Download Coil Gun II

ENGR 101 – Coil Gun II
Professor: Dr. Afroditi V. Filippas
TA: Umar Hasni
Safety Concerns:
This lab, while designed to be safe, utilizes some components and currents that could be
dangerous. You will also be building a projectile launcher. You will be required to be safe with
these systems. Unsafe and unprofessional behavior will NOT be tolerated. Your safety is
paramount, and the TAs will not hesitate to stop your work if you do not abide by required safety
measures.
Introduction: In this lab, you will use the coil gun circuit you created in the last lab to learn
more about the electromagnetic concepts that make the coil gun work. You will be working in
teams of three. Each team will have one circuit and three solenoids with which to do the lab.
Be sure to read through the entire lab procedure before starting.
Figure 1 – Coil gun circuit
Lab Procedure:
Arrive in lab and find
your assigned group
Listen to lab
instructions carefully
Prepare coil gun
circuit for testing
Begin taking
measurements
Diagnose/Re-test
Circuit
Supplies:

Coil gun circuit soldered onto board

Ruler

DC Power supply

Alligator clips

DMM

Projectile

Solenoids
In the lab:
Step 1. Use the DMM on the PXI system to measure the resistance of your
solenoids. Write down the resistance in your lab notebook. What is the
maximum resistance “seen” by the voltage source?
Step 2. Solder your coil gun circuit, leaving one wire “free” to allow for the
measurement of the current.
Step 3.
Weigh your projectile.
Step 4. Find what voltage your projectile starts moving at. Name this voltage Vmin.
This value may change for different coils, depending on topology, number of
turns, and other factors. Each team member must take measurements for their
their own solenoid and write the value of their Vmin in their lab notebook.
For each value of Vmin, measure the distance the projectile launches. Repeat this for
each solenoid. Then, start incrementally increasing the voltage as specified in
Step 5.
Table 1 below.
During the operation of the coil gun, “break” your circuit, and insert the DMM so that you
measure the current being drawn into the coil during the operation of the coil. This
current will be drawn instantaneously, so do your best to read the maximum value
immediately after closing the switch. Enter the values of the current into
Step 6. Table 1. Can you find a reference online that explains what is going on
with the currents and voltages in the coilgun?
Calculate the time it would take to charge your capacitor to 99% of the maximum
𝑡
voltage, given 𝑉𝐶1 = (𝑉0 − 𝑉𝑚𝑎𝑥 )𝑒 −(𝑅𝐶) + 𝑉𝑚𝑎𝑥 . Try to time your capacitor as you are
charging it to the maximum voltage in
Step 7. Table 1. What is the % difference between your theoretical calculation of
the charging time vs the actual measurement?
(You can do this at home) Using Ohm’s law and the values in
Step 8. Table 1, calculate the total resistance of the circuit. Compare to the known
values of the resistances in the circuit. What is your conclusion? Use Excel or
Matlab for this part of the exercise.
Step 9.
You will add a resistor R2 and computer the discharge time constant
and measure the time it takes to actually discharge your capacitor using a
stopwatch. Compare the discharge time calculated vs measured
R2
1
𝑅𝐶
Table 1: Distance traveled by projectile as a function of the supply voltage.
Voltage
supply [V]
Vmin
Vmin+ 1
Vmin + 2
Vmin + 3
7
8
9
10
11
Capacitor
voltage (fully
charged) [V]
Distance
Covered [cm]
Current [A]
Capacitor
charging
time [s]
Capacitor
discharging
time [s]
12
13
14
15
Report:
1. Introduction: 1-2 paragraphs – what is a coil gun and how does it work? What is
your “hypothesis” or otherwise the aim of this project?
2. Experiment/Design:
a. Describe the construction of the solenoids and the circuit. Your description
should be clear enough for somebody to replicate your experiment.
Include pictures and schematics. LABEL and CAPTION everything.
Refer to these images in your report.
b. What are the different physical phenomena that go into the operation of
the coil gun? How do they influence the performance of your coil gun?
What measurements did you take? What do they mean? What graphs can
you generate that demonstrate the different physical properties of the coil
gun?
3. Results:
a. Refer to your description in the Experiment/Design section of your report.
You will now need to start presenting your measurements and results.
b. In general, use graphs (preferred) or tables (sparingly) to present results.
For this report, graphs need to be used as they are more meaningful and
will help you describe trends.
c. All graphs MUST:
i. Have captions with descriptions.
ii. Be referenced and explained in your text.
d. Results are quantitative measures we use to prove our theories. What
theories have you proven here?
4. Conclusions:
a. 1-2 paragraphs. A conclusion is really a restatement of your original
“hypothesis” or aim and a review of whether you supported your
hypothesis or achieved your aim. You should reference your results to say
why or why not you did or did not achieve your goals, but keep this section
short. Be careful – you should never say that you “proved” something.
You have always “supported” your hypothesis or “not supported” your
hypothesis. Or, you have “met the requirements” of your design or “not
met the requirements” of your design.