BMP085 Test

BMP085 Breakout Pressure Sensor

·       Sami Yanikoglu

Description and Use

                  The BMP085 barometric pressure sensor is a low power sensor that can measure between 300 to 1100 hPa, measuring accurately down to a hundredth of a percent.  The sensor requires 1.8-3.6V, we will be using a 3.3V input.  The chip is designed to work with a microcontroller such as the arduino nano.  The data taken from the BMP085 chip will be sent from the arduino to the Parallax data logger to document the pressure periodically throughout the entire flight using the I2C bus.  The BMP085 is equipped with a temperature sensor which provides information necessary for the calculation of pressure.  Our code will bypass this sensor and use the ____? sensor for higher precision readings. 

The wiring of this chip to the arduino is show below along with the pin diagram.

http://www.hobbytronics.co.uk/image/cache/data/sparkfun/bmp085_2-500x500.jpg

                  We connected our BMP085 to 3.3V power and ground as well as the SDA and SCL pins.  The SDA pin transmits data to and from the arduino, and the SCL line is connected to the internal clock of the arduino.

                 

We are using the data logger in UART, or Universal Asynchronous Receiver Transmitter, protocol that requires ASCII characters to be sent or received in a serial signal from the Arduino.  These transmissions from the Arduino are sent through the Vinculum chip and encoded into digital signals in order to communicate with the data logger.  The data logger also has a Vinculum chip on board to decipher the ASCII code sent and handle the file system on the USB stick. 

Testing

                  Sample code written for the arduino can be found on the Sparkfun website, and was the basis for our initial testing of the BMP085.

Further testing of the BMP085 breakout pressure sensor must be performed to ensure its abilities at low temperatures when insulated.

Integration into Payload

This component will need to be soldered to a secondary board along with our temperature and humidity sensors that will be located at the edge of out payload.  This placement will ensure that the internal temperature of our payload from our other electronics doesn’t affect our readings.  Holes will also need to be placed close to the sensors for direct access to the outside conditions.