The system for ,
We all know how difficult it is to book and get an LPG cylinder through the government LPG booking and delivery system. We need to call the agency several time to book a cylinder and the main problem faced by the working class is that the booking can only be done after 10AM.At this time most of the working class people will be at busy at their day job. So unable to book gas on time is a common problem faced by many. Due to the ever increasing demand of cooking gas the agencies are finding it difficult to deliver the cylinder on time. With the current regulations imposed by the government on the number of cylinder issues to a particular costumer it’s going to be more difficult to manage proper delivery on time. So a system to manage all these problems will be of great use to the housewife’s especially the majority working class. An automated system to keep track of the cylinder level and book gas automatically is the best solution to the problem. We try to introduce a new system to track the level of cooking gas in the cylinder and an associated automated booking system. The gas level in a cylinder will be proportional to the total weight of the cylinder and we use this fact to know the percentage of gas left in the cylinder. We are building an embedded system hardware which will track the weight of the gas cylinder and thus approximately find out the percentage of cooking gas left in the cylinder. The weight of LPG filled is 14.2 kg so the total weight will be Tare WT(weight of empty cylinder)+14.2 kg. We can measure the total weight by using a load cell. A load cell is a transducer that is used to convert a force into electrical signal; this conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a strain gauge, the strain gauge measures the deformation (strain) as an electrical signal, because the strain changes the effective electrical resistance of the wire. A load cell usually consists of four strain gauges in a Wheatstone bridge configuration. The output of the load cell is given to an ADC and then to a processing unit consisting of the microcontroller. The microcontroller continuously monitors the gas level from the measured weight and alerts, sends SMS to the agency automatically for booking purpose. The SMS is sent by using a GSM modem connected to the microcontroller. The system also has an added feature of gas leakage detection which is implemented using a gas leak sensor. It gives necessary alert when gas leakage is detected.
Block Diagram
BLOCK DIAGRAM EXPLANATION
Gas detector
A gas detector is a device which detects the presence of various gases within an area, usually as part of a safety system. This type of equipment is used to detect a gas leak and interface with a control system so a process can be automatically shut down. A gas detector can also sound an alarm to operators in the area where the leak is occurring, giving them the opportunity to leave the area. This type of device is important because there are many gases that can be harmful to organic life, such as humans or animals. Gas detectors are usually battery operated.
A pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. Analog-to-digital converter. An analog-to-digital converter (abbreviated ADC, A/D or A to D) is a device that converts the input continuous physical quantity to a digital number that represents the quantity's amplitude. The conversion involves quantization of the input, so it introduces a small amount of error. The inverse operation is performed by a digital-to-analog converter (DAC). Instead of doing a single conversion, an ADC often performs the conversions ("samples" the input) periodically. The result is a sequence of digital values that have converted a continuous-time and continuous-amplitude analog signal to a discrete-time and discrete-amplitude digital signal.
Microcontroller
A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and input/output peripherals. Program memory in the form of NOR flash or OTP ROM as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications. Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes.
Relay
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal.
GSM modem
GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second generation (2G) digital cellular networks used by mobile phones.
Working
The system consists of a load sensor and LPG sensor. The load sensor is used for weighing the LPG cylinder. The LPG sensor is used for detecting the presence of methane gas. The output of load and LPG sensor is given to the ADC. The output of ADC is a digital signal, which is fed to the microcontroller. This microcontroller is programmed by embedded language with our requirements. When the LPG sensor detects the presence of methane gas, the buzzer connected with microcontroller section alert the user. This also triggers the relay and cut off the main supply. When pressure reduces, the microcontroller detects and automatically books the gas by an SMS, with the help of a GSM module.
COMPONENT DESCRIPTION
Micro Controller(ATMEL 89C51)
It is a low-power, high-performance CMOS 8-bit microcomputer With 4K Bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and incompatible with the industry- standard MCS-51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in system or by a conventional nonvolatile memory programmer. By combining a versatile 8- bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful micro-computer, which provides a highly flexible and cost-effective solution to many embedded control applications.
A/D Converter (ADC0808)
An analog-to-digital converter is a device which converts continuous signals to discrete digital numbers. Typically, an ADC is an electronic device that converts an input analog voltage (or current) to a digital number proportional to the magnitude of the voltage or current. This circuit demonstrates the interfacing of ADC0808 with 8051 microcontroller (AT89C51). The output is taken on the LEDs. This is an intermediate circuit, which finds lot of applications. ADC0808 needs an external clock to run. The circuit describes how a D-flip flop can be used to provide the external clock. The ADC0808M is a monolithic CMOS device with an 8-channel multiplexer, an 8-bit analog-to-digital (A/D) converter, and microprocessor-compatible control logic. The 8-channel multiplexer can be controlled by a microprocessor through a 3-bit address decoder with address load to select any one of eight single-ended analog switches connected directly to the comparator. The 8-bit A/D converter uses the successive-approximation conversion technique featuring a high-impedance threshold detector, a switched capacitor array, a sample-and-hold, and a successive- approximation register (SAR).
