In recent year, the control of Home Lighting System
has developed from standalone type to more complicated networking controls. Many building management system and even the security system have incorporate the control of lighting into their system as a total solution to their customers. However, there are still no single universal protocol for the building or lighting control system.
The lighting industry has developed a new standard for communication with electronic ballast. Electronic ballast is a common lighting device that is used in practically every building, factory or residential house. This standard called IEC 929 is an interface standard for communication between a controller and the electronic ballast. The standard for the control is called DALI, an acronym for Digital Addressable Lighting Interface. DALI is meant for home or industry use which has 2 wire communication connection between the master-slave and slave-slave. It is developed to reduce the cost of implementation.
Among the features that can be applied are dimming features and control for different grouping/section of the building.
The electronic ballasts can have up to 16 groups and each group can have up to 16 different lighting parameters for the lighting scenes. Each controller can controlled up to 64 electronic ballasts.
There are many ways to implement the DALI depending on the cost and requirements of a home or building. Most of the time, a microcontroller is used at both the slave and the master controller units as this is one of the most cost effective ways to implement the system.
Freescale Semiconductor has developed a prototype and solution based on DALI using its MC68HC908KX8 device. This is a good reference project for students and beginners to inter-networking of devices. The full application design
can be downloaded from Freescale Semiconductor website.
Thursday, December 10, 2009
X10 Home Automation Project
X-10 is a communication protocol designed for sending signals over 120 VAC wiring
. X-10 uses 120 kHz bursts timed with the power line zero-crossings to represent digital information. X10 components send signals through your home electrical wiring. There are 16 house codes and 16 unit numbers per house code available on your network for a total of 256 addresses. You can control multiple devices by setting them the same house code.
X10 plug in modules are now commonly used in the area of security
, lighting, control of TV, motion detectors and other applications. It should be noted if there is no filter at the house breaker box, signals can pass from one house to another and cause odd behavior. If you have problems with a device on a given house and unit code, experiment with other codes and see if the problem goes away.
X-10 transmissions are synchronized with the zero-crossings on the AC power line. By monitoring for the zero-crossings, X-10 devices know when to transmit or receive X-10 information. A binary ‘1’ is represented by a 1 ms long burst of 120 kHz, near the zero-crossing point of the AC. A binary zero is represented by the lack of the 120 kHz burst. The timing diagram is as shown below.
X10 Home Automation Project
This application note discusses the implementation of X-10 on a PICmicro MCU to create a home controller that can both send and receive X-10 signals. The reader may implement the home controller as is, or adapt the circuits and firmware
to other applications. A library of X-10 functions is provided to facilitate development of other X-10 applications using PICmicro microcontrollers.
It allows the user to program on and off times for up to sixteen devices, using a 2 x 16 liquid crystal display and five push buttons. A built-in light sensor can be used to turn on lights at dusk, and turn them off at The home controller is designed to facilitate experimentation with home automation using the PIC16F877A.
It will be a good project for final year students to embark on and hence gain a considerable experience in X10 wireless technology.
The application note of X10 Home Automation Project and its source codes can be downloaded from Microchip website.
. X-10 uses 120 kHz bursts timed with the power line zero-crossings to represent digital information. X10 components send signals through your home electrical wiring. There are 16 house codes and 16 unit numbers per house code available on your network for a total of 256 addresses. You can control multiple devices by setting them the same house code.
X10 plug in modules are now commonly used in the area of security
, lighting, control of TV, motion detectors and other applications. It should be noted if there is no filter at the house breaker box, signals can pass from one house to another and cause odd behavior. If you have problems with a device on a given house and unit code, experiment with other codes and see if the problem goes away.
X-10 transmissions are synchronized with the zero-crossings on the AC power line. By monitoring for the zero-crossings, X-10 devices know when to transmit or receive X-10 information. A binary ‘1’ is represented by a 1 ms long burst of 120 kHz, near the zero-crossing point of the AC. A binary zero is represented by the lack of the 120 kHz burst. The timing diagram is as shown below.
X10 Home Automation Project
This application note discusses the implementation of X-10 on a PICmicro MCU to create a home controller that can both send and receive X-10 signals. The reader may implement the home controller as is, or adapt the circuits and firmware
to other applications. A library of X-10 functions is provided to facilitate development of other X-10 applications using PICmicro microcontrollers.
It allows the user to program on and off times for up to sixteen devices, using a 2 x 16 liquid crystal display and five push buttons. A built-in light sensor can be used to turn on lights at dusk, and turn them off at The home controller is designed to facilitate experimentation with home automation using the PIC16F877A.
It will be a good project for final year students to embark on and hence gain a considerable experience in X10 wireless technology.
The application note of X10 Home Automation Project and its source codes can be downloaded from Microchip website.
Bluetooth Technology
Bluetooth technology is a radio frequency short range communications technology that was created with the intention of replacing wired cables that are used to connect various portable and fixed devices. The use of this technology will do away with the physical cables that connect devices. The key features are its low cost, low power and robustness in maintaining high level of security.
