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Electronic Circuit Designing: Multitasking With Circuits (Part 4)

Step: 8) Find reusable modules from the circuit diagram  

Whenever we do hardware designing, the first rule is to make it in modules that can be reusable. The modules that we make for this particular project may come useful in another project and hence reduce the development time for that project. Even if a module is in use and at the same time found to be useful in another project, we can build another copy of the same module keeping the circuit design and PCB design same. In short this method can save a lot of time and hard work in the development process.

The modules which I found to be reusable in another projects are marked in the circuit diagram with red colored boxes as shown below.    

Reusable Modules From Another Project In Circuit Diagram

Fig. 1: Reusable Modules From Another Project In Circuit Diagram

The module marked [A] can be called the IR RECEIVER module. Its purpose is to receive the IR rays and produce an output according to their intensity. This module can be used in other IR based projects. The module marked [B] can be called as the COMPARATOR module and can be used for the comparison process in other projects. This module has an output and inverted output. The module marked [C] is called the MONOSTABLE module. This module has two mono stables which can be operated separately. Even though there were two separate mono stable block in the block diagram we have selected this as a one single module due to the fact that a single LM358 IC is used to realize both the blocks. If we make it two different blocks we have to use two LM358 ICs with one of the comparator not used. The module marked [D] is called the RELAY module and it consist of three individually accessible relays. The module [E] is called the indicator module and can be used with indication purpose in all other circuits. The module marked [F] is called the regulator module and is obviously useful in all circuits. We haven’t made the piece of circuit representing the BISTABLE block into a module since we can realize the bi stable module with much simpler circuit than using a CD4017 which is basically a counter. Also there is no point is making the IR INDICATOR circuit with only an LED and a resistor into a separate module. 

We have selected the modules from the circuit not at all based on the block diagram of the project, but based on the reusability and the efficient utilization of the available components.

The reusable modules and their details are listed in the following table:

MODULE ID

MODULE

DETAILS

A

IR RECEIVER

This module can receive the IR rays and produce an analog output equivalent to the intensity of the IR light falling on it.

B

COMPARATOR

This module can perform the voltage comparison and level detection. It has an output and an inverted output as well.

C

MONOSTABLE

This module consists of two separate mono stable circuits each of them can be used individually with different time periods.

D

RELAY

This module consists of three RELAYS and all of them can be used individually.

E

INDICATOR

This module has two LEDs and only one of them will be ON at a time based on the current input voltage; expecting only either logic high or logic low voltage equivalents.

F

REGULATOR

This module can regulate the DC voltage at its output when operating on an unregulated DC voltage input.

Fig. 2: Modules And Details

At the moment we have a good idea of what all modules to be build. Now let me show you how to build and test the modules in the next step.

Step: 9) Build and test the modules individually

In this step we build modules one by one and test them individually. At the moment we should have all the components listed in the BOM with us. Also we need a good collection of tools to perform this step. Let me show you the tools which I’ve used to build the modules.

 Tools Required To Build Modules

Fig. 3: Tools Required To Build Modules

The tools that you can find the above figure are listed as follows;

  1- NOSE PLIER

  2- RULE

  3- CIGERRATE LIGHTER

  4-  HEAT SHRINK SLEAVE

  5-  STAR SCREW DRIVER

  6-  WIRE STRIPPER CUM CUTTER

   7- SCREW DRIVER

   8-  SMALL FILE 

   9-  BLADE

   10-  SOLDERING LED

   11-  SOLDERING PASTE

  12-  HACK SAW BLADE

  13- SCISSORS

  14- DESOLDERING GUN

  15 - SOLDERING IRON

Let us start with the module A) the IR RECEIVER module which is marked as shown below.

 IR Receiver

Module A) IR RECEIVER

IR Receiver Module A To Be BuildFig. 4: IR Receiver Module A To Be Build

The IR RECEIVER module has three lines running into it which is used to connect the module with other modules. Hence our hardware module also needs at least three connector pins. The pin numbers can be marked as shown in the following figure.

IR Receiver Module With Pin Outs

Fig. 5: IR Receiver Module with Pinouts

I have build a hardware module corresponding to this with male berg stick connector pins and is shown in the following figure.

 IR Receiver Hardware Module With Pin Configuration

Fig. 6: IR Receiver Hardware Module With Pin Configuration

I’ve covered the sides of the IR photodiode with an insulation tape to avoid IR light from unwanted directions.

The functions of the pins can be identified from the complete circuit diagram from where we have selected the above shown module and its circuit. The details of the pin outs are given in the following table.

