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22nd ASEMEP National Technical Symposium ENERGY CONTRAPTION DESIGN USING PLAYGROUND SEESAW FOR LIGTHING LOAD APPLICATIONS John Ray B. Abad Merryll D. Capucao Lynette Dane C. Legaspi Department of Electrical, Electronics and Computer Engineering Mapua Institute of Technology, Muralla, Intramuros, Manila,,

ABSTRACT Energy contraption is widely used to produce electricity by transforming different kinds of energy into electrical. One of the sources of energy contraption is from everyday human activities. The playground is used everyday by children and produces motion which can be converted to electrical energy. This study is about conversion of motion by children playing seesaw and storing it to a battery for future use. Using pneumatic principle, the mechanical energy from the motion of the seesaw is converted using the pneumatic principles. With the utilization of the microcontroller, the energy collected will be stored in the battery and will stop the charging once the battery is full. The energy that is stored in the battery will supply mainly lighting loads.


People are in search of renewable sources of energy nowadays. With increasing demand and decreasing resources, many seek new ways of converting different forms of energy to electrical energy. Contraption is a way in which a strange machine or apparatus is invented for a particular purpose Energy contraption nowadays has many applications in small scale or large scale. With further studies, it may be used to create a major source of renewable energy. By harnessing human power from the children playing in the playground, energy contraption could be further applied specifically in seesaw, merry-go-round, and swing. The mechanical energy produced by children’s play can useful and harnessed resulting to significant energy storage. According to Pandian(2004), the stored energy can be converted to electricity for powering basic, low-power appliances such a lights, fans and the like [1]. The concept of this study is the creation of a prototype of a seesaw to generate power through pneumatics. This study aimed to: 1. Design a prototype


2. Test the speed of compression of air from the pneumatic cylinders. 3. Determine the charging and discharging time of the battery 4. Design a controller circuit for the state of change of the batteries. The study aimed to provide free lighting to playgrounds, parks and rural areas. Using the energy generated by seesaw, the energy from children’s play will be converted into usable energy. If this will be implemented to many parks and playground there will be great power savings. This will introduce a new source of renewable energy especially in this country. The scope of this study is the generation of DC power by means of mechanical motion by the use of pneumatic cylinder installed in the seesaw. It will produce a small amount of power due to limited motion of the seesaw that is intended to supply only small lighting loads, particularly LED’s(Light Emitting Diodes). The study focused on the usage of seesaw as the medium of the pneumatic cylinders and not in other playground equipment such a merry-gorounds and swings. Battery will be used as a storage device and the amplification of the energy stored will not be covered by the study. 2. 0 REVIEW OF RELATED LITERATURE

Pandian (2004) conducted a study about Human Power Conversion System based on children’s play. It proposed a new method for harnessing human power based on children’s play in playground and public places, and on devices such as seesaw, merry-go-round, and swing [1]. When large number of children play in playground, part of the power of their play can be usefully harnessed resulting to significant energy storage. This stored energy can then be converted to electricity for powering basic, low-power appliances such as lights, fans, communications equipment, and so on. The method provides a low-cost, low-resource means of generation of electricity, especially for use in developing countries. The paper discussed the basic theory

