Over the Thanksgiving holiday and had a bit of time to sort out my accessory power setup, particularly for DC accessories.
To date, I’ve been using “one-off” options for the few DC accessories I have on the layout – for LED street lamps or building lights, I’ve just been using diodes and resistors in-line with the LEDs to step down the power for the LEDs:
While that’s been fine for the few LEDs on the layout, I wanted a more robust option for my Atlas O Palace Theater and Menards lit vehicle. For the theater, I’ve just been using a “wall-wart” plugged into a surge protector I use to power the track and accessories. And for the Menards vehicle, it’s been sitting unilluminated on the table top.
I considered using a dedicated DC transformer for the task but that seemed silly when I already had a dedicated accessory transformer that was nowhere near it’s load limit. I went through a number of iterations of transformers before I landed on my permanent solution:
- Lionel Type 1053 Transformer – While I had this on hand and it did the trick, it was deficient for my needs in a few regards.
- It’s only 60 watts, which should be enough to power basic accessories on the layout (mostly just lights), but that leads to my next point
- It ran hot. It may just be by design, but I wasn’t comfortable with how warm this transformer ran. Even with just powering lights, it ran hot to the touch. From a safety perspective, this raised some concerns
- No integrated overload protection. Because this transformer was manufactured in the late fifties, it lacks any circuit overload protection. I did purchase some 5A push-button breakers on eBay to install in-line for the transformer, but they never arrived
- Lionel CW-80 Transformer – I thought I’d found the solution with this iteration. 80 watts, integrated fan and overload protection. It ticked all of the boxes except for one:
- Dirty Sine Waves. Oh man, I wish I had researched this option more. While technically it outputs AC at the correct voltage levels, it does so in the most complicated fashion. Unlike traditional coil transformers which use induction to step down voltages (and thus passes through organic sine waves), this transformer “takes advantage” of modern solid-state electronics and spits out just garbage saw-tooth sine waves. This YouTube video highlights what I’m talking about. Long story short, due to the synthetic sine waves, I was getting unbearable flicker in my rectified circuits (Here’s an OGR post outlining what I was seeing). As one of the replies notes, I was also seeing flicker in regular incandescent bulbs, indicating this transformer was spitting out sloppy power
- MRC Dual Power O27 – Another transformer I had on-hand, while it’s way overkill for my needs, a bird in the hand… It has more than enough power to cover my needs, integrated overload protection, AND the power output, while not “organic”, is clean enough to power my DC circuits without inducing way too much flicker. This was the ultimate solution I went with, using the 14VAC fixed terminals to power my accessories
Once I sorted out my accessory power, I was ready to create my dedicated DC circuit using a (hefty) full bridge rectifier and a Buck step-down regulator. This was relatively simple – it gives me a consistent 4.5VDC source for my DC accessories:
Unfortunately my eBay-special buck regulator’s LCD screen does not work, however it shouldn’t be an issue since the regulator itself works and it lives under the table anyways. I may eventually replace it with a working one, but for now it’s doing the trick.
And the final result: