Flashlight Re-design Proposal
Flashlight Re-design Proposal Group name: Luz do Sol, Inc. Group Members: Amaris Rodriguez, Andrew Hollern, John, Fortunato, Karin Conte, and Diego Alves Guterres Palma Energy Conversion II October 14, 2014
I.
Introduction Routinely we live in contact with the most significant source of energy for our planet, and we almost never consider its importance as a solution to our problems of energy supply, without polluting or threatening our social and environmental means. Solar energy is the ideal alternative source, especially for some basic characteristics: it is abundant, permanent, renewable every day, does not pollute or harm the ecosystem and it is free. Consequently, the use of solar power increases considerably. Recent data already show that the cost of renewable energy source should be halved by 2018, which could make it even more accessible.7 Currently, there are a lot of different uses of solar power: planes, cars and more simple things like lifts, telephone booths, wheelchairs, calculators, toothbrushes or a flashlight, for example, which is the focus of this project. The project focused on the designing and constructing of a Li-ion rechargeable flashlight. Lithium ion batteries are a type of rechargeable batteries widely used in portable electronics, for the flashlight UltraFire 3.7V, 4000 mAh lithium ion batteries will be used. This type of battery has an energy density that is twice as much a nickel metal hydride battery (or NiMH) and three times more dense than a nickel-cadmium battery (or NiCd). Another difference of the lithium ion battery is the absence of memory effect (not addictive), and no need to charge the battery up to full capacity and discharge the battery fully, unlike NiCd battery. It tends to be much lighter than other types of rechargeable batteries of the same size. The electrodes of a lithium-ion battery are made of lightweight lithium and carbon. Furthermore, lithium is also a highly reactive element, meaning that you can store enough energy in its atomic bonds. Which means that will have a very high energy density for these batteries. A lithium-ion battery can store 150 watt-hours of electricity in 1 kg of battery. A battery pack of NiMH (nickel metal hydride) can hold at most 100 watt-hours per kilogram, although 60-70 watt-hours is most. A lead-acid battery has the capacity to store only 25 watt-hours per kilogram. Using lead-acid technology, it takes 6 kilograms to store the same amount of energy a lithium-ion battery 1 kg. This battery hold, their charge: a set of lithiumion batteries lose only about 5% of their charge per month, while NiMH batteries lose 20% in the same period. Also, the lithium-ion batteries can withstand hundreds of charge / discharge. Lithium-ion battery has a life of about 400-500 cycles (between 400 and 500 full charges from 0% to 100%). Each time you let the battery die before recharging it, you are using it a whole cycle. It is most preferable to replenish earlier. Another good point: their substances are not toxic. However, the lithium ion battery has some considerable drawbacks, for example: it starts to degrade as soon as they leave the factory, lasting only two to three years from the date of manufacture whether you use them or not and this batteries are extremely sensitive to temperatures. The heat causes the lithium-ion batteries to degrade much faster than usual and there is a small chance that if a lithium-ion battery fails, it catches fire.8 Further objectives of the project was to find ways to make the flashlight cost effective, while keeping the design easily useable. The initial goal of the flashlight was to make a flashlight that would be easily deployed for use in developing countries. The original design of the flashlight was a flashlight built inside a flashlight. This flashlight was cost effective as it used many recyclables that were abundant and free. However, the downfall of this flashlight was that it would not be easily mass produced and could have some functionality issues, as the design made it very difficult to fix anything that went wrong inside the flashlight. In order to correct these issues, the soda can exterior was switched for PVC pipe, making the flashlight more durable, and a reducer and PVC cap were used for the ends of the flashlight, making the inside easily accessible. Another change that was made was the movement of the switch from the bottom of the flashlight to the side and vice versa for the charging port. This change simplified the wiring that would need to be done inside the flashlight and reduce the amount of wire needed, which is important
because the copper wire was one of the more expensive materials used. The last and arguably the most important change to the soda can design was changing the battery pack from the batteries being wrapped in electrical tape to the batteries being housed inside a PVC pipe that is a size smaller than the PVC used for the body of the flashlight. This change is so important because it made the battery pack fit tightly inside the body of the flashlight, which means a filler would not be needed. A filling the space between the body of the flashlight and the battery pack was one of the more time consuming parts of making the soda can flashlight. Time could have been reduced for this part however an expensive spray foam material would have been needed. Overall, the new flashlight design aims to be able to be more producible, more cost effective, and more functional.
II.