PIN NUMBER

PIN

DESCRIPTION

1

+5V

This is the pin where the positive regulated 5V is applied

2

OUTPUT

This is the pin at which the voltage equivalent to the intensity of incoming IR light is obtained

3

GND

This is the pin where the ground is applied

 Fig. 7: IR RECEIVER Module Pin Description

Now it is time to test the IR module. Simply appy the +5V and GROUND and observe the voltage at the output using a multimeter. Use a TV remote to send IR rays to the module and observe the variation in the output voltage. The arrangement is shown in the following figure.

IR Receiver Module Testing With +5V And GROUND

Fig. 8: IR Receiver Module Testing With +5V And GROUND

Whenevre the IR light pulses from the TV receiver falls on the IR photodiode the output voltage at the pin 2 increases. If we completey cover the photodiode with our hand there won’t be any IR rays not even from the surronding falls on the it and the output voltage will be almost zero. The voltage at the pin 2 in normal condition will slightly increases with the increase in light intensity at the room.

If the module behaves as mentioned above then it is working fine and the test has been competed successfully for the IR RECEIVER module.

Thus we have build and tested the IR RECEIVER module successfully. Let us mark the pin outs back to the complete circuit diagram and select the Module B) the COMPARATOR module for the process of building and testing.

Comparator

Module B) COMPARATOR

 Module To Be Build And Test – Comparator

Fig. 9: Module To Be Build And Test – Comparator

The COMPARATOR module has five lines running into it which is used to connect the module with other modules. Hence our hardware module also needs at least five connector pins. The pin numbers for the module can be marked as shown in the following figure.

 Comparator Module With Pin Outs

Fig. 10: Comparator Module With Pin Outs

I have build a hardware module corresponding to this with male berg stick connector pins and is shown in the following figure

Comparator Hardware Module With Pin Configuration

Fig. 11: Comparator Hardware Module with Pin Configuration

The functions of the pins can be identified from the complete circuit diagram from where we have selected the above shown module and its circuit. The details of the pin outs are given in the following table:

PIN NUMBER

PIN

DESCRIPTION

1

+5V

This is the pin where the positive regulated 5V is applied

2

OUTPUT

This is the pin at which the voltage, either logic high or logic low is obtained after comparison of the input voltage with the voltage level adjusted by the variable resistor

3

INPUT

The input voltage to be compared is applied on to this pin

4

OUTPUT_INV

This pin produces exactly opposite logic voltage to the voltage generated by the OUTPUT pin.

5

GND

This is the pin where the ground is applied

Fig. 12: IR RECEIVER Module Pin Description

Now we need to test the COMPARATOR module. Apply the +5V and ground to the corresponding pins. Connect LEDs to each of the output pins. Connect positive lead to the pin and the negative lead to the ground. Set some voltage level by adjusting the internal variable resistor. Apply an external variable resistor to the input pin. The setup is shown in the following figure.

Comparator Module Testing With +5V And Ground

Fig. 13: Comparator Module Testing With +5V And Ground

One of the LED will be on and the other will be off initially. Vary the voltage by varying the resistance and observe the output. At a certain point the both the output will toggle its voltage logic and hence the on LED becomes off and the off LED becomes on.  Now vary the internal variable resistor and try again. This time you can find that the change of state will happen at a point further after the previous one.

If the module behaves exactly as mentioned above then it is working fine and the test has been completed successfully for the COMPARATOR module.

Thus we have built and tested the COMPARATOR module successfully. Let us mark the pin outs back into to the complete circuit diagram and select the Module C) the MONOSTABLE module for the process of building and testing.

Monostable

Module C) MONOSTABLE

Monostable Module To Be Build And Test

Fig. 14: Monostable Module To Be Build And Test

The MONOSTABLE module has four lines running into it which is used to connect the module with other modules. Hence our hardware module also needs at least four connector pins. The pin numbers for the module can be marked as shown in the following figure.

 Monostable Module With Pin Outs

Monostable Module With Pin Outs

Fig. 15: Monostable Module With Pin Outs

Note that the connection between the pin number 1 of the U4 and the cathode of the diode D3 has been made externally with the help of two extra pins marked as 3 and 5. The advantage is that now we can use the two monostables individually. This simple modification increases the pin number from four to six for this module. Let us call one of the mono-stable as mono-stable-A and the other monostable as mono-stable-B.

I have build a hardware module corresponding to this with male berg stick connector pins and is shown in the following figure.

MONOSTABE hardware module

 Monostable Module Testing With +5V And Ground

Fig. 16: Monostable Hardware Module With Pin Outs

The functions of the pins can be identified from the complete circuit diagram from where we have selected the above shown module and its circuit. The details of the pin outs are given in the following table.