RS232 Interface
RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit terminating Equipment). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pin out of connectors. The current version of the standard is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. An RS-232 port was once a standard feature of a personal computer for connections to modems, printers, mice, data storage, uninterruptible power supplies, and other peripheral devices. However, the low transmission speed, large voltage swing, and large standard connectors motivated development of the universal serial bus, which has displaced RS-232. From most of its peripheral interface roles. Many modern personal computers have no RS-232 ports and must use an external converter to connect to older peripherals. Some RS-232 devices are still found, especially in industrial machines or scientific instruments. The standard has been Telecommunications renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and most recently as TIA 232. The standard continued to be revised and updated by the Electronic Industries Alliance and since 1988 by the Industry Association (TIA). Revision C was issued in a document dated August 1969. Revision D was issued in 1986. The current revision is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. RS-232 was created for one purpose, to interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) employing serial binary data interchange. So as stated the DTE is the terminal or computer and the DCE is the modem or other communications device. RS-232 pin-outs for IBM compatible computers are shown below. There are two configurations that are typically used: one for a 9-pin connector and the other for a 25-pin connector.
MAX232
The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply TIA/EIA-232F voltage levels from a single 5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels. The driver, receiver, and voltage-generator functions are available as cells.
GSM Modem
This GSM Modem can accept any GSM network operator SIM card and act just like a mobile phone with its own unique phone number. Advantage of using this modem will be that you can use its RS232 port to communicate and develop embedded applications. Applications like SMS Control, data transfer, remote control and logging can be developed easily. The modem can either be connected to PC serial port directly or to any microcontroller. It can be used to send and receive SMS or make/receive voice calls. It can also be used in GPRS mode to connect to internet and do many applications for data logging and control. In GPRS mode you can also connect to any remote FTP server and upload files for data logging. This GSM modem is a highly flexible plug and play quad band GSM modem for direct and easy integration to RS232 applications. Supports features like Voice, SMS, Data/Fax, GPRS and integrated TCP/IP stack.
LPG Sensor
This is a simple-to-use liquefied petroleum gas (LPG) sensor, suitable for sensing LPG (composed of mostly propane and butane) concentrations in the air. This can detect gas concentrations anywhere from 200 to 10000ppm. This sensor has a high sensitivity and fast response time. The sensor's output is an analog resistance. The drive circuit is very simple; all you need to do is power the heater coil with 5V, add a load resistance, and connect the output to an ADC.
Description
The system consists of a pressure sensor and LPG sensor. The pressure sensor is used for weighing the LPG cylinder. The LPG sensor is used for detecting the presence of methane gas. The output of pressure and LPG sensor is given to the analog to digital converter (ADC). The output of ADC is a digital signal, which is fed to the micro controller. This micro controller is programmed by embedded language with our requirements. When the LPG sensor detects the presence of methane gas, the buzzer connected with micro controller section alert the user. This also triggers the relay and cut off the main supply. When pressure reduces, the micro controller detects and automatically books the gas by an SMS, with the help of a GSM module. The GSM module is interface with the micro controller with the help of RS232 and MAX232 interface.
We can use IC555 to generate a clock signal which is used as a clock to the micro controller. Here we can use the micro controller ATMAL895C1. It requires a frequency signal between 0 to 25 MHz. Micro controller can program with our requirements. The gas sensor is MQ-6, which is very sensitive to LPG. Load sensor used is CZL-601. It is a 45 Kg capacity single load cell, used to measure the weight of the gas cylinder. Outputs of both the sensors are in analog form it is converted to digital form by the help of an analog to digital converter. The analog to digital converter used is ADC0808. ADC0808 is connected to micro controller through P1.0 to P1.7 and P3.2 to P3.7. The P1 ports are used to give the digital output from the ADC to micro controller and port P3.2 to P3.7 are used to control the ADC outputs and received values from the ADC. Port TXD and RXD are used to communicate micro controller to MAX232. When a gas leakage or weight of the cylinder become low the micro controller identifies the situation and communicates with RS232 & modem and send appropriate message to the user. Also a buzzer is connected to alert the user when the presence of gas is detected. Three LEDs are connected to the micro controller through port P0.1 to P0.3 for level indication. Also a LED is connected to the port P0.4, to indicate the gas leakage. Ports P2.2 to P2.7 are used for connecting the relays. The relays are interfaced to the micro controller with the help of the IC ULN2003AN. It is used to cut off the main power supply.
