Demotech News
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News Fri Feb 21 (2003) -- Wed Apr 23 (2003)
News Wed Nov 13 (2002) -- Sun Jan 19 (2003)
More light out of less batteries |
Tue Nov 12 (2002) |
In Western economies a breakthrough is expected in the development of ever more effective Light Emitting Diodes. These components develop with the speed similar to computers: Fast improvement of functionality and steep reduction of cost in a short time.
In the circuits of the NightReader as developed and used up to now the LEDs are not the limiting factor regarding cost. Now it is the cost of generating electricity. With the NightReader working on near empty discarted batteries, Demotech could make a sort cut through this problem.
However we should prevent any loss of tension or current in the circuits used. Today Jos Knoop told me he found the right components to reduce the tension almost by half, as needed from the batteries to let the LEDs function. This means enormous progress for practical use. The chance to find four still useful batteries is far greater then the six to eight batteries as needed now.
I established a contact today among Jos Knoop and Jos Spanbroek of "De Spelerij". Jos Spanbroek has an interest in playfully used LEDs powered bij solar cells. He expects he can arouse a lively interest in the mind of young people if they find out how these LEDs function and how usefull they are. Jos Knoop will prepare a setup for demonstrating what can be dome in this field.
I am very happy with this cooperation, as I can learn a lot of the possibilities of a more general use of LEDs for illumination.
Senegal instead of Bangui |
Sat Nov 09 (2002) |
Willem is safely back from Bangui. He traveled with a group expats from Bangui to Cameroon and flew home from there. I do not expect the situation in Bagui to be stable soon and am forced to cancel the plan to go there. Instead I will visit Senegal for three weeks.
My plans for Bangui centered on the NightReader. In Senegal the issue is water lifting, with pulley and rope pump. I will accompany Ives Faye to his Keur Massou farm project. I expect to have plenty of chance to try the NightReader as well. Specially after sunset!
Wood burning stove build from stones |
Sat Nov 09 (2002) |
Together with Hans Baarslag and his two compagnions Johan and Zuhair, we made the first setup of the new design for a stove as described in the list . We experimented in Hans new workshop, a former cow shed with no heating.
This is what we are heading for:
The stove will have a table like model. It rest on a metal frame 30 cm above the ground and is about 1 meter high.
The stove is constructed out of concrete paving stones (60x40x6cm) for bottom and top. In between bottom and top two walls are masoned from ordinary bricks with mortar. This mortar is just a 1:1 mix from clay and sand. Fire-resistant concrete tiles for lining are only used where the wood is burning.
Air is pre-heated before ist reaches the fire. To attain a very high burning temperature the actual fire place is small. It is expected the fuel will be consumed at a slow pace. This is in contrast with nomal wood burning stone stove that burn their fuel fast.
The hot air on its way to the chimney is guided outside af the brick walls, behind metal sheets, that clamp inbetween the top and bottom. These metal sheets can be cut from a flattened oildrum.
Wood as fuel is fed into the fire from a pipe-like container positioned above the fire..The container is closed at the top
Bangui in trouble |
Sun Oct 27 (2002) |
Last contact with Willem van Tijen by telephone was on Friday. Willem reported hearing explosions. I expect him and the people from Medicins Sans Frontieres able to manage their present situation.
The chance to go to Bangui next month is small. Possibly I should divert the intended work to a location in Senegal.
From Bangui to Senegal and back |
Fri Oct 25 (2002) |
I plan to go to Bangui from the 15th of December for a month stay. My Senegalese friend Ives Faye asks me if I could make a return trip from Bangui to Dakar to prepare for the irrigation of his Keur Moussa farm project. Looking at the globe I discover these two towns are not that far apart comparing to the distance from Holland. He tells me the climate is fine around Christmas, cool, no mosquitos!
Today we practised cutting a ring out from a car tire. Cutting rubber is easy if only you use a sharp knive and force the sides of the cut into the rubber apart. If this is done well, rubber cuts like butter. But it takes practice to do it well.
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Step 1 is making a knive out of a broken hacksaw blade. Sharpen the tip and wind a strip of inner tire around the rest of the blade as a handle.
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Step 2 is pushing sticks inside the car tire that spread the flanges as much as they allow. |
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Step 3 is making a circular cut at the right place for the pulley. A circular line indicates where the side of the car tire fits against the flange of the steel wheel. The right place for the cut is just the width of a saw blade away from this mark. |
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Step 4 is dividing the ring into two equal halves. Measuring is done with a straight stick and a straw. |
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Step 5 is cutting the rings loose from the rest of the tire. Be aware very little force was needed. While one's hand is cutting one way, make sure your other hand is safely doing something helpful in the other direction.
Never your fingers should be in front of the knive.
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Newest model NightReader now in Bangui/CAR |
Mon Oct 21 (2002) |
Willem, since yesterdy again in Bangui for aircraft maintenance took with him from here
six NightReaders. I want more people to get user experience, also an expectation that this little device should become more widely available. The first user comments will come back in one or two weeks. I am ready to give follow up to that with improving on the present design.
