Projector lens details from Kinkajou team member Martin Tollliver:
I ordered a BW992BR and a BW1043BR from Boowon Optical to use as the beta prototype projector lens.
The 992 is the first lens listed on the page. The 1043 is no longer listed. I think they both did fine. We went with a 1/2" CCD lens because that is the approximate size of the microfilm image (1/2" square).
Condenser lens details from Kinkajou team member Joel Jaimes:
The lenses in the condenser were purchased from Edmund Industrial Optics in New Jersey (800) 363-1992. I still have their catalog. As to the focal lengths:
>> Plano-convex (part number F45-097) has an effective focal length of 25.0mm
>> Double-convex (part number F45-161) has an effective focal length of 35.0mm
The catalog doesn't show how to calculate the focal length for our condenser as a system, as it has three lenses. The focal length for a system (Fsys) consisting of two lenses with focal lengths of F1 and F2 would be: Fsys = [F1 * F2] /[F1 + F2 - d] The distance between the two lenses is d. [see Joel's senior thesis for more details]
The attached page contains an archive of an ongoing email discussion over the proper light source for the Kinkajou Microfilm Projector. The projector currently uses a LumiLEDs Luxeon Star V LED (5-watt Lambertian White, Part Number LXHL-MW1D) rated at 25 lumens. There are major issues with the LED heat and reliability. One proposal is to switch to a halogen bulb.
To join the discussion, please send us your comments either via email or by using the comments link below.
From: Tim McNerny
Date: Wed, 11 Feb 2004 14:27:18 -0500
I looked over the WPI projector report. It looks like they really did their due dilligence. Regarding the driver for the Luxeon LED, I noticed that there is currently no thermal feedback built into the drive circuitry. For the 1W LED, this may be less critical, but I predict that it will become an important issue for 5W LEDs.
I know from experience that Luxeon LEDs are easily damaged when they get too hot--either they fail "hard" or the gel inside gets cloudy. This means that "full brightness" is not a fixed voltage or current. Rather, it depends on the efficiency of the cooling system and the ambient temperature. A switching power supply will be a must for the 5W LEDs, either a clever analog circuit or a microprocessor-based design. The microprocessor can share the duty of driving the LED and charging and protecting the battery.
From: Tim McNerny
Date: Wed, 11 Feb 2004 17:46:03 -0500
> Heat is a concern with the 5W LED, hence the big heat sink
> and fan (you can see the optics assembly and the heat sink
> in the attached photo). I've also been interested in the
> possibility of cycling power to the LED at a high frequency,
> something not visible to the eye, as a way of reducing power
> consumption and heat loads.
Funny you should mention that, because the [0.1-watt LED] flashlight I showed you "chops" the power to the LED at just under 100kHz, and sure enough, your eye can't see it. But there's a catch: modulating the power reduces the apparent brightness. For a given cooling system efficiency and ambient temperature, there will be a an upper-bound on the DC voltage or the "chopper's" duty cycle used to drive the LED.
This is why you want a thermistor in close proximity to the LED to tell the driver if the LED is about to burn up (or lower its lifetime). The power supply can either reduce the voltage or reduce the duty cycle so it delivers less power to the LED, and thereby keep it within its specified temperature range. The good thing about a "smart" driver is that it can adapt. If the fan fails, or it is a particularly hot day, the projector won't be as bright, but at least it won't kill the expensive LED.
From: Tim McNerny
Date: Sat, 14 Feb 2004 02:57:24 -0500
I'm glad you got me thinking about reliability. It makes me want to recommend that we use off-the-shelf modules as much as possible. [...]
Using a fan in general bothers me somewhat, because it is the component that is most likely to fail in a dirty environment, but maybe it is a "necessary evil." At least they are cheap enough that we can probably afford to ship a spare with each projector. [...]
I'm starting to think that the Kinkajou product is 40% technology, 60% risk management. Then again, maybe I'm preaching to the converted.
From: Limor Fried
Date: Thu, 19 Feb 2004 19:21:23 -0500 (EST)
My reason for not using LEDs in this project is as follows:
1) really expensive (luxeon 5w is $40, 1W is $10)
2) 5w luxeons' life is not much better than halogens if white (a couple hundred hours) and are offcolour if cyan (dont know how bad this is)
3) they run at 3.5V, which means that either you run off of a 6V with a linear supply and lose 40% of your power to the resistor, or run a dc-dc converter, which is somewhat expensive ($5) and also is only 80% efficient. OR run 3 of them (1W?) in series on a 12V. thats probably the best way to do it with luxeons
1) halogens are about as efficient as LEDs
2) $5 a piece retail and $5 for a ceramic plug. (although perhaps cheaper for more than 10?)
