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Electronic Circuit Designing: Modular Approach (Part 5)

Table of Contents:

  1. Electronic Circuit Designing: Modular Approach (Part 5)
  2. Circuit building on PCB
  3. Plugging and Testing

Step: 10) Assemble the modules and test the assembled unit

We have built the reusable modules and we have a good idea from the circuit diagram about how their pins should be connected together. At this point we don’t have to worry about the internal circuits of the module and all we need to take care of is the pin outs and connections between modules and other components. The previous circuit diagram is re-drawn here based on this idea.

Circuit Assembly

Figure: the circuit diagram with modules

Now we can connect these modules along with the rest of the components in a single board or multiple boards and then interconnect the boards together. In this project I used two separate boards for connecting the entire things. Let us call the boards as BOARD_A and BOARD_B.

My plan is to include the RELAY module, INDICATOR module and the external connectors for audio-video and power in the BOARD_A and the rest of the circuit in BOARD_B. I’ve made such differentiation for the advantage of testing the audio-video switching process using the relays separately.  The following figure shows how the circuit is split across two boards; BOARD_A and BOARD_B.

Circuit AssemblingFigure: split the circuit into BOARD_A and BOARD_B


The BOARD_B includes the things enclosed in the green outline and the rest of the circuit forms the BOARD_A. The BOARD_A and BOARD_B is connected together using four pins marked as A, B, C and D. The above figure is redrawn more simply as shown below.

Board Assembling

Figure: BOARD_A and BOARD_B


The pin function details regarding the BOARD_B and BOARD_A is given in the following table.




This pin connects the ground line from the BOARD_A to BOARD_B


This pin provides the regulated voltage generated inside the BOARD_B to BOARD_A


This pin of the BOARD_B drives the relays inside the BOARD_A


This pin connects the VCC line from BOARD_A to the BOARD_B

 Table: BOARD_B pin details

Let us build the BOARD_A and plug in the modules and test it. The BOARD_A includes a RELAY module, INDICATOR module, power supply and audio-video connectors. We are not directly solder these components into the BOARD_A but solder their corresponding connectors only. The connector pins are then interconnected by using solder tracks.