Backyard Signals and Crossing Lights

mattman · **Joined:** Thu Jan 14, 2021 9:10 am **Posts:** 2

Thanks for the info. First I will try the poliatity swithing. Never occured to me. Second I will look into power suggestion. I have relitive short run and used sprinkler multi pair wire. It takes 24v in its regular application. I have on hand also transfrmers for landscape lighting. Dont recall right off but I think 200w out put. You think that would work? 12v pretty sure. thanks again,m-

jayrod · **Posted:** Fri Jan 15, 2021 3:05 pm

200W at 12V DC equates to 16.6A. That would be the maximum current you could draw from the transformer.

I don’t know how well filtered landscape transformers are, I haven’t opened one up. If it’s simply rectified, full wave, you wind up with 120Hz pulsed DC. Half wave would be 60Hz. It won’t really affect incandescent bulbs except for shortening their life a little. On pure DC like a battery, they’ll last longer. I don’t know right off how it will affect LEDs. They’ll flash at the pulse speed. 120 Hz wouldn’t be noticeable but 60Hz would be detectable. Filtered supplies smooth out the pulses.

Rick Rowlands · **Posted:** Fri Jan 15, 2021 4:37 pm

Jayrod,

What do you mean by pulsed DC? Does the voltage spike 120 or 60 times per second?

Trainlawyer · **Posted:** Fri Jan 15, 2021 6:13 pm

Gentlemen, this brings to mind a discussion where I believe the acquisition of material for the backyard display may have gotten somewhat out of hand... http://www.rypn.org/forums/viewtopic.php?f=1&t=28168&p=130817&hilit=Deptford#p130817

GME

jayrod · **Posted:** Fri Jan 15, 2021 6:16 pm

Rick - that analogy will work. It’s like the voltage turns on and off X cycles per second is the simplest way to put it. A simple filter utilizes an electrolytic capacitor to smooth those the pulses out. It stores a charge to fill in the gaps so to speak. That’s about as simple as I can explain it without getting technical. That’s why incandescent bulbs running on pure DC can last a lot longer - no thermal stress from the on/off cycling. Given the right circumstances, they can run for decades on DC.

mldeets · **Joined:** Thu Aug 05, 2010 2:06 am **Posts:** 411

Rick,
Here is a picture that may help. The pulsating DC would be unfiltered:

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mld

jayrod · **Posted:** Fri Jan 15, 2021 7:50 pm

Perfect illustration. The tops and bottoms of the sine wave or AC could be considered +12V and -12V (not to be confused with ground) respectively. The line through the middle is 0V. You only want the +12. Hence the full or half wave rectifier. The filter smooths out the bumps by filling in the the missing parts so your line becomes flat at +12V DC.