Accelerometers have a well established market, mainly 50g devices for airbag modules.


Figure (1.2) – Computing the adaptive threshold level
The three high-pass filtered accelerations are combined to one output signal a? by taking the 1-norm: i.e. summing their absolute values. The 1-norm was chosen instead of the more accurate 2-norm to make the algorithm less computationally intense. The output a? is zero when the device is not moving. Any movement in any direction results in an output signal. With the 1-norm the gain (the scale of the output signal), depends somewhat on the orientation of the device, whereas with the 2-norm the gain is uniform in any direction.

2. Literature Survey
In 1975, the performance to date of the Cactus ultrasensitive triaxial accelerometer, launched on the Castor satellite in May 1975, is described after a brief outline of its major design features. Qualification tests of Cactus have demonstrated a threshold lower than one billionth of a meter per second squared. The accelerometer is ten to twenty times more sensitive than previously developed devices. Amongst other things, Cactus will be used to determine the density of the atmosphere and to measure the impact of micrometeorites.
In 1987, this procedure was done as a follow up study for a NPH patient first evaluated by the Cleveland Clinic Foundation in 1987. The subject was asked to stand on a force plate with the dual-axis accelerometer headpiece on her head. She then stood quietly for six thirty-second periods, three with eyes open, three with eyes closed. During these intervals measurements were taken by both the force plate, measuring center of pressure, and by the accelerometer.
In 1991, a rotary accelerometer has capacitively coupled rotary and fixed thin film electrodes fixed to a substrate. The rotary electrode is angularly flexible and has a central hub secured to the substrate and spoke electrodes radially extending from the hub. Elongated electrodes are fixed to the substrate in circumferential positions on each side of each spoke electrode and in the same plane as the spoke electrodes.
Table (2.1) – Differentiate Sensors in Old & Recent Days
Features/Sensors
|
ADXL202
|
MMA7260Q
|
Selectable Sensitivity
|
+/-1.0 degree
|
1.5g/2g/4g/6g
|
Sleep Mode
|
More than 3?A
|
3?A
|
Turn On Time
|
Not too much fast
|
Fast
|
High Sensitivity
|
–
|
800 mV/g @ 1.5g
|
Design
|
Robust Design
|
Robust Design, High Shocks Survivability
|
Axis Sensitivity
|
X & Y-Axis
|
XYZ-Axis
|
Cost
|
Medium to High
|
Low
|
3. System Development


3.2 Principle of Operation:

Features/Sensors
|
MMA7260Q
|
MMA6200Q
|
MMA2260D
|
Selectable Sensitivity
|
1.5g/2g/4g/6g
|
±3g, ±11g
|
–
|
Sleep Mode
|
3 ?A
|
3 ?A
|
–
|
Turn On Time
|
Fast
|
0.5 ms Enable Response Time
|
–
|
High Sensitivity
|
800 mV/g @ 1.5g
|
–
|
Fast
|
Design
|
Robust Design, High Shocks Survivability
|
Robust Design, High Shocks Survivability
|
Robust Design, High Shocks Survivability
|
Axis Sensitivity
|
XYZ-Axis
|
XY-Axis
|
XZ-Axis
|
Cost
|
Low
|
Low
|
Medium
|
3.3.1.1.3 Pin Description:
Pin No.
|
Pin Name
|
Description
|
1
|
g-select1
|
Logic input pin to select g-level
|
2
|
g-select2
|
Logic input pin to select g-level
|
3
|
VDD
|
Power supply input
|
4
|
VSS
|
Power supply ground
|
5-7
|
N/C
|
No internal connection. Leave unconnected
|
8-11
|
N/C
|
Unused for factory trim. Leave Unconnected
|
12
|
Sleep Mode
|
Logic input pin to enable product or sleep mode.
|
13
|
Zout
|
Z direction output voltage
|
14
|
Yout
|
Y direction output voltage
|
15
|
Xout
|
X direction output voltage
|
16
|
N/C
|
No internal connection. Leave unconnected
|





3.5 Flow Chart:


Figure (3.13) – Acceleration signal during running

Figure (3.14) – Acceleration signal during walking
4. Hardware And Software

Figure (4.2) – PCB Layout (Top Side)

Figure (4.3) – Component Pads on the PCB

4.2 Software Description
4.2.1 Module Diagram:
Figure (4.5) – Module Diagram
4.2.2 Algorithm:
1) Accelerometer device attach or tie on hips.
2) Switch on the power supply of the project.
3) It is provide the power to the controller and the analog to digital converter.
4) By the power supply the sensor automatically turn on.
5) After turn on the sensor.
6) Start walking around there.
7) Sensor senses the all three directions.
8) Sensor taking the analog input from the three directions.
9) Those analog inputs given to the analog to digital converter.
10) After converting the analog to digital those signals given to the controller.
11) In the controller we are defining the all interfaces like buzzer interface, LCD interface etc.
12) Here, we are using the buzzer interface for the indication of the distance will cover.
13) There will be the LCD interface with the controller for displaying the steps counting what you will walk on the road or everywhere.
14) There is one button provided in the device for set and reset the device.
4.2.3 Flow Chart:
5. Result Analysis
- For the Normal Walking:
Serial No.
|
User Height in cm
|
Walking Angle set by Device
|
1.
|
181.5
|
68
|
2.
|
171.5
|
62
|
3.
|
170
|
60
|
- For the Different Situation:
Sr. no
|
User Height
|
Reading 1
|
Reading 2
|
Reading 3
|
Avg. Angle
|
1
|
181.5
|
6D
|
6F
|
70
|
6E
|
2
|
171.5
|
65
|
68
|
6D
|
69
|
3
|
170
|
63
|
67
|
6A
|
67
|
Sr. no
|
User Height
|
Reading 1
|
Reading 2
|
Reading 3
|
Avg. Angle
|
1
|
181.5
|
70
|
72
|
6D
|
70
|
2
|
171.5
|
65
|
67
|
68
|
67
|
3
|
170
|
63
|
65
|
65
|
65
|
Sr. no
|
User Height
|
Reading 1
|
Reading 2
|
Reading 3
|
Avg. Angle
|
1
|
181.5
|
73
|
6D
|
6F
|
6E
|
2
|
171.5
|
66
|
67
|
69
|
67
|
3
|
170
|
64
|
65
|
68
|
66
|
6. Applications
6.1 Applications:
7. Advantages And Disadvantages
7.2 Disadvantages:
8. Conclusion
Project Source Code
Circuit Diagrams
Project Datasheet
Filed Under: Electronic Projects
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