We ordered some giant capacitors that were a bit more giant than we had anticipated… so we decided to etch our own boards to achieve a solution that can fit all on one hand.
Result: capacitor bling
For our energy final, Mary, Maria Paula and myself plan on powering a lilypad arduino and LED POV by harvesting the energy from waving the LEDs around by using a coil and magnet.
First test: we wondered about the possibility of charging a lipo battery with the coil. We used a lipo charger/booster connected to a 110mAh 3.7V battery. We ran the AC current through a bridge rectifier, a 7805 and a bunch of capacitors to try to get a constant level voltage. The power from the coil was able to make the light on the charger blink but did not provide a constant 5V to charge the battery.
After consulting the all mighty Eric Rosenthal, he advised us to skip on the lipo battery and just use a BUNCH more capacitors because it would probably take hours to charge up that tiny lipo battery. Instead, we ran the AC current through a bridge rectifier, to 10 4700 uF capacitors, then to the 7805 and finally to the lilypad. That worked!!! Because we put all the caps before the voltage regulator, they were able to supply a more consistent voltage to the regulator for a more consistent voltage output. When we measured the voltage with the load on it, the meter read 3.6V.
Mary Fe, Maria Paula and I finally got our shake on! We learned that it is best to use thin copper wire wound very tightly and many many times to get the most voltage. The best coil we got can put out a max of 10 volts.
We soldered up a board with 6 LEDs, a bridge rectifier and 4 0.0047F capacitors in parallel to hold some of the charge.
Starting voltage: 0 V
Ending voltage: 8.5 V
Capacitance: 4 x 4700 microFarad
Starting energy: 0 joules
end: (0.5) * 4 * (0.0047 F) * (8.5V) * (8.5V)= 0.68 Joules
power = 0.68/ 20 secs = 0.034 watts
For our midterm project, we decided to make a wearable/mobile system that produces energy by 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 a neodymium magnet passing through it.
Our first attempt was a failure. It produced something around 0.06V (60 mV) and 4 miliAmps. The 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
The motor I was using is does not put out a lot of voltage so I had to back it up with a lot of capacitors. When there was no load on the circuit, I could charge all the caps up and get a steady flow of 5.2 volts. Once I hooked the arduio up with the LED blink sketch, it was only getting 2.5 to 3.5 volts after the load… so the arduino couldn’t stay on for more than a few micro seconds. :|
Total energy stored = 2.71 Joules
Average power over 2 minutes = 0.02 watts
If all potential energy was used in 10 seconds, average power = 0.27 watts
Measured Open Circuit Voltage (V) = 4.4V
Measured Short Circuit Current (mA) = >200mA
Pendulum Trio: David Rios, Anne-Marie Lavigne and myself. The measurements for our shaky pendulum can be found below.
Ideas and sketches we came up with for devices that could be powered by our pendulum:
Soup stirrer || potato/grape masher
This device uses our pendulum to drive a fulcrum and lever system. The pendulum is on one end of the lever. The other end will have our spoon or masher attached.
ACME rocket/firework launcher
Have a match or maybe a bunch of matches attached to the swinging end of the pendulum. The matches would hit a hard rough spot at the bottom of the pendulum swing causing them to ignite and light the fuse of the projectile. Then… KABOOM.
Pendulum powered camera
Using the same lever system as the first idea, the pendulum operates the shutter and the film advance of a manual film camera.
Swedish Greys - a WordPress theme from Nordic Themepark.