Materials a. Materials List and Cost List of materials Quantity
Price Per Unit($)
Price($)
12
0.10
1.20
Pipe 2 in × 8 in PVC/DWV Sch. 40 Plain-End Pipe9 Round Switch on/off10 Dc Power Jack 2.1mm Barre11
1 1
1.51 1.08
1.51 1.08
1
0.16
0.16
Charlotte Pipe 2 In. PVC Sch. 40 Socket Cap12 2 In. to 1.5 In. PVC Sch. 40 Reducer Coupling Awg 22 Wire 1ft (30cm)14
1 1
1.64 1.23
1.64 1.23
10
0.10
1.00
1
9.20
9.20
1
0.06
0.06
Duct tape (2 yards) Solder Wire 0.3mm 10m 18
1
0.30
0.30
1
2.79
2.79
1 In. Schedule 40 PVC Coupling 19 Springs (Old Pens)
1
0.48
0.48
6
0.00
0.00
Soda Can Aluminum Rubber Bands Cardboard (≈ 4in × 4in)
1 4 1
0.00
0.00
Description Led 10mm White2
3.7V 4000mAh Rechargeable Lithium Li-Ion Battery × 4 15
Heavy-Strength Aluminum Foil, 1 ft2
16
0.00 Total Cost This table shows that the final cost per flashlight was calculated to be $29.06.
III.
0.00 $20.17
Methods Design of the rechargeable LED flashlight prioritized maximum efficiency and inexpensive costs. The base of the flashlight would be made out of 2 inch diameter PVC piping. This was decided over a soda can base because it was simpler to put together and less dangerous. Furthermore, a soda can base would have to be cut out by hand with the use of an exactor knife.
One slip could result in someone getting seriously injured. PVC piping only needs to be clamped down and cut out with the use of a hand saw, which is less tedious and significantly less dangerous. The flashlight had parameters of no larger than 8 inches, thus the total length of the base would be 8 inches. One side of the base would have a PVC reducer attached onto it with an exit hole of 1 ½ inches. This was decided to be used as the initial mount for the LED disk attachment, since it allowed for better concentration of the light. The inside of this reducer would then have an aluminum weighing tray as well as possibly aluminum foil to allow for maximum light reflected. The other end would have a 2 inch cap so that the inside of the flashlight could be accessible after the flashlight was built. Other features attached to the base of the flashlight would consist of a switch, a charging port, and the LED lights mounted onto a cardboard/aluminum surface. The inside of the flashlight would contain a battery pack and wiring done in parallel, all of which will be later described in detail. The development of a battery pack was a great priority within the design process. The battery back had to connect all of the batteries without having any loose wire. Having loose wire alone could result in low performance of the flashlight. The battery pack was decided to be constructed out of 3 UltraFire 3.7 V Lithium Ion batteries wrapped together with electrical tape. The batteries would then be placed in PVC piping with a 1¾ inch diameter and a length of 2 inches. A cardboard disk would then be cut out so that it would be able to fit inside the PVC piping. To avoid the cardboard being lit on fire, it would also be wrapped up with electrical tape and have aluminum foil wrapped around it. This disk would serve as the connection between the batteries and the wires on the positive side. The other side would have another disk cut out with the same dimensions and also wrapped with electrical tape. This disk however would have small metal springs from pens/pencils twirled through it along where the negative sides of the batteries would touch. Aluminum foil would then be wrapped around the entire disk. This would serve as the connection between the batteries on the negative side. The inside of the battery would then packed with some kind of flame resistant material. The battery pack itself would then be adhered near the cap side of the base. Parallel wiring was decided for the flashlight, due to producing equal current throughout each LED. A series wired configuration would give far too many amps on the first LED, resulting in the LED being burnt out and no electrical current in the system. A total amount of 12 LED would be used for the 3 battery voltage output. The arrangement of the wiring would be connected as shown by Figure 1. This configuration was calculated to maximize the runtime as well as supply the same voltage to each LED, without burning them out. Each LED was found to have 15 Ω resistance for a total of 180 Ω resistance by using Ohm’s Law. With this calculation a resistor was not necessary in the circuit, which saves time and money. A switch would then be installed into the side of the flashlight by drilling a hole, dependent on the diameter of the switch. The charging port would be inserted on the bottom of the base and would be fitted by the same procedure. A disk made from an aluminum can would then be cut out to match the exit hole on the reducer with the use of scissors. This piece would then be drilled with a 1/8 th drill bit 12 times in equal-distant locations. The LED`s would then be put through these holes and attached with hot glue from the side back side. This LED mounted piece would then be hot glued onto the PVC reducer. Now that everything would be set up to their desired location, wiring from the battery pack will be soldered onto each piece as shown by Figure 2(Located in the Design Diagrams Section).