3) are manufactured in various wattages (5, 6, 10, 15, 20...)
4) come with glass-cover lenses, and reflectors in different spreads (10-30degree are available online)
5) manufactured to run directly off of 6 or 12 volts, so no power is wasted to passives such as resistors or DCDC convertors.
6) dont need a cooling system as long as there are vent holes
going with a halogen can drop your cost more than $25 and can increase your efficiency, which means a smaller battery. I think this is worth it. another nice thing is that you can still dim the lamp with a resistor. i use a 6V 5W MR-11 on my bike lite about 1.5" dia. they are sold online. you can also get MR-16's, 2" dia. MR-16s are slightly more popular, but it depends on your space considerations. the only sad thing about these halogens is that they are bi-pin, so you cant really go around plugging & unplugging them.
in my opinion, led lighting is good for one thing: color and color changing. they're not ready to replace filaments in low cost applications. they dont even come close :(
From: Limor Fried
Date: Mon, 1 Mar 2004 14:43:08 -0500 (EST)
> We've been using the LED in the current beta
> prototype for almost a year, include six demanding weeks in
> West Africa and travel all over the country. We've also had
> a model of the alpha prototype, which I think also uses the
> white 5W LED, on the floor of the Museum of Science since
> October, which counts as a kind of burn-out test:
> We haven't considered halogens before now. The original
> proof-of-concept, built in Spring 2002 with Saul's help,
> used a 1W red LED. I don't know if the 2.009 team ran a
> thorough evaluation of lighting options, or if they simply
> went with the 5W LED because it was a direct scaling of the
well, i just asked saul [griffith] about the 1W [LED he used in the proof-of-concept design] and he said "it was a different project, smaller scale" do you know the EE that decided on a 5W led? I still think its a poor idea. lots more lost power, a lot more cost. I have my 10W halogen bikelite setup (same formfactor as 5W bulb, i just need more light to scare cabs with ;) here on campus, we could just try it and see if it works. itll be here every day...attached to my bike! its got a dimmer switch so I can turn it down to 7W output.
> The urgent problem relates to completing a second-generation
> prototype design by the end of the semester, so that we can
> build them over the summer. Our hard target is that in
> September 2004, we have to deliver something like 50 units
> to World Education that will run for 500 hours over a six-
> month field test in Mali.
Sounds like theres two things: optics and bulb. but from last speaking to you it sounded like you were going to ahve to redesign the optics anyways since they cost $100. I really think a halogen is the right thing, it is lower power, and will last a thousand hours before bulb replacement. for a few dollars more per bulb we can get bayonet (like flaslight bulbs) instead of bi-pin, which is virtually foolproof for bulb-changing.
From: Limor Fried
Date: Fri, 5 Mar 2004 05:05:03 -0500 (EST)
> To carry on the LED vs halogen debate, I'd like to get your
> opinion about efficiency and heat. Will DelHagen pointed
> out that, although the LED may require a less efficient DC-
> DC converter to use the 12v power supply, the LED itself may
> be much more efficient in terms of converting electricity to
> light. Do you have any sense for how this works out?
well, its one of those things where you can read the numbers, or you could just try it. i think we'd have to just try it. i know that 'in theory' halogens and LEDs are about the same. but it sounded like you had more of a $ concern than efficiency concern.
> Second, heat. Right now, the LED is separated from the
> microfilm by the roughly 1.5" thick condensor lens. We
> haven't had any trouble with the microfilm getting
> overheated, but it isn't something we've thoroughly tested.
> Do you have any sense for the relative heat output of the
> halogen with respect to the LED?
that is a good question. im not sure. my halogen is in a metal casing and exposed to air so its quite cool. 1.5" is a pretty large distance.
From: Tim McNerney
Date: Fri, 5 Mar 2004 02:23:39 -0500 (EST)
Limor Fried makes a pretty convincing case that a small halogen bulb would be better than a 5W LED + switching power supply + heatsink + fan, in terms of cost, reliability, and development time. Also, the user interface for "your battery is low" is simple: the bulb gets dimmer. Plus we are more likely to find optics to match. I like the idea already.
