t Henderikus Allersma

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Last projects added

3D printer
Motorhome matters
Photo album with most recent photo's
Solving/making sudoku's (NEW sudoku booklet generator)
Ball falling in water.
Heater control system.
Cable for flash unit.
Steel ball falling in sand.

Allersma's professional website
Allersma's publications
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Development and improvement of systems

Mechanics, electronics, informatics, photography, etc etc


Name: Dr. Henderikus G.B. Allersma
Private researcher
Tel: +31653604224
Email: H.Allersma ipact.nl (to prevent automated searching E-address @ is not printed, use ...ma@ip...)
Allersma professional website
Allersma's publications
Hand written journal of 30 year farming (1901-1930) by Henderikus Allersma (in Dutch)

Actual areas of interest

3D printer
Motorhome matters
Private house matters.

Car, motorhome, bike

- Motorhome
Recently a motor home has been purchased. Although it is a new device several modification have been made to fulfill our requirements. The modifications and other matters can be found

- Private car

My first car

cruise control not working
To day we are drive a Mazda MPV (2003). However, also this car needs regular support to keep it on the road. Although Mazda cars are quite reliable products some curious problems had to be solved.
About two years age the cruise control did not longer work well. Very often the speed control ends in a way it ends when there is not enough motor power to maintain the speed. I tried many options to repair the device. However all the attempts seems not to help. Finally I found (after one year) that the mechanically control unit had a bad ground contact. This was not very logical, because the house was connected by a big bolt to the chassis and moreover a connector with more than 10 leaders was attached to the device. The problem could be solve by making an additional ground contact.

problem with lock sliding door.
The locking mechanism of the sliding door was not working well. In particular the electrical un-locking mechanism did hamper mostly. After removing the covering the locking mechanism was good visible. A first view did not show any problem. When activating the electrical actuator it seems that the actuator generates not enough power each time to unlock the door. After some observation it was believed that a spring which helps the actuator has lost some power in time. Therefore an additional spring has been installed in order to decrease the required force to un-lock the door. Up to now this suppletion has been solved the problem.

Private house matters

- Automated cat feeding machine. For more details click here.

- Time and wireless control central heating system. For more details click here.

- Air suction system kitchen
To avoid unpleasant smell in the kitchen during cooking an air suction system has been constructed. The inlet is above the cooking area and a ventilator of 300W blows the air in the open air. For convenience a system has been developed which automalically switches the ventilator depending on the cooking activities. Since quite a lot of air is displaced, particular in the winter period heat will be wasted. Therefore the ventilator has to run as short as possible. An electric cirquit has been build which supplies the following properties:
- automatic start, but with some delay, so that there is e.g. no action when boiling a can of water.
- quick start possible using timer switch, for the case that smelling matters are handled directly.
- direct stop possible by switching off the light.
- remote control of the rotation speed.

In order to control the suction capacity more efficiently a temperature controlled valve has been installed at one of the inlets of the suction system. This inlet is located above the micro wave oven. The temperature will rise if the oven is on , so that the valve will be set in open position.

- Repairing our TV
A strange behavior of the tv was that the screen goes on black at random moments. Actually it happen often at exciting moments we don't like to miss. Sometimes it happen several times in an hour period and sometimes it was ok for days. Knocking and bumping against the device was effective and also bending the board containing the electronic parts had succes, but it was difficult to locate the problem exactly. More or less by accident, when the open tv was up side down and turned on, lighting was visible at the solder connection of an electronic component. A closer look shows that the solder contact was cracked, resulting in bad electric contact. This could be repaired simply, so that the tv is operating well now.

A funny observation was that the colours could be affected by the following procedure: switch on the tv; place tv up side down; switch tv off; turn tv in normal position and switch power on. The colours are now disrupted. By doing the procedure in reversed order the colours become good again.

- Repairing motor micro wave oven
A micro wave oven contains a turn table to guarantee a regular radiation of the products. Unfortunately after some years the rotation of the table becomes irregular. It was a gradual process resulting at no rotation at all at the end. More close investigations show that the motor was a synchrone motor with a integrated gearing house. It could be opened rather easily, where is was visible that the magnetic rotor was separated from the bearing house with gear wheel. After cleaning the parts carefully polyester was used to fix the parts. Since the applied forces at the components are low it is believed that the repair is durable.

