ProtoCentral OpenPressure 24-bit,4-channel DAQ with ADS1220


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OpenPressure is a result of our work in trying to interface pressure sensors to an ADC as well as a display system based on Arduino. We found the ADS1220 to be a great chip that can directly take a 4-wire, 3-wire or a 2-wire sensor and give the digital output.

Combine this powerful functionality with an ATSAMD21 micro-controller and you've got your very own Arduino-based pressure and temperature sensor interface system.

OpenPressure

OpenPressure is meant to make interfacing, data streaming and visualization of pressure sensor data as easy as possible. You do not have to figure out how to connect a breakout board to an Arduino, as the OpenPressure board itself acts as an Arduino!

The board comes pre-loaded with the Arduino Zero/M0 bootloader and even basic Arduino code that reads the sensor output and displays it on a serial terminal interface. This means that, in most cases, you would only need to plug it into your USB port, open the serial terminal and data should start flowing out.

Know your board


OpenPressure

The USB port on the OpenPressure board will connect to your computer through a standard micro-B USB cable (the same one that is used for most mobile phones) and this will provide both power to the board as well transfer data to and from the board. Your computer should recognize the board as an "Arduino Zero bootloader" device and install the right drivers for it.

If USB is connected, the board is powered up through the USB interface itself. Make sure to turn the device ON using power switch shown in the figure.

Power


Power to the board can be provided through either of these sources:

A DC/DC boost converter is provided on the board to step-up the 3.7V from the battery to 5V for generating the voltage required for the on-board 5V bang-gap voltage reference. The band-gap reference provides a stable excitation voltage on the 'Vexc' pin of the board.

How to setup Arduino support for openPressure


OpenPressure is powered by the Arduino Zero board support file.The first thing you will need to do is to download the latest release of the Arduino IDE. You will need to be using version 1.6.4 or higher.

If you want to program your Zero while offline you need to install the Arduino Desktop IDE and add the Atmel SAMD Core to it. This simple procedure is done selecting Tools menu, then Boards and last Boards Manager, as documented in the Arduino Boards Manager page.

board_manager

Setup Arduino Sketch


We have provided a few Arduino sketch examples . They are designed to work right away with no changes. To make the examples work with your board, you simply need to upload the code to your board.

Connecting a standard pressure sensor


Pressure sensors usually come in DIP packages and these can be mounted on the prototyping area provided on one end of the board. Shown below is a picture of a standard Honeywell pressure sensor for air pressure measurement. The four leads of this sensor correspond to four connection points on a Wheatstone bridge.

This type of pressure sensor can be directly connected to the OpenPressure board which only four connections. The board already contains an on-board 5V voltage reference which can be used as the excitation voltage for the pressure sensor, while the positive lead of the output is connected to the AIN0 channel of the ADS1220 ADC and the negative lead connected to system ground.

Connecting a pressure sensor

Connecting a voltage output sensor (Geophone)


The ADS1220 contains an integrated programmable gain amplifier (PGA), allowing you to connect other voltage output sensors to this board directly without the need for any analog amplifier or other instrumentation. In this following picture is a connection of a Seismic geophone to the OpenPressure board.

Sparkfun has this SM-42 Geophone from I/O Inc. which measures the ground movement by converting the small movements into voltage. This is similar to a microphone, but instead of converting sound into, a Geophone converts the Earth's movements into voltage. These sensors are typically used for seismic exploration and seismic monitoring applications.

Connecting a Geophone

Check out this video on youtube