Project to develop Kinkajou for volume manufacture post 6 month field test. Institute for Manufacturing, Cambridge University (UK)
KINKAJOU VOLUME MANUFACTURE
1. Introduction and Project Context
The Kinkajou microfilm projector, designed as a teaching aid for rural communities in Mali, is approaching the completion of it’s third design iteration. Teams of students from Massachusetts Institute of Technology (MIT) and Worcester Polytechnic Institute have worked on the projector since its conception in 2001 as a low cost microfilm library. In summer 2003, a team of MIT students took the beta prototype to Mali to test the concept with the people it is designed to help. Design that Matters is now taking on the challenge of developing Kinkajou into a volume produced product, bringing the students’ ideas and desire to use their skills to help those less fortunate than themselves to a reality.
World Education has agreed to take 50 Kinkajous to teaching projects in rural Mali this September, for an extended test. The test will last 6 months and put Kinkajou through the most gruelling examination of its design and pedagogical value to date. The test offers an unrivalled opportunity to test the students’ design assumptions and research, as well as bringing Kinkajou one step closer to a permanent place in the lives of its intended users.
Kinkajou represents the first time that Design that Matters has attempted to develop a student project into a commercial venture themselves and as such is a pioneering project for the company. With this in mind a professional design engineer and a project manager have been recruited full time, to prepare Kinkajou for the World Education test. The beta prototype is already undergoing a dramatic design overhaul focused on increasing reliability and reducing cost through design simplification.
March 2005 will see Kinkajou return from Mali, bringing with it a wealth of invaluable information about its performance in the field. From here the design will undergo further evolution in order to develop a commercially manufacturable product. In order to achieve, bringing the 3rd generation Kinkajou to a position where it can be produced in numbers of 50 upwards; a manufacturing strategy must be developed. This strategy will vary depending on the numbers involved and will include further development of the design.
2. Project Phasing
Phase One - Analysis of Market Opportunity
At present, one client, World Education, has been identified as a potential customer for Kinkajou. World Education has worked closely with the project from an early stage and has invested heavily in the project. Around 5% of the communities in need of basic teaching equipment in Mali are covered by World Education projects, requiring up to 1700 projectors. This would make a massive difference to many peoples lives, however it represents only a minute fraction of the communities that could potentially benefit. Phase one of the project will involve an assessment of the potential market size for Kinkajou and simultaneous use this research to recruit possible clients. World Education projects in other countries, other charitable organisations with literacy schemes and government organisations will all be contacted. Alternative uses for derivative products will also be assessed such as medical libraries for field doctors.
Phase one deliverables:
Understanding of nature of market opportunity for Kinkajou
Database of potential clients, the quantities they would require and their desired benefits
Phase Two - Volume Based Scenario Development
As a result of the market analysis, a range of possible scenarios for manufacturing volumes will be created. These will vary both with quantity of the standard Kinkajou, and also in degrees of customisation to a client's desired requirements. High level manufacturing strategies will be developed for each scenario, and then the most appropriate strategy chosen to focus on. This choice will be made with consideration of a number of issues including achievability, risk, the opportunity for further development of the product and Design that Matters resource constraints.
Phase two deliverables:
High level manufacturing strategies for a range (3-5) of volume and customisation level scenarios.
A decision on the most appropriate scenario to study further
Phase Three – Design Development for Manufacture
With the chosen scenario to focus on, detailed manufacturing options will be evaluated. The design of the Kinkajou will be developed in order to make most effective use of the chosen forming and assembly methods. This stage will take into account the ease of repair of the product and replacement of consumable parts in the operating location.
Phase three deliverables:
Detailed manufacturing strategy describing how, where and at what cost the product can be made for at the specified volume and level of customisation
Quotes from manufacturing companies backing up these decisions
Proposal to manufacture Kinkajou for a unit cost of less than US$10
Phase Four – Communication of Recommendations
The final stage of the project will be to communicate the results of the project. This is particularly important in this case for two reasons: Firstly that the bulk of the material generated will not be used fully until March 2005, and secondly due to the rapid turnover of development teams. The nature of Design that Matters’ work dictates that only Tim Prestero and Neil Cantor have, and will, remain involved in the project for its duration. Teams of students take up and then pass on various aspects of the project throughout its lifetime. Because of this, thorough and clear documentation of the thought processes and decisions made is essential. Transparency, traceability and conciseness are therefore key to the successful handover of the projects results.
Three methods of project handover will take place:
A verbal presentation to Design that Matters
A collection of relevant written information and documentation integrated into the online Kinkajou Design Journal, for future projects teams to use
An exhaustive report of the findings, incorporating a chronological diary of design choices and reasoning
3. Phase Timing
An initial phase timing has being developed as follows:
Phase one (begins) 26th April 2004
Phase two 3rd May 2004
Phase three 10th May 2004
Phase four 24th May 2004
Presentation 4th June 2004
Illustration for second development report.
