12 volt led power supply

hi,gerald,may be you can connect the 1.5amp LED power on the left of LED strips,and another 2.5amp LED power supply right of the LED strips.....

whatever,you can have a try,tell me the result...

Gerald, yes, you can, provided that you isolate the supplies from each other by putting a diode in series with each supplies positive output before you connect the supply to the barrier strips. Personally, I'd just get another set of strips, use one for one supply, one for the other. safer that way.

I recommend against trying to parallel DC supplies.  Many of them could have common rails on the input and might interact as well.

Mason,I haven't received the lights yet  they have been shipped from China but i will not get them until August ,so i can't try anything right now,and as far as diodes are concerned i don't even know what they are,so thats out of the question. I think what gunrunner john & Fec  fan said sounds like it is the way to go,but i would still like to know if anyone has ever done this. Also can anyone tell me how long of a led strip can i connect to the 1.5 amp power supply,it doesn't say how many watts it puts out.    Thanks again.

Gerald, the 1.5A supply would put out a maximum of 18 watts at 12 volts(12 x 1.5= 18). Each individual led light will only draw about 0.06 watts.  the dropping resistor will use 0.2 watts, so the total for each LED would be less than 0.3 Watts.

 

hope this helps---

Fec fan, thanks for responding so fast, i am not sure if i understand the math,so if there are 300 led's in 1 reel,then i would multiply 300 x 0.3=90watts is that correct?

Actually, your math is suspect there.

 

In truth, there are 100 "groups" of three LED's each and each one requires 20ma at 12 volts for the full brightness.

 

100 * .02A * 12V = 24 watts, not two watts.

 

Just get a GEPS12-60. 60 watt 12vdc electronic power supply from GE. The industry standard for LED lighting driver. Built in thermal and over current protection. Get it from a sign supply or electrical supply. Around $80.00 with 5 year warranty. Available with separate or inboard dimming module. Uses standard florescent dimmer control that controls 0-10 v signal from the module. Also a 20 watt version.

There's no real reason to spend that kind of money to power the LED's.

OK, i understand that my 2.5 amp power supply will be more than enough for the 300 led reel i am getting,but i still don't know how many amps my 1.5 volt power supply will put out. Is there a simple formula i can use & i do mean simple, such as x-amount of led's( the reel kind ) for each watt or amp of power? Sorry for all the questions but i know very little about this type of electrical work.

john- you're right 24 watts is correct. OOPS!

 

Gerald-- You mean 1.5 amp don't you?(not 1.5 volt). Each segment of 3 leds needs between 10 to 20 milliamps (1 milliamp is 1/1000 of 1 amp). 100 segments at 10ma = 1 amp. 100 segments at 20ma = 2 amps. I just did a quick check of my 2 reels-- one runs at 16ma per segment, the other at 18ma per segment. this with a 12VDC supply. They are actually VERY bright!

hope i got this right this time.

Fec  fan,Sorry, i meant 1.5 amp ,so if i understand your answer 1 reel of 300 led's uses about 2 amps ,or as Gunrunnerjohn said 24 watts did i get it yet?

yes, Gerald. i'm sure the 2.5 amp will run  the 300 led reel. I think that the 1.5 amp may be just enough to run the full reel, but it will most likely get very warm as it would be operating at or over it's limit.

I think I'd limit the 1.5A supply to maybe 200 or so LED's.  No reason to try to run it over it's capacity.

 

Thanks to all for your responses i have a better understanding of what is going on now,i hope some day i can help somebody out the way you all helped me ,these forums are full of knowledgeable people .      Thanks Again

Hi John, There actually is a good reason to buy a quality driver. In the sign business for thirty years. Replaced just about every 1st, 2nd and third generation LED systems that we ever installed. I also have seen Chinese knockoff LEDs strips lose half their brightness ( measured lumens) in less than 6 months. After countless hours of warranty replacement, I go by the axiom that you usually get what you pay for. Sometimes not true, but rarely do you get more. IMHO, the GE TetraMax and MiniMax are the brightest , most efficient, the highest quality and have better color (temp) consistency than everything else out there. One 60watt should handle the biggest layout, and on a smaller one should last forever. Chinese knockoffs are like Plastic MPC locos. GE'a are like the Legacy version. Just MO based on actual experience. Tried the rest, only use the best. And I always add extras. Better to dim them down then try to retrofit more later. Especially when you embeds them in cast resin.

A couple of years ago we put 60,000 LEDs in a 30 foot tall foot tall soda bottle for an unnamed client at their corporate headquarters. Fully programmable RGB system. Approximately an 8 million-dollar project. Very similar to a highly detailed layout In the sense that I would hate to have to tear it apart to replace inferior LEDs in a couple of years.

While I won't dispute that quality is a desirable attribute, it's not always necessary to spend big bucks on something as simple as a LED power supply.  After all, this is not an $,000,000 project, right?

 

While this is my first experience with led's & i know very little about them,i will go the least expensive route this first time, i can always trade up in the future. However,i think it always a good idea to have other options available thanks to the excellent help here on the forum ,help is just a click away & as gunner john said this is not an expensive project or a big project at all so if i am not happy with the way things turned out ,i haven't lost much.  Bottom line, KEEP THE GREAT ADVICE COMMING!!!!

Depends how we calculate the value of our leisure time

I am curious if the inexpensive LEDs have gotten better when it comes to replicating warm white incandescents most of them have tended to be an unnatural blue white.