-Repairing fan central heater
In order to ensure a good combustionn of the gas during burning of the central heater the air is supplied by a mouse trap fan. The air is extracted from outside. The reason of the forced air supply is to prevent that the heater extracts air from the house. Because also a fan is in use to suction air from the kitchen and so on, an underpressure could be generated causing a bad burning heater. A disavantage of running part in the heater is that noise can be generated. In particular when te bearings get some play vibrations cause dat the metal cover sheets become in a noisy resonance. In the first instance it was believed that the ball bearings were dilapidated. Therefore they were replaced. The noise appeared to be reduced dramatically. However, quite soon the noise comes back again. A more detailled study shows that the ball bearings were still ok, but due to a lot of axial play in the system the axis of the rotor was weared. This causes some unbalance and so the fibrations. The problem was solved by removing a spring and some needles parts of the rotor, so that an axial movement of 5mm was allowed. A fresh ( not weared) part of the axis is now in the bearing. Furthermore the bearing has been fixed on the axis by two components polyester, so that axial movement will not wear the axis again. Now the repairing seem to be successful; the question is for how long. See below for some photographs of the situation.

- Modification CD player
To day several devices have to be connected to the audio amplifier. However, the amount of inputs are restricted. In order to add one more device without exchanging connectors, the CD player has been modified. The device is equipped with an extra connector, which is switched to the amplifier in the case the CD player is shut off. The switch consist of a relay wit a double contact. In rest the additional input is connected to the output, where the signal of the CD player is connected when the power is on. The diagram and real solution is shown below.

- Wireless transmission MP3 player to car radio
The radio of my car is just not from that generation which can play MP3 CD's. The MP3 format is attractive, because a large amount of titles can be stored in a relative small memory space. Recently I have digitized 60 LP's (from earlier times), which can be stored as MP3 format in about 2 Gbyte of memory. For inhouse use the music has been stored on CD's and DVD. But for the radio in the car another system was required. First a 2 GB memory stick with an audio output is purchased. The audio output is connected to a small FM radio transmitter. A specific frequency can be defined, so that the audio signal can be received by the car radio. A frequency has to be choosen which is not used by a strong radio sender.
In order to save batteries it is preferred that the system is powered by the battery of the car. The transmitter already has an optional 12V power input. However, the memory stick can only be powered by an AAA size battery. A special connector has been designed to feed the memory stick via the contacts in the battery compartment. A DC-DC converter has been applied to reduce the 12V battery power to 1.5 volt.

- Repair of water discharge tube
Because our house is built on a soil deposite which is sensitive for settlement, the house is founded on piles. The piles are driven to a sand layer at a depth of 18 meters. However, because the house is stabilized, problems can occur with the external connections (gas, water, discharge pipes). Gas and water are flexible tubes, so that the can deal with the difference in settlement. However, the discharge tube is of hard plastic which passes through a hole in a concrete wall and enters the soil at a depth of ca. 1 meter. After 10 year a settlement difference of about 0.4 meter occurs. This causes that the tube cracks, resulting in leakage and entering of soil in the discharge system. In order to repair this in a more durable way also in this case a flexible connection is realized. A flexible tube (length about 2 meter) with a diameter of 110 mm fits at one end into the discharge tube. At the other end the diameter of the flexible tube is streched so that it fits around the hard plastic tube. In order to create more space the layout of the tubes in the basement has to be changed somewhat.

- One way cat door
The cat is free to go in or out of the garage via a hole covered by a flap. The cat is also allowed to enter the living room. However, when we are not at home and during the night we do not always like that the cat enters the living room free. Also it is possible that strange cats are coming in. Furthermore it has to be prevented that the cat is locked in when once in the living room. For that reason there was a need for a one way cat door, prefably without electronics. Several designs have been tested, but in several cases the cat learns to open the door after a while. Finally it was succeeded to make a real cat proof design, where, the door can be opened easily from one side. In the reversed direction, however, the cat has to place his feet on a hinged platform which result in locking the door. The cat is trying every day to crack the system, but even after a year the cat did not find a solution. A diagram and some stages of the door are shown below.

- Automated window manipulator
For proper ventilation of the house a window in the inclined roof is usually open. However, when it is raining with wind, water (and sometimes snow) can be blowed trough the open window. In order to prevent a wet floor an automated system has been developed to close the window. The system is controled by a water sensitive sensor. When the sensor becomes wet the electric resistance decreases. Via a transistor a relay with a switch contact is activated, causing a rotation of 180 degrees of the manipulator. When the sensor becomes dry the relay is deactivated, causing again a rotation of 180 degrees. The rain sensor is heated by a small light bulb, to cause that the window will also be closed when dry snow is falling.


