# Motion powered battery

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# Overview

How often have you been going about your day, and your phone suddenly dies when you aren’t near an accessible outlet? You have to drop whatever you’re doing and completely change your schedule to get your phone to charge. This dilemma stems from our society’s constant reliance on electronic devices and the inconvenience of finding a consistent power source. This is what inspired the idea for our engineering design project.
For our engineering design project, we will be creating a motion powered battery. While there are some of these on the market with various designs, our motion powered battery will utilize the model of a shake flashlight. Ideally, we will be able to generate enough stored power to charge an electronic device (i.e. a phone) for a substantial amount of time.
Our three person team will design and build a magnet charging device that uses magnetic forces to generate an electrical current through a wire. We will be using an Arduino to measure the power output and determine if there is a need for a capacitor/resistor. Once the battery is charged, we hope to build power output terminals from the battery so that we can use it to power other things. We will put the entire design into a case to protect the external pieces from breaking.

# Team Members

• Katherine Laue
• Steven Schlau
• Henry Roberts
• John Fordice(TA)
• Denise Mell(Instructor)

# Objectives

• Generate voltage using changing magnetic fields from the movement of neodymium magnets
• Connect the generator to a rechargeable battery that would store power
• Encapsulate design using 3D printed pieces for more efficient power generation

Barring Major Set-Backs:

• For presentation purposes, create LED visual to represent the storage of power in battery

# Design

The visual design of our project will mainly consist of a tubular apparatus made of a PVC pipe section with a Teflon lined interior and a neodymium magnet that slides through the inside. Outside, there will be a copper wire coil wrapped around the tube which will be connected to the rechargeable battery, potentially with a resistor and/or capacitor between them. The battery will then have output terminals itself so it can change other devices in addition to being charged. Ideally, the battery will not have to be disconnected from our model to be able to charge other devices. This entire tubular design will be held in a more attractive encasing so as to look more desirable to a potential consumer.

Single Pipe Diagram

Electrically, our design will generate power as the magnet runs through the copper coil. Electrons will flow through the coil and then run into the battery where they will be created into chemical energy. In order to encase our pipes and wires, we will create a wooden box that will have 4 rectangular holes on both widths in order to slide shelves in. We will also have a wooden rectangular top that will be connected to the box by tape or a lever. In order to keep the pipes stable in the box, we will 3D print 4 shelves with 6 holes to slide pipes in. 3D printing the shelves will allow for more accurate holes which will make the ability to create and store power more precise.

# Challenges

## Initial Assessment

Our main challenge is more of a potential issue with the overall motion powered set up. Most motion powered devices only require small power outputs such as crank or shake flashlights. Existing motion powered devices such as AMPY's Move need vigorous movements such as running to generate power in a reasonable time span. Our device may need to be shaken very hard or for a long period of time to generate enough current and electrical energy to
a) charge the battery even a little
b) generate enough charge in the battery to use it to power other devices.
Once we have built our design, we hope to refine it to make it smaller. This could be a potential challenge as we will want to still generate a similar power output but have a smaller design that could be more attractive to a consumer.
We will need to experiment with different types of Teflon (sheets, spray, tape) to find the material that allows the magnet to slide through the tube with the most ease.

## Updates as of 4/20/2018

Our initial design was one large tube wrapped 250 times with wire. When we shook this design, it outputted 0.5 volts. We were pleasantly surprised that our original design worked but the design itself was too rigid. One of our primary goals was to take our original idea and make it smaller (easier to store). We ordered the smallest pipes and magnets we could find and planned on putting 12 pipes into our new design. What we didn't anticipate for was the fact that magnets are attracted to each other. The smaller our design got, the closer the magnets were to each other and the charges interfered with each other.
Box with 6 pipes

There are ways to block attraction of magnets but the cost alone does not make sense in the case of our project. In order to have the magnets be less attracted to one another, we used 6 pipes instead of the original 12 pipes. We were still able to get a reasonable amount of power but not as much as we originally hoped for.
Another problem we encountered was converting from AC to DC. When we were doing our original calculations we were measuring in AC which is useless if you want to charge an electronic device like a cellphone. When we converted from an AC current to a DC current, some of the current was lost which is common. We did not have as much voltage as we initially anticipated.
Lastly, when we were creating our presentation, we realized that our project did not have a way to demonstrate what was occurring internally. After talking to Professor Mell, we decided to use an LED light connected to an Arduino to give a visual of power being created and stored. Even though the LED did not have to do with out project and would not be on the finished product, it showed the people we presented in front of that our project was doing exactly what we said it was.