Testing will then begin on the performance of the flashlight. Areas of the flashlight being investigated will include how long it is able to last, how many lumens it produces, and how long it takes to charge the batteries. These results will be compared with the theoretically calculated values to show performance efficiency. The theoretical lumens was calculated by using the range of mcd given on the manufacturer’s website per LED and multiplying that number by the number of LEDS. The total mcd was converted to lumens by multiplying by the steradian, shown in part c of the Calculations section. The amount of lumens being produced and how long it last will be accomplished with the use of the Pasco 850 interface and the light sensor. Parameters such as how much light the flashlight gives off at varying distances and data of the amount of lumens over time will also be examined. The time it takes for the flashlight to stop producing light at a full battery charge will be accomplished by having the flashlight shining on the light sensor for at least 50 hours, maximum theoretical run time, and have the software record measurements at 30 min. intervals. Overall, measurements of the flashlight will determine the success of the building process, quality of the materials, and commitment of the team.
IV.
Calculations a. Theoretical Run Time (Battery Specifications) Battery Specifications: 3.7V and 4000 mAh 1 LED Specifications: current = 20 mA 2 𝑚𝐴ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 = 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑛𝑒𝑒𝑑𝑒𝑑 𝑓𝑜𝑟 𝐿𝐸𝐷𝑠
𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 =
4000 𝑚𝐴ℎ 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 20 𝑚𝐴 12 𝐿𝐸𝐷𝑠 × 𝐿𝐸𝐷
𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 =
12000 𝑚𝐴ℎ = 𝟓𝟎 𝒉𝒐𝒖𝒓𝒔 240 𝑚𝐴
3 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 ×
This calculation shows that our flashlight will be theoretically able to stay on for the duration of the competition. b. Theoretical Run Time (Actual Capacity of Batteries) Research shows that the actual capacity of each battery is approximately 2600 mAh instead of 4000 mAh.3 Modified Theoretical Run Time: 𝑚𝐴ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑛𝑒𝑒𝑑𝑒𝑑 𝑓𝑜𝑟 𝐿𝐸𝐷𝑠 2600 𝑚𝐴ℎ 3 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 × 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 = 20 𝑚𝐴 12 𝐿𝐸𝐷𝑠 × 𝐿𝐸𝐷 7800 𝑚𝐴ℎ 𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 = = 𝟑𝟐. 𝟓 𝒉𝒐𝒖𝒓𝒔 240 𝑚𝐴
𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 =
This calculation shows that our flashlight will not be able to stay on for the duration of the competition (44 hours). In order to ensure, the flashlight will be able to stay on for the whole competition another battery might be added or a few LEDs might be removed.
c. Theoretical Luminous Intensity of the Flashlight LED Specifications: Luminous Intensity per bulb = 14,000 to 16,000 mcd 2 𝑙𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝐹𝑙𝑎𝑠ℎ𝑙𝑖𝑔ℎ𝑡 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = # 𝑜𝑓 𝐿𝐸𝐷𝑠 × 𝐿𝐸𝐷 𝐹𝑙𝑎𝑠ℎ𝑙𝑖𝑔ℎ𝑡 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 12 𝐿𝐸𝐷𝑠 × 14,000 𝑚𝑐𝑑 = 168000 𝑚𝑐𝑑 = 168 𝑐𝑑 𝐹𝑙𝑎𝑠ℎ𝑙𝑖𝑔ℎ𝑡 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 12 𝐿𝐸𝐷𝑠 × 16,000 𝑚𝑐𝑑 = 192000 𝑚𝑐𝑑 = 192 𝑐𝑑 The theoretical luminous intensity for the flashlight is 168 cd to 192 cd. In order to convert cd to lux, the luminous intensity (cd) needs to be converted to luminous flux (lumens) cd = lumens/ steradian 4 steradians of a cone = 2𝜋(1 − 𝑐𝑜𝑠𝜃) 5 Beam angle = 30° 2 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑓𝑙𝑢𝑥 = 𝑙𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 × 𝑠𝑡𝑒𝑟𝑎𝑑𝑖𝑎𝑛 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑓𝑙𝑢𝑥 = 14 𝑐𝑑 × 2𝜋(1 − 𝑐𝑜𝑠30) Luminous flux = 11.8 lumens If the area the light covers is assumed to be 1 m2. The flashlight produces approximately 11.8 lux. d. Calculating the size of the resistor needed 3.4V Led bulb The batteries are 3.7V ILed= 20 mA Using Ohm’s Law: 𝑉 = 𝐼𝑅 𝑉𝑏𝑎𝑡𝑡𝑒𝑟𝑦 − 𝑉𝐿𝑒𝑑 = (𝐼𝐿𝑒𝑑) 𝑅 3.7 𝑉 − 3.4 𝑉 = (20 × 10−3 𝐴)𝑅 𝑅 = 15Ω
V.