22nd ASEMEP National Technical Symposium behind the method. Results of experiments on a laboratory prototype compressed air human power conversion system using a teeter totter (seesaw) are presented to illustrate the practical effectiveness of the method proposed by Pandian. 2.1 Mechanical to Electrical Conversion Smit and Associates(2009) stated that most human-power energy harvesting systems are used to power abundantly deployed sensor networks and mobile electronics. These systems scavenge power from human activity of derive limited energy from ambient heat, light, or vibrations. In most of these conventional methods, users must focus their attention on power generation at the expense of other activities. However, for suitable electrical power generation, energy could be harvested from everyday activities such as walking, running or even dancing. In this paper, systems that use human power by walking of running analysed, where an alternative system has been designed and implemented to generate energy from people dancing in a club environment. Its uses shown that power from walking can be extracted using the ystem, i.e., maximum 80-100 W to an average of 20-30 W over a period of 10 seconds. This previous study is related to the present study because it showed that normal human activities can be used to generate electricity. In here, the previous researchers presented the amount of energy that can produced by a dance floor. Last 2008, a design student Daniel Sheridan has created a simple seesaw which generates enough electricity to light a classroom. The device works by transferring the power, created by a child moving up and down on it, an electricity storage unit via an underground cable. He has calculated that five to ten minutes use on seesaw could generate enough electricity enough to light a classroom for an evening, for example. Many schools in Africa open their doors in the evening to much older pupils but are only to light their classrooms with candles or kerosene lamps [2]. This article discussed the feasibility of generating useful energy from seesaw. It was used to power classrooms in the previous design, while the present researchers will use it to power lightings on playground. 2.2 Motor and Generator Engineers call electric motors and generators “electrical machines�. The reason for this more general term is the same device may operate either as a motor or as a generator. Electrical machines convert mechanical energy to electrical. When conversion is from electrical mechanical, the machine is called a motor. When it is being used to convert from mechanical energy to electrical, the machine is called a generator. The advantage offered by DC machines is their versatility. The ability to develop high starting and breaking torques, to make quick reversals of rotations, to maintain constant mechanical power output or to maintain constant torque and to permit continuous speed variation over a range


as large as 4:1, make DC motors better suited to many industrial applications [3]. This is related to the present study because the design will make use of motor and generator to produce electricity. The concept of converting energy through motor and generator is important in this study.

2.3 Pneumatic Cylinder Pneumatic Cylinders offer a straight rectilinear motion to mechanical elements. Cylinders are classified as light, medium, and heavy duty with respect to their application. Selection of materials for cylinder components may depend greatly on this factor. Functionally, cylinders may be single acting and double acting. The piston rod of cylinders is given special treatment as it is a highly stressed part. For cylinder lubrication, mist lubrication is most common. To generate rotary motion, air motors may also be used. Vane type motors are more popular. Air motors have certain specific advantages over electrical motors. Proper maintenance of cylinders, motors, and various air-operated hand tools enhance their life expectancy to a great extent. The pneumatic power is converted to straight line reciprocating motions by pneumatic cylinders. A single acting cylinder, the compressed air is fed only in one side. Hence, this cylinder can produce work only in one direction. The return movement of the piston is affected by a built-in spring or by application of an external force. The spring is designed to return the piston to its initial position with a sufficiently high speed [4].

Figure 1. Parts of a Single Acting Pneumatic Cylinder. (1) Cylinder(tube); (2) End Cover; (3) Piston; (4) Piston rod; (5) U-cap seal; (6) O-ring; (7) Bush; and (8) Spring The Pneumatic Cylinder will be used as the main component of collecting energy from the seesaw. A single acting cylinder will be connected to the seesaw for the compressed air.

2.4 Energy Storage A battery is a device that cab store energy in a chemical form and then convert into electrical energy when needed. There are two fundamental types of chemical storage

