A Programmable Current Source

The usual engineering minutia takes up much of my week… Paperwork, documentation, purchase orders, meetings, etc. There are the occasional chances to just have a little electronic fun. Thus I greeted a request from a couple of our support astronomers with some enthusiasm. They needed a variable intensity light source for calibration of the OSIRIS spectrograph. This source sits inside an integrating sphere on the AO bench along with four spectral sources, small tubes of neon, argon, xenon and krypton.

One Amp Current Controller
The remote current controller PCB and case prior to final assembly
There was already a white light source in the calibration sphere, but control was limited to simply on or off. The spectrograph uses various filters that each let through differing amounts of light from the calibration source. This created problems during calibration, some sort of variable intensity source was needed. It also needed to be quite precise, with a well regulated output that would not vary during the hours a calibration script could run.

I set aside a bit of time each day to design and build the source. The last couple hours of the afternoon are best, at this point I have had quite enough paperwork. A chance to practice my trade sketching out the circuit, or simply sitting at the bench and soldering… Perfect.

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