GPS ( GLOBAL POSITIONING SYSTEM )

The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.

The GPS program provides critical capabilities to military, civil and commercial users around the world. In addition, GPS is the backbone for modernizing the global air traffic system.

The GPS project was developed in 1973 to overcome the limitations of previous navigation systems,^[1] integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realized by the U.S. Department of Defense (DoD) and was originally run with 24 satellites. It became fully operational in 1994.

Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS system and implement the next generation of GPS III satellites and Next Generation Operational Control System (OCX).^[2] Announcements from the Vice President and the White House in 1998 initiated these changes. In 2000, U.S. Congress authorized the modernization effort, referred to as GPS III.

In addition to GPS, other systems are in use or under development. The Russian GLObal NAvigation Satellite System (GLONASS) was in use by only the Russian military, until it was made fully available to civilians in 2007. There are also the planned European Union Galileo positioning system, Chinese Compass navigation system, and Indian Regional Navigational Satellite System.

 integrated mobile gps system

 gps reciever

gps reciever installed in vehicles

Long before Global Positioning System (GPS) arrived, researchers worked hard to arrive at a feasible solution to aid travellers from getting lost. Earlier, travellers used to rely on elaborate maps to track and monitor the route to their destination. But today, GPS technology has ensured hassle – free trips and increased safety for vehicle owners. The figure below illustrates a GPS satellite in orbit. 

GPS technology became a reality through the efforts of the American military, which established a satellite-based navigation system consisting of a network of 24 satellites orbiting the earth. GPS is also known as the NAVSTAR (Navigation System for Timing and Ranging).

GPS works all across the world and in all weather conditions, thus helping users track locations, objects, and even individuals! GPS technology can be used by any person if they have a GPS receiver.

Applications

This technique was initially developed for military applications. During 1980, the government decided to make it available for the civilian use as well. GPS has become an efficient tool in the field of scientific use, commerce, surveillance and tracking. GPS is used except in locations where it is difficult to detect the signal for example, underwater, subterranean location, inside the building and caves.

Civilian Applications

·         Navigation – Used by navigators for orientation and precise velocity measurements.

·        Geotagging – Map overlays can be created by applying location coordinates to photographs and other kind of documents.

·         Surveying – Surveyors create maps and verify the boundaries of the property.

·         Map-making – Used by civilians and military cartographers.

·         Tectonics – Detect the direct false motion measurement in earthquakes.

·        Geofencing – Vehicle, person or pet can be detected by using GPS vehicle tracking system, person tracking systems, and pet tracking systems.

Military Applications

·         Navigation – Soldiers can find objectives in the dark and unknown regions with the help of GPS.

·         Search and Rescue – Knowing the position of a downed pilot, its location can be traced out easily.

·         Reconnaissance – Patrol movement can be handled.

·         Target tracking – Military weapon systems use GPS to track air targets and potential ground before they are flagged as hostile.

·       GPS carry a set of nuclear detonation detectors (such as optical sensor, dosimeter, electromagnetic pulse sensor, X-ray sensor) which is a part of United States Nuclear Detonation Detection System.

·         Missile and projectile guidance – Targets military weapons such as cruise missiles, precision – guided munitions.

Remote Control for Toy Car

fig 1 

fig 2

Make any battery-operated toy car remote-controlled using this circuit. The circuit, consisting of an infrared transmitter-receiver pair, uses IR beam transmission to switch the toy car 'on' or 'off '. To operate the toy car, you need to hold the transmitter in your hand, keeping it pointed at the toy car which has the receiver fitted inside, and simply press a switch provided on the transmitter.
 
The transmitter works off 9V DC, while the receiver needs 6V DC. Fig. 1 shows the transmitter circuit. It is built around two BC558 transistors (T1 and T2), ,three BC548 transistors (T3, T4 and T5), IR LED1 and a few discrete components. 

Fig. 2 shows the receiver circuit. It is built around IR receiver module TSOP1738, two BC548 transistors (T6 and T7) and a few discrete components. In the transmitter circuit, there are two astable multivibrators. The first, built around transistors T1 and T2, produces a frequency of about 1.2 kHz. The second, built around transistors T3 and T4, produces about 38 kHz. IR LED1 is used to transmit the 38kHz frequency.  

In the receiver circuit, TSOP1738 receives the IR signal transmitted by IR LED1 of the transmitter circuit. The output of TSOP1738 is fed to transistor T6 via diode D1. The amplified signal is further given to relay-driver transistor T7. Relay RL1 energises to control the toy car.

