The Electronic Puzzle
Different Electronic Puzzle sets have been developed during a periode of some years. It started with different components in an ice box (2 litre) as shown to the right. The box below is the last version so long which contains four sets of the basic components in addition to different equipments for connection to a computer and sensors for measuring temperature and light. The box is home-made based on plywood (kryssfiner) and wainscot (panel) and it should be easy to make such boxes in a woodwork class in the school.
Box lid with an upper store from the main box:
The main box:
Above are the basic components in
the Electronic Puzzle,
1b: Current dividers (Strømdelere)
If these are connected to the batteri poles and the other components are connected between these, the red LED will light up and warn if there is a short circuit or overload which may damage the battery or other components.
2 Light Emitting Diode/LED (Lysdiode)
Note that a resistance protects the diodes so that connecting them wrong won't damage them.
3 Light bulb (lyspære)
The bulb should be 6V, 50mA which means that the transistors won't overload if they supply current to the bulb.
4 Buzzer (summer)
Makes a sound.
5 Switch (bryter)
This simple homemade switch may function as a mono-stable and bi-stable switch which can changes between two circuits, and it can therefore represent different types of switches.
6 Variable resistor (variabel motstand)
Note that an extra resistor protects the potensiometer. The resistance in the variable resistor then gets a lower limit of 100Ω, but it is no problem in ordinary circuits.
7 Contact (kontakt)
For connecting variable resistors or cables from distance or local courses.
7a Light Dependent Resistor /LDR (lysfølsom motstand)
7b Temperatur Dependent Resistor / NTC (temperaturfølsom motstand)
Note that the spacing between the two contacts in the middle is a standard which also is used for the shielded cables and therefore the sensors may be placed in a distance from the main circuit.
8 Transistor (transistor)
The transistors is protected with a resistor connected to the B-pin, and as long as the user don't let the red LED on the current divider keep shining, the transistor should be relative safe against erroneously use.
9 Kondensator (kondensator)
The reason for using two condensers on one component is that they often are used in pair and it is also easy to demonstrate what happens it two condensers are connected together.
Cables and paper clips for connecting to a battery
Printer cable (Skriverkabel)
51 General connection board (Generelt tilkoblingsbrett)
The connection board has 8+4 (12) output lines and 5 input lines which means all standard inputs and outputs in the old centronics standard. The 8 data-bits which normally carries codes for different letters is in the figure connected to 8 different LED's which is there to show the status for different lines. Note that the 17 contacts on the board are connected direct to the printer port in the computer and on should not connect output lines direct to ground because that could overload the printer port. Normally this direct connection to the printer port is ok and we have not experienced that the printer port has been damaged.
Connection board for morse training (Tilkoblingsbrett for morsetrening)
Signaling with morse-signals have shown to be a popular activity and a useful starting activity before introducing more modern information coding. Therefore a simple connection between morse-equipments that children can make and a computer is developed. There has also been developed a computer program that can receive and send morse codes through this board. Inside the computer the information is transformed to/from normal text on the screen/the keyboard. The batteri is connected to the board to support power when signal is sent from the computer/the board. To this board we can connect as many morse-stations we want, but only one may signal at a time - all other have to listen. The switch on the board is placed there to make it easy to input test morse signals. Note that if the computer input line which are used here is "hung high" (is 5V when not in use, normal on most computers), the computer will receive a everlasting signal and therefore we have to connect for example a LED to the line output from the board. That will keep the input to the computer low as long as we not push on the button or the computer it self makes signals.
Timing board (tidtakingsbrett)
When we want to measure small time intervals or measure time very accurate, we have to use electronics. If we have a computer, it is rather easy to us the printer port for time measuring with accuracy around 1 ms. The timing board to the right has two input lines (A and B) and in the figure there are connected two shielded cables which ends up in some variable resistors, for example LDR. The two potensiometers then regulates the level of light where the input signal shall switches between high and low. The power is supplied from output-lines from the computer and the program and the build in clock follows standards that makes it easy to make a program that can measure all sorts of time down to ms in an easy way. Because time is one component in velocity and acceleration, this equipment can also be used to measure these concepts if we make smal changes in the computer program.
