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Electronic Circuit Designing: Modular Approach(Part 2)

Table of Contents:

  1. Electronic Circuit Designing: Modular Approach(Part 2)
  2. Order & Explanation of Functional Blocks
  3. Waveforms into Timing Diagram

 

Step: 3 Functional blocks into block diagram

Up to this point we were developing the basic functions into specific functional blocks according to their requirements. Let’s take a look at what all functional blocks we have, it will give you an idea how far we advanced in the designing process.

Video Switching Circuit

Figure: basic functional blocks

Let’s take a quick look at the details of the blocks shown in the above figure.

BLOCK

NAME

FUNCTION

A

RELAYS

Switching the audio video signals using relays

B1

IR PHOTODIODE

Produce output according to IR light intensity

B2

COMPARATOR

Level detection of IR light from the TV remote

C1

MONOSTABLE SMALL

Continuous output from pulse train input

C2

MONOSTABLE LARGE

Trigger an output after a period of continuous input

D1

BISTABLE

Toggles the output for each and every input

D2

DRIVER

Current amplification for driving the relays

 Table: basic blocks and functions

Each of the blocks shown above can perform their own specified functions only. The entire blocks should perform together to give us a collective output. It will happen only when we connect the blocks together in the proper way. Next we are going to discuss how to connect these blocks together so that we have a complete block diagram for the device.

From the entire discussion so far you might already have a picture about the way of connecting these blocks together. The IR light from the TV remote triggers the working of the device and who receives the IR light pulses from the TV remote, the IR photodiode. Hence the working starts at the Block B1) IR PHOTODIODE. Let’s consider it as the 1st block.

The IR PHOTODIODE blocks output is level checked by the COMPARATOR block for the rest of the circuit, hence the Block B2) COMPARATOR block should immediate block after the Block B1). Thus the Block B2) COMPARATOR becomes the 2nd block.

The COMPARATOR block’s output is a train of pulses which should be converted to a continuous pulse using the MONOSTABLE SMALL block. Thus we can assume that the Block C1) MONOSTABLE SMALL block should immediately follow the Block B2) and Block C1) is the 3rd block.

The MONOSTABLE SMALL block’s output is meant to be used by the MONOSTABLE LARGE block for triggering its output after its timing period. Hence the Block C2) MONOSTABLE LARGE block should be the very next block to the Block C1) and Block C2) is the 4th block.

Each and every time the MONOSTABLE LARGE block produces an output, the BISTABLE block is the one which toggles its output, hence the Block D1) BISTABLE block should immediately follow the Block C2) and Block D1) is the 5th block.

The BISTABLE block should operate the relay block and is possible only through the DRIVER block. Hence the Block D2) DRIVER block follows the BISTABLE block and it is the 6th block.

There is only one more block left which follows the DRIVER block. It is the Block A) RELAYS which becomes the 7th block.

The above brief discussion about the connecting order of the blocks is simply represented in the following table

ORDER

BLOCK

NAME

1

B1

IR PHOTODIODE

2

B2

COMPARATOR

3

C1

MONOSTABLE SMALL

4

C2

MONOSTABLE LARGE

5

D1

BISTABLE

6

D2

DRIVER

7

A

RELAYS

 Table: order of the functional blocks