- GOTO PHOTOALBUM with most recent photo's

- Photography of falling steel ball in water

The aim of this project is to make nice and sharp photographs of a steel ball which is falling at a water surface. A composition of the different stages is shown here

- Photography of falling steel ball in sand

The aim of this project is to make photographs of a steel ball which is falling at a sand surface. A composition of the different stages is shown here

- Low budget wireless remote control

For several applications it is convenient if a camera can be controlled from distance. Ofcourse it is required that the camera has an input which can be connected to a remote control unit. The most simple and cheap sollution is to use a wired device. By means of buttons lines are connected to each other, resulting in making a photograph. The Canon 20D has a three pins connector (1,2,3). Connecting 1 and 2 wakes up the camera when it is in the sleep mode. When 1 and 3(2) are connected the autofocus system is activated and a photo is made. If 1,2 and 3 are connected together at the same moment nothing happen. Therefore some delay has to be generated after connecting 1 and 2.
For some applications, however, a wireless device is prefered. Although these devices are commercial avialble some disadvantages can be mentioned. Firstly they are rather costly, but more important is that they are using infrared protocol. This means that the distance is limited to a few meters and special tricks are necessary to control the camera from different directions. Therefore it was decided to develop an alternative system. The basis of the system is a wireless door bell, commercial available for a price of 8 euro (range ca 50 meters). The device contains a loudspeaker, which generates the bell tone. The cable to the loudspeaker is connected to two miniature reed relays (one with double contact). With help of a condensator the pulsating bell signal can be converted to a 3 volts power supply. The double relay is used to wake up the camera and to activate the second relay. Sufficient delay is now generated to enable focussing and making a photograph. The diagram and the rough electronic cirquit is shown below.

In the figure below the different possible connections are shown. The connector at the bottom side fits into the camera

In a similar way a mobile telephone is converted to a wireless remote controle device. Also in this case the leader to the bell is transformed to a 3 volts power supply by means of a condensator. With this device the camera can be activated World wide. Actually I did not yet have an application for this facility.

Below an application with the wireless remote control unit

- Home made extension cable between camera and flash unit

For some applications it is prefered that the external flash unit is not attached at the shoe of the camera, but placed at some distance from the camera. If the distance is not too long the communication between camera and flash can be realised by a cable. However, an adapter for the shoe at the camera is required and a new shoe has to be made which can hold the flash unit. Some stages of the manufacturing is shown in the picture below.

Five flexible pins are needed to make good contact when the adapter is placed in the shoe of the camera. The flexibility is obtained by cantilever arms (2). Beside the five contacts also a connection is required between the metals of the camera shoe and copy shoe (4).

- Dust free location for cleaning camera

A disadvantage of digital body camera's is that dust can enter the camera while changing the objectives. The dust can contaminate the CCD sensor and is mainly visible at photographs with large area's with homogeneous colour, e.g. a bleu sky. Therefore the sensor has to be cleaned regularly. Since in most area's lots of dust is flying around a dust arm location would be nice to perform the cleaning process. For this purpose a dust arm box is realized in which the camera can be cleaned without having the risk that new dust is entering the open camera. The wooden box has a double bottom.


The first bottom is of wood and contains a ventilator. The second bottom consist of filter material allowing passing the air which is blown in by the ventilator.


This couses an dust arm air flow outwards during cleaning the camera. An additional light spot makes that everything is good visible.

- Save use of canned air to clean CCD Sensor

- External power supply for Canon flash speedlite 580

Low budget solution for external power supply using dummy batteries. Only small modification of the door of the battery box is required. A cable with thickness of 1 mm can be used. For optimal operation a power supply of 6V, 1.5A is needed. But device also operates quite well at 5V, so that a power supply of an old PC can be used.


- Computer program to solve sudoku's

After solving 5 sudoku's I was sure that there must be a more easy way to perform this task. Therefore I have written a computer program (took about 3 days) which solves every sudoku with the standard layout. I was surprised that only three techniques were required to solve most (up to 4 star) sudoku's, being: one possible digit in a cell (naked single), a unique digit in an array (single cell) and two cells in an array with the same pair of digits (naked pair). For the more difficult ones some GUESSING is required. In this case the program takes randomly two cells with two possible digits and tries the four possible combinations (one must be good); resulting in two extra known cells. If this does not succeed the POWER TRIAL is activated. And finally the SUDOKU KILLER routine will be used, which finally solves each possible sudoku. Normally the solution takes less than 3 seconds. The power trial needs a maximum of about 120 seconds. The sudoka killer routine, however, can take more than 30 minutes. Times are based on 3 GHz computer.
twelve sudokus have been found up to now, which needs the most powerfull solving technique technique. Therefore it looks not very efficiently to optimize the program for reducing the longest processing time.
Be aware that a sudoku which is recognized by the program as very difficult is not necessarily a difficult sudoku for soduku specialists.
So, if you can't solve a sudoku download the program (sudokill-v11).
How does it work: Unfortunately I still program in BASIC under DOS, so open a directory, e.g. sudoku and download the program to this directory. The sudoku has to be placed in the same directory in a wordpad file (maximum size name is 8 characters) with the extension .txt (text document MS-DOS format), e.g.: example.txt
The digits are placed in 9 rows with 9 positions. Unknown cells are marked by entering zero. When starting the program only the name of the file has to be entered (no extension!!), e.g. example. The solution is appended to the input file. If the sudoku cannot be solved without gambling the program gives you a choice; gambling or not. If you are choosing for not the partly solved sudoku is appended to the input file, so that you can tray to find a solution which don't need gambling. An interesting finding is that in some cases the sequence of solution seems to determine if gambling is necessary or not.
For convenience a conversion routine is implemented. This routine converts the notations, as commonly used in internet forums, in a suitable format for the program. Sudokus written in several different notations can now be copied by drag and drop to the input file. See this document which notations can be used.
When the name test.txt is used as input file, simply the return bar can be hit when the program is asking for the file name.
The solution is written with different layouts to the input file. The layout at the end can be used in the drawing program Paint to generate a nice grid. First a grid has to be loaded in Paint; next the numbers can be entered by copy and paste (use time new roman, 20).

