After five and a half hours of work, here is the treadmill generator at work. The generator is not yet bolted down so that the project can be easily dismantled and transported.
Yesterday was an exciting day. I arrived at the home of my friends, Ray and Elizabeth, with my bicycle, fan motor, and voltmeter in hand. The plan was to attach the fan motor to a frame in such a way that the bicycle tire would rub against the shaft of the motor and thereby generate current. As we were unloading my car, I mentioned that I had been looking at DIY plans for a treadmill generator system; however, I had not been able to obtain a treadmill motor yet. Lo and behold, Ray and Elizabeth had an unused treadmill that they were willing to sacrifice for the project!
Above you can see the pictures of how we removed the motor from the treadmill, built a frame to stabilize the bicycle, attached a belt to the bicycle tire and the generator shaft, and then pedaled! We inadvertently attached the motor so that it produced negative voltage readings on the voltmeter. Therefore, we switched the red and black wires to compensate. Thank you to Ray and Elizabeth for spending their evening helping me and for donating wood, the motor, and other scrap parts. My next challenge is to learn how to connect the generator to the 12-volt battery to the charger receptacle. I think I will need a regulator between the generator and the battery. Then I probably need an inverter (to convert DC to AC) between the battery and the charger receptacle. Thank you to Jack at the Bicycle Exchange for the two bicycle generators and to my classmate, Sewedo, for filming this clip. Thank you to my husband for allowing me to sacrifice a box fan for the sake of the project.
It is time to start putting some of the pieces together. I have been brainstorming with my husband about the best way to connect a generator to the bicycle. At first I thought it would be more efficient and simpler to maintain if I connected the generator directly to the pedal mechanism (fewer parts = fewer places to lose energy and fewer places for problems to occur) However, now that I know I need to spin the generator as quickly as possible in order to generate enough power, I am leaning towards using the chain and sprocket system on the bike. I am planning to reattach the rear wheel or replace it with a larger diameter rim that I happen to have in my basement. The combination of the gears on the bicycle and the large diameter wheel will increase the rpm's of the generator shaft. Here is a picture of the bicycle frame with the large diameter wheel leaned up against it. I was planning to anchor the entire device, when I get to Haiti, by driving a stake into the ground and then sliding the middle post of the bicycle frame over the stake. This may or may not work if I use the larger wheel because I will have to build a small stand to raise the bicycle up off the ground so the wheel will move freely and not touch the ground. perhaps I will have to mount the whole device on a piece of wood. I checked with Mike at Interstate Battery regarding charging a motorcycle battery. He replied that this type of battery is usually 12 volt, which means that it requires 13.5 volts to 14.5 volts to charge it.
To store energy or not to store energy - that is the question. I took my generator back to B & B this morning to make sure I was testing the voltage output correctly. Yes, I had been measuring correctly and it does take a lot of drill speed to generate 4 or more volts. You can view the drill test in the movie clip below. Thank you to my husband for simultaneously running the camera and the drill. My questions for the day are:
1. Will I be able to generate enough voltage to charge a motorcycle battery? Should I use multiple generators? Do I need to find a way to step up the rpm's of the generator shaft so that it can generate more voltage with average pedaling? 2. Should I abandon the battery and just connect the circuit directly to a charger? In that case, there will be no stored energy and only one cell phone can be charged at a time. Maybe this is what I need to do for the first model. I could work on increasing the voltage on a second version. 3. I could get more voltage by using an alternator. Today a friend showed me instructions for how to build an alternator. Should I build an alternator instead of using a generator? Could I build a generator that would do the job? The good news is that I was able to scavenge a used bicycle from among the leftovers from my church's annual rummage sale. My husband and I deconstructed it yesterday until we had something that could fit in a suitcase. The bad news is that when I tried to repeat the generator test that the guys at B & B Electric Motor Company showed me last week I did not get the same result. I attached an electric drill to the generator, but I was only able to measure 1-2 volts, rather than 5-6. So, I will have to make another visit to B & B tomorrow for a review lesson. If this generator cannot generate 5-6 volts with a reasonable amount of pedaling, then I will have to find another one to work with.
A final piece of good news for today - I was able to purchase a voltage regulator and I ordered a rectifier.Hopefully by the end of the week I can assemble some components. I realized that I should fill in a little background information. During the last week of March, I searched online for existing bicycle-powered generators. I wanted to learn about the different components that would be required. Below are three of the projects I found. The first design uses a bicycle to charge a battery which then powers a laptop computer. The second generator differs because it uses an automotive alternator which contains a rectifier, capacitor, and voltage regulator. The developers of the project mention that an alternator is beneficial because it is durable and can withstand temperature extremes with minimal maintenance. This design is for educational purposes and powers a number of light bulbs depending on the amount of energy generated, or how fast the cyclist pedals. The third design uses a re-purposed bicycle headlight generator. The components of the circuit include a rectifier, a capacitor, and a voltage regulator, but no battery. I like the idea of using a battery so that energy can be stored and perhaps one person can generate enough energy to charge two or three cell phones.
http://www.instructables.com/id/How-To-Build-A-Bicycle-Generator/ http://makezine.com/projects/generator-bicycle/ http://makezine.com/projects/pedal-power-phone-charger/ My Friday afternoon was a learning adventure. First, I took my hand-me-down generator to Tom Sawyer Bicycle Shop to see if they had any advice about how to open it up to see the inner workings. The casing appeared to be in one piece. The owner of the shop was able to gently pry the plastic top off the generator to reveal that it was arranged oppositely to my first generator; this generator has fixed coils and a rotating permanent magnet in the center.
After looking at other bicycle-powered charger circuits online, I thought I might need a rectifier, a capacitor, and a voltage regulator. I decided to shop for/learn more about these devices. I started at Locke Electrical Supply since it is in my neighborhood. I went in an explained my project but they did not have any of the components I was looking for. They sent me to B & B Electric Motor Company. The guys at B & B were very friendly and helpful (and happened to be Friends University alumni). They were intrigued by my project and asked if my generator had AC or DC output. I assumed it was AC (if it even worked), but they offered to test it for me. They attached an electric drill to the generator shaft and used a digital multimeter to measure the current. It was AC and we were able to easily produce 6 to 7 volts. This was good news. A cell phone charger requires roughly 3-6 watts of power. Using the equation VI = P, 6 volts x 2 amps = 12 watts which would be more than enough to charge a single cell phone. The guys at B & B thought that the wire could easily handle 2 amps for several years of use. We also talked about the other parts of the circuit. The guys advised me that I would not need a capacitor to smooth out the pulses if I intend to charge a battery, rather than running directly to a cell phone charger. The alternator dilemma: my new friends at B & B asked if I had considered using an alternator for PedGen. I said that I had considered it, but was leaning towards using the bicycle generator. One of my concerns is the weight of an alternator. I asked if they knew how much one weighs and they estimated it to be about 30-40 pounds.If I were to pack that in a suitcase, that would take up the majority of the weight allowance. I left B & B and purchased my first digital multimeter! Other thoughts for the day: Would the pedal mechanism from a paddle boat be a better arrangement? A car battery will be a problem to transport or find on LaGonave. My husband pointed out that motorcycles are widely used as taxis on the island, so we could probably purchase a motorcycle battery when we arrive. |
AuthorCatherine Johnson is a student in the Masters of Science in Environmental Studies program at Friends University in Wichita, Kansas. Archives
July 2014
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