November 15, 2005
Assignment 4
I used a Force sensing resister to extract sensor data and save it in a database.
For now I am using the following pieces of code
php script
Processing code and Pic basic code
I get an error in the processing app and no readings in the list
Devel Library
=========================================
Native lib Version = RXTX-2.1-7pre17
Java lib Version = RXTX-2.1-7pre17
COM1
COM4
128.122.253.189
HTTP/1.1 200 OK
Date: Tue, 15 Nov 2005 04:31:15 GMT
Server: Apache/2.0.52 (Red Hat)
Content-Length: 84
Connection: close
Content-Type: text/html; charset=UTF-8
Could not connect: Access denied for user 'apache'@'localhost' (using password: YES)
Posted by Shagun at 01:31 AM
October 20, 2005
Final Assignment
The sensor which I am looking at here is a PS-2152 Pasport Spirometer. Spirometers are devices used to measure the volume of air inhaled or exhaled by the lungs. The device uses differential pressure transducers to measure the flow rates or the amount of air breathed in or out in a given duration of time.
Applications
Spirometry is the most basic and common methods to understand pulmonary lung functions. It may be useful to do the following:
1.To determine how well the lungs receive, hold, and utilize air
2.To monitor a lung disease
3.To monitor the effectiveness of treatment
4.To determine the severity of a lung disease
5.to determine whether the lung disease is restrictive (decreased airflow) or obstructive (disruption of airflow)
The above has been taken from this Respiratory Disorder link. More details can be found on it.
How a Spirometer works
The Pasport Spirometers comes with a mouthpiece which has a thin screen in the middle it. This mouthpiece gets connected to the flow head and the electronic enclosure. When the user blows into the piece, a small amount of resistance to the airflow is generated across the screen. Resistance leads to pressure difference which is measured by two airlines that lead to the 'differential pressure transducer' in the elctronic enclosure. The flow rate is determined by comparing the measured differential pressure to an onboard stored reference data. Flow rates over time are integrated to measure the total volume exchange.
Hence a number of readings and measurements concerning the ventilatory function of the respiratory system can be obtained from this method.
Spirograms
Graphic recordings of expirations are called Spirograms and help to visualise measuremtents.
The Forced Vital Capacity (FVC) measures the total volume of air exhaled during the maneuver. Speed of the expiratory airflow is quantified by the Forced Expiratory Volume in One Second (FEV1), and by the relationship of the FEV1 to the FVC, expressed as the FEV1/FVC ratio. These measurements are usually compared with
average values "predicted" for a subject based on their sex, age, height, and race. An FEV1/FVC that is below the lower limit of a subject's normal range for this ratio indicates probable airways obstruction.
More Details on this can be obtained on Principles of Spirometry
More Details on the Interpretation of Pulmonary Function Test (PTF)/ Manual
Types of Spirometers
There are broadly two types:
1. Volumetric Spirometers:
Directly measures air volume as a function of time. Eg Water-sealed, dry rolling seal and bellows spirometer
2. Flow-Type Spirometer
Measures airflow during a period of time and integrates the flows to get expired volume. Eg pneumotachometer, turbine, hot wire anemometer spirometers.
Difference between pneumotachometer and hot wire anemometer spirometers.
I am putting this extra bit of information as it confused me for a while. I was under the impression that that principally differential pressure sensors were the only mode of breath measurment. I saw this link with the anemometer and it clarified some of that confusion. Spirometer and attached flow head function together as a pneumatachomater
Pneumotachometer
Hot Wire Anemometer Spirometer
Electrical Characteristics
The Pasport PS-2152 Spirometers use the Integrated Silicon Pressure Sensor from the MPXV5004G series.
The pressure signal is transmitted to the silicon diaphragm inside the sensor. Dry air is used as the pressure media.The output signal relative to the pressure input is as follows:
Pin Descriptions
Pins 1,5,6,7 and 8 are internal device connections and are not connected to external circuitry or ground. Pin 2 is the Input Voltage pin and works at 5.0Vdc and I am supposing that it gets connected to the microprocessor. Pin 3 being ground and Pin 4 being the Output Voltage.
