The
logical simulator |
How
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Created it, 06/10/19
Update it, 06/10/19
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FOOT - NOTE :
Larger computer with the smallest pocket calculator, the digital technique is there. It develops each day more and intervenes in each field of your modern life in which electronics is present.
The goal of the experiments practice of digital technique and to allow you, by means of handling, to study the fundamental principles of this technique.
Through a series of programmed practical exercises in a progressive way, you will be able to easily assimilate the concepts exposed in the theory ; you will learn how to know at the same time the function and the use of the various electronic components usually used in industry, by carrying out the breadboard constructions.
Knowledge that you will have acquired of the basic circuits, could be wide later on, making it possible to you to specialize you in this technique ; with an aim of building, to repair and control any apparatus calling upon the digital technique.
You will find all the electronic components, resistances, condensers, integrated circuits, transistors, etc… in any electronic trade. It will be enough to choose the components well but we will give you all the characteristics with each practice, i.e. the values of resistances with marking as well as the condensers and of others still in order to facilitate to you well for your practical work.
A part only of the material of this first practice will be used immediately for the exercises ; the remainder will be employed thereafter, with the material complementary to the following series i.e. the 2nd practice, 3rd, etc…
It is thus advised to separate the components of which the use is not immediate and to place them in sure place.
For the execution of the assemblies, follow scrupulously progressively with the provided indications, even if if sometimes some can seem to you superfluous ; in this field, controls are never too many and even less useless.
IMPORTANT NOTE :
Not to remove the integrated circuits of anti-static foam (or the anti-static case) before their immediate use because they could be damaged irremediably.
By convenience, we will trace the electronic diagrams partially with each practice in order to better include/understand and we will explain you on their operation various and finally to simplify your work as well as the breadboard constructions.
Any similarity in report/ratio with our project, we would be held irresponsible. On the other hand, the logical simulator should not be marketed without our agreement under penalty of sanction because this site is completely free.
1. - THE LOGICAL SIMULATOR
In this practice, you will begin the assembly of the desk of the simulator illustrated in figure 1 heading “DIGILAB” which will allow the course of the program of the practical experiments envisaged in our project.
You will have the occasion to appreciate at the end of the assembly the utility and the convenience of use of the “Digilab” in the functional check of various types of integrated circuits or in the experimentation of an electronic circuit. Indeed, with a didactic aim or simply for the pleasure, it makes it possible to carry out relatively complicated breadboard constructions quickly, without requiring the use of the soldering iron and by avoiding the generally encountered difficulties when one does not have a suitable support for the circuit which one wishes to carry out.
Lastly, making possible the realization of test loops of all kinds, the logical simulator can be transformed into a test and testing device, useful for the individual checking of the integrated circuits of which the apparatuses based on the digital technique are made up.
1.1. - GENERAL CHARACTERISTICS OF THE SIMULATOR
It is appeared as a box whose higher face includes/understands 2 zones (figure 1).
On the zone of right-hand side are laid out the following elements:
Together of hexadecimal posting
It is together is formed by two hexadecimal bill-posters with matrix 4 x 7 points with circuit decoder and built-in memory allowing the visualization of numerical signals coded into hexadecimal about which we will speak later on.
Indicating whole with LED
Formed by 8 LED and their control circuit, this unit makes it possible to obtain a visual indication of the logical levels present in various points of the studied circuits.
Group connectors
This whole of connectors consists of 42 contacts giving access to all the functions of the simulator by simple insertion (without welding) of rigid wire constituting the connections.
Double oscillator of clock
They are two oscillating circuits with resistance and capacity (RC), independent one of the other, able to provide rectangular signals having the following frequencies :
first oscillator : 1 Hz, 10 Hz, 100 Hz
second oscillator : 1 kHz, 10 kHz, 100 kHz.
As the two oscillators are independent, two signals of different frequencies: one provided by the first oscillator and the other by the second will be simultaneously available on the group of connectors.
The commutation of the frequencies of each oscillator is done by the selection of resistances of suitable values.
Detector of change of state
This circuit makes it possible to carry out controls on the numerical signals, it allows, more precisely, to check the moment when a signal passes from one state to the other.
Together of mechanical reversers
The whole of reversers consists of four switches with 2 positions making it possible to have as many variables logical order; by actuating them, one can indeed make change the logical state of each variable by commutating a high state (1) or a low state (0).
Together of push-buttons
This unit is equipped with a debouncing system, making it possible to have on the group connectors, of faces of rise or descent free of the phenomenon of bounce due to the contact mechanics elasticity about which we will speak later on.
Support for integrated circuits
This support, 14 pins for integrated circuit, connected to the connectors, will make it possible to carry out the first experiments on logical circuits by which you will be able to concretize the theoretical explanations.
