ECE 477 Digital Systems Senior Design Project Rev 8/09

Homework 12: Environmental Impact Lifecycle Analysis and Ethical Challenges

Team Code Name: Defender Group No. 6 Team Member Completing This Homework: Brian Bentz

E-mail Address of Team Member:

Evaluation:

SCORE

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DESCRIPTION

10 /

Excellent – among the best papers submitted for this assignment. Very few corrections needed for version submitted in Final Report.

9 /

Very good – all requirements aptly met. Minor additions/corrections needed for version submitted in Final Report.

8 /

Good – all requirements considered and addressed. Several noteworthy additions/corrections needed for version submitted in Final Report.

7 /

Average – all requirements basically met, but some revisions in content should be made for the version submitted in the Final Report.

6 /

Marginal – all requirements met at a nominal level. Significant revisions in content should be made for the version submitted in the Final Report.

* /

Below the passing threshold – major revisions required to meet report requirements at a nominal level. Revise and resubmit.

* Resubmissions are due within one week of the date of return, and will be awarded a score of “6” provided all report requirements have been met at a nominal level.

Comments:

1.0  Introduction

The Defender turret based defense system is a turret-mounted coil gun that uses image processing to accurately target specified objects. Defender poses several challenging environmental and ethical concerns throughout the course of its life-cycle. During the manufacture phase, the printed circuit boards and various integrated circuits must be synthesized. During normal use phase, a significant amount of power must be supplied to the turret. Finally, during the disposal phase, many of the parts on Defender can be easily recycled, while others must be properly disposed of. All of these concerns must be addressed to assure minimum environmental impact during Defender’s life-cycle. On the ethical side, product safety is a huge concern. The high voltages, moving parts, and high projectile velocities can all lead to user injury. If it is commercialized, the device must also be properly distributed and tested so that it is FCC approved.

2.0  Environmental Impact Analysis

The main environmental concerns during the manufacture of Defender are the synthesis of the printed circuit board (PCB) and the integrated circuits (ICs). Most of the ICs are RoHS certified, which means the hazardous chemicals used to synthesize them were limited. However, there is still a significant negative impact on the environment during their manufacture. Generation of the PCB is also damaging to the environment because it requires the use of several poisonous and environmentally dangerous chemicals such as polytetrafluroethylene (Teflon) and lead. The amount of hazardous chemicals needed to produce the PCB and IC’s must be reduced in order minimize the negative effect on the environment incurred through the manufacturing phase.

Also involved in the manufacture of the turret are several natural resources. These natural resources are used to create the base of the turret, the coil, the barrel, and the rotator arm. To create the base of the turret, wide sheets of eighth-inch aluminum are used. To wind the coil, almost 100 feet of 18 gauge magnet wire is required, and an additional amount of brass and aluminum is needed for the barrel and rotator arm. All of these metals are in limited supply, and their production has a negative effect on the environment.

There are several things that can be done to reduce environmental impact during the manufacture of Defender. To reduce the amount of chemicals used in the synthesis of the PCB and ICs, the area of the PCB must be minimized as well as the number of ICs required for the control circuitry. To limit the use of natural resources, the base of the turret will be made as small as possible, and the coil will be designed such that it requires a minimum amount of magnet wire.

During the normal use phase of the product’s life-cycle there is little environmental impact except for power usage. The majority of this power goes to run the Atom board, motors, and high voltage capacitors. Without charging the capacitors, the system requires 90W to run. To charge and fire the capacitors, the system requires an additional 1.5 kJ of energy. These values are relatively high because of the large amount of power needed to run the Atom board and generate the high voltages required to charge the capacitors. To reduce the energy usage, the turret has been designed to only charge the capacitors when the system is about to fire, rather than leave them charged continuously.

The final phase of the life-cycle of Defender is the disposal stage. This is the stage where the product has become unreliable due to age and must be disassembled and thrown away. There are many challenges that come with the disposal of Defender because of the toxic nature of many of its materials, and the large amount of recyclable components. The PCB and ICs are obviously not biodegradable and must be properly disposed of because they contain lead. All of the aluminum, brass, and copper used to make the base, barrel, and coil can be easily recycled. Also, if they are still functioning properly, the high voltage capacitors and camera can be taken off and re-used because of their long life times compared to the rest of the system.

To encourage proper disposal of Defender, its distributor will be required to offer a monetary incentive for the customer to return the product. Once it has been returned, it can be disassembled and disposed of properly. The PCB and ICs can be taken to a waste disposal center, all of the parts including the capacitors and camera can be tested and re-used, and all of the metal can be recycled. This is the best method to minimize the environmental impact of Defender because it does not require the user to disassemble any parts of Defender.

3.0  Ethical Challenges

There are many ethical challenges facing Defender. The most significant of these are the plethora of safety issues that come along with building a turret mounted coil gun, which include high voltages, moving parts, and high speed projectiles. Each of these issues must be addressed to ensure that no harm comes to the user during normal operation of Defender.

To protect the user from high voltages, warnings will be placed on the base that power should be completely off before it is opened. Inside the base, there will be several visual indications if high voltage is present. A red LED controlled by the microcontroller will be on if the high voltage supply is enabled, and a neon bulb across the high voltage capacitors will glow if the capacitors are charged. It is not expected that the user will need to open the base of the turret, but these precautions are still necessary.

The fact that there are moving parts in the design may not seem like a safety issue, but it turns into one because of the high speed projectile. If there is an error in the code for example, the motors may move the barrel to a position that may harm the user if the coil were to fire. Therefore it is necessary to install stoppers on each side of the barrel to limit its range of movement.

The nature of the coil on the coil gun leads to the possibility that the projectile will be fired backwards through the barrel rather than forwards. This can happen because the electromagnetic force applied to the projectile is directed to the center of the coil, and once the projectile passes the center, the force points backwards. Normally this would only slow the projectile down, but if the rise time of the voltage pulse is too long, it could cause the projectile to fire backwards. To prevent this, a metal cap will be welded to the back of the barrel.

Along with the many safety concerns involved in the operation of Defender, there are also ethical implications involved with its distribution. This product has not been designed for public use, but if it were to be commercialized, its distribution would need to be controlled just as the distribution of guns is controlled. To purchase a system, the user would need provide several forms of identification and submit to a background check.

The electromagnetic interference (EMI) that is induced by the high voltage LC pulser on the coil gun is also a significant ethical concern. If Defender is operating in close proximity to other electronics, there is a possibility that any EMI given off when it fires could damage or destroy the electronics. Therefore it is important that the LC circuit be properly shielded to prevent damage. If this product were to become commercialized, it would need to be verified by the FCC before it could go into production.

4.0  Summary

The Defender turret defense system poses many challenging environmental and ethical problems. During its life-cycle, the system must be properly manufactured, operated, and disposed of in order to minimize its environmental impact. Of these phases, the disposal phase is the most important because it is here that the parts are recycled or properly disposed of. In order to protect the user, there are many safety precautions that must be made to protect against high voltages, moving parts, and high velocity projectiles. Warnings will be placed on the base, and stoppers will be used to prevent unwanted rotation of the barrel. The system will be shielded to minimize the effects of EMI, and if commercialized, a background check will be required in order to purchase the Defender system.


List of References

[1]  Frank G. Splitt, “Engineering Education Reform: A Trilogy” IEC, 2003 [online] Available: https://engineering.purdue.edu/ece477/Homework/CommonRefs/enviro_refs.pdf [Accessed April 14, 2011]

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