Since I’ve finally started back to do some work on a sadly neglected project, the Compact solar spectrograph, I thought it time to put together a proper neon-based spectral (wavelength) calibrator for this instrument.
I researched a few designs for the power supply, including a older Forrest Mim’s engineer’s notebook 555-based design shown below:
As well I took a look at the internal calibrator incorporated in Shelyak’s Lhires III spectrograph design which is the one I decided on. This uses a UC3843 PWM controller which, coming from the power supply industry, I’d used in design’s back in the 90’s and became familiar with. This circuit incorporates both PWM regulation control and voltage multiplier circuitry to provide a DC output of 100V. It appears to work well with a variety of neon bulb types.
Here’s a look at the completed card assembly:
This will be a nice addition to the spectrograph redesign upcoming over the next few months. Here is a nice document describing the general attributes of neon bulbs and a few silly circuits as well…Neon Lamp Information. Below is a wavelength chart of the neon gas spectral signatures to give some idea of the calibration coverage one would expect. There’s also some finer lines in the deep blue and violet end of the spectrum:
And speaking of the spectrograph redesign underway, here’s what it look’s like at this stage of development:
Quite a ways to go yet….back soon