Sorry SS. Didn't see your earlier post about the DC/DC converter. I'd seen that component on browsing, and thought it seemed ideal, but I'm not sure how to select one. Thanks for the links though.
That's the DC/DC converter I'd need?
In case it wasn't apparent, the DC/DC converter is exactly the kind of spice I wanted to add to this recipe. Taking the rectifier + capacitor formula and add an inexpensive tweak to improve the result.
I make no guarantees the whole thing won't go up in a flash and cloud of magic smoke.
Never took the PE exam, so you can't blame me!
Computer engineers weren't required to.
As far as picking the DC/DC converter, when I was looking, here are the parameters I was thinking about:
Load current of 1A (12W) based on the light. This means you want a converted rated at least 1A, I went for 2A as it will keep the temperature down and things will last longer. You might give up a little bit in efficiency, depending on the converter design, but it's going to be like 5 points of efficiency or something like that. Since you're dealing with cheap electronics, the extra de-rating is more important.
Input voltage somewhere between 12VAC and 24VAC, rectified and smoothed. Since the DC voltage peaks are going to be close to the peak voltage of the AC input, 24VAC RMS means a peak DC in the 33V range. 12VAC RMS would be around 16-17VDC. So a regulator that could accept at least 35V at the input.
Beyond that, I was looking at Amazon an there are a number a regulators that are cheaper per unit, but I figured you didn't need six, or ten. Having two gives you one to blow up in experimenting.
Also, if you look at various types, some have little single turn trimmer pots on them. The wouldn't do so well in a high vibration environment and you would definitely need to fix them in position with glue or nail polish. The one I linked has a multi turn trimmer which will make it easier to dial in 12V and be a little less susceptible to vibration related movement, though you might still want to fix the trim screw once you have it set.
For what you are doing, the parameters aren't too tight and there are lots of options. The one I linked is probably what I would order unless I had use for several more, in which case I might look at some of the higher count multi-packs.