Stamped sheet aluminum top plate contains dual film advance knobs.
This first development report for the Gamma prototype covers experiments on power consumption and temperature control on LED and incandescent light sources. Covers 15-29 March 2004.
Read the full report: [MS Word doc] [PDF]
See the full schedule: [PDF]
Attached is the current schedule incorporating the details of the PCB design. There is a conflict in the Gamma Build and P2 PCB availability. (P1 PCB is not intended for Gamma Build). I think we can work around this and still keep the project on schedule:
Task 19: Gamma Prototype Build- 4/22 to 5/12
Task 20: Evaluate Gamma Prototype- 5/13 to 5/26
Task 32: Test/Cal P1-4/28 to 4/29
Task 45: Test/Cal P2- 5/18 to 5/20
-Build Gamma as per schedule using either external driver or P1 PCB either external or best fit inside if possible, for beginning of evaluation
-prior to end of Task 20 retrofit P2 (task 45) and complete "full evaluation"
Other comments on schedule:
-dates in red have been changed from previous schedule, most significant the Production PCB build cycle extended to 30 days to avoid premium costs, to accomplish this we'll have to select and get to vendor early with preliminary design details to get into his queue.
-the projected "delivery date" for units to WE is 9/10, assembly starting 8/17, we should be able to make a partial delivery by the beginning of September.
-Schedules are traked by date located in the footer under file name.
The Luxeon Star LED has been tested, successfully, for 500 hours. The Gamma prototype of the Kinkajou has now been designed. The design will be reviewed on 21 April 2004, and then the prototype fabricated. The report, including pictures is at:
We had an extremely productive design review with MIT Mechanical Engineering Prof. Woodie Flowers, Kinkajou Alpha and Beta design team member Beto Peliks, MIT LFM team members Satish Krishnan and the Gamma design team. A number of questions and suggestions resulted in the following design modifications (detailed below).
DtM is grateful to the design review participants for their time and their great ideas. We would also like to thank the staff at the MIT Lab for Energy and the Environment, for putting up with DtM as we hog yet another afternoon in the conference room.
Allen and Woodie discuss the clutches
Clockwise from L: Allen Armstrong, Satish Krishnan, Woodie Flowers, Neil Cantor, Beto Peliks, Peter Fichter
>> “Intuitive” design, this suggestion was aimed at making it clear to the user how to interface with the product. Specifically this addressed the fasteners located on both the top and bottom of the unit, making it less than intuitive as to how one accesses the inside of the unit. Action is that alternate fasteners to slotted head screws will be used, consideration was also given to using pressed in fasteners on top of the unit (no obvious methods for removal)
>> Sliding cover/focus adjustment, concern was raised over dirt causing the channel to bind as well as confusion about the dual function of the focus knob/door retainer. Action is to eliminate sliding door and replace with a simple lens cap, leaving the focus knob serving only as the focus adjustment. Search for a commercial “lens cap” has begun, we would like to tether the cap to the projector to prevent loss.
>> The value of the “hinge” feature on the front extrusion for the bottom access door was revisited. Since the assembly utilized a number of screws requiring a “tool” the value of the hinge was diminished and we agreed to eliminate the hinge and replace with two additional fasteners. This simplification eliminates the need for a custom extrusion for the front, replacement with stock material.
>> Screws in general, recommendation was to utilize fasteners which can be power driven, consideration was given to both “Torx” and “Phillips” heads, it was agreed that the universality of Philips heads tools made these an appropriate choice. Concern was raised that the threads in the aluminum heat sink/structural element, might be vulnerable to damage with multiple removal/assembly. Inserts were recommended as a possible solution, no action was taken, the expectation is that the “base” will be infrequently removed by trained individuals.
>> Film guide/focus adjustment, need to make certain that any “edges” on the metal guide are properly deburred/finished to avoid damage to the film. Initial plan is to finish these by hand, mass production would seek to utilize an automated process, eg electro polishing.
>> Ruggedness of design, questions were raised as to the ability of the projector to withstand an accidental drop. Consensus was that the design might be vulnerable to damage if dropped from table height. A number of protective methods were discussed, including padded cases, external bumpers, similar to certain flashlights, and crushable “wire frames”. Emphasis will be to beef up the design where possible, with continued thought given to “protective” features.
These product management reports include updates to the project schedule and the product requirements sheet, and address various other aspects address of the ongoing Kinkajou redesign.