Design Diagrams a. Figure 1: 3D Diagram of the Flashlight
b. Dimensions Table 1: Summary of the Dimensions of the Proposed Flashlight Design
Dimension Length of flashlight Diameter of body of the flashlight Length of reducer ( used to contain the led array) Length of the pvc cap Length of battery pack casing (pvc) Diameter of battery pack pvc
Measurement (in) 8 2 1.75 2 2 1.75
c. Figure 2: Wiring Diagram
VI.
Conclusions a. Next step The flashlight design, proposed in this report, will be built. Some changes to the dimensions of the flashlight might be changed in order to simplify the building process. Some LED’s may be removed from the LED array depending on whether or not the LED’s will have enough room to be completely upright. It is important for the LED’s to be upright because it maximizes the light output. After the flashlight is built, it will be tested for its functionality through experimentally determining its runtime and light output over time. This testing will be completed after the flashlight is built. Next, the solar charging system will be made for the flashlight. The desired output for the solar charger is 3.7V.6 Therefore, the amount of solar cells need to output that voltage would be used to make the charging system. The solar cells will then be placed on a protective backing that would be light and easily stored. The optimal size for the charger would be a charge that is not bigger than the size of an average person’s hands and a charger that would be easily transported, for instance in a pocket or backpack. The solar charger will be used by having a wire from the charger to the charging jack on the bottom of the flashlight in order to charge the flashlight without having to remove the battery pack. Lastly, the entire system will be tested for its ability to charge the flashlight, the flashlight’s runtime and the amount of light the flashlight produces. VII. References 1. UltraFire Shop; http://www.ultrafireshop.net/UltraFire_Shop.php?category=4&view=productListPage 2. LEDs; http://www.taydaelectronics.com/led-10mm-white-water-clear-ultrabright.html?gclid=CJTP8qvP5bwCFVFo7Aod8gQAlQ 3. UltraFire Batteries Actual Capacity; http://www.dx.com/p/ultrafire-protected18650-3-7v-4000mah-rechargeable-li-ion-batteries-pair-91889#.VDxASfl4pgl 4. Candela; http://en.wikipedia.org/wiki/Candela
5. Steradian; http://en.wikipedia.org/wiki/Steradian 6. CandlePowerForums; http://www.candlepowerforums.com/vb/showthread.php?292082-3-0-3-6-37V-batteries-and-how-to-charge-them 7. Solar Technologies;
http://www.ecodesenvolvimento.org/posts/2013/julho/tecnologias-movidas-aenergia-solar-que-voce-nem#ixzz3G517ZRMt 8. Lithium Ion Batteries;
http://tecnologia.hsw.uol.com.br/baterias-ion-litium.htm 9. 2 in dia. PVC pipe; http://www.homedepot.com/p/Charlotte-Pipe-2-in-x-2-ft-PVC-DWVSch-40-Plain-End-Pipe-PVC-07200-0200/100585960?N=5yc1vZbuxy
10. Switch; http://www.amazon.com/Automotive-Round-Rocker-SwitchBlack/dp/B001TQMU3O/ref=sr_1_4?s=electronics&ie=UTF8&qid=1413253214&sr=14&keywords=switch+round 11. DC Jack; http://www.taydaelectronics.com/dc-power-jack-2-1mm-enclosed-frame-withswitch.html
12. Socket Cap; www.homedepot.com 13. 2 in Coupling; http://www.homedepot.com/p/DURA-2-in-Schedule-40-PVC-CouplingC429-010/100343722
14. Wire; http://www.taydaelectronics.com/awg-22-blue-hook-up-wire-1ft-30cm-solid.html 15. Batteries; http://www.amazon.com/Neewer%C2%AE-2400mAh-Rechargeable-Lithium-
16. 17. 18.
19.
Battery/dp/B006OFG08G/ref=sr_1_2?s=electronics&ie=UTF8&qid=1413253987&sr=12&keywords=rechargable+battery+pack+3.7 Aluminum Foil; http://www.walmart.com/ip/Reynolds-Wrap-Heavy-Strength-AluminumFoil-50-sq-ft/11027097 Electrical Tape; http://www.walmart.com/ip/3M-16720-Electrical-Tape-3-4-X-66ft/39193892 Solder; http://www.amazon.com/Umiwe-Solder-Soldering-AccessoryPeeler/dp/B00HFQF552/ref=sr_1_2?s=hi&ie=UTF8&qid=1413254482&sr=12&keywords=solder+wire 1 in Coupling; http://www.homedepot.com/p/DURA-1-in-Schedule-40-PVC-CouplingC429-010/100343722
I.