On the zone of left the orders relating to the feeding circuit are placed with which the simulator is provided, as well as the matrix with contacts for breadboard constructions.
Stamp with contacts
On this turntable, one can carry out the assembly and the electronic tests of circuits without having to carry out welding. It is thus possible to modify the circuit or to recover the components after the experiment. If one had employed a soldering iron, the reliability of the components could have been compromised.
Catch loudspeaker
This catch gives access to a loudspeaker placed inside the box.
Switch of walk/stop
This switch makes it possible to apply the tension sector to the feeding circuit of the simulator placed inside the box.
The electric characteristics of the food are as follows :
Tension of entry : 220 V
Output voltage : 5 V
Intensity of the maximum current of exit : 1,5 A
Protection of the exit against shorts-circuit
Protection interns against the thermal overloads.
Nomenclature for the construction of the logical simulator is as follows :
1 printed circuit 17 x 18 cm and adhesive bands of 1,5 mm (approximately)
1 pile of 4,5 V
10 resistances 220 W - 1 / 4 W tolerance ± 5 % (red - red - chestnut - but)
9 resistances 15 kW - 1 / 4 W tolerance ± 5 % (Chestnut - green - orange - but)
6 resistances 4,7 kW - 1 / 4 W tolerance ± 5 % (yellow - purple - red - but)
1 resistance 12 kW - 1 / 4 W tolerance ± 5 % (chestnut - orange red - but)
2 resistances 150 kW - 1 / 4 W tolerance ± 5% (chestnut - green - yellow - but)
2 resistances 1,5 MW - 1 / 4 W tolerance ± 5 % (chestnut - green - green - but)
1 electrolytique capacitor with the tantalum of 0,33 µF - 10 V
1 ceramic condenser disc of 330 pF
8 LED of 6 mm
10 transistors BC 238B
3 supports standard standard for integrated circuits (14 pins)
3 supports professional standard for integrated circuits (14 pins) 2 for the bill-posters + 1 per ICX
1 integrated circuit MM 74C74
1 integrated circuit MM 74C14
1 integrated circuit MM 74C00
2 hexadecimal bill-posters with matrix 4 x 7 points of type TIL 311 or its equivalent
2 connectors with 32 contacts on line
2 crocodile clips with cap (1 black and 1 red)
1 flexible wire braid red - black (approximately 30 cm each one)
8 screws f 3 x 6 mm
4 threaded hexagonal spacers
1 roller of welding
4 switches with two positions (reversers)
2 push-buttons (reversers)
The components know-evoked are reserved only for the assembly of the printed circuit, with regard to for the food, transformer, fuse, regulator, box, etc… will be given to you in the following practices including certain integrated circuits for the numerical experiments.
2. - COMPONENTS USED IN THE PRESENT PRACTICE
1 printed circuit 17 x 18 cm and adhesive bands of 1,5 mm width (approximate)
1 pile of 4,5 V
8 resistances 220 W - 1 / 4 W tolerance ± 5 % (red - red - chestnut - but)
6 supports for integrated circuits 14 pins (3 standards + 3 of the professional type)
2 connectors with 32 contacts on line
2 crocodile clips with caps (1 black and 1 red)
8 LED (electroluminescent diodes)
1 flexible wire braid red - black (approximately 30 cm)
4 screws f 3 x 6 mm
4 threaded hexagonal spacers
1 roller of welding
You must have a screwdriver, grips brucelle, cutting pliers, soldering iron and of an universal controller.
We measured for and it against conceiving the project of the logical simulator on several practices and the breadboard constructions ; because we are conscious that certain people will not be able this to allow to trace the tracks with adhesive bands on the printed circuit or to practically buy all the components. But however, we did everything to facilitate the tasks of them.
You can also visit the sites which are specialized in the field of manufacture of printed circuits into simple or in double face (tracks with adhesive bands) in their asking for an estimate via the search engines by typing in the zone “Printed circuit”.
In fact, this printed circuit is not quite complicated bus while looking more closely as you can see it in figures 2 and 3, this same gating circuit on the higher face (or with dimensions screen prints) indications on the site of the components (figure 2) while figure 3 represents the layouts of the adhesive bands or coppered to which we voluntarily spaced the adhesive pastilles and bands in order to better distinguish in order to be able to correctly trace them on a printed circuit of dimension 17 x 18 cm. It is quite obvious, between two adhesive bands has a separation from 2 to 3 mm and this, to avoid any short-circuit.
Figure 2 represents the site of the components and the dimensional aspect.
Figure 3, as for it, illustrates traced bands adhesive or coppered on a printed circuit, it is enough to recall the latter for use with fine personnel.
The use of the supports for the integrated circuits offers the advantage of being able to use the latter without having to weld them, thus, if necessary their replacement will be easy and fast.
It should be known that there are two types of supports. They differ between them by the technique from realization from the pins, represented in figure 4.
