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The resultant costs in the last row of Table 5 indicate that the final product will become extremely affordable when production exceeds 10000.  The closest comparable product on the market sells for almost $25 <ref name = "Barefoot"/>, so the costs of $12.95 / unit at 10000 produced, and $5.17 / unit at 100000 produced are very reasonable.  If mass production is undergone, and up to 100 000 are made, the final cost of $5.17 plus any additional profit margin markups will be much cheaper than the prototype cost which includes the initial circuit cost of $8.67 + any additional part costs associated with construction.
The resultant costs in the last row of Table 5 indicate that the final product will become extremely affordable when production exceeds 10000.  The closest comparable product on the market sells for almost $25 <ref name="Barefoot"/>, so the costs of $12.95 / unit at 10000 produced, and $5.17 / unit at 100000 produced are very reasonable.  If mass production is undergone, and up to 100 000 are made, the final cost of $5.17 plus any additional profit margin markups will be much cheaper than the prototype cost which includes the initial circuit cost of $8.67 + any additional part costs associated with construction.


=== Prototype ===
=== Prototype ===

Revision as of 01:54, 31 March 2010

Template:425inprogress


Project Description

  • The main goal of this Mech425 project is to design a simple, cost effective indoor light source that can be used in areas of the world that do not have access to electricity or functional lighting at night. If this design proves successful and viable, the technical specifications as well as methodology and costs will be available to anyone who has access to the internet or to programs such as the One Laptop Per Child (OLPC) Program.


  • The proposed design utilizes a recycled bottle and cap (with a cap diameter equal to or greater than that of a 2L pop bottle) as a portable, durable platform for a high efficiency LED lighting system that is charged using a small solar panel. The bottle cap will house the lighting equipment, will act as the bulb ballast and the pop bottle will act as the diffuser and stand.


  • The Mech425 project guidelines and background can be found here

Background

LED Technology

LED is an acronym for a lighting system known as a light-emitting diode. LED's are semiconductors that emit light when a junction is exposed to a forward biased electrical charge (electro luminescence). This application will use white LED's, which can be used as a much more efficient replacement for incandescent light bulbs. The main advantages of LED use are the efficiency and lifespan compared to standard incandescent bulbs. First of all, LED's produce many more lumens/watt of light than incandescent bulbs, resulting in a reduced power requirement as well as increased running time when powered by batteries. They also have extremely long lifetimes (anywhere from 100 000 to 1 000 000 hours) compared to incandescent bulbs (1000-2000 hours) [1][2] [3].

These qualities have made LED lighting ideal for grass roots, low power applications such as this project, and have been used in similar endeavors. Some examples include:


Barefoot Power, which develops AC and solar lighting products for the developing world and is involved with projects such as Lighting Africa and The Lumina Project [4]

SOLLIGHT TM, which is a solar LED system designed for wide mouthed water bottles [5]

Cosmos Ignite Innovations, which provides lighting solutions for developing nations. [6]

Lighting Issues Around the World

Approximately two billion people, almost 30% of the world population has no access to electricity, relying on fuel-based lighting, such as kerosene wick lamps and candles. This is a very dangerous alternative that is unsafe, expensive, and provides very inefficient lighting. Being limited by the amount of sunlight during the day makes it very difficult to perform tasks efficiently at night. The main problem is that these tasks include homework or studies by adults and children, and without proper lighting, reading books or chalkboards is impossible. This presents a barrier to education and economic development not to mention literacy improvement. Efficient, self sufficient lighting can therefore impact the well being of people who cannot function efficiently after the sun has set. [7]


A major push to switch to LED lighting is the widespread use of dangerous, expensive fuels such as kerosene. Kerosene is very expensive for people living in poverty. In places such as rural India, purchasing enough kerosene to light a small household can represent more than 4% of a household budget. The light that these kerosene lamps produce is also very inefficient; LED’s can produce more than 200 times the useful light. For example, an entire village can be lit using less energy than a single 100W normal bulb [8].


