Projects
Electrical EWB
ewb.maharashtra@gmail.com
Meetings:
Thursdays @ 7pm in Everitt Lab 50 (West end of basement)
Introduction:
At EEWB (Electrical Engineers Without Borders) we are driven by a simple idea: use the latest integrated circuit technology to develop cheap and efficient solutions to electrical engineering problems in developing countries. The idea for such a group initially came out of EWB (Engineers Without Borders) projects, in which members needed help with their circuits. It seemed terribly inefficient to have a few electrical engineers working in each EWB project considering there was a large degree of overlap on some of these efforts. Our membership is also driven out of a desire to apply what we have learned in the classroom to real-world problems. It was with this passion that we formed EEWB with the hope of modularizing the task of circuit design in EWB, with the expectation that we would learn a thing or two about building prototypes that could eventually be applied on a broader scale.
Needs:
EEWB is primarily composed of EE's but we also do a fair amount of ME and CS. If you are interested in what we are doing feel free to shoot us an email.
History:
The true beginning of EEWB was before Fall 2009 when we started calling it EEWB, with our first initiative -- the Maharashtra project. The Maharashtra project was a collaborative EWB project that helped a village in the Maharashtra province of India successfully transform their off-grid power system. Unlike most other EWB projects, we didn't go abroad. Instead, we communicated with people on the ground in India about their needs and helped them develop solutions. The village was primarily powered by solar panels and a wind turbine, which charged 12V batteries (car batteries) for use in individual homes at night. Our group designed efficient AC (from the turbine) to DC and DC (solar panel and turbine) to DC (step down and stabilize to 12V) power conversion circuits. Our primary contact in India, Michael, was somewhat experienced with circuit design and had plenty of spare parts available. He was a tremendous resource who reconstructed and tested our designs in the field.
A secondary need of the village was for some sort of battery over-discharge protection. If you discharge a rechargeable battery beyond a certain point (below a certain voltage), it becomes permanently discharged. We designed a simple circuit that would shut off the battery (with an open circuit) when the battery voltage fell below a certain set point. The optimal voltage changes with ambient temperature and usage so we made it adjustable with a potentiometer. For added durability, we also made them enclosed in a waterproof housing and mailed the village some prototypes. Shortly thereafter we received some feedback that the battery protectors were working great but that they'd like some warning that the battery was about to shut off. To accommodate the request, the EEWB team added a flashing red LED warning light.
Shortly after the Maharashtra project, we were connected with the Arial Home Foundation, a non-profit organization that seeks to "offer a low cost, panel manufacturing "factory-in-a-box" to any philanthropic or government organization in the world that is building schools, clinics, or homes for poor families." One of the specific goals of the Foundation was to equip Arial homes with the capability to have hot water even if the house could not be connected to a reliable energy grid. The most logical direction was solar, as on average, the sun emits 100mW/cm2 of free and sustainable energy on a daily basis. You just need to use that energy to heat up water, store it in an insulting tank for when the sun goes down or clouds show up, and you have yourself off-grid hot water. The Arial Home Initiative recognized that a solar water heating system would be ideal, but commercial systems were far too expensive for the Arial Homes in developing countries. So the Foundation designed an ingenious and cheap structure for capturing solar energy using a black water bladder that fits on the roof of the Arial Homes. They lacked expertise for the next step, however, which is where EEWB came into the picture. We designed the electronics for monitoring the various temperatures and running pumps to move the water from the ambient storage tank, to the roof, and then finally to the insulated hot water tank. With the task of staying confined to a limited budget, we used the open source Arduino microcontroller hardware that can be built with off-the-shelf components for about $20. The Arduino can be easily programmed with open source software in a language similar to C to monitor a number of analog or digital inputs and output digitally. In the software we designed, a state machine that cycled the system through pumping, waiting, draining, etc. states. Pumps and valves could be controlled via the digital outputs from the Arduino while temperatures were monitored via the analog inputs with temperature ICs or thermocouples (for higher temp applications).
Ongoing Projects:
Water level sensor: One concern with the system was that the water supply could get low or that the hot water tank could become full. The system needed to know what the water levels were in the storage tanks. As such, we designed a water-level sensor for this application and identified a pressure-based approach. We used a Freescale manufactured integrated circuit, which outputs a voltage proportional to pressure difference (over a chosen range) and since gauge pressure is proportional to depth, the IC outputs a voltage that's proportional to depth when comparing the ambient pressure to the gauge pressure. So we built a simple device out of PVC pipe that was tapped at the end cap for connecting to the pressure sensor while the interior of the pipe was exposed to the surface air pressure. The Ardunio just needs to monitor an additional voltage for each tank to know their respective water levels.
Water Meter: With the success of Arial Home's initiatives in Mexico, Palestine and other locations, they have envisioned and begun work on a larger scale Arial Home community. The land has been purchased for a 300-home community (around 1,500 people) 16 miles northeast of Ensenada, Mexico. In this dry region, water is a major usage concern, as is the cost of building, monitoring and maintaining a water distribution system. The community would like to buy their water in "bulk" from the utility company then store and distribute it from a central location. Because of EEWB's successful work on the previous project, we were engaged to develop a method for monitoring water usage electronically, which could be reported to a central server for billing and maintenance purposes. You can buy water meters today that will do this but they run in the ballpark of $100 and are prone to mechanical failure of the moving parts. The current worldwide infrastructure also requires a "meter man" to come out and physically read the water meter each month or two, which is a gross inefficiency that developing countries cannot afford. We relied on Bernoulli's fluid dynamics principles in combination with advanced pressure differential integrated circuits to design and optimize a $10 water meter (not including the Arduino). The meter produces a voltage that is quadratic in the flow speed of water through a PVC pipe by measuring the pressure difference between incoming and outgoing flow. With our simple design it takes a single person about 30 minutes to build a meter and another 30 minutes for testing and calibration. We then use an Arduino (it can be the same Arduino used for the solar water heating system) to convert the flow rate to a total volume of water consumed. The next step is then to develop a method of reporting this information to a central server either wirelessly or otherwise, thus eliminating the "meter man" from the cost equation. One unique advantage of our meters is that they can provide real-time monitoring of the water consumption and distribution infrastructure, allowing for rapid identification of leaks for optimal consumption of a very limited resource.
Reporting: We are working towards having all of the information recorded in an Arial Home be sent wirelessly back to a central server for optimal resource allocation. This project is in the very preliminary stage and we are still considering many options.
New Projects: We are always seeking new projects and in particular, EWB projects. If any EWB projects need help with cricuit design please contact us!