Examination of the
Integrated circuit LM 555 |
Preparation
of the material |
|
|
Return
to the synopsis |
To
contact the author |
Low
of page |
Created it, 06/10/19
Update it, 06/11/01
N° Visitors
The first part of this practice will enable you to finish the assembly of Digilab. For that, you will install a loudspeaker inside the box. This loudspeaker will be connected with a catch jack assembled on the metal panel.
You will carry out then a series of experiments, highlighting the flexibility of a timer integrated circuit. By its electric characteristics, this last lends itself to a large variety of applications.
1. - END OF THE ASSEMBLY OF THE DIGILAB
Among the material in your possession, take the following elements :
The loudspeaker of 12 W.
Two springs of fixing of the high speaker (according to your assembly).
Four screws autotapping machines of 2,2 x 9,5 mm.
Four discs Ć 6 x 3,2 mm.
A catch miniature jack female.
A miniature card male jack.
A twist of flex-wire red and black of section 0,25 mm˛
You can now pass to the phase of assembly by conforming you to the following instructions :
a) First of all, withdraw from Digilab all the connections and components relating to the last experiment.
Disconnect then Digilab of the catch sector then unscrew the four screws autotapping machines of fixing of the metal front face and place the latter beside Digilab without disconnecting the various connections.
b) Place the catch jack female in the hole of the front face located by initials SPK. You will intercalate the disc between the front nut and face as indicated in the figure 1-a. Respect the position of the catch jack as indicated in the figure 1-b.
c) Cut two pieces of flex-wire of 0,25 mm˛ of section, one red and the other black, of approximately 30 cm length.
Weld an end of the black wire to strip 1 of the catch jack and an end of the red wire to strip 2, as illustrated on figure 2.
d) Twist the two wire red and black between them and weld the two loose leads with the thimbles of the loudspeaker as illustrated on figure 2.
e) By deferring you on figure 3, lay out the loudspeaker with the site envisaged in the box of Digilab (according to the model). Block the loudspeaker by means of the two springs and of the four screws autotapping machines of 2,2 x 9,5 mm by intercalating four discs Ć 6 x 3,2 mm.
f) Place the metal panel on the box without fixing it, then connect the card in the catch sector.
You now will prepare a cord equipped with a male card jack.
This cord will enable you, initially, to check the assembly of the loudspeaker, then to thereafter connect the loudspeaker to an electronic circuit.
The male card jack consists of two parts, like illustrated appears 4-a.
To carry out the assembly of the card jack, proceed as follows :
g) Unscrew the sleeve isolating from the male card jack and thread this one in the catch jack female assembled on the panel of Digilab like illustrated appears 4-b. This will facilitate the work of welding to you on the male card jack.
h) Fold towards the outside the end of the grounding lug 1 of the card, as that appears figure 4-b.
Galvanize the central contact 2 by depositing sufficient welding so that tin runs in the hole of contact 2.
i) Take the two pieces of red and black wire approximately 20 cm length. Strip the ends on approximately 5 mm ; twist the bits of the driver then galvanize the ends.
j) Reduce to 2 mm one galvanized ends of the red driver and weld it onto the central contact 2 of the card jack. Take care that the red insulating sleeve is in contact with the point of welding (figure 4-b).
k) Galvanize strip 1 of the card jack and weld an end of the black flex-wire there (figure 4-b).
l) Rectify strip 1 as indicated figure 4-c and screw up the sleeve on the card jack.
m) Twist between them the two drivers red and black of the cord carried out and after having reduced to 2 mm their loose lead, approximately weld onto each one of them a small piece of galvanized stripped rigid wire of 1 cm length.
In this way, the two ends of the cord could be introduced into the holes of the matrix.
When you finish the cord, it must such as be represented figure 5.
1. 1. - CONTROL OF THE ASSEMBLY
Prepare the controller for the measurement of resistances on the gauge W x 10 and with the card jack introduced into the corresponding catch put the test probes in contact with the loose leads of the cord.
You must find a value ranging between 10 and 14 W.
If you find a value zero, there is a short-circuit, probably on the level of the catch jack.
You will thus have to check the weldings on the level of the latter.
If you find a value infinite, check that the weldings are well carried out or that the loudspeaker is not cut.
When this control is finished, you can definitively fix the metal panel on Digilab with the four screws autotapping machines.