Following last week's design review, changes have been incorporated in the model to address items developed in the review. Major changes include elimination of the sliding lens cover and hinges, improvements in the optical path, provision of a "crash cage", and improved sealing.
Following a design review on 21 April 04, the Gamma prototype design has been altered in the following respects:
The extruded heatsink has been revised to receive in a slot the front plate, which now has no hinges. This permits elimination of 4 screws. The heat flow path has been improved by moving a screw slot outside the path. Two additional screw slots have been added, and they have been enlarged to permit use of a self-threading steel insert.
The front plate (projection lens plate) has been converted to a cut-off piece of flat aluminum stock, eliminating the need for a special extrusion. In the process, the sliding lens cover and the hinges have been eliminated. The area in contact with the cover gaskets has been increased.
The cover plates have lost their hinge halves, and additional screw holes have been added for fastening.
A felt sealing washer has been added to the film advance knob assembly.
A third condenser lens has been added and the optical path lengthened by allowing the projection lens to protrude from the front plate. This allows use of a dipped vinyl lens cap in lieu of the sliding door.
The film gate has been revised to accommodate the changed projection lens position.
A pair of deformable guard rings (made from 2mm stamped soft aluminum sheet) have been added to protect the protruding lens and the body of the projector from damage in the event of a fall. The rings will absorb the fall energy by deformation, and can be bent back close to original position, or replaced. The new screw attachment of the covers makes this addition possible.
Thank you to Steve Fantone and Paul Rose of Optikos for their invaluable help in adapting the plastic lenses from Fisher Price toy projectors to this application.
Team members Peter Fichter and Allen Armstrong reviewing the Kinkajou optics design with Optikos CEO Steven Fantone (center).
Optikos engineer Paul Rose in the lab, testing the Kinkajou optics layout.
Paul’s optical design printout
The Gamma prototype design is now complete, and machining begun. A number of detail changes have improved producibility. The major ones are the elimination of the pressed contour in the covers and a redesigned aluminum cage that can be water-jet cut flat, and bent to shape. Two acceptable quotes have been received for the extruded heat sink. 90% of the purchased parts and material for the prototype has been received. The optics have been redesigned to incorporate 3 condenser lens elements and the projector lens housing has been redesigned to fit a tethered lens cap used on propane bottles.
A sectioned view through the optics path shows the close spacing between the LED and the first condenser element made possible by inclusion of a third condenser lens (a duplicate of the second element) to reduce the focal length. The condenser lenses are plastic aspherics taken from the Fisher-Price "Show-and-Tell" toy projector. The projector lenses are taken from the eyepiece of the Fisher-Price "Viewmaster" toy telescope. The projector lens is larger (19mm v 8mm) than that in the Beta prototype, and will permit more light to be delivered to the screen. The exact spacing of the elements is still to be determined by experiment.
The section through the microfilm reel shows the larger bearing permitted by elimination of the recess in the cover, the one-way clutch to allow the film only to be tensioned by the hand knob, and the leaf spring mounted on the bottom plate that creates some friction on the reel, while pushing it up into place. Film is changed by working with the projector in an inverted position, removing 7 screws holding the bottom plate.
This view of the exterior shows the impact cage (which will deform plastically, absorbing energy if the unit falls to the ground, and can be bent back into shape by hand). The screws formerly attaching the front plate to the extrusions have been eliminated by including a slot in the extrusions and use of multiple screws top and bottom for the covers. All of these changes were enabled by the decision to eliminate the hinged covers, and accept that entering the unit to change film will entail somewhat more effort. The original reasons for adding the pressed contour to the covers were to protect the knobs by depressing them into the surface, and to stiffen the cover so that hinges and two screws would put adequate pressure on the sealing gasket. The addition of the cage and additional screws have achieved these objectives in other ways. The covers can now be cut on a water jet machine, or punched out without needing the presswork tooling. This view also shows a power switch, although it is to be replaced with a sealed switch, which will have a slightly different appearance.
The view from underneath shows the relationship of the optics assembly to the printed circuit board that mounts the LED. A thermistor on the board will monitor the LED temperature and reduce power if it gets too high.
For the prototype, the heat sinks will be cut from solid aluminum by a CNC mill, but the 75 pilot projectors will use extrusions, which will cost about $7 apiece in the pilot quantity, to go down to $3.55 each in quantity production. The covers, cage and film gate will be cut out by water jet for the prototype, and possibly also for the pilots. The optics barrells and spacers are screw machine parts.
Exploded view of the gamma prototype. See the pdf version [PDF]
We expect the prototype to be complete by 24 May.
