Multiple Outputs Analogy

We are now at ease working on multiple outputs and I hope that we are ready to tackle some more questions but with some new things are to be learnt. Let us make this a bit interesting and let us introduce multiple outputs as well.

Now we will take multiple inputs and multiple outputs. The inputs would be same for all the outputs yet the set of control instruction for each output will be different. Let’s take an example:

A	B	SUM	CARRY
0	0	0	0
0	1	1	0
1	0	1	0
1	1	0	1

We need to implement a half adder that adds two bits and output is SUM and Carry.

Let’s design a truth table for it first here we are adding two bits and hence forth we will get sum and carry

1.   When A = 0 and B = 0 in that case no sum is generated as well as no carry

2.   In case when A = 0 and B = 1 the sum will be 1 and no carry will be generated.

3.   Similar to the upper case the sum will be 1 and carry zero when A = 1 and B = 0.

4.   For the last case we see that both the inputs A and B are high and therefore their sum will be 10; i.e. 0 will be considered as sum and 1 will be carry.

In case we have to design relay logic for such an case or simply we want to verify the half adder logic electrically using switches in that case we consider the switches to be A & B, and definitely we have two outputs here Sum and Carry; so two relay coils.

A	B	SUM
0	0	0
0	1	1
1	0	1
1	1	0

Keep in mind the outputs are separate they have no influence on each other as well they have different logics of operation.

Let us consider the table for Sum first.

The output turns ON in only two conditions first when

 A=0 and B=1 or second when A=1 and B=0.

Check out the highlighted words and they will tell you about how to get a Boolean equation from them

 Let us design the relay logic for the SUM first

 Negated switch that is A (bar) or B (bar) are notified by NC switch where else Normal switch by NO. A dot(.) between two switches shows they are connected in series and a sign of +(sum) tells they are parallel to each other

Keeping this in mind we can design the relay logic diagram for them.

Once done let us turn towards the second output that is carry.

Checking out the truth table it can be clearly figured out that the output for the CARRY goes high in only one condition A = 1 and B = 1, i.e. both the switches are pressed or inputs high.

As there is only one condition we will have a equation such as;

A . B  =  CARRY

Hence forth the relay logic for this can also be easily penned, need not to make a separate diagram just use the same line and neutral from the previous figure, in the same way that we have in our home separate switchers for fan and lights but they all are connected parallel through the same power supply.

Now take a multiple output analogy question form the RLD practice question and try it out.