Rover 5 tracked robot chassis

Rover 5 is a new breed of tracked robot chassis designed specifically robotic usage and carried PCB circuit. The chassis can be upgraded into two or four motors and encoders making it ideal for mecanum wheels. There are two brushed DC motors with 210mA free run and 2.4A of stall current at 7.2V. The body was created by durable plastic and it can move for 1km/hour. 

As u can see, picture above show the internal body of robot chassis which contain 2 motors in left and right side. Each motor connected with 2 wires (red and black) for supply and also ground. These wire will connected to TIP120 on the circuit and interface with ATmega328.

The instructions provides by an ATmega328  are HIGH or LOW. High means 5 volts and Low is 0 volts. The operations of TIP120 is like a switching mode that control the input for the motors. 

Referring to the table above, a gas sensor will operate when the analog output for the sensor is more than 2.1 volts,meanwhile obstacle sensor will detect the object in front of the robot when analog output is more than 1.6 volts.

Once the gas sensor detecting a liquefied petroleum gas or obstacle sensor detecting a barrier, the motor an buzzer will automatically switch off.

There will be 3 line sensor operating the system especially the motors. When line sensor 1 detecting a black line, both motor of the robot will be on. On the other hands, if line sensor 0 or line sensor 2 will control either motor 1 or motor 2 to move.

Voltage regulator (IC 7805)

IC 7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs. The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide. 7805 provides +5 volts regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels.

The regulator functions by using a diode to clamp the output voltage at 5 VDC regardless of the input voltage. Excess voltage is converted to heat and dissipated through the body of the regulator. If a DC supply of greater than 12 volts is used, excessive heat will be generated and the board may be damage. If a DC supply is less than 5 volts is used, insufficient voltage will be present at the regulators output.

For this project, input for all sensor should be equal to 5 volts. As mentioned before, all the sensors produce an analog output  within range 0- 5 volts. Therefore, this IC7805 are used to operate the system. 

Distance sensor

An infrared proximity sensor shines a beam of IR light from an LED, and measures the intensity of light that is bounced pack using a phototransistor. If you stare at the sensor, you can see one of the LED’s  glowing slightly red as some of the IR falls into the visible-light spectrum. A new approach was developed that not only gives object detection at a longer range than previous method but also offers range information for certain type of sensors. These new rangers all use triangulation and a small linear charge coupled device (CCD) array to compute the distance and/or presence of objects in the field of view.  The basic idea is this: a pulse of IR light is emitted by the emitter.  This light travels out in the field of view and either hits an object or just keeps on going.  In the case of no object, the light is never reflected and the reading shows no object.  If the light reflects off an object, it returns to the detector and creates a triangle between the point of reflection, the emitter, and the detector. 

The angles in this triangle vary based on the distance to the object.  The receiver portion of these new detectors is actually a precision lens that transmits the reflected light onto various portions of the enclosed linear CCD array based on the angle of the triangle described above. The CCD array can then determine what angle the reflected light came back at and therefore, it can calculate the distance to the object.

When the distance is far or increases the output voltage is decreasing gradually. But when the IR sensor is near to the obstacle the output voltage will increase. The value of output voltage is useful as a reference for the microcontroller (ATmega328). For a gas leakage detector system, if the output voltage is higher than a set point level, the DC motors will be turn off. But if the output voltage is lower than the set point the DC motors will be operated. The set point can be created in the program. This means that to one value of the output corresponds two values of distance. This problem can be avoided by noticing that the object is not too close to the sensor.

Gas sensor (MQ5 sensor)

MQ5 sensor is used in gas leakage detecting equipments in the industries and house. It has high sensitivity to liquefied petroleum gas (LPG) and small sensitivity to alcohol and smoke. The characteristics of this sensor are fast response, stable, long life and have simple drive circuit.

When a dangerous levels of gas vapors are detected. A detectors measure a gas concentration and the sensor responds to a calibration gas, which serves as the reference point or scale. Usually the reference point or scale is in voltage (V). The calibration of MQ5 is important in order to compare the sensitivity of MQ5 when detecting oxygen gas or liquefied petroleum gas (LPG). For an example, if the MQ5 sensor detects oxygen gas it might produce a low value of output voltage but when it detects other gases especially LPG gas it will produce a high value of output voltage. The output voltage value is between ranges 0 until 5 volts.