Introduction Routinely we live in contact with the most significant source of energy for our planet, and we almost never consider its importance as a solution to our problems of energy supply, without polluting or threatening our social and environmental means. Solar energy is the ideal alternative source, especially for some basic characteristics: it is abundant, permanent, renewable every day, does not pollute or harm the ecosystem and it is free. Consequently, the use of solar power increases considerably. Recent data already show that the cost of renewable energy source should be halved by 2018, which could make it even more accessible.7 Currently, there are a lot of different uses of solar power: planes, cars and more simple things like lifts, telephone booths, wheelchairs, calculators, toothbrushes or a flashlight, for example, which is the focus of this project. The project focused on the designing and constructing of a Li-ion rechargeable flashlight. Lithium ion batteries are a type of rechargeable batteries widely used in portable electronics, for the flashlight UltraFire 3.7V, 4000 mAh lithium ion batteries will be used. This type of battery has an energy density that is twice as much a nickel metal hydride battery (or NiMH) and three times more dense than a nickel-cadmium battery (or NiCd). Another difference of the lithium ion battery is the absence of memory effect (not addictive), and no need to charge the battery up to full capacity and discharge the battery fully, unlike NiCd battery. It tends to be much lighter than other types of rechargeable batteries of the same size. The electrodes of a lithium-ion battery are made of lightweight lithium and carbon. Furthermore, lithium is also a highly reactive element, meaning that you can store enough energy in its atomic bonds. Which means that will have a very high energy density for these batteries. A lithium-ion battery can store 150 watt-hours of electricity in 1 kg of battery. A battery pack of NiMH (nickel metal hydride) can hold at most 100 watt-hours per kilogram, although 60-70 watt-hours is most. A lead-acid battery has the capacity to store only 25 watt-hours per kilogram. Using lead-acid technology, it takes 6 kilograms to store the same amount of energy a lithium-ion battery 1 kg. This battery hold, their charge: a set of lithiumion batteries lose only about 5% of their charge per month, while NiMH batteries lose 20% in the same period. Also, the lithium-ion batteries can withstand hundreds of charge / discharge. Lithium-ion battery has a life of about 400-500 cycles (between 400 and 500 full charges from 0% to 100%). Each time you let the battery die before recharging it, you are using it a whole cycle. It is most preferable to replenish earlier. Another good point: their substances are not toxic. However, the lithium ion battery has some considerable drawbacks, for example: it starts to degrade as soon as they leave the factory, lasting only two to three years from the date of manufacture whether you use them or not and this batteries are extremely sensitive to temperatures. The heat causes the lithium-ion batteries to degrade much faster than usual and there is a small chance that if a lithium-ion battery fails, it catches fire.8 Further objectives of the project was to find ways to make the flashlight cost effective, while keeping the design easily useable. The initial goal of the flashlight was to make a flashlight that would be easily deployed for use in developing countries. The original design of the flashlight was a flashlight built inside a flashlight. This flashlight was cost effective as it used many recyclables that were abundant and free. However, the downfall of this flashlight was that it would not be easily mass produced and could have some functionality issues, as the design made it very difficult to fix anything that went wrong inside the flashlight. In order to correct these issues, the soda can exterior was switched for PVC pipe, making the flashlight more durable, and a reducer and PVC cap were used for the ends of the flashlight, making the inside easily accessible. Another change that was made was the movement of the switch from the bottom of the flashlight to the side and vice versa for the charging port. This change simplified the wiring that would need to be done inside the flashlight and reduce the amount of wire needed, which is important
because the copper wire was one of the more expensive materials used. The last and arguably the most important change to the soda can design was changing the battery pack from the batteries being wrapped in electrical tape to the batteries being housed inside a PVC pipe that is a size smaller than the PVC used for the body of the flashlight. This change is so important because it made the battery pack fit tightly inside the body of the flashlight, which means a filler would not be needed. A filling the space between the body of the flashlight and the battery pack was one of the more time consuming parts of making the soda can flashlight. Time could have been reduced for this part however an expensive spray foam material would have been needed. Overall, the new flashlight design aims to be able to be more producible, more cost effective, and more functional.
II.