Bluetooth was made possible by the Bluetooth Special Interest Group(SIG) which was founded by Ericsson, IBM, Intel, Nokia and Toshiba in the year 1998. The objective was to develop an open specifications for short range wireless connectivity. More than 1900 companies have since joined the SIG and the numbers are increasing day by day.
Specifications
The specifications provide developers the link layer and application layer definitions which are used to support both voice and data applications. The spectrum of frequency used is in the unlicensed ISM(Industrial, Scientific and Medical) band at 2.4 Ghz to 2.485 GHz using spread spectrum and frequency hopping. As this is a free band, there is no cost for the use of Bluetooth compared to cellular phones where one must subscribe to use the network of GSM or CDMA.
IEEE 802.15.1 standard is used in the development of Bluetooth enabled products. The versions used are Ver 1.2 with data rate of 1 Mbps and ver 2.0 with data rate of up to 3 Mbps. The range of operation depends on the device classes. They are:
Class 3 – 1 meter range with maximum permitted power set at 1mW.
Class 2 – 10 meters range with maximum permitted power set at 2.5mW.
Class 1 – 100 meters range with maximum permitted power set at 5mW.
Bluetooth Applications
The technology allows the data and voice transmissions to be handled simultaneously. Hence, Bluetooth applications have been used in communications solutions such as hands free headset, mobile phones, laptop, PDA, printers, mouse, keyboard, MP3 players and fax machines amongst others. As this technology is made available in the global scale, one will be able to find many products that exhibit such capability.
In Voice over IP (VOIP) application, Bluetooth headsets are being used as wireless extensions to the PC audio system. As VOIP becomes more popular compared to wired phone, Bluetooth may be used in Cordless handsets, with a base station connected to the Internet link.
One good link for free downloading of Bluetooth technology design is from IVT Corporation. It is a world leader in providing Bluetooth Technology and Fixed-Mobile Convergence(FMC) Solutions.
Bluetooth was made possible by the Bluetooth Special Interest Group(SIG) which was founded by Ericsson, IBM, Intel, Nokia and Toshiba in the year 1998. The objective was to develop an open specifications for short range wireless connectivity. More than 1900 companies have since joined the SIG and the numbers are increasing day by day.
Specifications
The specifications provide developers the link layer and application layer definitions which are used to support both voice and data applications. The spectrum of frequency used is in the unlicensed ISM(Industrial, Scientific and Medical) band at 2.4 Ghz to 2.485 GHz using spread spectrum and frequency hopping. As this is a free band, there is no cost for the use of Bluetooth compared to cellular phones where one must subscribe to use the network of GSM or CDMA.
IEEE 802.15.1 standard is used in the development of Bluetooth enabled products. The versions used are Ver 1.2 with data rate of 1 Mbps and ver 2.0 with data rate of up to 3 Mbps. The range of operation depends on the device classes. They are:
Class 3 – 1 meter range with maximum permitted power set at 1mW.
Class 2 – 10 meters range with maximum permitted power set at 2.5mW.
Class 1 – 100 meters range with maximum permitted power set at 5mW.
Bluetooth Applications
The technology allows the data and voice transmissions to be handled simultaneously. Hence, Bluetooth applications have been used in communications solutions such as hands free headset, mobile phones, laptop, PDA, printers, mouse, keyboard, MP3 players and fax machines amongst others. As this technology is made available in the global scale, one will be able to find many products that exhibit such capability.
In Voice over IP (VOIP) application, Bluetooth headsets are being used as wireless extensions to the PC audio system. As VOIP becomes more popular compared to wired phone, Bluetooth may be used in Cordless handsets, with a base station connected to the Internet link.
One good link for free downloading of Bluetooth technology design is from IVT Corporation. It is a world leader in providing Bluetooth Technology and Fixed-Mobile Convergence(FMC) Solutions.
Battery Tester Project Using LM3914 IC
This objective of this project is to design and build a battery tester that is able to test various types of dry cell and rechargable battery with a voltage of less than 2V. Configured as a bar graph battery level indicator, the LM3914 IC from National Semiconductor senses the voltage levels of the battery under test and drives the 10 LEDs to ON or OFF based on the voltage that is detected. The current driving the LEDs is regulated by using the external resistor R1 and hence limiting resistors are not required.
The schematic shows the simple connections where the reference voltage at pin 8 of U1 can be adjusted by adjusting the variable resistor VR1. The voltage at pin 8 will set the maximum scale of the LED. In testing dry cell battery of 1.5V, set the voltage at pin 8 to 2.0V. Each of the LED will thus represent 200mV when lighted up.
If testing of rechargable battery such as NiCd or NiMH is required, set the reference voltage to a lower value such as 1.5V as the typical voltage of a rechargable battery is approximately 1.2V.
