Created it, 06/10/19
Update it, 06/10/25
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3. - CONTROL OF OPERATION OF MATRIX A 840 CONTACTS
Ensure you before very that the assembly of the finished digilab is presented in the form of illustrated on figure 3. Carry out then a control not under tension of the matrix by conforming you to the following indications :
3. 1. - CONTROL NOT UNDER TENSION
Strip the two ends of a piece of insulated canned
wire and introduce one of its ends into the first contact in bottom on the right
of the first line of 25 contacts (figure 10).
Same manner, prepare the ends of a second insulated
canned wire and introduce an end into the last contact on the left of the same
contact system.
Lay out the controller on the gauge W
x 1000 and put the test probes in contact with
the loose leads of two wire. The needle indicates a resistance of 0
W confirming that the two contacts in
question are electrically connected.
Put two wire in the extreme contacts of the line
located just above that which you have just controlled and check that in this
case also the ohmmeter indicates a resistance of 0
W.
Proceeding in the same way, check continuity between
the extreme contacts of the remaining contact systems.
Carry out a similar control on the columns of 5 contacts. A
complete control would require the checking of all the lines and columns and all
the contacts constituting the matrix. However, a control of the connection
between the first and the last contact of each line and column are sufficient to
be normally ensured of the correct operation of the matrix.
3. 2. - CONTROL UNDER TENSION
Prepare the ends of six pieces of black insulated
canned wire and as many pieces of red wire isolated from suitable length and
carry out the connections illustrated on figure 11. Notice that the red wire is
used for the connections relating to the contact systems leading to the contact “+”
while the black wire is used for the contact systems connected to the contact “-”.
You ensure that the loose leads of the pieces of
wire connected to the last contacts on the left of the two higher and lower
lines are isolated between them. Respectively feed the circuit by connecting the
two red and black crocodile clips to the poles (+)
and (-) of the pile of 4,5
V.
Lay out the voltmeter on the continuous gauge 10
V and put in contact the end of the red wire (connected to the second
contact system on the basis of bottom) with the red test probe. Put the black
test probe in contact with the end of the black wire of the first contact system
as illustrated by figure 11. The needle must indicate a tension equal to that of
the pile is approximately 4,5 V.
Carry out same control on the four higher contact
systems by putting the test probes red and black in contact with the ends of red
and black wire connected at the end of these lines. In this case also, you must
obtain a tension of approximately 4,5 V.
The connections carried out during this control are those which are usually done for the use of the matrix. In this manner, indeed, the tensions (positive and negative or masses) are available on the higher side as on the lower side of the matrix thanks to the eight contact systems. This will be very practical to feed the circuits assembled on the columns of contacts located in the central zone of the matrix.
The use of red and black wire of connection respectively for the positive and negative lines of food makes it possible to distinguish those in an immediate way.
Take care of always respecting this convention even if if thereafter, it is not expressly any more indicated.
Having finished the control of the matrix with contacts, you can pass to the realization of the experiments planned for this practice.
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