Based on the picture above, MQ5 have 6 pins (2 A, 2 B and 2 H). Pins for A should be attach together and then connect with the pin H for become an input connection. On the other hands, pins B will be the output connection, meanwhile the other H pin become grounded. Before the sensor connects to theATmega328 pins, it should face some calibration with lighter gas using a multi-meter to identify differences of voltage output value in normal condition (normal atmosphere) and worst condition (when detecting any presence of liquefied petroleum gas). During normal condition, the voltage output is less than 1.5 volts. When the MQ5 detected the gas produce by the lighter, the voltage output is 2 volts and above. This output values are important because it will be useful data during program writing.

Figure below shows the connection wires of gas sensor (MQ5) at the analog pins of ATmega328.

Light sensor (LDR sensor)

A light sensor generates an output signal indicating the intensity of light by measuring the radiant energy that exists in a very narrow range of frequencies basically called "light", and which ranges in frequency from "Infrared" to "Visible" up to "Ultraviolet" light spectrum. The light sensor is a passive devices that convert this "light energy" whether visible or in the infrared parts of the spectrum into an electrical signal output. Light sensors are more commonly known as "Photoelectric Devices" or "Photo Sensors" because the convert light energy (photons) into electricity (electrons).

Light dependent resistors (LDR) are very useful especially in light or dark sensor circuit. Normally the resistance of an LDR is high, sometimes as high 1000kΩ, but when they are illuminated with light resistance drops dramatically. There are just two ways of constructing the voltage divider, with the LDR at the top, or with the LDR at the bottom:

In LDR sensor operation, means light must shine into the light dependent resistance for the circuit to be activated. When the light level is low the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. Consequently the lamp does not light. However, when light shines onto the LDR its resistance falls and current flows into the base of the first transistor and then the second transistor and automatically turning the lamp on. The preset resistor can be turned up or down to increase or decrease resistance, in this way it can make the circuit more or less sensitive. During troubleshooting the LDR sensor, i have tabulated all the data of an output voltage value with different resistance value produce by the LDR sensor.

Based on the figure below, the input of the LDR is only 5 volts and the value for the resistor is 10kΩ. Generally, this sensor was constructed based on voltage divider rules and the voltage output is depending on the change in resistance value of the LDR sensor. The input for IC741 has two input pins from one pin from the voltage output and another one is from the ground. Once the voltage enters the IC741, the IC741 will amplify the voltage by multiplying it gain (dB). Output for IC741 will inject to the relay and automatically switch on the lamp.

Figure above shows the circuit of light sensor (LDR circuit)

IR sensor (Line sensor)

Nowadays, in electronic market provides variety of IR sensor. Infrared (IR) sensors have become indispensable tools for several industries. However, not all frequencies of light within the infrared spectrum behave the same. There are a number of methods which can be used to build a line following robot. In general there are three different types of line followers which are single light, two lights, and three lights sensor model. On the other hands, besides using a complete sensor which it can easily find in the market, an infrared LED transmitter and receiver can be used to detect the line.

The reason of selecting this type of IR sensor is because it has good range which is fulfil the requirement for robots. It is very low cost and can be constructed on general purpose PCB. Besides that, it is very small in size which is best for robots. For obtain a good result, the number of transmitter and receiver can be increase. Thus, it has good immunity to ambient light and waves are invisible to eyes.

IR LED is used as a source of infrared rays. It comes in two packages 3mm and 5mm. 3 mm is better as it is require less space. IR sensor is nothing but a diode which is sensitive for infrared radiation. This infrared transmitter and receiver were known as IR Tx-Rx pair.

Pictures below shows the results after done with designing the PCB line, etching, components placement and soldering procedures.

Referring to the picture below, the input for the line sensor circuit is 5volts max. There are 3 pin for voltage output which are Vout 1(V1), Vout 2 (V2) and Vout 3 (V3). These output voltage pins are important to the system because every each of output pin will produce a different output voltage value which is directly connecting to the IC.

When IR sensor detects line, the voltage output is high but when it did not detect any line the output voltage is low. During troubleshooting the circuit, the result when detecting line is 1.59 volts and 0.14 volts is when it not detecting any line. On the other hands, each of voltage output pins control left and right motors.

Tip 120 as power transistor

A transistor is a semiconductor which is a fundamental component in almost all electronic devices. Transistors have many uses including switching, voltage or current regulation and amplification. Transistor controls a large electric output signal with changes to a small input signal. Since a large amount of current can be controlled by a small amount of current, a transistor acts as an amplifier. Transistor also acts as switch which can open and close many times per second.