I have bought a bunch of $7 rolls of warm-white LED's, and they've been exactly what I expected for my passenger cars.  I'm not at all unhappy with them, and I'd sure not spend a lot more for what I see as the same functionality.

 

Hi John Now I am a bit confused. Why would you want to use a Constant voltage DC driver for a passenger car? I would think that you would just use a rectifier with a DC voltage regulator. But for a layout I would definitely go with a well protected electronic driver. I have seen numerous instances where these LED strips have actually's ignited and caused major fires. Having read most of your posts over the last year and a half I do realize that I would not be concerned for you because you do seem to have a great amount at working knowledge of circuit protection devices. But put some of those strips in a foam-based layout that doesn't have the proper fire retardant coating applied and you have a recipe for a major problem. Initially everyone in the sign industry thought LEDs are really safe because they were low-voltage versus 30,000 V milliamp neon. Turned out not to be always the case. We have had an instance where the fire inspectors and the insurance were all looking at the wiring as the suspect. Hours of lab investigation later it was revealed that all it took was one faulty resistor on the strip to ignite what turned out to be an extremely flammable plastic. Luckily it was a glass facade building because it contained the fire but the glass was a drippy burned plastic mess combined with melted aluminum. After a similar event where a landmark neon sign that had recently been retrofitted with thousands of feet of this stuff also caught on fire was this product recalled. And it was UL listed for damp and wet locations. Imagine if it was installed in a packed nightclub. Just MO. A fire can ruin an expensive engine as easily as a voltage spike and also a lot more.

I actually use a constant current source for lighting passenger cars, it keeps the intensity constant over varying input voltages.  A voltage regulator would probably work as well.  With most passenger cars, I use 20ma constant current.  It would be very difficult to start a fire with that amount of current.

 

The stuff you're talking about is using thousands of LED's, and a lot more current than anyone here would be using.  I've been using LED's for longer than I can remember in a variety of applications, and I've yet to ever see one start a fire or even get hot.  I've seen a couple pop from excessive voltage, but there was no fire, only little plastic pieces.

 

 

Hi John, I understand what you are talking about. And yes LEDs never get hot themselves. It was a case of a single resister on a multiple Led flexible strip that ignited the strip that was flammable. The drivers themselves are rarely larger than 60 watts. Used in multiple feeder circuits. A 30 ft long logo can have as many as twenty five drivers all with their max rated runs. No individual circuit is more than 5amps on the secondary and less than an amp on the primary. And we usually divide those secondaries also. But the electronic drivers will shut down if overloaded and the LEDs will not light. And in your case, not really a problem. I was envisioning someone less knowledgeable hooking up a long string of those LEDs with a 12volt Dc power supply, undersized wiring or worse, oversize unfused wiring on flammable foam scenery. I have also seen test setups using the simple 12v Dc wall warts where if you plug in the power supply first and then connect the secondary jack to the strip the whole strip fries instantly. Never seen it happen with the GE drivers. And I can understand as an engineer, why sometimes the extra cost is not justified for a particular application. But a I previously expressed, if I were to convert all of my scenic lighting to LEDs, I would invest in one quality dimmable driver. And if I get around to converting my rolling stock, I will probably just use screw in LEDs. Because they keep getting less expensive but mainly because I am lazy. Not really but too many other projects going. The old Cost, Quality, Time triangle. It has never been the qty of LEDs or the actual LEDs that have caused the problems. And rarely the wiring. It has been primarily the PC strips themselves. I really enjoy reading your posts and also all the feedback and advice you have given me. Not only regarding trains but engineering and electronics in general. Many times you have helped me re adjust my approach when it comes to problem solving. Thx FMH

FYI The chances of those actually being RoHS compliant and also UL Listed is very Low. And if Listed, I would be really interested in reading the complete listing for the approved application. Those strips were removed from most sign applications because the Waterproof claims never meet any of the tests. Again not a major problem, but in damp areas, I would be aware of galvanic corrosion. I have replaced too many that looked like leaky batteries after just a couple of seasons outside.

I was thinking about using a PC ATX power supply for my non train, DC power needs on my layout.  I was looking at a 380 watt supply, fairly quiet fan, with +3.3V@20A, +5V@20A, +12V1@17A, +12V2@17A rails.  I believe these are already regulated, but adding in more regulators at whatever I'm trying to power (loss of about 1.2 Volts) wouldn't be that bad.

 

Cost of the supply would be about $55, but would probably power all the LED strip lights for lighting the layout (mix of cold and warm strips), and any scenic needs.

 

Any thoughs on why this might be a bad idea?

If you use the PC supply, I'd fuse each circuit from the supply independently.  However, they are cheap power and lots of it.

 

The strips I have claim to be RoHS and CE listed, but they're not waterproof.  Very few applications around the layout require waterproof stuff, nothing else is waterproof.  Again, for the types of uses you're talking about, these may not be suitable, but that's not what is being considered here.  You're talking industrial uses where you have a large quantity of them in a far more demanding environment.

 

I spent years building avionics, and we had very demanding specifications for most of the equipment, however, I don't build my layout to that kind of standard, and I don't believe it's necessary.   I think we're comparing apples and bananas, totally different situations.  I seriously doubt anything we do on our layout would be suitable for aircraft use.

 

I usually pick up used PC power supplies. They work very well and only minor modifications are needed and you get the 12 & 5VDC outputs. Just google , modify pc power supplies and you'll find all the information you need on how to convert them.