Embedded Files
Multi-Function Pedometer
Eshwar Chukkapalli
Introduction:
The best way to measure the physical activity of a person in a particular day is to measure the number of steps taken by the person during the period. The present project provides a solution to one such issue in the form of pedometer. The idea of the current project is to provide user with step counter with temperature and humidity measurements as accessories. The project also evaluates the usage of FSR (Force Sensitive Resistor) as compared to traditionally used technology of accelerometers.
Project Requirements:
Measure the number of steps taken during an activity period.
Measure the temperature and humidity of the surrounding area.
Provide user interface to display the data measured to the user.
Low power operation of the device.
Components
MSP430F5438A
FSR 0.5"
SHT75
LCD - 2x16 character display
Rowley's CrossStudio for MSP430
Results:
The project can be divided into three segments based on software coding i.e. the FSR used step counter,Temperature and humidity from SHT75 and LCD as visual interface.
FSR:
The FSR coding is based on IO port interrupts. The interrupt is triggered from the high to low transition on presence of load on FSR. The figures 1 show the response from FSR on a event.
Figure 1:Response on event from FSR
SHT75:
The SHT75 operates on Pseudo I2C protocol and hence has extensive procedures to operate. The major functions are sending a transmission start signal, write to SHT75 to measure temperature or humidity and read the digital data provided by SHT75.
The figures 2,3 and 4 show the transmission start, write and read signal to and from SHT75 respectively.
Figure 2: Transmission start signal
Figure 3 :Write signal to measure Temperature to SHT75
Figure 4: Temperature data from SHT75
The Temperature and humidity measurement made in the test were 26.12°C and 21.27 % respectively.
LCD:
The 2x16 character LCD chosen was a 3.3 V LCD Sparkfun with ST7066 as controller and driver. The operation was pretty simple. Figure 5 shows the screen demonstrating the count of steps.
Figure 5: Count from FSR
Complete system:
Figure 6: System with components in operation
Future work:
Cross check the count from events by using a traditionally used sensor such as Accelerometer.
Provide an effective Visual interface using a wireless communication protocol to provide results on devices such as watch.
Use the FSR to provide the pressure information on different sections of foot to form an effective biomedical device.
Conclusion:
The FSR can be a viable alternative to Accelerometers as a step counter but the type of information provided in each case will be different. The information from accelerometers will on the stride length and speed of walking while the data from FSR will be the amount of pressure applied on the foot which can find applications in orthotic treatment. SHT75 is a reliable temperature and humidity sensor.
Report abuse