Examination
of a monostable integrated circuit redéclenchable “CD 4528” |
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Created it, 06/10/19
Update it, 06/10/26
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7. - SIXTH EXPERIMENT : OPERATIONAL TEST OF MONOSTABLE REDÉCLENCHABLE
As you learned in theory 6 (digital electronics), the monostable ones are divided into “non-redéclenchable” and “redéclenchable”. One classifies them in one or the other category according to their behavior vis-a-vis the periodicity of the impulses of order.
If, after having sent a first impulse to the entry of monostable a redéclenchable, one applies a second impulse before that of exit of monostable is finished, this one is prolonged of a time equal to that past between the first and the second impulse of order.
On the other hand, monostable “a non-redéclenchable” is completely insensitive to one second impulse of order, as long as it did not return in its at-rest state.
Operation different from these two types of monostable is highlighted in the timing charts of figure 10. According to applications, it can be useful to exploit the particular characteristics of one or other circuit.
7. 1. - REALIZATION OF THE CIRCUIT
a) Disconnect the food and remove all the components and the connections relating to the preceding experiment.
b) Insert on the matrix the integrated circuit MM 74C74 in the position indicated by the figure 11-a and carry out the circuit illustrated by this figure while serving to you as a resistance of 1 MW, of a condenser of 1 µF and a diode 1N 4148 or its equivalent.
For the moment, do not put the diode D2 (1N 4148) and do not carry out the connections appearing in dotted on this figure.
You thus carried out the circuit of the figure 11-b; it is about monostable “a non-redéclenchable” functioning in a way completely similar to that of the third experiment. In this case, entry PRESET is used instead of entry CLEAR and for this reason, the connections are a little different.
7. 2. - OPERATIONAL TESTS
a) Connect the food : the LED L0 will be extinct or remain lit during a short moment; the circuit is then ready for the test.
b) Actuate the P0 button now : the circuit functions into monostable exactly like the circuit of the third experiment, the LED L0 ignites during 1 second approximately.
c) Actionnez the button P0 first once so that L0 ignites, then again support one or more time on P0 before L0 does not die out. You note that the result is the same one, i.e. L0 remains lit during the same time of 1 second.
d) Insert in the matrix the diode D2 (1N 4148) and carry out the connections indicated into dotted to the figure 11-a or 11-b.
e) Actuate the P0 button and while the LED L0 is lit, press again on the P0 button.
The LED L0 remains lit more than one second, which means that the impulse of exit of monostable was prolonged one second when the P0 button was supported one second time.
f) Press several times on the P0 push-button while the LED L0 is lit.
You notice that it remains lit all the time during which you continue to support and slacken the P0 button more provided that rate is sufficiently fast, i.e. once a second. This occurs because each time an impulse of order arises on the entry of monostable, the condenser discharges by the diode connected to entry CLOCK ; consequently, the terminal voltage of the condenser cannot reach the value necessary so that entry PRESET determines the change of state of the rocker and puts an end to the impulse of exit.
8. - SEVENTH EXPERIMENT : EXAMINATION
OF AN INTEGRATED CIRCUIT MONOSTABLE REDÉCLENCHABLE
With this handling, you will check the operation of the integrated circuit CD 4528 container two monostable “redéclenchables” having identical characteristics.
As you see it on the diagram of figure 12, each monostable A three entries located by letters A, B and CD ; A and B are the entries of order, CD being the entry of restoring (CLEAR).
This integrated circuit also requires for each one of monostable resistance Rext and an external Cext condenser, like the MM 74C221 considering previously.
However, unlike this one, the duration of the impulse of exit of the CD 4528 is obtained by multiplying the product Rext x Cext by a coefficient K which also takes account of the value of the supply voltage.
In this case, for a tension of 4,5 V, this coefficient is equal to 0,13. Thus with Rext = 2,2 MW and Cext = 10 µF (values of the components which you will use in this experiment), the duration of the impulse of exit will be of 0,13 x 2,2 x 10 = 2,8 seconds approximately without taking account of the tolerances of the components.
8. 1. - REALIZATION OF THE CIRCUIT
a) Disconnect the food and remove all the components and the connections relating to the preceding experiment.
b) Insert in the matrix the integrated circuit CD 4528, a resistance of 2,2 MW and a condenser of 10 µF as indicated figure 13-a. Carry out the connections indicated on this same figure.
c) Put SW0 and SW1 both on position 1.
The figure 13-b illustrates the diagram of the circuit carried out
8. 2. - OPERATIONAL TESTS
a) Connect the food and observe the LED L0 : if it ignites, put the monostable one at zero by temporarily commutating SW1 on position 0 and while then bringing back it on position 1. The functions of entries A, B and CD of the CD 4528 being the same ones as entries A, B and CLR of the MM 74C221, write the table of operation of monostable considered while following the procedure described for the monostable MM 74C221.
Compare the data obtained with those deferred in figure 14 ; if you note divergences, remade the test with more attention.
Now, you can check the particular characteristic of the CD 4528, namely that it is redéclenchable.
b) By maintaining SW0 and SW1 on position 1, actuate on several occasions and quickly the P0 button, without leaving with the LED L0 time to die out.
You note that the monostable one behaves indeed like monostable the redéclenchable of the preceding experiment
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