The present latest model uses only one LED, using 10 mA, 2.5 V because it emits yellow light. the diffusion angle, meaning the width of the ligt beam is wide, 70 degrees. The cost about 20 Euro cents if bought in some quantity.
These NightReaders are constructed as if done with local aids, apart from the electronic components: wood for the handle, roof sheet for the shade wiring from a scrapped car. The little pincer made out of a bicycle wheel spoke proves to be very usefull for making the tiny holes.
Keeping components on one side of the thin wooden circuit board and soldering on the opposite site works well. Cross over interconnections are made by bit of insolated wiring placed over the electronic parts.
I look for smarter circuits. Jos Knoop researches on a more appropriate tyristor, Marc came up with a source for relevant info at the website "Circuits on Line"(see forum page NightReader). I will do some testing myself to get an idea how long the NightREader takes to drain the energy out of used batteries with a to low voltage for practical use.
Ten newest model NightReaders to go to Bangui next week |
Fri Oct 11 (2002) |
Monday next, my son Willem travels to Bangui in the Central African Republic for aircraft maintenance. Now I work on ten NightReaders of the using-next-to-empty-batteries type, that he could take with him. The first prototype that Willem took there three weeks ago was received with enthusiasm by the local people that he contacted through the Medcin Sans Frontieres. With this new series of ten, I work on a wider base for local experimentation, as up to now I had no practical experience of how the gadget would function. Expecting similar positive response, I prepare to visit Bangui mid December for 4 weeks stay. Other project should be presented there as well, such as the rope pump, the Demo Sticks and the pulley.
I should present pictures here of these items, but my PC has broken down, so I can not access the image folder.
The design for the NightReader gets a better base. Paula worked on the method for making the battery bags. Jos Knoop checked the electrical circuit for limiting tension for the two LED's used in the NightReader. He supports the circuit as advised to me by Frans Spiering. It has to be checked if an extra condensor should be added parallel to the resistor that governs the tension produced by the transistor.
I found it difficult to decide on the wiring between the electrical components, but the outcome is satisfying for the time being. The outcome is: components and insolated bits of wiring on the outward side of the mounting board, all soldering of components an wires on the other side. This safeguards components from being damaged by a hot soldering device. In practice, the wiring results in a protective cover over the electrical components. It proved easy to solder with primitive means. It was well possible to visually check these connections.
The mounting board is actually the little wooden handle, with the middle section reduced to 3 mm.. It proved easy to make little holes to pass the electric wiring. I used a sharpened bicycle spoke, bent in a special way (soon an image will be made available).
Again Willem will stay in Bangui for only one week. News on how the NightReaders will perform will soon be known.
I-mode for Diary |
Wed Oct 09 (2002) |
Demotech is a dwelling made out of ideas in which some people sometimes live. It may help to gather these ideas under the one name "Demotech", but sometimes it feels more real to present oneself not as "We, the company", but simply as I, the writer.
As I, Reinder van Tijen, write these news items, I could also write them as personal comments, as a kind of diary. I expect reporting on progress with Demotech work, will be nicer work if I can do it from a personal point of view.
There is a good reason to start today in this "I-mode". New today is the ease of adding NEWS to this page. Marc programmed all the buttons for easy access and this is the first time I use them.
Real news today is the stack of battery bags and holders for electronic parts, both in preparation for the NightReaders to be taken next week to Bangui in the Central African Republic. I am fascinated by the enthusiasm on reception of the first NightReader by the local people. I want to know how it works out when more people will use this little light. Kim, the anthropologist, working in Bangui for Doctors without Borders, will listen to the comments and let me know what people think about it.
The plan to go to Bangui myself takes more shape. I hope to verify the NightReader fulfills a real need. If so, I hope to encourage local manufacture. The design as it is now, should make this possible.
I-mode, diary fashion of writing news starts today, as Marc has programmed useful buttons to facilitate this. News was working with my neighbor Paula on NightReader parts to be shipped to Bangui next week.
NewNews! |
Sat Oct 05 (2002) |
Again some improvement in the way this news item is organized. "News" was a separate HTML-file, now it is a subrecord, organized like the other sub-records. Similar as with the other sub-records, it is possible to react to any item of 'news' in a forum page.
When 'news' has become 'old news', it will be linked to the sub-record to which this item is related.
New way of displaying the subrecords |
Fri Sep 20 (2002) |
Marc has written some PHP code for Demotech's SQL database to display in each record all the subrecords that belong to it. These sub-records, such as the publications listed in the record 'Publications' are from now on automatically displayed in a list. The title of the subrecord is clickable, as to faciliate access. Also a summery will be displayed together with a small picture for each sub-records.
It will take some time to write these summaries, before we can wipe the old way of displaying.
News Mon Sep 16 (2002) -- Thu Aug 08 (2002)
News Mon Jul 01 (2002)
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