Controlling a Spectrometer with a Raspberry Pi Motivation Spectrometer-to-Pi What We Did

Controlling a Spectrometer with a Raspberry Pi
and Stephen
1 – University of Miami, Coral Gables, FL 33146, United States Of America
2 – Princeton University, Princeton, NJ 08544, United States Of America
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)
Connection Diagram
It has two important pins
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)
The SPEX 1404 spectrometer
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.