I’ve now completed construction of the Gamma prototype. Thanks to Beto Peliks for his help with the MIT water-jet machine, which cut out the sheet metal parts: the covers, bumpers and film gate components. The heatsinks were cut on a CNC Bridgeport mill and the cylindrical parts on a 10” South Bend lathe. The sheet metal parts were bent on an arbor press using a 1” wide 90º punch and die. Threaded inserts for M4 screws were installed in the heatsinks with an M4 capscrew mounted in a “hand tapper” to keep the insert aligned with its hole. (A hand tapper looks like a small drill press with a hand crank instead of a motor.)
Project engineer Allen Armstrong (L), product manager Peter Fichter, and first light with the Kinkajou gamma prototype.
Gamma prototype inverted with bottom plate and film reels removed.
When power was first applied to the LED, illumination level varied unacceptably across the screen image, being bright in the center, and quite dim at the sides. This was traced to a too-large distance from the LED to first condenser lens surface caused by a combination of three effects:
1. The LED was not retained by the printed circuit board, as that’s not available yet, but instead by nylon 4-40 screws, whose heads caused the mock PCB to be too far from the LED. The condenser lens mounts to the PCB, so it was moved also, about 1.5mm..
2. The condenser lens housing was mistakenly machined 1.1mm too long, also moving the first lens surface away, because the dimensions were taken from the surface that was too long.
3. In designing the optics, we were vague in communicating whether the LED-to-first surface distance was measured from the chip or from the surface of the lens included in the LED package.
These errors cause the condenser lens to focus the source image near the film plane rather than in the projector lens, and the image is smaller than the microfilm, so that the edges of the film receive only stray light.
Moving the lens closer has largely solved the observed problems. The light level is now quite uniform across the image, and quite bright. The image is 4 feet wide at 7.5 feet from the projector. There is some “halo” around the text letters, and focus deteriorates near the left edge. Still readable, but not in focus. Optikos have suggested a slight curvature of the film plane, and this will be incorporated in a revised film gate design, necessitated by the optimum focus point found to be 9.8 mm from the first projector lens surface, rather than the predicted 15.2mm.
The film transport system works as hoped. The one-way roller clutches incorporated in each of the two knob shafts prevent the film being “pushed” backwards. The knobs can only pull on the film, action is smooth and the drag springs hold the film from unwinding without causing excessive turning friction.
The focus knob permits fine control of the focus. My first impression is that it will be needed in the final product, because sharp focus really improves the screen image.
I noticed that the square holes in the centers of the two microfilm reels differed in size by 0.3mm, which is enough to cause the loose reel not to be well located. We’ll want to ensure that we get all our reels from one supplier, and size the drive squares to fit.
The prototype will be turned over to Tim McNerney tomorrow, along with the mechanical bits he needs to do his testing of the PCB.
These product management reports include updates to the project schedule and the product requirements sheet, and address various other aspects address of the ongoing Kinkajou redesign.
This was another excellent productive design review, again with MIT Mechanical Engineering Prof. Woodie Flowers, Kinkajou Alpha and Beta design team member Beto Peliks and the Gamma design team. Joining us were Owl Engineering product designers Peter Costa and Chris Homes.
The concentration of this design review was the Gamma prototype as currently configured. Given the committed delivery date of September 1, we wanted to focus on any perceived problems or short comings which could jeopardize the field evaluation. Issues are as discussed not according to priority.
For design issues and recommended actions, read the report: [MS Word file]
Back row from L: Owl Engineering Peter Costa, Woodie Flowers, Owl Engineering Chris Homes
Right side from R: Neil Cantor, Denise Kulawik, Peter Fichter, Tim McNerney, Beto Peliks
Two views of the Kinkajou Gamma (minus the crash guard)
DtM is grateful to the design review participants for their time, their great ideas, and for putting up with our lousy coffee. We would also like to thank the Media Lab for arranging this excellent temporary office space for the summer.
Following our decision to reduce financial exposure by producing just 10 units, I have redesigned the Kinkajou Gamma prototype (maybe it's now the Delta?) to use a stock heatsink (Aavid 60520) instead of the custom extrusion. I've included Peter's excellent handle design and large rubber bumpers to cushion falls. The projection lens is pulled inside the case to maintain the present, effective, optical design with the flat heatsink. A zero-power glass window will be added for protection in lieu of the plastic lens cap.
The reel drives are unchanged:
The Aavid heat sink forms the rear of the housing. Luckily, it's 250mm wide, just enough to house the reels, condenser lens and switch. The PCB fits behind one of the reels. The LED, PCB and condenser optics are unchanged.