When testing the battery, take note of the polarity of the probe to the terminals of the battery. T1 is to be placed on the positive terminal and T2 the negative terminal of the battery.
The schematic shows the simple connections where the reference voltage at pin 8 of U1 can be adjusted by adjusting the variable resistor VR1. The voltage at pin 8 will set the maximum scale of the LED. In testing dry cell battery of 1.5V, set the voltage at pin 8 to 2.0V. Each of the LED will thus represent 200mV when lighted up.
If testing of rechargable battery such as NiCd or NiMH is required, set the reference voltage to a lower value such as 1.5V as the typical voltage of a rechargable battery is approximately 1.2V.
When testing the battery, take note of the polarity of the probe to the terminals of the battery. T1 is to be placed on the positive terminal and T2 the negative terminal of the battery.
Color Sensor
Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the coloured filter glass plates determine which of the LDRs would get triggered. The circuit makes use of only �AND� gates and �NOT� gates.
When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which colour it is. Similarly, when a secondary coloured light ray falls on the system, the two primary glass plates corres- ponding to the mixed colour will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is.
When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted :
1. Potmeters VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs.
2. Common ends of the LDRs should be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions
Wednesday, August 12, 2009
Fire Monitor
This project “Fire Monitor” is used to monitor the Temperature of two Rooms and if the sensor found any fire in the Room then the alarm will be switched ON until the Fire is put off else the Reset button is pressed. The Fire was sensed by using the Thermistor. The Thermistor is a passive device which has a Negative Temperature Co-efficient (NTC), i.e when the temperature increases then the resistance of the Thermistor will decrease. A analog comparator is used for the fire sensor circuit , at normal temperature the output of the comparator is low, and if there is any fire hazard, then the temperature increases and therefore the resistance of the Thermistor decreases and the output of the comparator goes High which Trigger the Microprocessor though the PPI 8255. Then the Microprocessor will switch ON the Alarm for fire. The above system is monitored and controlled by the 8 bit Microprocessor. The Microprocessor continuously monitors the two sensors and if any one of the sensor sense Fire then it latches the sensor and the microprocessor switch on the Alarm according to the software stored on the RAM.
FRIENDLY CHARGER FOR MOBILE PHONES
Most mobile chargers do not have current/voltage regulation or short-circuit protection. These chargers provide raw 6-12V DC for charging the battery pack. Most of the mobile phone battery packs have a rating of 3.6V, 650 mAh. For increasing the life of the battery, slow charging at low current is advisable. Six to ten hours of charging at 150-200mA current is a suitable option. This will prevent heating up of the battery and extend its life. The circuit described here provides around 180mA current at 5.6V and protects the mobile phone from unexpected voltage fluctuations that develop on the mains line. So the charger can be left ‘on’ over night to replenish the battery charge.
The circuit protects the mobile phone as well as the charger by immediately disconnecting the output when it senses a voltage surge or a short circuit in the battery pack or connector. It can be called a ‘middle man’ between the existing charger and the mobile phone. It has features like voltage and current regulation, over-current protection, and high- and low-voltage cut-off. An added speciality of the circuit is that it incorporates a short delay of ten seconds to switch on when mains resumes following a power failure. This protects the mobile phone from instant voltage spikes.
The circuit is designed for use in conjunction with a 12V, 500mA adaptor (battery eliminator). Op-amp IC CA3130 is used as a voltage comparator. It is a BiMOS operational amplifier with MOSFET input and CMOS output. Inbuilt gate-protected p-channel MOSFETs are used in the input to provide very high input impedance. The output voltage can swing to either positive or negative (here, ground) side. The inverting input (pin 3) of IC1 is connected to 12V stabilised DC voltage developed across zener ZD1. This makes the output of IC1 high. After a power resumption, capacitor C1 provides delay of a few seconds to charge to a potential higher than of inverting pin 2 of CA3130, thus the output of IC1 goes high only after the delay.
In the case of a heavy power line surge, zener diode ZD1 (12V, 1W) will breakdown and short pin 3 of IC1 to ground and the output of IC1 drops to ground level. The output of IC1 is fed to the base of npn Darlington transistor BD677 (T2) for charging the battery. Transistor T2 conducts only when the output of IC1 is high. During conduction the emitter voltage of T2 is around 10V, which passes through R6 to restrict the charging current to around 180 mA. Zener diode ZD2 regulates the charging voltage to around 5.6V.
When a short-circuit occurs at the battery terminal, resistor R8 senses the over-current, allowing transistor T1 to conduct and light up LED1. Glowing of LED2 indicates the charging mode, while LED1 indicates shortcircuit or over-current status. The value of resistor R8 is important to get the desired current level to operate the cut-off. With the given value of R8 (3.3 ohms), it is 350 mA. Charging current can also be changed by increasing or decreasing the value of R7 using the ‘I=V/R’ rule.
Construct the circuit on a common PCB and house in a small plastic case. Connect the circuit between the output lines of the charger and the input pins of the mobile phone with correct polarity.
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