor output, slow-down characteristic has been achieved:

Figure 2.14 – Screenshot of the slow-down characteristic with a 50 Ohm resistor

2.4: Equivalent Circuit Model

Use your results to determine a simple circuit model using capacitors and resistors:

2.4.1 Internal losses the mechanical losses of the flywheel are compensated by the electrical power input in the steady state. From your V-I plot of Task 1 determine a circuit model of the mechanical losses using resistors – you will need to consider if this model is linear or over what range it can be approximated as linear.

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Results:

Figure 2.15 - Equivalent Circuit

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2.4.2 Energy Storage model. Taking the diameter of the CD-ROM to be 12cm and mass to be 14g find an expression to determine the kinetic energy stored by a flywheel. Using this calculate an equivalent capacitor value at each speed and plot as a function of speed. From this determine a suitable equivalent circuit model for the flywheel’s stored energy using capacitance – again decide if this model is linear or non-linear with voltage.

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Results: f=120Hz, r=12cm, m =14g, then
,
,
Where “k” is a constant, for my case k=0.3, then:
I=0.3*0.014*0.00001

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3.0 INTRODUCTION TO LABVIEW

Aims
To measure the charge & discharge of a Supercapacitor using Labview - PC based instrumentation technique. Read the whole worksheet before starting!

Introduction

Labview is a PC based instrumentation package widely used for automated measurements. It uses graphical programming to develop a ‘vi’ (Virtual Instrument) whereby the PC controls interface devices attached to it, collecting a processing real-time data. This experiment uses an National Instruments DAQ Module (USB-6002) as the interface device, connected to the PC (Labview) via USB. A Labview vi is provided that runs a simple data logging programme displaying the voltage in real time and provides a facility to capture the data in a text file for processing.

3.1: Checking operation of the USB-6002

Connect the USB-6002 to a USB port. Check the PC finds device (Devices and Printers).
Connect a 0-10V power supply to pin AI 0 ‘gnd’ and ‘+ve’ (first 2 pins on input connector
Open Labview / Open a blank VI Open Functions Palette (right click on Control Panel)/Measurement I/O / DAQmx- Data Acquisition Add DAQ Assistant / Select Analog Input / Voltage Select Dev 1 (USB-6002) / channel ai0 Set the Terminal Configuration to RSE (unbalanced) Set the Terminal Configuration to RSE (unbalanced) The ‘connections’ tab illustrates which terminals should be connected (hard-wired0 The vi will capture data for a time determined by the number of samples to be recorded and the sample data rate. For instance setting ‘Samples to Read’ to 1k and ‘Rat’ to 1k will record 1 s of data. The graph will auto-scale – but can be set to a fixed scale by typing Ymin and Ymax directly (and un-ticking ‘auto-scale’ box). Run the vi and confirm it measures the voltage on port Ai1 on the USB-6002. Make notes and take appropriate screenshots of your work and paste into your eLog to confirm the USB-6002 is operational

Screenshots that are represented below demonstrate functionality of USB-6002 that has been connected to PC:

3.2: Measuring the Charge of a Supercapacitor

Using Labview to record the charging characteristic of a capacitor from a constant current source.:

3.2.1 Using Appendix A create a suitable data logging vi – or download the Labview vi ‘super_cap1415#2.vi’ from Moodle.
Paste a copy of the vi in your eLog - both ‘Front Panel’ and ‘Block Diagram’

Results

Figure 3.1 - Front Panel

Figure 3.2 - Block Diagram

3.2.2 Measurement of capacitor charging

* Switch off the Power Supply. * Set it to +2.0V and adjust the current limit to 300mA. DO NOT EXCEED 2.0V! * Connect the Power Supply directly to a 30F Supercapacitor (ensure polarity correct on the capacitor) * Connect AI 0 ‘gnd’ and ‘+ve’ of the USB-6002 across the capacitor. Ensure the positive of the Supercapacitor is connected to ‘+ve’. * Run the vi. The voltage displayed should be zero (n.b. ensure the Supercapacitor is fully discharged). * Press ‘Record’, then switch on the Power Supply. Labview should display the Supercapacitor charging. * Once the capacitor voltage has reached 2.0V (i.e. is fully charged) press ‘Not record’.

Paste a screen grab of the vi displaying the charging characteristic

Results

3.2.3 The captured data is stored in the text file C:\log\super_cap.lvm. (Suggestion - rename this to ‘charge.txt’ to prevent your results from being written over in 3.3.) Use EXCEL to plot the charging characteristic. Compare this to the theoretical curve and discuss any differences.

Results:

Figure 3.3- Charging Excel Plot of a Super capacitor

3.3: Measuring the Dis-charge of a Supercapacitor

Using Labview to record the dis-charging characteristic:

3.3.1 Measurement of capacitor dis-charging

* Disconnect the supply – ensuring the Supercapacitor is charged. * Connect one end of a 6.8Ohm, 1W resistor to GND / Negative of the 30F capacitor. * Press ‘Record’, then connect the other end of the resistor to pin 16 / Supercapacitor positive terminal. Labview should display the Supercapacitor dis-charging. * Once the capacitor voltage has reached 0V (i.e. is fully dis-charged) press ‘Not record’.

Paste a screen grab of the vi displaying the dis-charging characteristic

Results

3.3.2 The captured data is stored in the text file C:\log\super_cap.lvm. (suggestion - rename this to ‘dis charge.txt’ to prevent your results from being written over.) Use EXCEL to plot the dis-charging characteristic. Compare this to the theoretical curve and discuss any differences.
Results; EXCEL Plot

Figure 3.4- Dis-charging Excel Plot of a Super capacitor Charging and dis-charging curves which have been obtained experimentally, plotted by using Excel have some difference comparing to theoretical curves of charging and dis-charging capacitor. Theoretical curves have gradually increase and decrease, meanwhile during experiment has been reached sharp decrease dis-charging characteristic of a capacitor.