Three of the supports which you will use in this practice are of professional type (figure 4-a) with contacts tulip obtained by turning. They are particularly adapted to the integrated circuits having rather fine and fragile pins. This type of contact is able to ensure a better connection from the electric point of view, even after many insertions of the component.
The three other supports are of standard type (figure 4-b) adapted to an everyday usage.
For a correct assembly of these supports, attentively consult the remarks concerning their orientation, because according to manufacturers, the system of reference mark of pin 1 differs somewhat (figure 4).
Diodes LED are equipped with two electrodes (anode and cathode) having to be correctly identified at the moment of the assemblies : in the contrary case, the LED can be damaged.
Figure 5 shows you how to distinguish cathode from the anode of a LED.
2. 1. - HOW
TO CARRY OUT A GOOD WIRING
Before beginning the work of the assembly, it is wise to draw your attention to some remarks which will enable you to carry out good weldings.
As you could note it by observing the lower face of the printed circuit (side tracks of copper, figure 3), the pastilles on which you must carry out the weldings in the majority of the cases are very brought closer. It is thus necessary to use a soldering iron with a very fine breakdown ; moreover, the power of the soldering iron must lie between 15 and 25 Watts in order not to damage the pastilles or the components to be welded. Iron will be provided with a transformer of insulation or will be disconnected during the welding.
It is also essential to use welding with the tin of good quality and whose diameter does not exceed 0,75 Misters.
The material that you have at your disposal or to buy recently must answer these requirements perfectly ; to in no case, you should not use welding or a soldering iron not fulfilling the requirements indicated above.
After each point of welding (figure 6), have care to clean the point of the breakdown of the soldering iron with a sponge (or a cotton rag) maintained wet constantly.
To carry out a good welding, practice as follows :
support the breakdown of the soldering iron so that the point touches
simultaneously the terminal of the component and the copper pastille to be
welded.
develop the end of tin precise where the terminal to be welded is in contact
with the point of the breakdown and maintain it in this position until a
sufficient quantity of tin melted to form a drop of the dimension of the
pastille.
maintain the soldering iron in contact with the pastille and the terminal time
necessary so that tin spreads the pastille of course and coats the terminal to
be welded ; this time can vary from 3 to 5 seconds.
Avoid keeping too a long time the soldering iron in contact with the point of welding bus differently you are likely to damage the copper track or the component.
During these operations, it is wise to move the breakdown around the point slightly to be welded to support the molten tin deposit and to cover totality with the copper pastille in a uniform way.
As soon as the welding is not cooled (never blow above to cool it), you will be able to cross, if necessary, the surplus part of the terminal welded by means of the cutting pliers.
A good welding must appear brilliant, smooth and the silver plated color. The copper pastille of the printed circuit and the terminal of the component must form only one block like illustrated in the figure 7-a).
So on the other hand, the welding has an irregular and granulous aspect, or arises as a mercury ball (figure 7-b), it acts of a cold welding due to the incomplete fusion of tin on the parts to be assembled. This is caused either by a too low temperature of the breakdown of iron, or by a bad application of the breakdown on the elements to be welded not allowing the diffusion of heat. It is possible to cure a cold welding, while heating again and while bringing, if need be, a little welding and by making sure that it diffuses well.
In all the cases, you recall that for each welding, it is advisable to use a correct quantity of tin by taking the maximum of precautions so that it does not overflow on a pastille or a close track not connected thus creating a short-circuit as illustrated in the figure 7-d.
The protective varnish covering the tracks with copper not having to be welded should prevent this possibility which is however not excluded and can occur because of the inevitable tolerances of manufacture.
In the figure 7-c, one can see how a good welding arises whose execution requires a detailed attention because of the presence of two copper tracks côtoyant the point to be welded and who must remain isolated about it.
If, by tin excess, you are in one of the cases represented figure 7-d, it would be necessary to eliminate this excess from welding which overflows of the pastille while serving to you as the braid to unsolder.
In figure 8, one can see how this operation is carried out : the braid is posed on tin to remove, and by supporting the point of the breakdown of the soldering iron onto the braid, this one warms up, dissolves tin that it absorbs. It is often necessary to take again the welding in question by avoiding this time overflowing.
Before beginning work, you recall need for proceeding with the maximum of precautions and care during phases of work envisaged, because of the complexity (although progressive) of the circuits to be realized and the use of miniaturized components.
It will thus be necessary for you, before beginning an assembly, always reading with attention all the phases of work without neglecting no, you will be able to then pass to the execution of each operation indicated by scrupulously respecting the instructions given.
In each case, avoid passing to the following experiment before to have concluded the preceding one until its term.
While taking this advice, you will ensure yourselves of a maximum of success in the realization of your work practice and you will extract the maximum of profit from these experiments.
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