Making the switch to solar powered LED lighting systems not only presents a more cost effective, efficient alternative, but also a much safer one. According to the World Health Organization, indoor air pollution from kerosene and other burned fuels used for indoor lighting and cooking is the cause of more than 1.5 million deaths annually [8]. There is also additional risk of fire when using kerosene, giving yet another reason to switch to LED lighting.

LED Light Source Design Requirements

The design must fulfill the following functional requirements in order to be an appropriate solution to the lighting problem:


  1. System Cost: The cost of the system must be minimized as much as possible in order for people in developing countries who survive on as little as $1 per day to afford it without marginalizing food and shelter requirements. If the cost is too high, people will not be able to cover the overhead, and will not be able to benefit from safe, efficient lighting.
  2. Simplicity: The design must be as simple as possible in order to minimize overhead costs and complexity. This simplicity will lead to increased durability and lifespan.
  3. Maintenance: The design must be easy to maintain, with little to know technical knowledge required. It must therefor be a contained unit that requires no additional maintenance other than initial installation.
  4. Self Sufficient: The light must be able to charge and run itself without any additional charging or battery replacement. The solar cell must fully charge the battery when exposed to peak sunlight during the day, and the battery must retain the charge without replacement over a long period of time.
  5. Environmental Impact: The production and operation of the light must be optimized with regards to environmental impact. This means that the component choice must maximize the use of recycled materials and the end of life disposal must produce minimal impact.
  6. Ease of Use: The installation and use of the light must be as simple as possible in order to minimize the chance of confusion or degradation due to misuse.


The functional requirements have been weighted according to relative importance with respect to applications in developing nations. The results are shown in Table 1.

Table 1: Design Functional Requirements
Function Requirement Importance Weighting
System Cost 50
Simplicity 10
Maintenance 10
Self Sufficient 10
Environmental Impact 10
Ease of Use 10
Total Weight 100


Each of the functional requirements and their relative importance will be considered in the design of the LED lighting system. The first step is to design the circuit that will power the LED.

Circuit Design

The first step in this light source design is the circuitry. A solar charged battery light circuit is relatively simple, because the energy input can be modeled as an external power source, and the battery can be charged constantly without backward current flow using a diode. The only problem with compact LED lighting systems is the limitation of voltage from small battery packages. AAA's and AA's (which will be used in this application) are limited to maximum 1.5V, which is half of the optimum voltage for a white LED. This problem leads to two distinct circuit design solutions; one that is simple and runs the LED at 3V but requires 2 batteries and one that is complex that runs the LED at the full voltage through the use of a voltage booster. The circuit diagram for the simple solution can be seen in Figure 1.


Figure 1: 2 Battery 'Simple' Circuit

Ortho View
Simplified Wiring Schematic


This simple solution would result in suitable performance but would require 2 batteries (which is relatively expensive and environmentally costly)and depending on the LED choice, would not need a resistor. This layout can possibly extend the life of the light because it is running at a slightly lower voltage.


The components required the 'simple' circuit with 2 batteries totaling approximately 3V will be:


Battery:



Solar Panel:



Resistor:

Not required due to the limited voltage being supplied.


The diagram for the single 1.5V battery with a more 'complex' wiring solution can be seen in Figure 2.


Figure 2: Solar Charged 1.5V Boosted LED Lighting Wiring Schematic ('Complex' Layout)

Ortho View
Boosted Wiring Schematic


This 'complex' solution would result in optimum lighting quality from the LED, but would significantly increase the cost of parts and manufacturing as well as limit the life of the device (voltage boosters are limited to a few hundred hours of runtime, depending on the voltage increase required[9]). The inductance based voltage booster can be made from a ring of ferrous material wrapped in 2 separate copper wires, and provides a simple, relatively cheap solution to the lack of voltage produced by the battery [10]. The main advantage is the reduction in reliance on 2 batteries, hence reducing the cost and environmental impact. [11]


The components required the 'complex' circuit with for a single 1.5V source boosted to approximately 4.5V will be:


Battery:



Solar Panel:



Resistor:



Circuit Economic Analysis

In order to determine which of the two wiring options is more suitable to this low cost, simple application, a simple economic evaluation must be performed. Whichever option provides a more cost effective parts and labor outcome will be used in the final design. Tables 2 and 3 show the summary of parts and costs in order to determine the total individual circuit costs. Please note that the labor costs have been approximated based on the possibility of manufacturing in China where the labor rate is lower [12].

