Week : 15 (fyp sem 2)

Title : Relay

Objective : To connect a relay with automatic spray air freshener

Content / procedure :

What is relay ?

 - A relay is an electro mechanical switch used for driving heavy current loads in electronic circuits. Relay interface the electronic circuits with high voltage AC and there is complete galvanic separation between the two. When current passes through the relay coil, magnetic field develops which attracts a lever and changes the switch contacts. The contacts can be used to connect AC or DC loads which may then turn On / Off the load depending on the contact connections.

- A relay allows one circuit to switch on a second circuit which is completely separate from the first one. For example, a battery operated circuit can operate AC loads through a relay. There is no electrical connection inside the relay between the two circuits so that total galvanic isolation is possible.

Relay contacts 

- Typically a relay has three contacts. A moving contact called Common(Comm) and two fixed contacts. These are Normally Closed (NC) andNormally Open (NO). AC / DC is connected to the Comm. Contact. NO contact is used to connect the circuit / Gadget when the relay triggers. In this case, the circuit/Gadget remains off when the relay is Off. NC contact is used to break the supply when the relay energize. In this case the circuit / gadget remain operating until the relay energize. Contact rating is also important to drive the load. Typical relay contacts are rated for 4 Amps current. If the load is a high current one like Motor, Heaters, Inverters etc, relays having high rated contacts ( 16 Amps or higher) is necessary. These types of relays are called as Industrial type relays. If the contact rating is lesser than the load current, contacts may heat up and fire may break due to sparking.

 

Relay contact symbol

 PCB Relay

-  These are small sized relays that can be directly soldered on the PCB to make the circuit board compact. Like other type s of relays, PCB relays are available with the rating of 5 V, 6 V, 12 V, 24 V etc. Coil ratings may be 100 to 400 Ohms. Pin connection of PCB relay is shown below.

 Result / Analysis : The connection of relay and automatic spray is shown below.

Week : 14 (fyp sem 2)

Title : Automatic spray air freshener  as pepper spray

Objective : Using the automatic spray air freshener  to replace pepper spray

Content / Procedure : The automatic spray air freshener that i will use is shown below.

 

Result / Analysis :

-          I will use only the mechanical part of automatic spray and remove the timer circuit from the equipment.Then the automatic spray will be connected with relay from the project circuit. Purpose of doing this because it is necessary to ensure that the spray funtion at specified time by using microcontroller.

Conclusion : I did not remove the timer circuit of this spray yet.I will update later about this equipment.

 Week : 13 ( fyp sem 2)

Title : Component for password door security with motion detector and pepper spray circuit

Objective : To design project circuit

Content /  Procedures :

Component list :

-         - Resistor

-         - Capacitor

-         - Reset button

-         - Transistor

-         - LED as power indicator

-         - Diode

-         - LCD screen display – display words and password digit

-         - 4 x 4 Keypad for key in password

-         - PIC16F877A as microcontroller

-         - Buzzer

-         - Motion detector

-         - Magnetic sensor

-         - Relay

-         - Power connector

Result / Analysis : 

Conclusion : This circuit connection is not complete yet because relay is not connected to the spray.

Week : 12 ( fyp  sem 2)

Title : Components to build up the home prototype

Objective : To build up container to put the circuit board for password door security and other equipments such as keypad,motion detector and pepper gas spray

Contents / procedure : The equipments to build up the home prototype..

(1) Ruler
(2) cardboard
(3) twist tape
(4) medium hinge
(5) PCB stand
(6) double side tape
(7) perspex glue
(8) cutter
(9) perspex cutter
(10) perspex

Result / Analysis : This is my sketch for the home prototype..

Conclusion :I will build up this home prototype after settle with hardware and software of the project.