Exploded view of the Kinkajou "delta" prototype. See the pdf version [PDF]
Comparison of the Kinkajou beta and delta prototypes.
The "delta", or fourth-generation, Kinkajou microfilm projector prototype has made the leap from SolidWorks to reality. Only a few design changes remain: making more room for the circuit board, and changing some parts of the housing from aluminum to plastic.
The Kinkajou "delta", or fourth-generation, prototype
From left, project electrical engineer Tim McNerny, lead engineer Allen Armstrong, and product manager Peter Fichter discuss the new prototype.
An early prototype of the new Kinkajou driver circuit.
Some research into the Freeplay radio's crank generator suggests that it might not be the ideal solution for our application. David Gordon Wilson's book Bicycling Science suggests that the best output we could hope from from a one-handed crank generator would be 15 watts, which would yield a 1:3 crank-to-use ratio for the Kinkajou (ie one hour of cranking for every three hours of use).
We are now looking into solar lanterns as a potential off-the-shelf integrated power supply for the Kinkajou--one that has the added benefit of supply the classroom with light when the projector is off. Unlike the Freeplay radio, which consumes less than one watt, many solar lanterns are designed to store and supply power for fluorescent bulbs consuming 10 or more watts. Some lanterns even include a 12V DC power outlet, for running radios and tape recorders.
"ITDG's consulting subsidiary ITC have developed a low cost Solar Lantern designed to make this source of energy more accessible. The lantern, now in prototype, can provide up to six hours of high quality light, or a combination of light and radio output to bring news and information to households." -- from the ITDG website. Here is a summary of the ITDG solar lantern project. Here is a final report on the Glowstar product development process (PDF). Additional specs are available through Sollatek, the lantern manufacturer, for example this lantern spec sheet (PDF).
Attached is the revised delta prototype design drawing along with a bill of materials for the housing and mechanical assemblies. [PDF file]
DtM lead electrical engineer Tim McNerney reports that the Kinkajou has passed over a week of rigorous environmental testing with no failures. Tim ran the Kinkajou through the following temperature cycle from Sep 26 through Oct 06, in a climate-controlled oven with the projector running constantly on a 12v power supply.
5 minute warm-up, 30 minutes at 120F;
5 minutes cool-off, 30 minutes at 32F
We can also report that the Kinkajou is not appropriate for use in 120C environments, as we discovered when a glitch in the oven controller lead to death-by-melting for one prototype Kinkajou!
Two observations on the current design. First, the edges of the heat sink fins as delivered from the manufacturer are too sharp. As a safety concern, we will chamfer the edges of the heat sink fins in the production run.
Second, there seems to be a risk of a "guillotine effect" where the cord can get pinched between the handle and the upper inside edge of the ABS side panels. We will investigate this further--if necessary, we can also chamfer the edge of the ABS panels in the production run.
This Fall, Design that Matters and World Education are launching a two-year pedagogical test of the Kinkajou Microfilm Projector in the adult language classrooms of 45 rural villages in Mali. To meet the start of teacher training in Mali on December 6th, we have to ship all 45 Kinkajou Projectors by Wednesday Nov 11th, next week! All of the parts have finally arrived, but the schedule has been very tight and DtM lead engineer Allen Armstrong has been working frantically to assembly the 45 Kinkajou projectors.
Volunteers to the rescue! This Sunday afternoon, we had a "Screw the Kinkajou" party at Allen's workshop to help with the mechanical assembly. The team made tremendous progress and saved our bacon!
DtM and the Kinkajou project are very grateful for the help of the following volunteers, who sacrificed a beautiful Fall afternoon to labor away in our dungeon sweatshop in Lexington: MIT MacArthur Genius and all-around Appropriate Technology Whiz Amy Smith, DtM Graphic Designer Tyler Kemp-Benedict and her husband, Master Screwdriver Operator Eric Kemp-Benedict, MIT ESD grad student Stephanie Dalquist and MIT 2.009 student Jenny Hu. Official DtM mascot Nikko made a brief appearance, to roll around in the wood shavings and investigate all the gadgets on the floor.
The Kinkajou Gamma design team is putting the finishing touches on our 45-unit production run for World Education in Mali. Product Manager Peter Fichter has finished building all of the Kinkajou power packs, Lead Mechanical Engineer Allen Armstrong is wrapping up production of the projectors, and Lead Electrical Engineer Tim McNerney is running final tests on the driver code. The team has done an amazing job of leaping over the usual, extraordinary last-minute hurdles to deliver an outstanding product.
