I'm planning an installation of twelve 12VDC deck post cap lights, each drawing 1.6 watts. The manufacturer says the lights must be driven by a DC supply. They offer a system that uses a 50 watt supply with proprietary patch cords and splitters to connect the lights. I prefer to use less expensive standard 12/2 wire and a standard low voltage landscape transformer. What I'm finding is that most "standard low voltage transformers" output AC, not DC. Those that do output 12VDC have no built-in timers, dimmers or photocell functions. They're just power transformers that are on 24/7. What I want to do is install the power supply in the basement and turn on the lights at dust and turn them off 6 or 8 hours later. Dusk-to-dawn would be a reasonable alternative. My question is, what would a professional lighting installer use? I suppose one could use an external timer and photocell or convert 12VAC to 12VDC after the transformer but surely there's a proper power supply for 12V DC landscape lights.
I'm not sure why you're going with DC. I've put in many systems with 12 volt AC transformers with built in timers and or photo cells. The lights I've used are all LED or incandescent and they run on AC. I've got 15 fixtures in my backyard using LED bulbs hooked up to a 12 volt AC transformer. The bulbs will take AC or DC so I went with the AC. Check with some different manufacturers or do some checking at your home stores or lighting stores. They have plenty of fixtures, bulbs, etc that run on AC.
Get the ac model and wattage you want then put a simple full wave bridge rectifier on it. A full wave bridge is 4 diodes that’s it ac goes in on the 2 terminals with squiggly lines and DC comes out on the + and - working with low voltage (the output of the transformer is simple it’s only 12-17v depending on how large a transformer and how heavily loaded. Full wave bridges in the 35 amp range can be found on E-bay for around 10$ 20 amp around 4$ all the ones I looked at had well over 60 v PIV and most 300-1000 watts so they will do just fine (I think 35 amps is the code max but if you are LED’s the space station would be able to see you at 35 amps...
Most of the electronic dusk to dawn type controls will be fine turning the transformer on and off but there are low voltage ones also.