Table 2: 2 Battery 'Simple' Circuit Cost
Component Price Information Vendor
AAA Battery [13] $0.53 BTY NIMH 1000 mAH AAA Hotock Group
AAA Battery [13] $0.53 BTY NIMH 1000 mAH AAA Hotock Group
Diode [14] $0.28 Schottkey 60V 15 mA Diode STMicroelectronics
Switch [15] $0.45 DPDT Slide Switch Anticsonline
LED [16] $0.68 5mm White LED PCToys
Solar Panel (4V) [17] $5.48 4V 60 mA 0.24W Keawin
Labor [12] $1.20
TOTAL $9.12


Table 3: 1 Battery 'Complex' Circuit Cost
Component Price Information Vendor
AAA Battery [13] $0.53 BTY NIMH 1000 mAH AAA Hotock Group
Diode [14] $0.28 Schottkey 60V 15 mA Diode STMicroelectronics
Switch [15] $0.45 DPDT Slide Switch Anticsonline
Transformer $0.45 Ferrous ring with coil N/A
Resistor [18] $0.20 271-1321 10K resistor Radioshack
Transistor [19] $0.11 BC549 30V 100mA limit Fairchild Semiconductors
LED [16] $0.68 5mm White LED PCToys
Solar Panel (2V) [20] $3.90 2V 70 mA 0.14W Keawin
Labor [12] $2.10
TOTAL $8.67


The excel file can be seen here: File:Wiring Cost Comparison.xls


The more complex, voltage boosting circuit is the least expensive to produce because of the lower power requirement for the solar cell as well as the reduction in number of batteries required. The only limiting factor may now be the lifespan of the voltage boosting transformer, which can be maximized by using high quality components as well as standardized construction procedures. The overall cost of $8.67 CAD is slightly higher than originally predicted for the wiring component of the design, but it can be minimized if it is mass produced. Also, if the product efficiency and environmental impact can be optimized, then the additional price is worthwhile.

Bottle Cap LED Fixture Design

There are two main methodologies that have been explored in order to develop a suitable appropriate technology designation for this design. The first of which relies on mass production (or at least semi-mass production) to justify the housing design as well as the parts purchases. The methodology relies on recycling all parts, which would be relatively difficult where there is little technology available, and designing based on parts available. The first methodology has been applied to develop a single part and assembly methodology that can be mass produced using injection molding and labor in China. The second methodology has been applied through the development of a prototype that utilizes the most recycled components as possible.


Custom Designed Fixture

Required Parts

The mass production design requires a larger investment on the part of a sponsor or company in the short term, but will provide people with a reliable, water resistant, efficient lighting source that requires minimal maintenance. This design involves the production of a central component housing with the purchase of multiple electrical components. The parts required for the design are as follows:


Table 4: Parts List and Description
Part Name Information CAD Representation
1 x Housing To be produced Housing
1 x LED 5mm, White, 3V LED Light Bulb
1 x Transistor BC549, 30V, 100mA, NPN Transistor
1 x Diode IN5711, 70V, 15mA, DO-35 Diode
1 x Resistor 271-1321, 1/4W, 1kohm Resistor
1 x Transformer Ferrous Ring Transformer
1 x AAA Rechargeable Battery NIMH AAA, 1.2V, 1000mAH Battery
1 x Plastic Washer 15.5mm Plastic Washer Washer
1 x Switch DPDT Slide Switch Switch
2 x 3mm Screw 3mm Threaded Flat Screw Screw
1 x Solar Panel 2V, 70mA, 0.14W Solar Panel

Housing

The part that must be manufactured is the housing for all of the components, and it can be seen in Figure 3, with it's dimensioned engineering specifications in Figure 4. It can be made in China using injection molding in order to minimize the overall cost of production. The bottom concave surface around the LED must be sprayed with a reflective paint in order to maximize light projection into the luminaire (bottle).