PIN NUMBER

PIN

DESCRIPTION

1

+5V

This is the pin where the positive regulated 5V is applied

2

INPUT_A

This is the pin at which the pulse for triggering the mono-stable-A should be applied. 

3

OUTPUT_A

This is the pin at which the output of the mono-stable-A is obtained.

4

OUTPUT_B

This is the pin at which the pulse for triggering the mono-stable-B should be applied

5

INPUT_B

This is the pin at which the output of the mono-stable-B is obtained.

6

GND

This is the pin where the ground is applied

 Fig. 17: MONOSTABLE Module Pin Description

Now let us see how can we test the MONOSTABLE module. No need to connect anything on the mono-stabel-A and mono-stable-B input pins. Connect an LED on the output of both monostable towards ground. Give +5V and ground to the corresponding pins. The set up is shown in the foowing figure.

Monostable Module Testing With +5V And Ground

Fig. 18: Monostable Module Testing With +5V And Ground

When we power up the module, both the LEDs will be on initially. Within one or two seconds the LED connected to the PIN3 (OUTPUT_A) becomes off but the LED connected to the PIN4 (OUTPUT_B) remains on. After some 15 – 19 seconds the LED connected to the PIN4 becomes off also.

If the module behaves exactly as mentioned above then it is working fine and the test has been completed successfully for the MONOSTABLE module.

Thus we have built and tested the MONOSTABLE module successfully. Let us mark the pin outs back into to the complete circuit diagram and select the Module D) the RELAY module for the process of building and testing.

 Relay

Module D) RELAY

Module To Be Build And Test – RELAYFig. 19: Module To Be Build And test – RELAY

As you can see from the above figure that the RELAY module has eleven lines running into it which is used to connect the module with other modules. Hence our hardware module also needs at least eleven connector pins. But we should built the modue in such a way that we can utilize the components to their maximum. The pin numbers for the module can be marked as shown in the following figure.

 RELAY Module With Pin Outs

Fig. 20: RELAY Module With Pin Outs

Note that all the interconnection between reays are avoided for this module and all the 5 pins of a particular relay has been taken out and is made available through pins. The advantage is that we can access the individual relays with their freewheeling diode seperatey if we need so. This method increses the number of pins to fifteen.

I have build a hardware module as per the above mentioned details with male berg stick connector pins and is shown in the following figure.

relay hardware

RELAY Hardware module With Pin Outs

Fig. 21: RELAY Hardware Module With Pin Outs

The functions of the pins can be identified from the complete circuit diagram from where we have selected the above shown module and its circuit. The details of the pin outs are given in the following table:

PIN NUMBER

PIN

DESCRIPTION

1

R1_LN

One end of the coil of the relay R1 is available at this pin. The other end is available at R1_LP. Only negative or ground voltage should be applied to this pin

2

R1_NC

This pin is connected to the Normally Closed (NC) pin of the R1 relay.

3

R1_NO

This pin is connected to the Normally Open (NO) pin of the R1 relay

4

R1_COM

This pin is connected to the common pin of the R1 relay

5

R1_LP

One end of the coil of the relay R1 is available at this pin. The other end is available at R1_LN. Only positive voltage should be applied to this pin.

6

R2_LN

One end of the coil of the relay R2 is available at this pin. The other end is available at R2_LP. Only negative or ground voltage should be applied to this pin

7

R2_NC

This pin is connected to the Normally Closed (NC) pin of the R2 relay.

8

R2_NO

This pin is connected to the Normally Open (NO) pin of the R2 relay

9

R2_COM

This pin is connected to the common pin of the R2 relay

10

R2_LP

One end of the coil of the relay R2 is available at this pin. The other end is available at R2_LN. Only positive voltage should be applied to this pin.

11

R3_LN

One end of the coil of the relay R3 is available at this pin. The other end is available at R3_LP. Only negative or ground voltage should be applied to this pin

12

R3_NC

This pin is connected to the Normally Closed (NC) pin of the R3 relay.

13

R3_NO

This pin is connected to the Normally Open (NO) pin of the R3 relay

14

R3_COM

This pin is connected to the common pin of the R3 relay

15

R3_LP

One end of the coil of the relay R3 is available at this pin. The other end is available at R3_LN. Only positive voltage should be applied to this pin.

Fig. 22: MONOSTABLE Module Pin Description

Now let us see how can we test the RELAY module. Connect all the positive pins to the +5V and negative pins to the ground via a switch. Give +5V to all the common pins and connect LEDs to all the NO and NC pins. Such an arrangement is shown in the folowing figure.