# Ethical Concerns

In terms of ethical concerns, our project does not have any pressing issues but there is the possibility of a safety hazard. Our project deals with wires and electricity. The box we created to encapsulate our design is not waterproof. If someone was using our product outside or in a backpack and it was raining, there is the possibility of electrocution. Our product does not generate a huge amount of power but this possibility brings to light some concern.
In addition, our design right now is impractical. It is very bulky and could cause problems if someone is trying to hold it while exercising. Also, if someone has it in their backpack they could have some back pain arise from the weight. Our next goal is to concise our project using smaller pipes and magnets thus making the shelves and overall design smaller. This would mean there is less weight and less likelihood of a customer having a problem.

In the end, my partners and I believe that the benefit of this device far outweighs the potential problems. The Motion Powered Battery allows people to charge their phone even without an outlet. If someone's phone died on a hiking trip and a problem arose, they would be able to call for help after using our design. In the future, we want to create an even smaller design but also a container that is water proof to fix these ethical concerns. For now however, our project is functional and allows customers to charge their phone just by shaking the box. This provides safety as described above and time.


# Budget

• PVC pipe - [link] - $14.54 • Teflon (Different Types)- [link] -$9.09
• Neodymium magnet [link] - $17.66 • Rechargeable battery [link] -$9.99
• Box Container(Wood)- $4.99 • Capacitor [link] -$0.99
• Electrical tape [link] - $4.50 • 3D printed shelves - provided by Systems Laboratory • Arduino -$24.20

Total: \$94.92

# Final Design and Solutions

## 3D Printed Shelves

Shelf top view

We 3D printed two sets of 2 shelves, each with 6 holes to put the PVC pipes between. We created our design using the program Solid Works. Each shelf was 3.5 inches long, 2.5 inches wide and 0.3 inches in height. In order to have the shelves hold the pipes, we created holes that did not go all the way through. Each hole had a radius of 0.34 inches and a depth of 0.25 inches (0.05 inches left of solid depth). As we talked about in our updated challenges, we did not account for the attraction between magnets. Instead of using all 6 holes and pipes, we ended up only using three pipes in each set of plates. On the left side of our box, we had our pipes be in the top-left hole, the bottom-middle hole, and the top-right hole. In order to further prevent attraction through the shelves, we placed the right side pipes on the bottom-left hole, the top-middle hole, and the bottom-right hole. The shelves slid into the four slits in our box making it secure without any adhesive reinforcement. Our box design also allowed the easy removal of the pipes by sliding the shelves up and out after taking the lid of the box off. This design, especially with the 3D printed shelves, makes it very easy if any maintenance is required on the tubes because nothing is glued/taped down.

## Arduino Code

Figure 1: LED and Voltage Arduino Code

In order to measure the voltage output from our motion powered battery, we used the Arduino circuit board to measure it. The output current from the bridge rectifier circuit ran into the input of the Arduino, which was then hooked into a computer. The computer ran a program to measure the voltage and used it to light up an LED powered by the Arduino. The code can be seen in Figure 1. The top half of the code deals with taking in the voltage from the motion powered battery. It runs a constant loop that takes in the sensor value from one of the Arduino inputs and converts it into the correct units for measuring voltage, and then prints out those values every 200 milliseconds. The bottom half of the code deals with lighting up the LED on the Arduino. This LED was used for presentation purposes to show that the battery was producing voltage. The code uses if statements that use the voltage value calculated above and turns on the LED if the voltage value rises above 1.0 V, and turns it off if it drops below that 1.0 V. We chose 1.0 V as our threshold value because our max voltage value was around 1.5 V, so 1.0 V is achievable but not easy to obtain.

## Bridge Rectifier Circuit

Figure 2: Bridge Rectifier Connected to Motion Powered Battery

A bridge rectifier is an arrangement of four diodes in a bridge circuit configuration which provides the same output polarity for either input polarity. The shaking motion with the changing magnetic field outputted a raw AC current which needed to be converted to DC to power a battery. We built a bridge rectifier circuit to facilitate this conversion. Our bridge rectifier is made up of four diodes which process the positive and negative currents, switching the negative currents to positive currents. We then added a capacitor (it's a passive two-terminal electrical component that stores potential energy in an electric field) to smooth out the voltage into a more linear fit, rather than the absolute value of a sine graph.
Additionally, to connect the uninsulated copper wires to the bridge rectifier circuit, we soldered the ends to connection wires. This ensures that as the wires bend that they don't break connection. Once soldered, we glued the copper wires and the ends of the connection wires into the box so they would not move when shaking. The ends of the connection wires were attached to the bridge rectifier.
Looking at Figure 2, the orange wire to the left of the bridge rectifier takes the output voltage from the battery and inputs it into the circuit. This then sends it through the bridge rectifier and then to the capacitor. From there the white wire takes the new DC current after the capacitor stores it and sends it to the Arduino to measure the voltage. Then the yellow wire from the Arduino sends the current back into the bridge rectifier circuit, which is then sent to the other yellow wire and back into the battery where the circuit starts over.