The TIP120 also known as Darlington transistor. It was designed as a medium power switching transistor and can be used to switch a motor on and off. This type of transistor can use a small current to switch and amplify a much larger current to the motor or other load such as buzzer. The controlling pin on the transistor or base is sensitive to too much current, so the circuit required a 1k Ω or 2.2kΩ resistor coming from the output pin into TIP120. This transistor coupled with a motor power supply and will allow the circuit to run a DC motor and empower the circuit to activate many other devices. Therefore, for this project i used a TIP120 because it can pass more current especially if i add a heat sink on the transistor and handle larger load.

Troubleshooting the PCB line

After done with etching procedure, a PCB line should be check by using a multi-meter. This is important to ensure each component that will be install on the circuit board able receive a voltage and current and operate perfectly. Basically before soaking the copper board into the hydrochloric acid, the printed PCB line sometimes are not connected or dotted line. This problem can be fixing by drawing back those dotted line with a black marker pen and then continue soak the copper board into the acid.

Below picture shown the dotted line on the copper board

Making a connection troubleshooting using multi-meter.

Thus, the complete etching board will be drill to make a hole for electronic component placement.

Etch a single sided PCB

Etching is a printmaking process and where the excess copper is removed to leave the individual tracks on the circuit board. A muriatic or hydrochloric acid is important because it is used to remove the cooper layout on the circuit board.

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Etch a single sided PCB

Etching is a printmaking process and where the excess copper is removed to leave the individual tracks on the circuit board. A muriatic or hydrochloric acid is important because it is used to remove the cooper layout on the circuit board.

The copper board can be cut into a necessary size needed and then clean it using a paper towel from any dust. Make sure our hands clean from any oil before touching the circuit board. Then place the pcb layout on a copper board and stick it using a masking tape.

Thus, get ready with a clothes iron and set the iron on the hottest setting to allow the iron get hot. Before start ironing the circuit board, use a thick clothes such as kain pelekat to sandwiching the copper board.

Firmly press the iron onto the back of the PCB layout for about 20 seconds and repeat the same method for more than 5 minutes. Without moving the iron, press board very hard for 1 minute to provide perfect heat to the circuit board. Then slowly move the iron around the copper board with a lot of pressure. After done with these methods, make sure the circuit board fully cool before removing the PCB layout from the copper board. 

Pour some hydrochloric acid on a plastic container and soak in the copper board into the acid. Wait for 4 minutes and shake the container slowly to remove the copper layout from the board.  The copper layout can be easily separate from the board by this method. Repeat the same method for 3 or 4 times to get a fully circuit board.

Separates the circuit board from the acid and leave it for 2 minutes. Wash the circuit board using clean water and brush the copper layout side using a sand paper. Repeat the same method until the copper layout completely removed.

Printed circuit board layout

PCB (Printed circuit board)

Printed circuit board is primarily an insulating material used as base, into which conductive strips are printed. The base material is generally fibreglass, and the conductive connections are generally copper and are made through an etching process.  The main PCB board is called the motherboard; the smaller attachment PCB boards are called daughter boards or daughter cards.

PCB board design defines the electrical pathways between components. It is derived from a schematic representation of the circuit. When it is derived, or imported from a schematic design, it translates the schematic symbols and libraries into physical components and connections

PCB layout

The PCB layout is a mirrored positive one- black on white. The PCB layout is printed 1:1 on paper by using a laser printer or copier machine. The laser printer or copier toner will not run out when it gets wet or oily. Therefore by using a laser printer the output will be fine and form in high quality of printing. It might be possible that the toner texture on the layout prints from the laser printer is not dense enough and passes too much light. However, results might be improved by setting the toner density.

OBJECTIVES

Gas leakage detector systems carry a positive objective that can be accomplished and might affect the world. The objectives consist of:

i.                     To upgrade and improve the existing system and device to detect any presence of flammable gas in         all industry or home.

ii.                     To reduce potential hazardous and prevent any major damage and accident in our country.

iii.                     To make sure all the data collected by all type of sensor involved continuously and it will be processed without any failure.

iv.                     To enhance a better function of the system in the future.

v.                     To expand the radius of detecting gas comparing with the existing system.

