Powering handmade street lamps!

An old computer power supply would give you 12 volts DC with all the power you need, plus a lot more, for about $10. No rectifier needed. You could use the DC on buildings and older AC solonoids to quiet them down, i.e. crossing gates.

Many choices for 12 volts on eBay. Here's one: New Jersey USA free shipping.

I use one of those battery packs for starting a car. Mine has a cigarette lighter plug in I use that for the output. That is pure DC and FREE

Consolidated Leo posted:

Many choices for 12 volts on eBay. Here's one: New Jersey USA free shipping.

Wow- now that's cheap. If I buy the AC to DC pack, then I have no need for the rectifier in the first place ☺ 

What amperage do you think is appropriate for <50 LED's?  I don't suspect I'll be running more than 40 on one bus.

Your turntable manual link doesn't work (for me anyway).  I think you meant:

http://www.atlaso.com/partspdf...Turntable_Manual.pdf

I don't think the issue is how to get 12V DC whether from your existing transformer or from a $2 DC-output wall-wart.  Many options for minimal cost.

Instead it's how to deal with the "resistor" that comes with the pre-wired/pre-soldered 12V LEDs.  As the youtube video says, for the wall mounted LEDs the resistor "blob" makes for a mounting challenge.   I don't see how you could thread that through a streetlamp post.

For realistic-sized street lamps you will probably need to use tiny SMD/SMT surface-mount LEDs which are genuinely tiny and difficult to work with and solder to.  You can buy LEDs for a penny or two and the resistor (for 12V DC operation) for another penny or two.  Curiously enough it's probably the thin-gauge wire that would be your biggest cost - maybe 5-10 cents per foot for 30 gauge solid Kynar wire frequently used for hooking up to surface-mount LEDs.  Anyway, I think you greatly expand your options if you use pre-wired surface-mount LEDs (maybe 50 cents each)...and then solder the resistor yourself after the LED has been installed into whatever streetlamp or wallmount fixture.  Or, if soldering is not in your comfort zone, you can find 12V pre-wired surface-mount LEDs (with resistor):

As shown in the youtube video, no problem using 5mm pre-wired 12V LEDs  for roof-tops, water-towers, bridges, etc. as you generally have plenty of mounting space to install the built-in resistor.

Figure on 20 mA or 0.02 A per LED ... so 50 LEDs would be 1 Amp.  But note that a 2 Amp supply might be only another buck or two so why not splurge!  Anyway, note that there are neat screw-terminal adapters to convert the coaxial-barrel output connector to wires.  Some eBay sellers like the one Leo shows even include one of these - or you can buy one separately for 50 cents or so.

You can always count on Stan to point out alternatives. Placement is indeed an issue for your lighting project. I don't know what the pre-wired SMT leds would be like to work with but the ones from the video are somewhat large. We can help you figure out what resistor values you need; that's not a big problem. You may want to give that some thought.

I would choose the wall wart that gives you room to expand. Stan did the math. I would go for the 2 watt version for less than $5. Stan claims that these units can be had for about $2 from China but I can't seem to find them. Under $5 from a US seller is pretty good I'd say; and no long wait time.

Consolidated Leo posted:

.. I would go for the 2 watt version for less than $5. Stan claims that these units can be had for about $2 from China but I can't seem to find them. Under $5 from a US seller is pretty good I'd say; and no long wait time.

I think Leo meant 2 Amp version...which would be 24 Watts.  Watts = Volts x Amps = 12V x 2 Amps.

Here's one for less than $2 (free shipping) from Asia.  I recommended the screw-terminal adapter which bumps up your out-of-pocket.  As Leo shows, you can pay a bit more and get it faster coming from a US located seller.  If going through Amazon though, look carefully as it may be coming from Asia even though it appears you're buying it from a US seller.  Note that I don't provide direct eBay links since they are subject to deletion by OGR per terms-of-use.

Again, I think the real challenge is settling on a type/style of LED that can be installed in street-lamps if a resistor is pre-built into the LED wiring for 12V DC operation.  As mentioned above, the LEDs themselves are cheap, the resistors are cheap.  It comes down to what your light fixtures look like, if you're comfortable soldering tiny parts, your eyesight, patience, etc. etc.

Here's 0603 size surface-mount LED for 2 cents a piece.  0603 means 0.06" x 0.03".  These would fit in most any O-gauge lampshade or lamp fixture.  It's very tiny and can be a challenge to solder wires to.  Of course many other sizes of LEDs both smaller and larger.  You can buy pre-wired surface-mount LEDs with or without the resistors.  On eBay or wherever just search on "pre-wired" or "pre-soldered" in addition to "12V" or whatever type of LED you're interested in.

Stan has you covered on this stuff! If you buy some of the end conectors you might as well buy extra cause you can uses them down the road!

stan2004 posted:

Figure on 20 mA or 0.02 A per LED ... so 50 LEDs would be 1 Amp.  But note that a 2 Amp supply might be only another buck or two so why not splurge!  Anyway, note that there are neat screw-terminal adapters to convert the coaxial-barrel output connector to wires.  Some eBay sellers like the one Leo shows even include one of these - or you can buy one separately for 50 cents or so.

 

Thanks, Stan, that's helpful!! I'm flexible working with soldering, but I think something that small would be out of the question for me! I liked working with the Woodland Scenics surface mount LED's (about 1/4" in size). I've been searching the depths of Ebay, and haven't found anything prewired in that size!! I will be throwing some of those round, bulb-type 5mm LED's in there for some bridges and other buildings. I think I will go with the 12v, 2a version so that there's no shortage of juice.

Thanks, everyone, for your suggestions this far! I hope to get started on this project sometime in the next couple of weeks as to provide the finishing touches on the layout before I get visitors for Christmas!

Aaron Buczek posted:

...

I liked working with the Woodland Scenics surface mount LED's (about 1/4" in size). I've been searching the depths of Ebay, and haven't found anything prewired in that size!!

Do you mean the WS stick-on style?  Those plug into their proprietary Just Plug controllers so don't have the magic resistor for 12V DC operation.  And at ~$5 a pop they can be somewhat spendy!

If you don't mind firing up the soldering iron, here's another thought.  Since you're using 12V DC, take a look at those 12V LED strips the guys are using in passenger car lighting.  You can un-solder and remove individual surface-mount LEDs.  In general the cost-per-LED will be a penny or two which might be even cheaper than if you buy the LEDs separately.  Yes, this could save you a few pennies here and there but wait...there's more.

One nice thing about the WS stick-on lights is the stick-on convenience.  But you can solder your own wires to an LED on a strip...and then cut the strip.  Voila!  Now you have a stick-on surface mount LED for a couple pennies!  Note the LED strips are adhesive backed.  This photo is from a different thread but illustrates the idea.

Here's another idea for 12V LED strips.  They bundle groups of 3 LEDs into a section.  Each section only required 1 resistor (that black component on the right).  So to the extent you can group LEDs in threes, this can save some wiring and such in a DIY situation - you only need 1 resistor instead of 3.  Or you can start with a LED strip section and, as-needed, remove an LED and run two extension wires from the pads on the strip to an LED.  

Not that power is an issue if you're only talking 50 LEDs or so...but operating ~3V LEDs one-at-a-time (one resistor per LED) from ~12V essentially means only 25% of your power is going to the LED and 75% is wasted as heat in the resistor.  By operating 3 LEDs stacked in-series (as is done with LED strips) you essentially cut the current requirement by a factor of 3.  The common argument about operating lights "in-series" is if one goes out, all 3 go out.  I think this is a hold-over from the days of incandescent bulbs and now just a footnote with the reliability and life-times of modern LEDs.