Working of the circuit is simple. Initially, when no IR beam is falling on sensor TSOP1738, the relay remains de-energised and the toy car doesn't move. When switch S1 is pressed, the IR beam falls on TSOP1738 and its output goes low. Transistor T6 cuts off and transistor T7 conducts to energise relay RL1 and move the toy car.

Assemble both the circuits on separate PCBs. Enclose the transmitter PCB in a suitable cabinet, with IR LED1 affixed on the front side and switch S1 on the top of the cabinet. Keep the 9V battery inside the cabinet.

Enclose the receiver PCB inside the toy car, with TSOP1738 fitted such that the transmitted IR beam directly falls on it. Fix switch S2 on the body of the car and the relay inside the car. Use a 6V battery to operate the toy car receiver unit. 


courtesy: EFY

door KnocK alarm With timer

 

This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input sensor.  The  piezoelectric  element  plate is fixed at the centre of the door wing by using a cello tape. Apply a small quantity of adhesive at the edges be- tween the plate and the door. Extend wires  about  1-1.5  metres  from  the piezoelectric to the circuit.

IC NE555 (IC1) is configured in monostable mode. When it gets an input pulse its output goes high for a period set by VR1, resistor R5 and capacitor C3. IC UM66 (IC2) is used as a melody generator. When the door is knocked at, the piezo plate generates an input pulse, which is amplified by transistor T1.

The  amplified signal  triggers  the timer IC NE555 and its output pin 3 goes high to enable the melody genera- tor. Music is heard from the speaker LS1. After the set time period, the melody sound stops.

Assemble the circuit on a general- purpose PCB and enclose in a suitable case. Fix the piezo element at the door and place the speaker in a central room inside the house using long wires. The circuit works off 5-12V DC. The music time can be adjusted through VR1 by changing the R-C time constant of the timer.

TV REMOTE USED TO CONTROL HOME APPLIANCES

 

 This circuit is designed to switch on/off any home or industrial appliance  by  using  the  TV/ DVD remote controller. The circuit can be operated up to a distance of 5-10 metre depending on the remote used.

The  circuit  consists  of  a  step- down   transformer   X1   (6V-0-6V, 250mA secondary), 5V regulator 7805 (IC1), two 5V, 1 change-over (C/O) relay, a timer NE555 IC (IC2), an IR receiver module (IRX1 TSOP1738) and some discrete components. The circuit works on regulated 5V, which is derived from X1 and regulated by IC1. Home appliance is controlled either by pressing any key on the re- mote or by manually pressing switch S1 to ‘on’ state.

The TV/DVD remote controller produces 38kHz frequency. The IR receiver module operates at this fre- quency. It is used to control relay RL2. The relay triggers IC2, which is wired in a bistable mode to control the home appliance connected at the contacts of relay RL1.

Timer IC2 toggles relay RL1 when switch S1 is pressed momentarily. Threshold and trigger input pins 6 and 2 of IC2 are held at one-half of the power supply voltage (5V) by resistors R2 and R3. When output pin 3 of IC2 is high, capacitor C4 charges through resistor R4, and discharges when the output pin 3 is low. When switch S1 is pressed, capacitor C4 voltage is applied to pins 2 and 6 of IC2, which causes the output of IC2 to change from low to high, or high to low. When switch S1 is released capacitor C4 charges or discharges to the original level at the output pin 3 of IC2.

At normal condition, when IR rays are not incident on TSOP1738, its out- put at pin 3 remains high. When any TV remote key is pressed, IR rays fall on the TSOP1738 and its output goes low. At the same time relay RL2 ener- gises for a few seconds through pnp transistor T2 (BC558).

  The working of the circuit is sim- ple. Initially, when there are no IR rays falling on the IR receiver module, its output remains high. Transistor T2 is in cut-off condition. Relay RL2 does not energise and hence IC2 does not toggle.  As  a  result  home  appliance connected at the contacts of relay RL1 remains switched off.

When you press any remote key for the first time, IR receiver module’s output goes low and collector of the transistor T2 goes high. Relay RL2 energises and triggers IC2. Output of IC2 goes high and relay RL1 energises to switch on the appliance. Once relay RL1 is energised it remains in that state. So the appliance which is con- nected at the contacts of relay RL1 remains switched on.

Now when you press any remote key the second time, relay RL2 ener- gises and re-triggers IC2. Output of IC2 goes low and relay RL1 de-energises to switch off the appliance. Once relay RL1 de-energises it remains in that state. So the home appliance remains off. This cycle repeats when any key of the TV remote is pressed to switch on/ off the home appliance.

Assemble the circuit on a general- purpose PCB and enclose in a suitable cabinet. Fix TSOP1738 and switch S1 on front side of the cabinet. Place trans- former inside the cabinet and mains power cord at the back of the cabinet.

 

COURTESY:EFY