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Accelerometer based sensor for controlling wheel chair

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In this project we use two circuit. One is transmitter and second is receiver circuit. In the transmitter circuit we use 3 Axis accelerometer base circuit and on the receiver end we use small WHEEL CHAIR with RF receiver circuit. In the transmitter circuit we measure the value of 3 Axis accelerometer and converted into digital with the help of ADC 0809. ADC converts the data from sensor and proceed to the microcontroller for further conversion. Microcontroller. Microcontroller gets the hex data from the accelerometer and converted into ASCII code for LCD display. LCD display the X—Y—Z values and display the values on the LCD. At the same time microcontroller gets the data and compare inside with pre-defined variables. As we change the position of hand, values are change automatically and change values are also shown on the LCD. We use the readings of accelerometer for WHEEL CHAIR movements. We use one encoder circuit and one transmitter circuit with the microcontroller circuit for wireless transmission. We specify four variables for the WHEEL CHAIR motion. As the position of hand change, data from the controller is also changes automatically. We gets a four output from the controller. Pin no 5,6,7,8 is the output pins for encoder. We use HT12 E encoder for serial communication. Data from the microcontroller is connected to these pins of encoder and transmits via pin no 17 of the encoder. Output from the pin no 17 is connected to the Rf transmitter module. Rf transmitter module gets the signal from the encoder and transmit via Rf frequency 433 Mhtz. We use 2 by 16 lcd with port 0.



Components used:
STEP DOWN TRANSFORMER

Step down transformer from 220 volt Ac to 9-0-9 ac. We use step down transformer to step down the voltage from 220 to 9 volt ac. This AC is further connected to the rectifier circuit for AC to DC conversion. Transformer current rating is 750 ma .



How is this time then calculated?
The speed with which a microcontroller executes instructions is determined by what is known as the crystal speed. A crystal is a component connected externally to the microcontroller. The crystal has different values, and some of the used values are 6MHZ, 10MHZ, and 11.059 MHz etc.
Thus a 10MHZ crystal would pulse at the rate of 10,000,000 times per second.
The time is calculated using the formula

Accelerometer based sensor for controlling wheel chair

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Introduction

An accelerometer is a device that measures the proper acceleration of the device. This is not necessarily the same as the coordinate acceleration (change of velocity of the device in space), but is rather the type of acceleration associated with the phenomenon of weight experienced by a test mass that resides in the frame of reference of the accelerometer device. For an example of where these types of acceleration differ, an accelerometer will measure a value when sitting on the ground, because masses there have weights, even though they do not change velocity. However, an accelerometer in gravitational free fall toward the center of the Earth will measure a value of zero because, even though its speed is increasing, it is in an inertial frame of reference, in which it is weightless.
With the help of the accelerometer we can control the movement of any WHEEL CHAIRtic arm or movement or control of any electrical appliances. If we install our accelerometer to our hand, then it is possible to control any thing with the help of our hand . So in our project we use accelerometer to control the direction of any WHEEL CHAIRt . With the help of four different motion we control the direction of WHEEL CHAIRt for forward, reverse left and right.

Reset Circuitry:

Pin no 9 of the controller is connected to the reset circuit. On the circuit we connect one resistor and capacitor circuit to provide a reset option when power is on
As soon as you give the power supply the 8051 doesn’t start. You need to restart for the microcontroller to start. =Restarting the microcontroller is nothing but giving a Logic 1 to the reset pin at least for the 2 clock pulses. So it is good to go for a small circuit which can provide the 2 clock pulses as soon as the microcontroller is powered.
This is not a big circuit we are just using a capacitor to charge the microcontroller and again discharging via resistor.

ANALOGUE TO DIGITAL CONVERTER:

ADC is very important part in this project. Here we use 0809 adc. This adc is 8 channel multiplexer and analog switch also. To select the desired channel we use 3 bit address. . In this project we give a input to the pin no 26. Pin no 26 is a o number input . so to select this input we connect all the address pins to the zero level.. Pin no 23 ,24,25 is the address pins so we ground all the pins to zero point.. By this we select the IN0 and we connect a thermo sensor to this point. Pin no 11 is the positive supply pin and connected to the regulated 5 volt dc power supply. Pin no 13 is ground pin so it is connected to the ground pin.

BASIC NOTES ON THE ADC

Analogue to digital converters are among the most widely used devices for data acquisition. Digital computers use binary values, but in the physical world everything is analog. Temperature, pressure ( wind or Liquid), humidity, and velocity are a few examples of physical quantities that we deal with every day. A physical quantity is converted to electrical ( voltage, current) signals using a device called a transducer. Transducers are also referred to as sensors. Although there are sensors for temperature, velocity, pressure, light, and many other natural quantities, they produce an output that is voltage ( or current) . Therefore, we need an analog to digital converter to translate the analog signals to digital numbers so that the microcontroller can read them, A widely used ADC chip is the ADC0804.

ADC0804 CHIP

The ADC0804 IC is an analog to digital converter in the family of the ADC800 series from National Semiconductor. It is also available from many other manufactures. It works with +5 volts and has a resolution of 8 bits. In addition to resolution, conversion time is another major factor in judging and ADC. Conversion time is defined as the time it takes the ADC to convert the anlog input to a digital number. In the ADC0804, the conversion time varies depending on the clocking signals applied to the CLK R and CLK IN pins, but it cannot be faster then 110 microsecond.

ANALOG GROUND AND DIGITAL GROUND

These are the input pins providing the ground for both the analog signal and the digital signal. Analog ground is connected to the ground of the analog Vin while digital ground is connected to the ground of the Vcc pin. The reason that we have two ground pins is to isolate the analog Vin signal from transient voltages caused by digital switching of the output D0-d7, such isolation contributes to the accuracy of the digital data output. In our discussion, both are connected to the same ground; however, in the real world of data acquisition the analog and digital grounds and handled separately.