Production Run of the Kinkajou Delta Prototype
Packaging for delivery
Projectors bound for West Africa, specifically adult literacy courses in 45 rural Malian villages
Behold, the Kinkajuice!
Developed by MIT students in the 2.009 class, the Kinkajuice has great potential as an efficient way to charge batteries in places where electricity is hard to come by. Based on an erg (rowing) machine, the Kinkajuice uses the long muscle groups of the legs and back to get a long power stroke, which is converted to DC power and stored in an attached 12V battery. The efficiency of the Kinkajuice is significantly higher than that of bicycle chargers or hand-cranks.
Kinkajuice Team members
The Kinkajuice was originally designed as an alternative way to power a Kinkajou that didn't require a solar panel. Given the right plug, the Kinkajuice should be able to power at 5-15W device.
Made for each other...
As part of the Design that Matters visit to Mali in November of 2004, team member Christine Lin brought along a Kinkajuice for field testing.
Christine Lin demonstrating the Kinkajuice at an elementary school in the villlage of Sebenakoro
A young girl giving the Kinkajuice a try at the Institute for Popular Education in Kati
Constant-current power supply for Luxeon 5W LED with low-voltage warning and shut-off
Software Documentation, as shipped to Mali in first 45 prototypes, November 2004
Author: Tim McNerney
Revision: 12/14/2004 17:21
The microprocessor-based driver circuit for a 5W Luxeon LED implements
a constant-current power supply, with automatic shut-off if the
battery falls below approximately 10.5V, and visible warning below
kled-doc.txt - documentation for the software and hardware design
main.c - software source code
kled-rev1-final.zip - a zip archive of the Gerber file
kled-rev1-schematics.pdf - a PDF copy of the circuit schematic
led-driver-rev1-07-29-04-2145.ddb - Protel 99SE CAD database (original source of the schematics and PCB artwork)
Use of the Kinkajou projector by IF&LS in India for daytime primary group education in rural areas is being explored. IF&LS offers a multimedia based projection system for group learning, but its cost and power requirements are limitations in many rural villages.
The difficult challenge for Kinkajou is that the curriculum content requirement includes text and color graphics, typically of photographic quality. Our current experience has been with content limited to monochrome text and simple graphics (black and white). The addition of color to images will increase the base density, adversely affecting light transmission, i.e. visible brightness.
We have conducted preliminary experiments using 35 mm Kodachrome images cut to 16mm format, to determine overall image brightness. Surprisingly, under "ideal" viewing conditions, ie darkened room, images were reasonably bright. We are sufficiently encouraged to proceed with production of sample color microfilm containing "typical" IF&LS content to demonstrate the systems potential.
Cutting a 35mm slide down to 16mm
Fitting the slide into the Kinkajou
Decent brightness under good conditions
We will also continue to pursue design solutions which will increase the available illumination, including improved transmission efficiency in the optics and higher power LEDs.
A human-generated power supply system, based on an easy-to-use and readily available foot treadle, can generate enough electricity to power the Kinkajou, concludes Lindsey Cameron, an Engineering undergraduate at Harvard. Lindsey recently accompanied the DtM team to Mali in March for a field test of the treadle design, which she developed as part of her Senior Design Project.
Over the course of the past year, Lindsey has been working to create a proof-of-concept prototype for a sturdy, low-cost alternative to the Kinkajou's existing power supply system, which currently relies on an expensive solar panel and parts not available in Mali. After examining the efficiency and feasibility of other potential energy sources, including hand-cranks and bicycles, Lindsey selected the foot treadle for its low cost, significant energy output, high availability, and user-friendly nature. Her final sytem combines a sewing machine, DC generator, charging circuit, battery, and status light indicators into a cost-effective power supply and battery-charging device. Since almost all villages in Mali already have sewing machines with foot treadles, the design reduces the capital costs required and even presents an opportunity for income generation for the local tailor.
A treadle, with fly wheel and foot pedal
During the field test, Lindsey brought her prototype to 6 villages in southern Mali, where 16 Malians, ranging in age from 7 to 60, tested it and provided valuable data and feedback. The field data suggests that the average user could completely charge the battery in 26 minutes of work, and the majority of users reported that the treadle was easy to use. The device was also tested by a local tailor, who set a record for energy output and loved the idea of another profitable use for his own sewing machine. Lindsey also presented the prototype to World Education and USAID Mali for a design review. Both organizations were impressed by the design's low cost, adaptability, and reliance on local materials, and made several suggestions for how to increase performance and ease of use.
Lindsey (left) watches as a volunteer tests out the device in Mali