Materials a. Materials List and Cost List of materials Quantity
Price Per Unit($)
Price($)
12
0.10
1.20
Pipe 2 in × 8 in PVC/DWV Sch. 40 Plain-End Pipe9 Round Switch on/off10 Dc Power Jack 2.1mm Barre11
1 1
1.51 1.08
1.51 1.08
1
0.16
0.16
Charlotte Pipe 2 In. PVC Sch. 40 Socket Cap12 2 In. to 1.5 In. PVC Sch. 40 Reducer Coupling Awg 22 Wire 1ft (30cm)14
1 1
1.64 1.23
1.64 1.23
10
0.10
1.00
1
9.20
9.20
1
0.06
0.06
Duct tape (2 yards) Solder Wire 0.3mm 10m 18
1
0.30
0.30
1
2.79
2.79
1 In. Schedule 40 PVC Coupling 19 Springs (Old Pens)
1
0.48
0.48
6
0.00
0.00
Soda Can Aluminum Rubber Bands Cardboard (≈ 4in × 4in)
1 4 1
0.00
0.00
Description Led 10mm White2
3.7V 4000mAh Rechargeable Lithium Li-Ion Battery × 4 15
Heavy-Strength Aluminum Foil, 1 ft2
16
0.00 Total Cost This table shows that the final cost per flashlight was calculated to be $29.06.
III.
0.00 $20.17
Methods Design of the rechargeable LED flashlight prioritized maximum efficiency and inexpensive costs. The base of the flashlight would be made out of 2 inch diameter PVC piping. This was decided over a soda can base because it was simpler to put together and less dangerous. Furthermore, a soda can base would have to be cut out by hand with the use of an exactor knife.
One slip could result in someone getting seriously injured. PVC piping only needs to be clamped down and cut out with the use of a hand saw, which is less tedious and significantly less dangerous. The flashlight had parameters of no larger than 8 inches, thus the total length of the base would be 8 inches. One side of the base would have a PVC reducer attached onto it with an exit hole of 1 ½ inches. This was decided to be used as the initial mount for the LED disk attachment, since it allowed for better concentration of the light. The inside of this reducer would then have an aluminum weighing tray as well as possibly aluminum foil to allow for maximum light reflected. The other end would have a 2 inch cap so that the inside of the flashlight could be accessible after the flashlight was built. Other features attached to the base of the flashlight would consist of a switch, a charging port, and the LED lights mounted onto a cardboard/aluminum surface. The inside of the flashlight would contain a battery pack and wiring done in parallel, all of which will be later described in detail. The development of a battery pack was a great priority within the design process. The battery back had to connect all of the batteries without having any loose wire. Having loose wire alone could result in low performance of the flashlight. The battery pack was decided to be constructed out of 3 UltraFire 3.7 V Lithium Ion batteries wrapped together with electrical tape. The batteries would then be placed in PVC piping with a 1¾ inch diameter and a length of 2 inches. A cardboard disk would then be cut out so that it would be able to fit inside the PVC piping. To avoid the cardboard being lit on fire, it would also be wrapped up with electrical tape and have aluminum foil wrapped around it. This disk would serve as the connection between the batteries and the wires on the positive side. The other side would have another disk cut out with the same dimensions and also wrapped with electrical tape. This disk however would have small metal springs from pens/pencils twirled through it along where the negative sides of the batteries would touch. Aluminum foil would then be wrapped around the entire disk. This would serve as the connection between the batteries on the negative side. The inside of the battery would then packed with some kind of flame resistant material. The battery pack itself would then be adhered near the cap side of the base. Parallel wiring was decided for the flashlight, due to producing equal current throughout each LED. A series wired configuration would give far too many amps on the first LED, resulting in the LED being burnt out and no electrical current in the system. A total amount of 12 LED would be used for the 3 battery voltage output. The arrangement of the wiring would be connected as shown by Figure 1. This configuration was calculated to maximize the runtime as well as supply the same voltage to each LED, without burning them out. Each LED was found to have 15 Ω resistance for a total of 180 Ω resistance by using Ohm’s Law. With this calculation a resistor was not necessary in the circuit, which saves time and money. A switch would then be installed into the side of the flashlight by drilling a hole, dependent on the diameter of the switch. The charging port would be inserted on the bottom of the base and would be fitted by the same procedure. A disk made from an aluminum can would then be cut out to match the exit hole on the reducer with the use of scissors. This piece would then be drilled with a 1/8 th drill bit 12 times in equal-distant locations. The LED`s would then be put through these holes and attached with hot glue from the side back side. This LED mounted piece would then be hot glued onto the PVC reducer. Now that everything would be set up to their desired location, wiring from the battery pack will be soldered onto each piece as shown by Figure 2(Located in the Design Diagrams Section).