Figure 3: Housing Design

Ortho View Front View Bottom View
Ortho View Front view Bottom View


The engineering drawing is shown in Figure 4.


Figure 4: Housing Dimensions

Dimensions

Assembly

The assembly process is performed as follows:

  1. Construct the circuit shown in Figure 3, leaving the solar panel and switch wires disconnected
  2. Insert the connected LED,transistor, diode, resistor, transformer and battery into the housing in that order
  3. Feed the wires for the solar panel and switch through the hole of the plastic housing cap
  4. Apply glue to the edges of the cap, and press it into place, making sure to line up the flat edge with the switch location
  5. Slide the switch into the side opening
  6. Thread the 3mm screws into the switch screw holes to secure it in place
  7. Connect the switch wires to the leads on the back side of the switch
  8. Connect the solar panel wires to the leads on the reverse side of the solar panel
  9. Apply glue to the top lip of the housing (square section)
  10. Line up and set the solar panel on the top lip of the housing (bottom side down, making sure to tuck the wires into the opening
  11. Hold the panel in place until the glue has set, and the panel is firmly set in place


The assembled final product can be seen in Figure 5 and the dimensioned engineering specs can be seen in Figure 6.

Figure 5: Final LED Fixture Design

Ortho View Front View Bottom View
Ortho View Front View Bottom View


Figure 6: Assembly Dimensions

Dimensions


Installation Into Bottle

Installing the light fixture is very simple.

  1. Cut a 175 mm hole in the center of the recycled pop bottle cap using a sharp knife
  2. Insert the end of the assembled fixture through the hole (through the top of the cap)
  3. Push it in until it reaches the lip approximately 3/4 of the way up the housing
  4. Force the lip through the hole and stop when the housing is completely inserted into the cap
  5. Thread the cap with the fixture installed onto the top of the bottle to complete the luminaire
  6. If the bottle is top heavy, which may happen in tall or small diameter bottles, it can be inverted to rest on the solar cell


Step 1 Step 2 Step 3
Ortho View Front View Bottom View
Cut 175mm hole Push fixture through the cap Screw cap assembly onto bottle


Prototype

Circuit Construction

Cap Assembly Construction

An online walk through for the construction of the voltage booster portion of the circuit can be seen HERE

Economic Considerations

The custom designed fixture will require very high investment in the short term, but if mass produced, costs could be reduced drastically, making it a viable solution. The prototype solution has lower initial costs, but buying individual parts for each reproduction could be more expensive than mass producing a design. An economic feasibility analysis will be performed in order to determine which is more feasible over the long term.


Custom Designed Fixture

This portion of the economic analysis has been based on the paper Early Cost Estimation for Injection Molded Parts [21] produced by Dr. O. Kazmer. The paper presents a valid model for predicting the overall production costs involved in tooling and producing injection molded parts, such as the housing portion of this design. He also generated a Java Applet that calculates individual unit costs based on the number of parts produced [22], which I used as a general model to predict costs over several production stages.


The same assumptions and part costs used in the initial circuit analysis have been applied to this analysis, with the addition of the Kazmer cost model and the results are as follows:


Table 5: Mass Produced LED Fixture Economic Analysis
Number of Units Produced 1 100 1000 10000 100000
Housing Cost / Unit ($) [22] 967.65 102.73 33.47 10.91 3.55
Labor Cost / Unit ($) [12] 1.20 1.20 1.20 1.20 1.20
Total Parts Cost / Unit ($) 6.72 3.36 1.68 0.84 0.42
Total Cost / Unit ($) 975.15 107.29 36.35 12.95 5.17


The economic analysis spreadsheet can be seen here: File:Mass Production Economic Analysis.xls


The resultant costs in the last row of Table 5 indicate that the final product will become extremely affordable when production exceeds 10000. The closest comparable product on the market sells for almost $25 [23], so the costs of $12.95 / unit at 10000 produced, and $5.17 / unit at 100000 produced are very reasonable. If mass production is undergone, and up to 100 000 are made, the final cost of $5.17 plus any additional profit margin markups will be much cheaper than the prototype cost which includes the initial circuit cost of $8.67 + any additional part costs associated with construction.