RELAY Module Testing With +5V And Negative Pins To Ground

Fig. 23: RELAY Module Testing With +5V And Negative Pins To Ground

In the above figure, K1 is the switch and A, C, E are the LEDs connected to the NC pin of the relays and B, D, F are the LEDs connected to the NO pins of the relays. Suppose when power up the K1 is open then the LEDs A, C and E conducts through the common pin to +5V since they are connected to the NC pin. When the K1 is closed the NC opens and NO closes to the common. Hence the LEDs B, D and F conducts through the +5V through the common pin. In short if the K1 is open LEDs A, C and E glows only and when the K2 is closed the LEDs B, D and F glows only.

If the module behaves exactly as mentioned above then it is working fine and the test has been completed successfully for the RELAY module.

Thus we have built and tested the RELAY module successfully. Let us mark the pin outs back into to the complete circuit diagram and select the Module E) the INDICATOR module for the process of building and testing.

Indicator

Module E) INDICATOR

Module To Be Build And Test – Indicator

Fig. 24: Module To Be Build And Test – Indicator

As you can see from the above figure that the INDICATOR module has three lines running into it which is used to connect the module with other modules. Hence our hardware module also needs at least three connector pins. The pin numbers for the module can be marked as shown in the following figure.

 Indicator Module With Pin Outs

Fig. 25: Indicator Module With Pin Outs

I’ve buit the hardware for the INDICATOR module with male berg stick connector pins and the image of that hardware is shown in the following figure.

Indicator Hardware Module

Fig. 26: Indicator Hardware Module

The functions of the pins can be identified from the complete circuit diagram from where we have selected the above shown module and its circuit. The details of the pin outs are given in the following table:

PIN NUMBER

PIN

DESCRIPTION

1

GND

This is the pin at which the ground or zero voltage should be applied

2

INPUT

The input voltage can be applied to this pin. Only logic zero or logic high voltage should be applied.

3

+5V

The positive 5V should be applied to this pin.

Fig. 27: MONOSTABLE Module Pin Description

Now let us see how can we test the RELAY module. Connect the +5V and ground to the respective pins and connect a key to the input pin. The arrangement is shown in the following figure.

Indicator Module Testing With +5V And Ground

Fig. 28: Indicator Module Testing With +5V And Ground

Suppose the switch marked as K1 is open then the Red LED glows only and when the switch K1 is closed the Green LED glows only.

If the module behaves exactly as mentioned above then it is working fine and the test has been completed successfully for the INDICATOR module.

Thus we have built and tested the INDICATOR module successfully. Let us mark the pin outs back into to the complete circuit diagram and select the Module F) the REGULATOR module for the process of building and testing.

Regulator

Module F) REGULATOR

 Module To Be Build And Test – Regulator

Fig. 29: Module To Be Build And Test – Regulator

As you can see from the above figure that the REGULATOR module has three lines running into it which is used to connect the module with other modules. Hence our hardware module also needs at least three connector pins. The pin numbers for the module can be marked as shown in the following figure.

 Indicator Module With Pin Outs

Fig. 30: Indicator Module With Pin Outs

I’ve buit the hardware for the INDICATOR module with male berg stick connector pins and the image of that hardware is shown in the following figure.

 

 Regulator Hardware Module With Pin Outs

Fig. 31: Regulator Hardware Module With Pin Outs

The functions of the pins can be identified from the complete circuit diagram from where we have selected the above shown module and its circuit. The details of the pin outs are given in the following table.

PIN NUMBER

PIN

DESCRIPTION

1

VCC_RAW

The unregulated positive voltage can be applied to this pin

2

GND

The ground of the input unregulated power supply can be applied to this pin. This pin is common for both the unregulated input and the regulated output

3

+5V_OUT

The regulated positive 5V output is obtained from this pin

Fig. 32: MONOSTABLE Module Pin Description

Testing the REGUATOR module is very simple. Connect the unregulated voltage at the input pins and observe the voltage at the output pins using a multimeter. The arrangement is shown in the following figure.

Regulator Module Testing

Fig. 33: Regulator Module Testing

If the voltage reading in the multimeter represented as ‘V’ in the above figure remains constant at a value very close to 5V, then the REGULATOR module is working fine.

Thus we have built and successfully tested all the reusable modules individually. Now let us mark the pin outs of this module also back into to the complete circuit diagram as shown below.

 

Circuit Diagram of Regulator With Module’s Pin Outs Marked

Fig. 34: Circuit Diagram of Regulator With Module’s Pin Outs Marked

Now we are ready to move on to the final step of this deveopment process in which we assembly the modules into a circuit board.