Beckman DU530 Spectrophotometer CFL Spectra

I’ve continued to do some work with the DU530 (see previously blog posts).

I decided to see if I could drive the grating motor and register the spectra from a CFL light through the grating.

As shown above I used an EasyDriver and Arduino to drive the stepper. This showed some slipping (using a 200ms square wave generated from the Arduino to drive the step input). The CFL bulb was just jammed into the lamp box. You can fairly easily see the spectra coming out the grating:

I then registered the output of the far side photodiode using a 10M gain transimpedance amplifier. I continuously ran the stepper and monitored the output on a scope:

Spectra recorded on my scope

This matches the spectra published online extremely well, though the resolution is limited in the scope recording:

Obvious next step would be to record the output with an ADC/microcontroller, this would let me do slower scans. I’m also concerned that the motor is occasionally slipping, which suggests I might want to review the stepper driver…