A special version of the program (sukibatc)(last update at 23-03-2008) can handle batches. This option is e.g. used to solve the sudokus given in the TOP 1465.. The one-liners can simply be copied to the input file by drag and drop.
Only sudokus written as one-liners can be handled. If the one-liners are imbedded in text the content of whole pages can be copied to the input file because non significant text between, before and after the one-liners is eliminated automatically (there is no guarantee that exceptions exist where it will not work). Duplications in the list are eliminated, also.
The program needs a control file in which the name of the input file (e.g. sin) and output files (e.g. sot) is defined. Also some counters have to be set. The program, control file and input file have to be placed in the same directory. From August 2007 an additional file solsot.txt is generated containing the problem and solution as one-liners. Also a separation is made between very simple (newspaper level) sudokus and the more difficult ones.

The content of the control file looks like (don't remove or add lines)

'name input file; max 8 characters (type without extension .txt!)
'name output file; max 3 characters (type without extension .txt!)
'index output files
'index input lines
'number of lines input file; type 0 if not known

I believe there exist no sudoku at this moment, which cannot be solved by this program. If somebody find one, please let me know.

- Computer program to make new sudokus

After some modifications of the program which solves sudokus a program has been created which generates new sudokus. The program can be downloaded here (totalsu). The program generates a file with one-liners; separate files for each sudoku and a text file where the numbers are given in a grid (unfortunately up to now only a simple presentation). The text file can be read by word, so that a booklet can be made of the generated sudokus.
A control file (control.txt) is needed to supply some data to the program (don't remove or add lines to this file). Also a file is generated containing statistics of the appearance of a certain number of clues.
The sudokus are rather easy to solve. The lowest amount of known fields reached up to know is 21.
This is how it works: The program starts with an empty field. Randomly 22 digits are placed, in such a way that the numbers obey the rules. After this procedure the program tries to solve the sudoku. If the sudoku cannot be solved the program starts again with an empty field. If there is a solution (mostly with some guessing) a new sudoku is born. Actually the program is not displaying this sudoku because only sudokus with 22 or 24 known fields are generated in this case. In the next step digits are removed randomly from the complete matrix. Each time it is checked if the sudoku can be solved. If not the digit is placed back and a new tray is done. This random procedure is repeated until less than 35 known field are left. Then each digit is tested systematically if it can be removed or not. This results mostly in sudokus with 24, 25 or 26 known cells. A filter can be defined to generate only sudokus with e.g. 21 known cells. This is about 1 of 300. The generation of a sudoku takes a few seconds.
Since only three solution techniques are defined in the solution program the sudokus can always be solved by using these three techniques.

- Computer program to solve a mathematical puzzle

This program solves puzzles like:


The letters ABCDEFGHJK have to be replaced in such a way by a digit, that the calculation is valid. The input of the program has to be placed in a .txt file, like:

( NOTE: it is also allowed to enter non-captures )
The solution will take some time, up to more than an hour is possible. So in contradiction with the sudoku program you will have a fair chance to win from the computer.
Recently (April 2009) the ins and outs of program have been improved somewhat. Also, the speed has been optimized by programming that a letter at the left of a digit is not allowed to be zero and that there are not two letters with the same value. A new option is that a choice can be made by giving the solution at once or for each letter apart. In this case you can use the progam to verify your findings during solving the puzzle.

- Computer program to examine the in's en out's of the deformation tensor

This program allows you to examine the deformation in a body under stress. As a result of external forces a body will be deformed. The visible deformation is dependent on: the strain, the direction of major strain, the rotation and the volume change. The mentioned parameters can be varied interactively, where the effect is visualised in a dynamic deformation field. How does it work: download the program in some directory and start the program by mouse click.
I am afraid that some basic knowledge about stress and strain is required to appreciate this program.

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Rover on Mars
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Live on Mars??

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This page has last been edited March 2013 by Henderikus Allersma