2. - EXAMINATION
OF THE INTEGRATED CIRCUIT LM 555
This integrated circuit was especially designed to function like timer. It priest with a large variety of uses.
He can, in particular, function into monostable or astable, and deliver impulses varying of some µs to several mn.
This circuit can be used in alarms, the indicators, the plays of light for neon signs and in general in much of circuits which ensure of the functions of temporization.
Its supply voltage can vary + 4,5 volts with + 16 volts. Therefore, it can be used in the circuits containing components TTL (supply voltage of 5 volts), or containing components CMOS.
Its exit can provide a maximum current of 200 mA, which enables him to order loads claiming an important current.
The duration of the impulse of exit delivered by the LM 555 is practically independent of the supply voltage.
If this tension varies between 5 volts and 15 volts, the variation of the duration of impulse does not exceed 1 %. It will thus not be necessary to feed this circuit with a stabilized or controlled power supply.
Its operation is also far from depend on the temperature, at least in the range of the ambient temperatures where function the majority of the electronic assemblies.
This circuit also exists in a double version : they are the 556.
It should be noted that this circuit is not really a numerical component but rather a hybrid component like the monostable circuits or astables seen before in theory 6.
During following experiments, you will see some applications of this circuit and in particular a device allowing the measurement of the frequencies.
2. 1. - OPERATION OF THE INTEGRATED CIRCUIT LM 555
We will reconsider the operation of this circuit already seen in theory 6. Figure 6 represents its synoptic diagram.
This circuit is composed of two comparators (one is the comparator of threshold, the other the comparator of release) and of a rocker R.S.
The exit 
of the rocker orders a transistor and a buffer
; this last reverse the output signal and can provide a current of 200
mA.
Rocker R.S. is ordered by the exits of the two comparators.
That of the comparator of release is connected to
the entry SET of the rocker.
When the tension on the entry of
release becomes lower than 1 / 3 Vcc, the
exit of the comparator passes on the level H,
therefore the entry SET is activated and the
exit
of the rocker passes on the level L.
The transistor of discharge is then blocked (equivalent with an open switch).
For the comparator of threshold, operation is
similar.
When the tension on the entry of
threshold (entered noninverseuse of the comparator) exceeds 2
/ 3 Vcc, the exit of the comparator passes on the level H.
In this case, the exit
of the rocker passes on the level H and the
transistor of discharge is saturated (interruptory
closed), whereas the exit of the buffer passes on the level L.
There is an entry of tension of order making it possible to vary the two thresholds of reference, on the one hand on the inverseuse entry of the comparator of threshold and on the other hand on the noninverseuse entry of the comparator of release.
The entry RESET of the integrated circuit is active on a level L and makes it possible to force the exit of the LM 555 on the level L.
Figure 7 represents the stitching of the LM 555.
3. - PREPARATION
OF THE MATERIAL
Take in the stock of material in your possession the following components :
1 integrated circuit LM 555
1 integrated circuit MM 74C193
1 integrated circuit MM 74C04
1 integrated circuit MM 74C74
1 integrated circuit MM 74C08
1 integrated circuit CD 4040
2 diodes 1N 4148
1 resistance of 1 MW - 1/ 4 W - tolerance 5 %
1 resistance of 120 KW - 1 / 4 W - tolerance 5 %
1 resistance of 47 KW - 1 / 4 W - tolerance 5 %
1 resistance of 12 KW - 1 / 4 W - tolerance 5 %
1 resistance of 10 KW - 1 / 4 W - tolerance 5 %
2 resistances of 6,8 KW - 1 / 4 W - tolerance 5 %
2 resistances of 1 KW - 1 / 4 W - tolerance 5 %
1 resistance of 4,7 KW - 1 / 4 W - tolerance 5 %
1 resistance of 68 KW - 1 / 4 W - tolerance 5 %
1 potentiometer trimmer of 10 KW.
2 electrolytique capacitors with the tantalum of 10 µF - 12 V
1 electrolytique capacitor with the tantalum of 1 µF - 12 V
1 condenser of 0,1 µF
2 condensers of 0,01 µF
1 condenser of 330 pF
1 twist of insulated rigid wire (red, black, green).
|
Click
here for the following lesson or in the synopsis envisaged to this end. |
High
of page |
 Preceding
page |
Following
page |