Testing will then begin on the performance of the flashlight. Areas of the flashlight being investigated will include how long it is able to last, how many lumens it produces, and how long it takes to charge the batteries. These results will be compared with the theoretically calculated values to show performance efficiency. The theoretical lumens was calculated by using the range of mcd given on the manufacturer’s website per LED and multiplying that number by the number of LEDS. The total mcd was converted to lumens by multiplying by the steradian, shown in part c of the Calculations section. The amount of lumens being produced and how long it last will be accomplished with the use of the Pasco 850 interface and the light sensor. Parameters such as how much light the flashlight gives off at varying distances and data of the amount of lumens over time will also be examined. The time it takes for the flashlight to stop producing light at a full battery charge will be accomplished by having the flashlight shining on the light sensor for at least 50 hours, maximum theoretical run time, and have the software record measurements at 30 min. intervals. Overall, measurements of the flashlight will determine the success of the building process, quality of the materials, and commitment of the team.
IV.
Calculations a. Theoretical Run Time (Battery Specifications) Battery Specifications: 3.7V and 4000 mAh 1 LED Specifications: current = 20 mA 2 𝑚𝐴ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 = 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑛𝑒𝑒𝑑𝑒𝑑 𝑓𝑜𝑟 𝐿𝐸𝐷𝑠
𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 =
4000 𝑚𝐴ℎ 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 20 𝑚𝐴 12 𝐿𝐸𝐷𝑠 × 𝐿𝐸𝐷
𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 =
12000 𝑚𝐴ℎ = 𝟓𝟎 𝒉𝒐𝒖𝒓𝒔 240 𝑚𝐴
3 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 ×
This calculation shows that our flashlight will be theoretically able to stay on for the duration of the competition. b. Theoretical Run Time (Actual Capacity of Batteries) Research shows that the actual capacity of each battery is approximately 2600 mAh instead of 4000 mAh.3 Modified Theoretical Run Time: 𝑚𝐴ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑛𝑒𝑒𝑑𝑒𝑑 𝑓𝑜𝑟 𝐿𝐸𝐷𝑠 2600 𝑚𝐴ℎ 3 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 × 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 = 20 𝑚𝐴 12 𝐿𝐸𝐷𝑠 × 𝐿𝐸𝐷 7800 𝑚𝐴ℎ 𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 = = 𝟑𝟐. 𝟓 𝒉𝒐𝒖𝒓𝒔 240 𝑚𝐴
𝑅𝑢𝑛 𝑡𝑖𝑚𝑒 =
This calculation shows that our flashlight will not be able to stay on for the duration of the competition (44 hours). In order to ensure, the flashlight will be able to stay on for the whole competition another battery might be added or a few LEDs might be removed.
c. Theoretical Luminous Intensity of the Flashlight LED Specifications: Luminous Intensity per bulb = 14,000 to 16,000 mcd 2 𝑙𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 𝐹𝑙𝑎𝑠ℎ𝑙𝑖𝑔ℎ𝑡 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = # 𝑜𝑓 𝐿𝐸𝐷𝑠 × 𝐿𝐸𝐷 𝐹𝑙𝑎𝑠ℎ𝑙𝑖𝑔ℎ𝑡 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 12 𝐿𝐸𝐷𝑠 × 14,000 𝑚𝑐𝑑 = 168000 𝑚𝑐𝑑 = 168 𝑐𝑑 𝐹𝑙𝑎𝑠ℎ𝑙𝑖𝑔ℎ𝑡 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 12 𝐿𝐸𝐷𝑠 × 16,000 𝑚𝑐𝑑 = 192000 𝑚𝑐𝑑 = 192 𝑐𝑑 The theoretical luminous intensity for the flashlight is 168 cd to 192 cd. In order to convert cd to lux, the luminous intensity (cd) needs to be converted to luminous flux (lumens) cd = lumens/ steradian 4 steradians of a cone = 2𝜋(1 − 𝑐𝑜𝑠𝜃) 5 Beam angle = 30° 2 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑓𝑙𝑢𝑥 = 𝑙𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 × 𝑠𝑡𝑒𝑟𝑎𝑑𝑖𝑎𝑛 𝐿𝑢𝑚𝑖𝑛𝑜𝑢𝑠 𝑓𝑙𝑢𝑥 = 14 𝑐𝑑 × 2𝜋(1 − 𝑐𝑜𝑠30) Luminous flux = 11.8 lumens If the area the light covers is assumed to be 1 m2. The flashlight produces approximately 11.8 lux. d. Calculating the size of the resistor needed 3.4V Led bulb The batteries are 3.7V ILed= 20 mA Using Ohm’s Law: 𝑉 = 𝐼𝑅 𝑉𝑏𝑎𝑡𝑡𝑒𝑟𝑦 − 𝑉𝐿𝑒𝑑 = (𝐼𝐿𝑒𝑑) 𝑅 3.7 𝑉 − 3.4 𝑉 = (20 × 10−3 𝐴)𝑅 𝑅 = 15Ω
V.
