My name is Kenan, I’m a rising junior at Trinity School, and my starter and main projects here at BlueStamp were the MintyBoost USB charger and the Vertical Axis Wind Turbine (VAWT), respectively. I chose these projects due to my fascination with energy and electricity generation. I find that wind turbines will be a key part of our future energy generation and consumption, and I wanted to learn more about this field and gain some experience in it. I chose the MintyBoost as my starter project because I felt that it would be a good introduction to the VAWT since both projects have to do with energy generation of some sort.
During my time at BlueStamp, I feel like I have gained many skills and much knowledge which are useful in both engineering and everyday life. I have learned how to solder and have practiced soldering multiple times while here. I have explored a lot in electricity, electronics, and circuits. Knowing more about how charging and powering devices work has made me more aware of all the effort and attention put into what may seem to be the simplest of pieces. The MintyBoost made me more aware of the power of what many people often disregard, batteries, and the VAWT gave me greater appreciation for the difficulties of wind and other renewable energies. I value all of the experience that I have gained while at BlueStamp.
Final Blog Post
My main project was the Vertical Axis Wind Turbine. I started off this project by building the electronics for the circuit. The stepper motor I used was bipolar, meaning it can spin in either direction, so the circuit had to be compatible with this motor. I therefore used a rectifier circuit, which uses a series of diodes to direct the current down the correct path and convert the AC from the motor to DC. Because the turbine’s speed can vary depending on the wind, the current and voltage can fluctuate with it, so I added a capacitor to steady the flow of current and decrease how much the LEDs flicker. Although the original design only required 1 LED, I later found that adding more LEDs in parallel with each other, 5 in this case, provided a brighter overall glow without slowing down the turbine much.
Next, I built the main structure for the turbine. I used an aluminum rod for the main shaft of the turbine around which the sails turn. This shaft is held steady by the two acrylic base pieces, which are held up by three hex standoffs. The aluminum shaft is held up by a shaft collar which rests on the bottom acrylic base piece with a thrust cage assembly between them to decrease friction. Attached to the shaft inside the base is an acrylic gear which, when spun, spins another gear that is attached to the motor, turning the motor and generating electricity. The shaft spins when wind hits the aluminum sails, which are held in place and attached to the shaft by two acrylic sail pieces. These sail pieces are held in place by two shaft collars and glue.
One problem I faced was that the turbine was not spinning fast enough. To help solve this problem, I decreased the turbine’s weight by removing excess aluminum from the rod and replacing two shaft collars which originally helped hold the sail pieces in place with glue. I then cut out new, deeper aluminum sails to help the turbine catch more wind and therefore spin more easily.
I then attempted to make the turbine compatible with charging USB devices. My first challenge was to make the output voltage consistent. As more components are added onto the protoboard, the circuit’s overall resistance increases, making the motor harder to spin. This causes the turbine to spin slower, generating less voltage. For example, with nothing attached to the circuit the turbine can put out about 11V, but, with an LED, there is only about 2V. A phone, which was my main goal with this charger, can only take about 5V. I therefore added a voltage regulator to the circuit in case the voltage went too high, and I incorporated my MintyBoost starter project to boost the voltage in case it went too low. Although I had optimized the voltage, the current was still not enough. A phone needs at least half an amp, or 500mA, to charge properly. My turbine, however, even with nothing plugged in, could only give off a maximum of about 50mA. In order to fix this problem, I tried adding a transistor in an amplifier circuit to boost the current. However, I was unable to successfully integrate the amplifier circuit with my rectifier circuit. I therefore determined that the probability of being able to charge a phone with this turbine was low, so I decided to instead leave the turbine as a light with the LEDs.
For my second milestone, I built the main structure of my turbine. I first built the base, consisting of two acrylic disks held together by three hex standoffs. These disks both have holes in their centers for the aluminum rod, serving as the turbine’s shaft, to go through. A shaft collar attached to the bottom of the shaft rests on a thrust cage assembly, which rests on the bottom acrylic disk. This shaft collar supports the shaft, and the thrust assembly reduces the friction of the shaft as it spins, resulting in easier rotation. Attached to the rod by another shaft collar between the two disks is an acrylic gear, which is connected to another gear. This second gear is attached to a motor, which is connected to a circuit and an LED, as explained in my previous post. Moving up the shaft, there is another shaft collar directly underneath the upper disk that stops the shaft from being pulled out of the top of the base and keeps it in place. Above the base are two three-pronged acrylic sail pieces, which are attached to the shaft by four more shaft collars. These acrylic pieces have slits in them that secure three curved aluminum sail pieces.
When a strong enough wind hits these sails, it spins them and their attached acrylic sail pieces. These pieces spin the main shaft, which turns the gear attached to it. This causes the gear attached to the motor to rotate, resulting in the spinning of the motor, generating electricity that moves through the circuit and lights up the LED.
For my first milestone, I have set up the electrical components for the turbine, consisting of the wiring on the breadboard and the stepper motor. I began by setting up the required wiring on the breadboard. I then connected the motor to the breadboard and manually spun it to test that the circuit worked. When the LED did not light up, I discovered that I had grounded my circuit incorrectly and that some of the diodes had been placed incorrectly. After fixing these issues, the circuit is now functional.
The stepper motor generates electricity when it is spun, in this case by the wind pushing on the attached sails. The spinning uses electromagnetism inside the motor to generate current, which then passes through the breadboard to the LED, lighting it. I needed a bipolar stepper motor so that it can work no matter which way it is spinning. The breadboard setup had to accommodate this bipolarity, so I used a rectifier circuit. This rectifier circuit takes the current from the motor, no matter which way it turns, and directs it so that it flows properly through the LED and lights it correctly. This is done by using the diodes to control the direction of current and move it down the right path. The capacitor helps keep this current steady by storing energy while the motor is spinning, and releasing energy when the turbine is not generating electricity. This helps prevent the LED from flickering and creates a steadier glow.
For my starter project, I constructed the MintyBoost portable USB charger. I began this project by soldering the resistors onto the circuit board. A total of five resistors in all, there was one 3.3k resistor, two 75k resistors, and two 49.9k resistors. Next, I soldered the two ceramic capacitors into the circuit. Following this, I soldered the diode and the IC socket onto the circuit board. I then soldered the power inductor onto the circuit board, and then the two electrolytic capacitors. Next, I soldered in the battery holder, capable of holding two AA batteries, and then inserted the boost converter chip into the IC socket. To make sure the circuit was complete, I placed batteries into the battery holder and used the multimeter to check the voltage. Once I had confirmed the proper amount of voltage, 5V, I soldered the USB type A converter into place and confirmed that it worked by charging a device with this charger.
This charger works by using the change of voltage caused by the batteries. This voltage change creates a current across the circuit, resulting in the generation of power. In this circuit, the 3.3k resistor is used to help the current capability of the boost converter chip. The boost converter chip itself generates 2V of additional voltage, since the batteries do not create enough voltage by themselves. The other resistors also help the flow of current, but are also used by many devices to help figure out what type of charger is plugged in. The capacitors in this circuit help stabilize the flow of current. Specifically, one of the ceramic capacitors helps ensure that the output voltage remains consistently at 5V, while the other ceramic capacitor helps the boost converter chip generate a steady voltage. The Schottky diode makes sure that power from the boost converter chip flows in the right direction and is not reversed, and the power inductor stores power from the boost converter chip and helps convert the power to higher voltage. Finally, the USB connector allows this power to flow into and through the device, charging it.