INFO about 3D TV

How 3D glasses work

3D glasses are indispensable to enjoying 3D effect. Find out how these create the 3D effect

Manuj Arora

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NOVEMBER 2012: As the cinematic experience radically changed from B&W to colour and the current 3D/4D/6D, so did the TVs in our homes. Bulky TV sets have given way to slim LCD and LEDs TVs—more recently, those equipped with 3D technology.

India is on the verge of 3D boom. The same kind of glasses as provided in movie theatres are required to enjoy a 3D movie in 3D effect on a 3D TV set. If you remove these glasses and watch the same movie with naked eyes, the incredible 3D experience would vanish and you would land up viewing distorted/blurred pictures.

Clearly, 3D glasses are indispensable to enjoying 3D effect. Here is how these create the 3D effect.

Fundamentals
The 3D effect relies on creating an illusion of depth to the viewer. To understand what this means, simply watch your thumb with both your eyes, then close one eye as you keep watching the thumb with the other eye. Now close this eye and open the previous one. Repeat this twice or thrice. You will see as if the thumb is shifting back and forth. This back and forth distance basically arises due to the depth created in visualising the thumb with different eyes.

This simple phenomenon is the basis for developing the 3D glasses. The movie screen actually displays two images. The glasses are designed to feed different images into our eyes. These let one of the images to enter one eye and the other image to enter the other eye. This is achieved using either of two ways: red/green or red/blue 3D glasses, and polarisation.
Red/green or red/blue 3D glasses
In this system, to produce the 3D effect, two images are displayed on the screen—one in red and the other in green or blue. The colour filters on the glasses allow only one image to enter each eye. This lends depth to the image, making it appear 3D to our brain.

However, the image quality with this method is not as good as with the polarised system. The reason is it somehow restricts some of the actual colours of the scene as it applies filtration by means of the colour itself.

Polarisation
This method uses differently polarised lenses to feed different images into our eyes. The system comprises two synchronised projectors to project two respective views of an image, each with a different polarisation. The glasses have a pair of differently polarised filters at 90 degrees to each other. As each filter passes only that light which is similarly polarised and blocks the light polarised in the opposite direction, each eye sees a different image. Thus two different images reach our eyes, creating a sense of depth leading to very high-quality 3D effect.

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The author is a software engineer at AMDOCS DVCI, Pune

Mobile Based water pump controller

Cellphone-Based Remote Controller for Water Pump

Abdul Nasir K.T.

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Inconvenience in switching on a water pump installed in a remote farm is a common problem faced by farmers. Many circuits have been developed to solve this problem. Most of them are expensive and microcontroller-based. Here we present a cellphone-based remote controller for water pump. By calling the cellphone attached to the controller, the water pump can be directly activated.

Circuit and working
Fig. 1 shows the block diagram of cellphone-based remote controller for water pump. Fig. 2 shows the circuit. The circuit is built around DTMF decoder IC MT8870 (IC1), timer NE555 (IC2) wired as monostable multivibrator and a few discrete components. The main component of the circuit is IC MT8870. This DTMF decoder has band-split filter and digital decoder functions. It offers the advantages of small size, low power consumption and high performance.

Fig. 1: Block diagram of cellphone-based remote controller for water pump

Fig. 2: Circuit of cellphone-based remote controller for water pump

Once monostable timer IC2 is triggered, its output goes high for the preset time period. The time period depends on the values of resistor R7 and capacitor C4. It can be adjusted between 8 and 50 minutes using pot-meter VR1. The high output at pin 3 of IC2 energises relay RL1 to switch on the water pump.

The triggering pulse for IC2 is generated by DTMF decoder IC1 and the arrangement of diodes D1 through D5. Std pin of IC1 provides a high pulse when a valid tone-pair is received. Transistor T1 conducts only when outputs Q0 through Q2 and Std are high simultaneously. This can be achieved by sending digit ‘7’ through DTMF.

The water pump controller is connected to a dedicated cellphone through connector J1 with auto-answering mode enabled. The DTMF signal sent from the user end is decoded by the DTMF decoder and the corresponding binary-coded decimal (BCD) value appears on outputs Q0 through Q3. In this circuit only three of them are used.

Working of the circuit is simple. To switch ‘on’ the water pump, call the cellphone connected to the controller circuit and press ‘7’ once the ring stops. LED1 will glow to indicate that the water pump is switched on. The water pump turns off automatically after the preset time. LED1 turns off simultaneously.

Construction and testing
An actual-size, single-side PCB for cell-phone-based remote controller is shown in Fig. 3 and its component layout in Fig. 4. Suitable connector is provided on the PCB to connect the cellphone. Assemble the circuit on a PCB to minimise time and assembly errors. Carefully assemble the components and double-check for any overlooked error. Use suitable IC socket for MT887 and NE555 ICs.

Fig. 3: An actual-size, single-side PCB for cellphone-based remote controller

Fig. 4: Component layout for the PCB

Use relay RL1 with contact current rating capable of carrying the water pump’s current.

To test the circuit for proper functioning, press switch S1 and verify 5V at TP1 with respect to TP0. Connect the cellphone to the controller using connector J1. Call this cellphone and press ‘7’ once the ring stops. At the same time, verify high-to-low triggering pulse at TP2. TP3 now should be high for the preset time period.

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The author is a final year B.Tech (electrical and electronics engineering) student at MG University. His areas of interest include embedded systems and power electronics