## Tubular Set Up with Neodymium Magnet

PVC pipe wrapped 250 times in uninsulated wire

We used neodymium magnets to facilitate the change in magnetic field. The magnets slid side-to-side in the PVC tubes, causing a current to flow through the wires wrapped around the tubes. The PVC pipe we used had an inner diameter of 3/8 inches. The neodymium magnets had a diameter of 5/16 inches and a width of 1/8 inches. We experimented with different lengths of magnets in the tube, with a goal of generating the most consistently high voltage, to have enough magnets connected so they would not flip in the tube. We found that by connecting four magnets, resulting in a length of 4/8 inches to prevent flipping, we were able to generate the highest voltage. When we added 5 or more magnets, we found that not only did the motion powered battery a sufficient amount more but also that it was harder to shake back and forth because the magnets did not move as smoothly through the pipe. We deduced this was due to the overall weight making it harder to shake at the force needed to produce a high voltage.

# Results

## Project Recap

In this increasingly digital age, we find that the battery life of our devices is not improving at the pace of our growing usage. Thus, our devices are often out of charge, which can be frustrating when we are not stationary with a charger and outlet nearby. To combat this, we created a motion powered battery, that although requires reasonably vigorous shaking, will output voltage over 1.25 volts. Six total tubes, each with four neodymium magnets inside, all wrapped with 250 coils of uninsulated copper wire, outputted said voltage. A bridge rectifier circuit modified that voltage from an AC current to a DC current. We met all of our primary goals and most of our secondary goals, the main one of which that we did not meet was connecting the battery to an electronic device. We ended up connecting our box to an Arduino to measure voltage, and illuminate an LED accordingly. However, this proved better for demonstration purposes. We created a motion powered battery, that although requires reasonably vigorous shaking, will output voltage over 1.25 volts. We met all of our primary goals and most of our secondary goals, the main one of which that we did not meet was actually connecting the box to a battery to charge. We ended up connecting our box to an Arduino to measure voltage, and illuminate an LED accordingly. However, this proved better for demonstration purposes.

## Future Considerations

Motion Powered Battery

Although we were able to meet all of our primary goals, there are many improvements we could do to further refine our design. One problem that arose when making the Motion Powered Battery was the voltage output. We should be able to achieve a higher output voltage then we were getting with less vigorous shaking. We could do this by adding springs to the ends of each tube. The springs would have to be non-metal though in order to prevent attraction to magnets. In the future it would also be beneficial to create a different design for the 3D shelves. In our calculations we placed the tubes too close together in the shelves. The magnets would not move due to their close proximity. If we redesigned the shelves having 4 holes in each corner, they would be a farther distance and we would be able to add one more additional tube to each side making it 8 tubes total instead of 6. We also would want to invest in a smoother PVC pipe lining. Although we added Teflon to the inner barrier of the tubes, there was still a good amount of friction due to the low quality of the product. If we found a smoother internal pipe, this would lower the friction and therefore produce a bigger output of voltage. When we originally bought our products we weren't sure how much room there should be between the neodymium magnets and the pipes. If we were to do this project again we would buy neodymium magnets that fit better with the tubes leaving some room but not too much. Although our magnets were a little bit smaller in diameter then the pipes, they were too small creating friction lowering the voltage. Also, we would like to invest in copper coated neodymium magnets. Thinking in the long term, this would prevent deterioration of the magnets. There is no buffer for the magnets to not break down. Every time you shake the box, the magnets are rubbing against the pipe. This would allow the Motion Powered Battery product to last longer without this maintenance. As mentioned above, we also hope to connect our product to an electronic device to charge it. With the changes we've suggested, the future product could become very popular in the technology/cellular industry. Lastly, we realized other potential uses of our product beyond just normal human movements. Now, our product only creates power when it is shaken from side to side. When thinking of this new idea we realized that our current box could be mounted to a car wheel or the bars connected to a train’s wheels. We got this idea because of the back and forth motion of the train cars. It is the exact motion of our product and if we had one Motion Powered Battery on every wheel we would conduct a huge voltage due to the constant and vigorous movement of the box.