Controlling a Spectrometer with a Raspberry Pi Anastasia 1 Tyryshkina, Brendon 2 Rose, and Stephen 2 Lyon 1 – University of Miami, Coral Gables, FL 33146, United States Of America 2 – Princeton University, Princeton, NJ 08544, United States Of America Motivation What We Did Our lab has a spectrometer (SPEX 1404) that can be controlled only manually. The manual control is inefficient, inaccurate, and difficult to use. First, we had to learn the SPEX 1404 spectrometer The Raspberry Pi can be utilized as an inexpensive solution for a computer control of the spectrometer. The Raspberry Pi can produce only CMOS pulses (high: 3.3V, low: 0V) Spectrometer-to-Pi Connection Diagram It has two important pins 1. 2. Direction pin: sets the direction for spectrometer to scan Step pin: spectrometer steps 1/4000 of a nanometer in wavelength with each pulse the pin receives Requires TTL signals for each pin (high: 5V, low: 0V) Design a converter box to translate CMOS pulses from the Pi into TTL pulses for the spectrometer (fig 4) Design the control program with a friendly interface Figure 1: Size Figure 2: GPIO pin layout What is a Raspberry Pi? A fully functional micro-computer Inexpensive: 35$ + price of SD card Small: 85.60mm x 56mm x 21mm (fig 1) Pre-packaged with Linux and Python programming language Sends and Receives information through 26 GPIO (General Purpose Input/Output) pins (fig 2) GPIO pins can output 0V or 3.3V Ethernet port allows for remote control of the Pi Use Python language + RPIO library module Set the scan direction by setting the GPIO pin #12 to High or Low Scan the spectrometer wavelength by sending the step TTL pulses using the GPIO pin #18 Control the number and rate of pulses to make sure the spectrometer does not skip steps Create user friendly interface (fig 3) Control Raspberry Pi remotely (Remote Desktop Control, FTP and SSH) Conclusions The SPEX 1404 spectrometer was successfully interfaced with the Raspberry Pi. Wavelength of the spectrometer can now be accurately and conveniently controlled using a computer program. Future work might involve designing a Raspberry Pi interface for a digital voltmeter to read a signal from the detector diode. Together, these will create a fully functional system. Figure 3: Spectrometer Control Interface This material is based upon work supported by the National Science Foundation under Grant No. EEC-0540832.
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