BENEFITS / CONTRIBUTIONS

The characteristic of liquefied petroleum gas (LPG) is flammable. By using the gas leakage detector, a presence gas such as butane or propane can be detected. It is part of the project purpose. Otherwise, this project able to:

i.         Reduce and avoid any possible incident especially explosion.

ii.       Avoid any major damage to the buildings.

iii.      To prevent serious injuries and breathing difficulties among the factory employees.

iv.   Reduce the global warming

METHODOLOGY

            A block diagram can be produce after done with a literature review on the principle operation, a technology and program involve, sensors involve and other. The gas leakage detector sensor requires more than one sensor such as MG5 gas sensor, LDR sensor, IR distance sensor and line sensor. Two small DC motor are needed to move the device from one location to another location. A gas leakage detector sensor also completed with alarm and buzzer system.

Block diagram

Figure 1.3: Block diagram for gas leakage detector system

Referring to the figure above, a MQ5 gas sensor is used to detect any presence of liquefied petroleum (LPG). When it detects any leakage of liquefied petroleum gas (LPG), a data will be send to the microcontroller which is A Tmega 328. The microcontroller will process the received data and automatically turn the siren or alarm on. A line sensor is optically detecting the specific line placed on the floor and move only on the specific line. A data received from the line sensor will be send to the microcontroller and run the DC motor (L293D). Furthermore, a light dependent resistor sensor or known as LDR sensor is used to detect the light surrounding the device. A data from this sensor will be read by the microcontroller and turn the lamp on. This will happen when the device moves into a dark places where no light on that area but it will automatically turn the lamp off when there is a light detect by the LDR sensor. The function of infrared distance sensor (IR distance sensor) is to detect any presence object against it. When it faces an external object or humans, it will send the data to be process by the microcontroller and turn on the buzzer to notify the user and organic life against it.

Table 1.4: Input, process and output of the block diagram

INPUT

1. .      Push button start and stop – Use to start and stop all the operation of gas leakage detector system.
2. .      MQ5 gas sensor – An electronic device use to detect any presence of propane or butane gas.
3. .      Line sensor – Is a sensor which only detect a black line on the floor.
4. .      LDR sensor – This sensor will be used to detect the light or dark area.
5.     IR distance sensor – It can detect any existing obstacle against it

         

          PROCESS

1.      ATmega 328 – Can store all the data written by the user and control all the system for gas   leakage detector system.

OUTPUT

1.      Alarm – Able to produce a high volume of sound and use to notify the user if any gas detected.

2.      DC motor – A low voltage motor use to move the device.

3.      Lamp or LED – Provide a indicator light when operates in a dark area.

4.      Buzzer – Notify the user if any obstacle block the device.

INTRODUCTION

          Liquefied petroleum gas or known as LPG or liquid propane gas is a flammable mixture of hydrocarbon gases as a fuel in heating appliances and also widely used in automobile or manufacturing sector. Liquefied petroleum gas (LPG) consists of two different type which is propane and butane. Propane has a lower boiling point compare to butane and it is stored at a higher pressure. Both of the substances are the liquefied petroleum gases most commonly found commercially. Butane is commonly used for mobile heaters and leisure applications through warmer months while propane is predominately used for domestic heating, cooking and industrial applications. Thus, propane is stored in bulk tanks which can be situated above ground or underground. Liquefied petroleum gas provides benefits to the world such as it produces less exhaust emission and it is cheaper than petrol. However, it also is potentially hazardous and it is a flammable gas which can cause a major damages and harmful to organic life such as humans and animals.

            A gas detector is use to detects any presence of various gases within an area and commonly use as part of a safety system. To avoid and reduce the negative effects, a liquefied petroleum gas (LPG) gas sensor is made as gas detection equipment used for detecting propane gas in industrial settings, home and automotive. It is an ideal sensor to detect any presence of a dangerous liquefied petroleum gas (LPG). It is easily incorporated into an alarm unit, to sound an alarm or give a visual indication of the liquefied petroleum gas (LPG) concentration. The sensor has excellent sensitivity combined with a quick response time. The sensor is also design to sense other gas leakage such as iso-butane, LNG and cigarette smoke.

            A gas leakage detector system is made to improve any existing sensor installed in the industry of manufacturing or automotive and even at home. The purpose of this device is also to avoid and reduce any harmful to the humans or animals and any major damages to any buildings. The system made able to moves the sensor device all around the selected area where liquefied petroleum gas (LPG) is applied and sound the alarm when detecting any presence of a dangerous liquefied petroleum gas (LPG) which carry a flammable characteristic.