Analogous RC-measuring (analog RC-måling)
A computer is based on two values/levels which we often call '0' (no voltage) and '1' (voltage, around 5V in the printer port). In our daily life we are surrounded by analogous quantities such as light and temperature. Often we want to measure more than two values for light as we do with the timing board above (over and under a chosen limit). Much of our modern electronic equipments are used to measure or sample analogous signals as light, sound and other in a more accurate way than two levels. The board on the left do just that and it uses the same principle as modern electronic equipments. In addition to making quite accurate measurement, it also serves as a simple example which may help us to understand the basics in modern electronics.
This board have two analogous input (A and B) where we see a shielded cable which for example leads to a LDR (Light Dependent Resistor) and a NTC (Temperature dependent resistor). It also has a power connection where we can connect a 4,5V battery, but it is not always necessary if it is possible to get som power from one of the lines out from the printer port. In addition to the variable resistor in the end of the shielded cable, there is also connected a condenser to each port (red and green in the picture). The mode of operation is then that a computer program opens a transistor so that the condenser is charged. The computer then measure the time from the charging stops till it gets a signal of uncharged condenser through the other transistor. Because the discharging of the condenser goes through the variable resistor, there will be a connection between discharging timen and the light or temperature value and the program may be calibrated to measure for example temperature with a resolution of 0.01°C.
Load speaker (høytaler)
When experimenting with the Electronic Puzzle, a load speaker is useful and here we will recommend to pick out some load speakers form ruined electronic equipment before throwing it away. The picture shows a load speaker (or a microphone) from a telephone. Note that a load speaker normally also can be used as a microphone.
Electro motor for direct current (elektromotor for likestrøm)
Electronic equipment as cassette player and other equipment with for example automatic output for CDs or cassettes have some smal electro motors which should be picked out before sending away ruined equipment. The picture to the left shows an electro motor from a video-recorder which function well on voltage around 4,5V. Note that motors should have just 2 input contacts as shown here and you should only pick up motors that runs om direct current with low voltage. Other motors may be difficult to operate or it may only operate on dangerous high voltages. Note also that those small electro motors may function as generators and they produce direct current when they are manually turned around. The motor in the picture have got a bottle top on the axis to hold a homemade fan made of a bottle.
Some electro motors can be driven direct from a printer port, but normally we have to get current from an other source that can give more power (battery). We then get control signals from the computer. It is possible to by power transistors for that use. The board on the right shows a home-made power transistor that can deliver 3 times more power than one transistor and it can be used to control the power input to an electro motor.
Step motor (stepmotor)
A step motor is a motor that is driven by electrical current, but it differs from ordinary motors because it may be stopped in many different angels with exact value. The step motor to the left is from an disk drive from an older computer and it has been used to position the read/write head in different tracks on the floppy. This motor normally need a rather advanced controlling unit, but it is rather easy to control it by using four of the output lines from a printer port on a computer.
Powersupply which may change current direction (kraftforsyning som kan snu
When we use a computer to control an electro motor or a step-motor the signals from the computer have low power, and therefore we have to get more power from another source (a battery). The board on the right gets power through the red and black lines from the left and gets signals through the four blue lines. The output is then the four orange lines. If we uses half of the board we can control an normal electro motor and make it go both directions with different speeds controlled through a simple computer program through two output lines from the printer port. If we use the whole board, we can control a step motor in the same way through a slight more complex computer program.
Here we have shown some general basic boards, but there are no limits for what sort of board the user can make for different usage. The main principle here is that we use some cheap basic components and puts them together in a well arranged way so that it is easy to understand what is going on in the different parts of the puzzle. A normal procedure is then to experiment with the electronic puzzle that is shown above, and if the result is something useful, it is then possible to make some more compact boards which are more useful in practice but usually less easy to understand by just looking at them.
13.2.04 Erling Skaar