3. TS1 3BA
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IMPORTANT
Before you start please read the following instructions
carefully.
1. This assignment forms part of the formal assessment for this
4. module. If
you fail to reach the required standard for the assignment then
you will be
allowed to resubmit but a resubmission will only be eligible for
a Pass
grade, not a Merit or Distinction.
You should therefore not submit the assignment until you are
reasonably
sure that you have completed it successfully. Seek your tutor's
advice if
unsure.
2. Ensure that you indicate the number of the question you are
answering.
3. Make a copy of your answers before submitting the
assignment.
4. Complete all details on the front page of this TMA and return
it with
the completed assignment including supporting calculations
where
appropriate. The preferred submission is via your TUOL(E)
Blackboard
account:
https://eat.tees.ac.uk
6. push. The
rungs of the ladder diagram must contain interlock contacts
which prevent
both outputs being on at the same time.
2. Redesign and improve the pelican crossing ladder diagram
given of
FIGURE 1 of lesson PLC - 6 - 2 by adding timer rungs and
counter rungs
between rungs 12 and 14 (or any similar workable scheme)
together with
the necessary contacts inserted in the amber and green man
lights of rungs
7 and 10, etc. The chart below shows the required sequence of
events.
Note that a section of the chart is repeated a total of 16 times.
The time
intervals are given below.
Time periods 1 2 3 4 5 6 7 ....... 35 36 37
Green road light ON ON OFF OFF OFF OFF .......... OFF OFF
ON
Red road light OFF OFF OFF ON OFF OFF .......... OFF OFF
OFF
Amber road light OFF OFF ON OFF ON OFF .......... ON OFF
9. have an
initial start signal and thereafter can be free running. A reset
control and
timer to clock the shift registers must be provided.
STEP No. OUT0 OUT1 OUT2 OUT3 OUT4 OUT5
RESET all outputs off RESET
1 ON 1
2 ON ON 2
3 ON ON ON 3
4 ON ON ON 4
5 ON ON ON 5
6 ON ON ON 6
7 ON ON 7
8 ON 8
9 ON ON 9
10 ON ON ON 10
11 ON ON ON 11
12 ON ON ON 12
13 ON ON ON 13
11. exact same digital value as the analogue input value.
(c) State briefly why a PLC A/D module haveing 4 analogue
input
channels would probably not incorporate 4 internal A/D
circuits.
(d) State briefly which of the two digital output values in (a) is
the more
accurate and why.
5. Explain briefly the technique of multiplexed switching of
analogue
signals.
6. The diagram of FIGURE 1 shows a 3 input R/2R digital to
analogue
converter circuit. By working back from the output (or
otherwise) to find
the equivalent input resistance in order to determine the input
voltage,
show that the output voltage values for the following digital
input
combinations are as shown below.
(i)
(ii)
12. (iii)
(iv)
A B C (volts)
0 0 0
1 0 0
0 0 1
4
12
or
1
3
out
in
in
V
V
V
0
1
12
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