22nd ASEMEP National Technical Symposium batteries: The rechargeable or secondary cell, and the nonrechargeable, or primary cell. In term of storing energy or discharging electricity,, they are similar. Battery is comprised of at least one but possibly many such cells appropriately connected and these cells are where the actual action storage and discharge takes place. All electrochemical cells consist of two electrodes separated by some distance. The space between the electrodes is filled with an electrolyte which is an ionic liquid that conducts electricity. One electrode is the anode and it permits electrons to flow out of it. The other electrode is the cathode which receives the electrodes. The energy is stored in the particular compounds that make up the anode, cathode and the electrolyte such as zinc, copper, and SO4, respectively. Series and parallel connections of batteries are the options to increase the Ampere-Hour capacity or voltage and even both in accordance to what is needed. Ampere-Hours are normally used to indicate the amount of energy a storage battery can deliver [5]. Battery will serve as the storage device of the design. It will be the source of supply for the lighting loads. The connections of the battery, parallel or series may be considered to increase either the voltage of the Ampere-hour capacity of the storage device. 2.5 Microcontrollers A microcontroller is a single device which follows instructions, reads information, stores information communicates, measures time, and switches things on and off. It also does other things, depending on the model. If you are the type of person who likes to take thing apart you will find microcontroller in all kinds of places. The most common place is under the hood of almost any car produced since 1985. Consumer items include televisions, compact disc players, washing machines, telephones, and microwave oven. Office computers use microcontroller in addition to their man processor to control peripherals such as keyboards and printers. Automated manufacturing systems use microcontrollers in production equipment such as robots and conveyor lines [6]. This study made use of microcontroller to regulate the flow of voltage for battery storage. 2.6 Air Pressure Engine Air pressure engines are engines in air pressure are employed as motive force. From the extreme lightness and mobility of air, it has been frequently proposed to employ it as a medium for transmitting motion to machinery at a considerable distance from the prime mover. Among the first who attempted this is the celebrated Papin, who invented the steel-yard safety-valve. He employed a fall of water to compress the air in a cylinder, through the medium of an intervening piston and he connected this cylinder to another, at the mouth of a mine a mile distant, by means of a pipe of that length. In the second cylinder was another piston, the rod of which was intended to work a set of pump;


but, contrary to expectation, the compression of the air in the first cylinder produced no movement in the piston of the second. Papin subsequently attempted to bring his scheme into use in England, but did not succeed. Afterwards, however, he erected great machines in Auvergne and Westphalia for draining mines, but so far from being effective machines, they would not even begin to move. He attributed the failure to the quantity of air in the pipe, which must be condensed before it can condense the air in the remote cylinder he therefore diminished the size of this pipe, and made his water machine exhaust instead of condense, and had no doubt that the immense velocity with which air rushes into a void, would make a rapid and effectual communication of power. But the machine stood still as before. Near a century after this, an engineer at an ironfoundry in Wales erected a machine at a powerful fall of water, which worked a set of cylinder bellows, the blowtype of which was conducted to the distance of a mile and a half, where it was applied to a blast furnace; but notwithstanding every care to make the conducting pipe very air-tight, of great size, and as smooth as possible, it would hardly blow out a candle. The failure was ascribed to the impossibility of making the pipe air-tight, but above ten minutes elapsed after the action of the piston in the bellows, before the least wind could be perceived at the end of the pipe, whereas the engineer calculated that the interval would not exceed six seconds. The foregoing particulars are taken from Dr. Robinson’s Natural Philosophy, art [8]. Air pressure engines will be used to rotate the generator. Concepts behind the air pressure engines and how it works is important.

3.0 EXPERIMENTAL SECTION 3.1 Materials In creating the system, the following materials were used (refer to Figures 3 to 9) : Pneumatic Cylinder, check valve, hose, air tank, pressure gauges, FRL, air motor, DC generator, battery. According to Figure 2, for the whole system, the materials were connected together to form the seesaw.. Additional fittings were added for compatibility of the materials connected. Some of the parts of the system were brought second hand. The air tank was brought from a shop of unused tank of compressor. The tank does not have specification but, based on the measurement, the tank has a volume of 4.5 gallons. Another material that was bought second hand is the air motor; the motor was from unused car buffing tool. The generator was bought second hand. There are no available specifications, but it produces 12 V, however, through testing, the specification were determined. As this study went along, the design of the system was also modified. One of the modifications is the removal of the flywheel from the original design of the system. Though the implementation of the flywheel proves to prolong the

22nd ASEMEP National Technical Symposium rotation of the generator resulting to production of greater amount of electricity, it was not added anymore due to time constraint. This seesaw will be added to the solar panels as a back-up up for the charging system of the batteries. Referring to Figure 10,, the actual installation of the project is located at Hospicio de San Jose, Quiapo, Manila.

