Progress So Far

Over the course of the past few weeks, much progress has been made on the Open Source Spectrometer, although the name is still up for debate. 

Using TI sample code the following has been made to work:

• The microcontroller running code accepts a buffer of 255 bytes and flips the case of any alphabetic characters received over serial.
• The driver allows a windows application to interface with the hardware over USB2.0
• A demo application, written in C++, now allows the sending of buffers to the microcontroller and receives the processed data back. This is a very fast process, since USB can be thoeretically 480 megabits/s. Currently, we are transferring small buffers, so most of the overhead is in dealing with the individual buffers, but high speed will allow us to easily transfer greater than 4kb buffers many times a second. 4kb is the smallest a buffer could be, since we are using 12 bit ADCS (12 bits per pixel), and we have 2048 pixels.

A CAD design of the Open Source Spectrometer has been drafted and is being further revised.

And Tim Cantwell made a pretty cool visualizer program that displays a spectrum on a grid, which will be able to be added into the interface functionality to show data from the spectrometer once the hardware is more complete. His program is written in C++, using open frameworks and openGL for rendering/GUI.

Project Overview

Open Source Spectrometer (OSS)
RCOS Spring 2013

The Team: Jorel Lalicki, Monica Kosciuk, Justin Jones, Jonah Gruber, Andy Lynch, Brian Barnes

Why:
Physics education in High School and College covers light (and other electromagnetic waves). While there are a variety of hands on experiments that demonstrate, for example, that white light is composed of many wavelengths of light, there are few that can quantify the results in a cost effective and accurate manner. Spectrometers are most practical way of taking measurements of a light source. A spectrometer takes input light and measures the relative power present across a large array of discrete detectors. The data is then processed, and visualized as a graph of energy vs. wavelength. Spectrometers can be incredibly versatile—the following are a few examples of how such a device could be used in High School education to supplement and enhance the student learning experience.

Chemistry: 
A spectrometer can be used to measure absorbance of different wavelengths of light. A student could identify molecules present in a solution by first taking a reference measurement of a high CRI source such as an incandescent bulb, and then subtracting a measurement of the same light source after passing through the sample. The peaks give a unique ‘fingerprint’ for the compounds absorbing the light.

Physics: 
When teaching about the electromagnetic spectrum and color mixing, a hands on lab could be used to demonstrate how different colored filters/light sources combing. The spectrometer can be used to prove that, even though our eyes perceive the combination of Red, Green, and Blue light sources as white, they are still separate wavelengths.

Ecology/Environmental Science/Biology:
One common use of spectrometers is to identify and detect chemical pollutants in water samples. A low cost, durable, portable spectrometer would enable students to perform measurements and experiments in the field, and analyze the results in the classroom later.

The OSS Spectrometer project aims to make low cost OSHW spectrometers available to educators. A modular design will allow the OSS.S to be used in a variety of applications, including existing optical equipment with fiber optic connections, as well as direct light apertures for use with lighting fixtures/LEDs. Simple open source software will allow for basic use without a steep learning curve. The goal is a 10 second setup, where the spectrometer gets plugged in via USB, you start the spectrum visualizer, and adjust vertical scaling (a function of sample integration time).

Existing Products:
There currently exist several commercial, portable, visible light spectrometer solutions, such as those produced by Ocean Optics, Spectral Evolution, or ASDI. The main problem with these products is the prohibitive cost. For example, the Ocean Optics USB2000+, the spectrometer used by the Undergraduate Optics Lab classes at RPI, costs $2771 for the unit. The proprietary software needed to run the spectrometer (and only usable for spectrometers made by this company) costs an additional $209. However, the markup on these devices is ridiculously high. Even if you get the optics involved manufactured in a high end US optics lab, the cost is still only around $100. The sensor involved is in fact a Sony ILX511B, which was designed for use in barcode scanners. The software does little other than visualize real time data from the sensor on a graph. The Open Source Spectrometer will leverage low cost optics and components to produce a quality device that is capable of being used for analytical measurements in a High School/College classroom.

There have been several attempts to bring a low cost open source spectrometer to market. These have either failed due to funding shortcomings (there was a Kickstarter for a project in 2011 that failed to raise adequate funds to begin development), or due to hardware limitations (the mySpectral Spectruino is actually in production/available, however, due to bandwidth limitations of transferring the data over serial, it is unable to compete with native USB solutions). The mySpectral Spectruino has developed open source control software that we hope to be able to port to our new hardware platform.

Technology:
The spectrometer hardware consists of a opaque enclosure that houses a holographic diffraction grating (reflective) or transmission grating, and a linear B/W CCD or CMOS detector. These detectors are commonly used in barcode scanners, and consist of a single row of pixels, with no focusing lenses or coatings. There is then a interface circuit that reads the detector and sends the raw data to the computer for processing and display. That is it...the hardware itself is pretty straightforward. Of these components, the interface circuit is by far the most complex, and consists of a microprocessor, as well as high speed, high resolution A/D converters.

Name:
It got called a few things throughout the project description; the name is still being decided, although it will most likely have ‘Open Source’, and ‘Spectrometer’ in it.