PCB DESIGN, ETCHING AND DRILL

Assalammualaikum..

The next step for our project, we construct our circuit PCB design by using Diptrace software. After that, we done our etching and drill the PCB board at level 1, UniKL BMI.


PCB Design

Figure 1.0 Circuit diagram

We are using Diptrace software to make the circuit compact. After we done the simulation, the next step is as follow.

Etching

Figure 1.1 PCB board 

The etching process involves sheets of metal, usually made of copper or zinc, and acid used to etch the print onto the metal.  The more complicated the etching, the more time consuming and expensive it will be. We are using the following board to etching the circuit. Below are the steps that we done before we go to the next steps.

Drill

Figure 1.2 Drill box and tools

A drill is a tool fitted with a cutting tool attachment or driving tool attachment, usually a drill bit or driver bit, used for drilling holes in various materials or fastening various materials together with the use of fasteners. The attachment is gripped by a chuck at one end of the drill and rotated while pressed against the target material. The tip, and sometimes edges, of the cutting tool does the work of cutting into the target material. This may be slicing off thin shavings (twist drills or auger bits), grinding off small particles (oil drilling), crushing and removing pieces of the workpiece (SDS masonry drill),countersinking, counterboring, or other operations.

CIRCUIT FOR WET DIAPER DETECTOR

Assalammualaikum..

Figure 1.0 Circuit Diagram

Figure 1.0 Schematic diagram

As shown above in figure 1.0, we are using battery 9V as a power supply for this circuit. The operation is when we put the sensor on the diaper, we manually switch it ON until the sensor sense the presence of the wetness. 

The basic operation for this circuit is when the sensor sense the presence of wetness, it will give the signal through the I.C NE555. From pin number 3, it will produce the output via LED and buzzer. The LED will lights up and the buzzer will trigger. 

The component listed below :

1. R1 - 10k

2. R2 - 1k

3. R3 - 100k

4. C1 - 1uF

5. Battery 9V 

6. IC NE555

7. Buzzer

8. BC109C

9. LED

10. Switch

11. Sensor

     

BLOCK DIAGRAM DESCRIPTION

Assalammualaikum..

The block diagram for our project is as simple as this. 

Description of the block diagram:

The sensor will detect the input which is moisture and wetness. 

After that, it will sent the signal to the I.C NE 555. The output is at pin number 3. 

At this part, the output will divide into two part. The first part is buzzer and the second part is L.E.D. When the buzzer trigger, the LED will lights up at the same time. 

This is the result for our project. From here, the parents guardian will alert to the presence of the wetness. 

I.C NE555

Assalammualaikum..

An I.C NE555 is a component for our project which is Wet Diaper Detector (W.D.D). The purpose of using this component is to make a time delay or oscillation when the sensor detect the wetness on the diaper. Actually, the NE555 is a monolithic timing circuit that is highly stable controller able to producing accurate time delays.  

Figure 1.0 Image of NE555 

In time delay (operation mode), highlights in here, the time is controlled by one external capacitor and resistor. The circuit may be triggered and reset on falling waveform. the output structure can source and sink up to 200mA.

The NE555 is available in lastic and ceramic package with 8 pin connection. The image of NE555 is as below:

Figure 1.1 Pin connection from top view 

Figure 1.2 Block Diagram NE555

By referring to the figure 1.1 and 1.2 pin connection from top view and block diagram NE555:

1. Pin number one is the ground of the I.C. 

It connects to the 0V power supply.

2. Pin number two is the trigger in the circuit. 

Pin 2 has control over pin 6. 

If pin 2 is LOW and pin 6 LOW, output goes and stays HIGH. 

If pin 6 HIGH and pin 2 goes LOW, output goes LOW while pin 2 LOW. 

This pin has a very high impedance (about 10M) and trigger about 1uA.

3. Pin number three is the output. 

Pin 3 and pin 7 are 'in phase'. 

Goes HIGH (about 2V less than rail) and LOW (about 0.5V less than 0V) and will deliver up to 200mA.

4. Pin number four connected to pin number 8. 

Connected HIGH via 100k. It must be taken below 0.8V to reset the chirp.

5. Pin number five is the pin that is not connected to any pin or circuit.

A voltage applied to this pin will vary the timing of the RC network.

(quite considerably)

6. Pin number six is the threshold.

This pin has a very high impedance (about 10M) and will trigger with about 0.2uA.

7. Pin number seven is the discharge.

Goes LOW when pin 6 detects 2/3 voltage but pin 2 must be HIGH. 

If pin 2 is HIGH, pin 6 can be HIGH or LOW and pin 7 remains LOW. 

Goes OPEN (HIGH) and stays HIGH when pin 2 detects 1/3 rail voltage (even as a LOW pulse) when pin 6 is LOW. 

Pin 3 and 7 are 'in phase'. 

Pin 7 is equal to pin 3, but pin 7 not go high - it goes OPEN. 

But it goes LOW and will sink about 200mA.  

8. Pin number eight is the voltage supply.

It connects to the positive power supply (Vs). 

This can be any voltage between 4.5V to 15 DC, but commonly it is 5V DC when working with digital ICs.

Each of the pins is connected to the circuit which consists of over 20 transistors, 2 diodes and 15 resistors.