Figure 5. Air Pressure Tank

Figure 2. Proposed Layout of the Contraption

Figure 6. Air Pressure Gauge Figure 3. Pneumatic Cylinder ( CKD Air Cylinder CMAZ – 30’ x 32” – CA-RE)

Figure 4. Pneumatic Check Valve

Figure 7. Left : Air Motor(25,000 rpm max), Right : DC Generator(12 V, 0.8 A 750rpm)


22nd ASEMEP National Technical Symposium

3.2 Procedure One of the determining factors in this study is the rate at which children play. This is essential because the average amount children play the seesaw will affect the charging time and capacity of the battery. Number of children the seesaw is exposed to may also be considered but that will not be focused of the study. To be able to compute the time a battery charges is dependent on how many cycles an average play t the seesaw can be made in a given time. Based from Tables 1, 2 and 3, it can be observed that from 10 to 600 psi, the higher the pressure the higher the time and number of cycles it takes for the air pressure to increase by 5 psi. Also, if there are two pairs playing the seesaw, there are minimal difference in the number of cycles compare to the number of cycles if only one pair is playing. But there is a significant difference in the number of hours the tank can be filled. The researchers tested the number of cycles made playing the seesaw in slow, average and fast play.

Figure 8. Car Battery(12 V, 40 A-h, Motolite)

Rate of Filling the Tank Range(psi) Cycles Time(s) 1 pair 2 pairs 1 pair 2 pairs 0-5 psi 13 14 33 31 5-10 psi 8 9 11 20 10-15 psi 8 9 20 20 15-20 psi 10 8 25 17 20-25 psi 8 7 20 17 25-30 psi 12 11 28 22 30-35 psi 11 13 26 28 35-40 psi 13 12 31 24 40-45 psi 13 12 32 26 45-50 psi 13 17 32 34 50-55 psi 14 13 35 29 55-60 psi 16 10 37 20 Table 1. Rate of Filling the tank at 5-psi interval

Figure 9. Bearings and Fittings

Table 2. Computation of the number of cycles and rate of filling the tank for 60 psi Total Cycles 1 pair 139 2 pairs 135 Total Time(min) 1 pair 2 pairs

Figure 10. Actual Image of the Contraption


5.5 4.8

22nd ASEMEP National Technical Symposium The number of cycles it takes to fill the tank depends on the area of the cylinder. Also, the amount of air that enters the tanks depends mainly on the volume of air where the pneumatic cylinder travels. To prove the researcher claimed that: due to testing, the fitted pressure of air tank drives the air motor to produce 14.4 V to 15 is 60 psi.

constant. The pressure for this graph is at the tank side. Figure 14 shows the characteristics of current and pressure. As pressure rises, the current is held constant. The pressure for this graph is plotted also at the tank side. Figure 15 shows that at regulated output pressure (14 psi), the behaviour of voltage is constant. But the current shows an erratic behaviour due to the sudden decrease in pressure.

Table 3. Computation of mass of air in tank Tank Capacity Calculations 91.5785 0.08206 298 18.92706 4.08 60 25 5

tank size(US gal) mass of 1 mol of air=29 gm

3.157879 mol

Figure 11. Testing of voltage produced by the generator.



0 0

10 Time (s) 20


Figure 12 Pressure vs. Time

PSI vs. Voltage

100 PSI

The number of cycles it takes to fill the tank depends on the area of the cylinder. Also, the amount of air that enters the tanks depends mainly on the volume of air where the pneumatic cylinder travels. To prove the researcher claimed that: due to testing, the fitted pressure of air tank drives the air motor to produce 14.4 V to 15 is 60 psi. An excel program was used to determine the number of cycles for the tank to reach 60 psi. The result of 117 cycles is close to the actual cycles of 139 cycles. Figure 11 shows the testing of the voltage generated by the generator. Using this, the number of cycles can also be expressed mathematically by the given equation:

f =

PSI vs. Time

100 PSI

M(air)-gm R T(room)-K V(air)-L P(motor)-atm P(motor)-psi T(room)-C V(air)-US gal


mKTroom (equation 1) Penv vq


Where: f –number of cycles (frequency); K-pressure constant; Troom-room temperature; Penv-atmospheric pressure (1atm); V-volume per cycle; q-cylinder capacity