Microcontroller Connections
Here is a how it is connected in the device.
Using the MPXV5004GC7U(absolute pressure sensor) instead of the MPXV5004DP (differential pressure sensor)
Datalogging by Sending Raw Values
Other Links and projects
Similar sensor with two outputs
Thermistor-based Breathing Sensor for Circadian Rhythm Evaluation
Motion Capture
Frequency Content of Breath Pressure and Implications for Use in Control
INTERACTIVE MULTI-MEDIA PERFORMANCE WITH BIO-SENSING AND BIO-FEEDBACK
Breathe Actuated Triggers
Breath-o-Matic
Posted by Shagun at 11:22 PM
September 25, 2005
Assignment 3
The sensor which I am looking at is a Force Sensing Resistor (FSR)from Interlink Electronics.
The part number of the model is 402 and it is 0.5" in diameter. The approximate thickness of the sensor is around 0.018". The FSR is a polymer thick film (PTF) device which exhibits a decrease in resistance with an increase in the force applied to the active surface.
Applications
The sensor allows one to detect and measure the change in the applied force and also the rate at which the force is changing. It could detect contact or touch. Identify force thresholds and trigger actions.Its force sensitivity is optimized for use in human touch control of electronic devices.The FSR sensors have wide usage in the commercial and industry arena. The Applications range from medical, automotive to recreational and Industrial.
Electrical Characteristics
At the low force end of the force-resistance characteristic, a switch like response is evident. This turn-onthreshold, or ‘break force”, that swings the resistance from greater than 100 kΩ to about 10 kΩ (the beginning of the dynamic range that follows a power-law) is determined by the substrate and overlay thickness and flexibility, size and shape of the actuator, and spacer-adhesive thickness (the gap between the facing conductive elements). Break force increases with increasing substrate and overlay rigidity, actuator size, and spacer adhesive thickness.
At the high force end of the dynamic range, the response deviates from the power-law behavior, and eventually saturates to a point where increases in force yield little or no decrease in resist-ance. A saturation point is reached.
There are two two solder tabs on the sensor. One goes to the microcontroller and the other goes to +5V, and a fixed resistor to ground. The FSR feeds a varying voltage to the microcontroller. The fixed resistor provides a path to ground. The current will follow the path of least resistance, from the 5V source through the FSR to the microcontroller.
Click here for the user guide and more electrical interfaces with FSR's
Posted by Shagun at 06:02 PM
September 21, 2005
Assignment 2
To Output the Sensor changes over time using Processing.
It took me a while to get into the pcomp shop and firmware lab again. However not having taken any pcomp related last semester was a needed break. The slow process of getting the materials together, wiring the board to getting the 'blinky' to work was nerve racking. That done, I got down to looking for a suitable sensor. I chose the sensor Eric and I had used for the mailbot. It was a Sharp IR proximity sensor.
The code I used was Toms original code. I didnt improvise it atall except to change the threshold once in a while. The code on the pic was the Peak-finder code to, as the name suggests, find the peak value of the sensor over time. The pic communicates to the serial port of the PC. The Processing code graphs the value of the byte sent from the pic.
Posted by Shagun at 11:00 AM
September 20, 2005
Sensors in everyday life
In India, human beings act as sensors. They check the tickets before one boards the train, they man the traffic in the sweltering heat where there are no traffic lights. They would absolutely do anything done electronically in the rest of the world. Wonder why. Anyway, I miss the human interaction sometimes but not always. The convenience is immense when systems are electronic. Surprisingly my day doesnt involve as many sensor interactions maybe because I dont have an I pod or a coffee maker. Some are as follows
- Subway enty card scanner
- elevator doors
- Smoke alarms
- Security alarms
- Traffic lights
- Touch pad on the computer
- Shop doors
- I wonder if microwaves or dishwashers have any kind of sensors
- Remote control
- Door sensors in the trains
- Metal detectors
- I card scanner in the Bobst
Posted by Shagun at 12:08 AM