Design Diagrams a. Figure 1: 3D Diagram of the Flashlight
b. Dimensions Table 1: Summary of the Dimensions of the Proposed Flashlight Design
Dimension Length of flashlight Diameter of body of the flashlight Length of reducer ( used to contain the led array) Length of the pvc cap Length of battery pack casing (pvc) Diameter of battery pack pvc
Measurement (in) 8 2 1.75 2 2 1.75
c. Figure 2: Wiring Diagram
VI.
Conclusions a. Next step The flashlight design, proposed in this report, will be built. Some changes to the dimensions of the flashlight might be changed in order to simplify the building process. Some LED’s may be removed from the LED array depending on whether or not the LED’s will have enough room to be completely upright. It is important for the LED’s to be upright because it maximizes the light output. After the flashlight is built, it will be tested for its functionality through experimentally determining its runtime and light output over time. This testing will be completed after the flashlight is built. Next, the solar charging system will be made for the flashlight. The desired output for the solar charger is 3.7V.6 Therefore, the amount of solar cells need to output that voltage would be used to make the charging system. The solar cells will then be placed on a protective backing that would be light and easily stored. The optimal size for the charger would be a charge that is not bigger than the size of an average person’s hands and a charger that would be easily transported, for instance in a pocket or backpack. The solar charger will be used by having a wire from the charger to the charging jack on the bottom of the flashlight in order to charge the flashlight without having to remove the battery pack. Lastly, the entire system will be tested for its ability to charge the flashlight, the flashlight’s runtime and the amount of light the flashlight produces. VII. References 1. UltraFire Shop; http://www.ultrafireshop.net/UltraFire_Shop.php?category=4&view=productListPage 2. LEDs; http://www.taydaelectronics.com/led-10mm-white-water-clear-ultrabright.html?gclid=CJTP8qvP5bwCFVFo7Aod8gQAlQ 3. UltraFire Batteries Actual Capacity; http://www.dx.com/p/ultrafire-protected18650-3-7v-4000mah-rechargeable-li-ion-batteries-pair-91889#.VDxASfl4pgl 4. Candela; http://en.wikipedia.org/wiki/Candela
5. Steradian; http://en.wikipedia.org/wiki/Steradian 6. CandlePowerForums; http://www.candlepowerforums.com/vb/showthread.php?292082-3-0-3-6-37V-batteries-and-how-to-charge-them 7. Solar Technologies;
http://www.ecodesenvolvimento.org/posts/2013/julho/tecnologias-movidas-aenergia-solar-que-voce-nem#ixzz3G517ZRMt 8. Lithium Ion Batteries;
http://tecnologia.hsw.uol.com.br/baterias-ion-litium.htm 9. 2 in dia. PVC pipe; http://www.homedepot.com/p/Charlotte-Pipe-2-in-x-2-ft-PVC-DWVSch-40-Plain-End-Pipe-PVC-07200-0200/100585960?N=5yc1vZbuxy
10. Switch; http://www.amazon.com/Automotive-Round-Rocker-SwitchBlack/dp/B001TQMU3O/ref=sr_1_4?s=electronics&ie=UTF8&qid=1413253214&sr=14&keywords=switch+round 11. DC Jack; http://www.taydaelectronics.com/dc-power-jack-2-1mm-enclosed-frame-withswitch.html
12. Socket Cap; www.homedepot.com 13. 2 in Coupling; http://www.homedepot.com/p/DURA-2-in-Schedule-40-PVC-CouplingC429-010/100343722
14. Wire; http://www.taydaelectronics.com/awg-22-blue-hook-up-wire-1ft-30cm-solid.html 15. Batteries; http://www.amazon.com/Neewer%C2%AE-2400mAh-Rechargeable-Lithium-
16. 17. 18.
19.
Battery/dp/B006OFG08G/ref=sr_1_2?s=electronics&ie=UTF8&qid=1413253987&sr=12&keywords=rechargable+battery+pack+3.7 Aluminum Foil; http://www.walmart.com/ip/Reynolds-Wrap-Heavy-Strength-AluminumFoil-50-sq-ft/11027097 Electrical Tape; http://www.walmart.com/ip/3M-16720-Electrical-Tape-3-4-X-66ft/39193892 Solder; http://www.amazon.com/Umiwe-Solder-Soldering-AccessoryPeeler/dp/B00HFQF552/ref=sr_1_2?s=hi&ie=UTF8&qid=1413254482&sr=12&keywords=solder+wire 1 in Coupling; http://www.homedepot.com/p/DURA-1-in-Schedule-40-PVC-CouplingC429-010/100343722