Figure 13. PSI vs. Voltage

PSI vs. Current

100 PSI

4.0 RESULTS AND DISCUSSION Figure 12 shows the relationship of pressure and time. The group conducted six trials, starting with 80 psi up to 30 psi. The higher the pressure, the longer the time will it take to drain the tank. Figure 13 shows the characteristics of voltage and pressure. As pressure rises, the voltage is held


50 0 0.4



Current (A)

Figure 14. PSI vs. Current

22nd ASEMEP National Technical Symposium


M. Smit “Abstract” Human-Powered Small-Scaled Generation System for a Sustainable Dance Club, 2010 pp. 439


McPherson and George, An introduction to Electrical Machines and Transformers, John Wiley and Sons, 1990.


S. R. Majumdar, “Pneumatic cylinders and air motors” in Pneumatics System Principles and Maintenance, McGraw-Hill, 1995


A. Ter-Gazarian, Energy Storage for Power Systems, Peter Peregrinus Ltd., 1994


Peter Spasov, What is a microcontroller? And what is it used for in Microcontroller Technology the 68HC11, NJ: Prentice Hall, 1993.

Voltage (V)

Voltage vs. Current at each PSI reading in tank 14.6 14.5 14.4 14.3 0.4

0.6 Current (A) Figure 15. Voltage vs. Current


5.0 CONCLUSION Based from the results the system, the seesaw energy contrapment system generates small but significant amount of electrical energy which can be stored to a battery and can be used for lighting loads. The addition of the seesaw in the solar panel is a good auxiliary source of power and can be implemented to compensate the power generation and the charging of the battery system. Further development of the system is highly recommended in order to increase the power generation efficiency. Pneumatics as energy converters can also be applied in various playground equipment such as seesaw, swing, and etc. Also, the charge controller is essential in regulating the energy collected from the system.

6.0 RECOMMENDATIONS Long air tubes are also losses in air pressure transmission leading to longer time to reach the prescribed pressure. Increasing the number of seesaw with the prescribed system can also improve the time for filling the tank, increasing the time of the rotation of the air motor, thus, longer time for the generator to produce power. If the said recommendations are considered for the system, higher power generation efficiency is expected.

7.0 ACKNOWLEDGMENT The authors would like to thank Department of EECE, Mapua Institute of Technology, Power Electronics Laboratory, Kraft Philippines through Ace Saatchi and Saatchi and the above creator for all of the blessings and guidance.


S.R. Pandian, " Abstract," A Human Power Conversion System Based on Children's Play, 2010 pp. 54


9.0 ABOUT THE AUTHORS John Ray Abad, Merryl D. Capucao and Lynette Dane C. Legaspi are all BS Electrical Engineering graduating students of Mapua Institute of Technology. They took up specialization courses on Power Systems Protection as part of their undergraduate curricula. All of them are now reviewing for the Registered Electrical Engineer (REE) Board Examination this coming April.

Michael C. Pacis is a Registered Electrical Engineer with a BS EE and Master of Engineering-Electrical Engineering (M.Eng’g-EE) Major in Power Systems degree from MAPỦA Institute of Technology. At present, he is taking up his PhD EE (Power Systems) at the University of the Philippines-Diliman. His research interest includes Power System Protection, Renewable Sources of Energy, Distributed Generation and Smart Grids. He is the adviser of the authors in this project. Jesus M. Martinez, Jr. is a graduate of Mapua Institute of Technology, Manila, Philippines, with a degree of Bachelor of Science in Electrical Engineering (1999) and Bachelor of Science in Electronics and Communications Engineering (2000). A Registered Electrical Engineer, he is a full-time faculty member of the School of Electrical, Electronics and Computer Engineering of the Mapua Institute of Technology. His field of interest includes Power Electronics, Control Systems and Signal Processing. He is also the adviser of the authors in this project.

22nd ASEMEP National Technical Symposium


Energy Contraption Design Using Playground Seesaw for Lighting Load Applications