Prototype

Conclusions

--S. Gennings 01:53, 31 March 2010 (UTC)


References

  1. Appropedia, "LED Lighting", http://www.appropedia.org/LED, Accessed March 23, 2010
  2. Marktech Optoelectronics, White LED's, http://www.marktechopto.com/Engineering-Services/white-leds.cfm, Accessed March 24, 2010
  3. Theledlight.com, "Technical Information", http://www.theledlight.com/LED101.html, Accessed March 23, 2010
  4. Barefoot Power, "Barefoot Power", http://www.barefootpower.com/, Accessed March 20, 2010
  5. Simply Brilliant, LLC, "Sollight",http://www.sollight.com/products/lc200.cfm, accessed March 20, 2010
  6. Cosmos Ignite Innovations, "Mighty Light", http://www.cosmosignite.com/product-brief.htm, Accessed March 20, 2010
  7. A. Seigel, "Energy Cool: Lighting up the developing world, http://www.huffingtonpost.com/a-siegel/energy-cool-lighting-up-t_b_201954.html, Accessed March 23, 2010
  8. 8.0 8.1 Sebitosi A.B., Pillay P., New Technologies for Rural Lighting in Developing Countries: White LED’s, Cape Town University c2007, Accessed March 23, 2010
  9. Linverter, "Linverter- Run four superbright white LED from one or two 1.5v batteries", http://www.linverter.com/, Accessed March 24, 2010
  10. Z. Kaparnik, Make a Joule Thief, http://www.emanator.demon.co.uk/bigclive/joule.htm, Accessed March 24, 2010
  11. EDN, "1.5V battery powers white LED driver, http://www.edn.com/article/CA454645.html, Accessed March 24, 2010
  12. 12.0 12.1 12.2 12.3 China.org.cn, "Average salary increase of urban workers rises to six year high, http://www.china.org.cn/government/central_government/2008-04/02/content_14111192.htm, Accessed March 25, 2010
  13. 13.0 13.1 13.2 Hotock Group, "4x NIMH AAA 1.2V", http://cgi.ebay.ca/4-PCS-Rechargeable-AAA-1000-mAh-1-2V-NI-MH-NIMH-Battery_W0QQitemZ260571034826QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3cab3e74ca#ht_3890wt_1009, Accessed March 25, 2010
  14. 14.0 14.1 Digi-key Corp, DIODE SCHOTTKY, http://ca.digikey.com/1/1/369732-diode-schottky-70v-15ma-d0-35-1n5711.html, Accessed March 25, 2010
  15. 15.0 15.1 Anticsonline, 10 Pack Expo DPDT Slide Switch, http://www.anticsonline.co.uk/1154_1_1311617.html, Accessed March 25, 2010
  16. 16.0 16.1 PCToys.com, "5mm White LED (4 Pack)", http://www.pctoys.com/840556011286.html, Accessed March 25, 2010
  17. ebay, 4V 60mA 0.24W solar panel PV solar power 2.4v battery, Accessed March 25, 2010
  18. Radioshack, 1K ohm 1/4 Watt Carbon Film Resistor,http://www.radioshack.com/product/index.jsp?productId=2062343#, Accessed March 25, 2010
  19. Digi-key Corp, "TRANS NPN LN 30V 100MA BC549", http://parts.digikey.com/1/parts/1003194-trans-npn-ln-30v-100ma-92-bc549.html, Accessed March 25,2010
  20. ebay, 2V 70mA 0.14W solar panel PV solar power PCB panel, Accessed March 25, 2010
  21. Kazmer, O, Early Cost Estimation for Injection Molded Parts, http://kazmer.uml.edu/Staff/Archive/XXXX_Inj_MOld_Cost_Estimation.pdf, Accessed March 30, 2010
  22. 22.0 22.1 Kazmer, O. Java Injection Molding Cost Estimator, http://kazmer.uml.edu/Software/JavaCost/index.htm, Accessed March 30, 2010
  23. Cite error: Invalid <ref> tag; no text was provided for refs named Barefoot
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