# Harvest Shake

As continuation of our project, we built the tube and connected to a circuit with 4x more capacitance. We were able to light up 6 LEDs easily. =)

Starting voltage: 0 V
Ending voltage:  8.5 V
Starting energy: 0 joules
Ending energy: 0.5 * 4 * (0.0047 F) * (8.5 V) * (8.5 V) = 0.68 joules
Time: 20 secs
Power: 0.030 Watts (it is the same power we got in the previous alternative – YAY!)

Last, but not least, we transformed our circuit into a wearable (work still in progress)

# Shake shake

For our midterm project, we decided to make a wearable/mobile system that produces energy either shaking or beating it.

First, we thought about using piezos, but they produced almost no current with high voltage peaks. Inspired by shake-lights, we proposed to build a shaking system with copper coil and magnet passing through it.

Our first attempt was a failure. It produced something around 0.06V (60 mV) and 4 miliAmps.
Problem was: the coil was too small. We needed a LOT more wire.

We tried other coils and started getting some more interesting numbers. The coil on the left in the first picture produced a bit more than 10V! The middle one 5V and the smallest reached 2.5V.

To calculate Power, we measured the voltage difference when charging up a capacitor. Doing the math, we reached the following numbers:

Starting voltage: 1.5V
Ending voltage: 6.5V
Capacitance: 4700 microF
Starting energy: 0.5 * (0.0047 F) * (6.5 V) * (6.5 V) = 0.0992875 joules
Ending energy: 0.5 * (0.0047 F) * (1.5 V) * (1.5 V) = 0.0052875 joules
Difference: 0.0992875 – 0.0052875 = 0.094 joules
Time: 3 secs
Power: 0.031 Watts

I believe our next step is to build a tube in order to get more out of the magnet movement.

# Pendulum Energy

(a) Calculate the energy stored (in joules) in your pendulum using the mass and height measurements, and record this online. (b) Using the duration you measured, calculate the average power, in watts, at which this initial energy was transfered to the environment. (c) If you used all the initial potential energy in 10 seconds, what would the power be?

Mass = 6kg;
Initial height = 1m;

(a) Gravitational Potential Energy = mpg;
(6kg)*(9.8((m/s)/s))*(1 meter) = 58.8 joules

(b) Let’s supposed our pendulum stopped completely in 2 minutes.
Average power = (58.8 joules) / (120 seconds) = 0.49 watts

(c) Power = Energy / time
(58.8 joules)/(10 seconds) = 5.88 watts

# Pendulum

In class, we were tasked with building a pendulum and competed to see which design would remain in motion for the longest time. Our group selected a weight item with the largest mass we could find and tried to maximize the length of the cord. Our approximate measures are defined in the diagram below:

Mass = 6kg
Height = 4m

Since our pendulum was built in the japanese room, where the soft lab is, we agreed that the energy from the pendulum could be utilized to power sewing machines. Tom said his grandmother had an old sewing machine powered by pushing on a plate near the floor. Do you think this would work?