University of Wisconsin-Madison Physical Sciences Lab

Archive for July, 2015

From Many, One

Wednesday, July 22nd, 2015

UW-Madison’s Forest Products Lab contacted PSL with an interesting problem. The computer, which runs a Spex Fluorolog 2 Fluorescence Spectrometer, needed to be upgraded since it was 20 years old. Unfortunately, the card that talks to the spectrofluorometer inside the computer wasn’t compatible with modern PCs. PSL Electrical Engineer Dan Wahl created an instrument, called RetroSPEX, which translates signals to and from the spectrofluorometer into a standard USB port.

The left image is the side that connects to the spectrofluorometer, the right image is the USB connection.

In order to design the instrument, Dan needed to reverse engineer the connections, understand what needed to be controlled and how to control the components. Armed with that information, he was able to design:

“The RetroSPEX controller combines a Microprocessor + FPGA + ADC/DAC + High voltage power supplies into a compact form. The connectors on the back panel of the RetroSPEX match the cabling of the original instrument.”

The new and old computers, with the RetroSPEX instrument on the far right.

Once the instrument was designed, a text based application programming interface (API) was created to make the computer be able to issue command, through the RetroSPEX instrument. Since the API isn’t user friendly, James Luscher Engineering Services was hired by the Forest Products Lab to write a Python-based user interface.

A screenshot of the user interface.

This is a spectrum captured by the spectrofluorometer following the installation of the RetroSPEX unit.