I am planning to use LED lighting on the new section of my layout and if I am happy with the results, I may retro fit the old sections as well, replacing the fluorescent lighting. The problem is I am having a difficult time figuring out what components I will need. My google searches give me lots of people selling LED equipment but almost no how-to information. Even using this website’s search for “LED lighting” gave me zero hits.
Last week I saw a deal on LED strips so I took a flyer and I bought two 5 meter spools plus a dimmer and a driver thinking that was what I would need. It now looks like I probably should have bought an adapter either in addition to or instead of the driver. In my ignorance, I thought that is what the driver was for.
The dimmer looks pretty straight forward. It has a male connector on one end and a female on the other. The male end fits the female connector which is on one end of the strips. On the other end of the strips are red and black wires. I was hoping I could daisy chain a number of strips together, but with no male connector, the only way to connect two strips would be connecting the red and black wires and that would limit me to hooking just two together. It appears that the company that sold me this equipment has an adapter with a male connector so I am guessing I would hook that to the female connector on the dimmer and then hook the dimmer’s male connector to one of the strips.
Now I’m trying to figure out where the driver would fit in, if at all. It has a three prong plug on one end and on the other are brown and blue wires. I tried hooking these to the red and black wires on the light strips but nothing happened. There is no on off switch on this driver, so I am not seeing a purpose for this.
I know I probably should have asked more questions before starting to buy stuff, but that’s where I am at now, so I need to know what else I need to buy. Also, is there a connection that will let me daisy chain multiple strips to a single adapter or will I need a seperate adapter for each strip?
jecorbettAlso, is there a connection that will let me daisy chain multiple strips to a single adapter or will I need a seperate adapter for each strip?
This depends on how they terminate the far end of the light strip. Some do provide a plug for adding more LED strips. Many don't, but all this really involves is soldering red and black wires from the respective sides of the bus wires to the next LED strip.
There is usually a maximum limit of how many LED light strips can be added together in a single string, but it's a pretty large number you'll probably not exceed.
Mike Lehman
Urbana, IL
What do you mean by "driver"? If it is a 12VDC system then it just needs a 12VDC transformer with a high enough amp rating to power the system. This should feed into the dimmer and then output from the dimmer connected to the light strips.
There aren't any real standards for connections to LED "movie reel" strips and components, or for the colors of the wires. So unless you buy everything as a kit you can count on some splicing and soldering, and a meter comes in handy. I've found that soldering wires to the LED strip is no harder to do than to the wiring for running trains, but if the strip came with pigtails they should work too.
Just a few important things to making it work.
If you can't get it figured out it would help to provide links to exactly what you have.
Huntington Junction - Freelance based on the B&O and C&O in coal country before the merger... doing it my way. Now working on phase 3. - Walt
For photos and more: http://www.wkhobbies.com/model-railroad/
Most of the sites I've been checking into for LED strip lighting sell drivers based on the current requirement of the strips you plan to light. These drivers use a circuitry much like a computer power supply as opposed to the brute force of a huge transformer.
There are two kinds of drivers as well - those that can be dimmed, and those that can't. Obviously, the dimmable drivers cost more. Also the type of dimmer switch you use with these drivers isn't your standard incandescent wall switch dimmer. While it does mount the same as a standard wall dimmer, you have to use a magnetic dimmer to properly dim those LED drivers. No different than a standard transformer, you can't install (safely) a dimmer switch to the 110 volt input of a transformer.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
HObbyguy What do you mean by "driver"? If it is a 12VDC system then it just needs a 12VDC transformer with a high enough amp rating to power the system. This should feed into the dimmer and then output from the dimmer connected to the light strips. There aren't any real standards for connections to LED "movie reel" strips and components, or for the colors of the wires. So unless you buy everything as a kit you can count on some splicing and soldering, and a meter comes in handy. I've found that soldering wires to the LED strip is no harder to do than to the wiring for running trains, but if the strip came with pigtails they should work too. Just a few important things to making it work. Polarity must be correct (pos to pos and neg to neg). Directions that come with the transformer and dimmer should tell you which color is which, or it should be marked on them. And the strip should be marked to show which side is pos and which is neg. You can only connect so many in series due to the capacity of the strip to carry the current. Instructions with the strip should tell you how long is OK. This depends on the density of the LEDs on the strip. But, there is no limit to the number of strips that can be connected in parallel as long as the power supply is big enough. Make sure the power supply has enough amp capacity for all the strips. And make sure that the dimmer is rated high enough to carry the load. Finally if you are running lots of power then make sure the feed wire gauge that you use is enough for all the DC current. If you can't get it figured out it would help to provide links to exactly what you have.
I didn't know about the polarity issue. I switched the wires on the driver and the string lit right up. Unfortunately, the dimmer switch doesn't have bare wires on either end so the choice is to cut the connector on the input end and hook the bare wires to the driver or buy an adaptor with a male connector. I looked a little closer at this driver and it says it is waterproof which tells me it might be intended for outdoor low voltage lighting. If that's the case, I was planning to do that this summer so I may put this one aside until then and get an adaptor with a connector.
I did a search on "LED driver" and it looks to me like these are power supplies (transformers) marketed for use with LED lighting to make sure that each LED sees the proper voltage. But the movie reel strips that are readily available have built-in resistors to keep the LED voltage at the proper operating range for the rated input voltage to the strip. So as long as the correct voltage is supplied to the strip it should work fine. I think? Guess its not quite as simple as I thought.
The power supply for my above-layout lighting came from an LED supply company but it looks like a regular constant voltage laptop computer AC adapter. I am quite sure that is exactly what it is. And I am powering short LED strips for buildings on the layout right from the 12VDC wall-wart used for turnout controls and panel indicators. It all works fine.
A lot of the LED stuff is waterproof for outdoor applications and no downside there. Your choice whether you cut and splice, or try to work it out with adapters. Safety is not an issue since its low-voltage DC, so making connections is really no different than wiring the RR.
From one of the suppliers:
High power LEDs are non-linear devices. If a low voltage is applied to an LED it does not conduct. As the voltage increases, it passes a threshold value when suddenly the LED starts to emit light and the current sharply increases.
If the voltage continues to rise by even a small amount, the LED can overheat and burn out. The trick is to operate the LED in the narrow band between full off and full on.
Graph 1: Useful operating area for high power LEDs [Ta=25°C]
To run the LED in the safe operating area (shown in red in the graph) you need an LED driver, a special type of power supply that regulates the output current rather than the output voltage.
HObbyguyTo run the LED in the safe operating area (shown in red in the graph) you need an LED driver, a special type of power supply that regulates the output current rather than the output voltage.
A simple current regulator is needed.
This should work for any input voltage less than the max of the lm317 plus the LEDs. This should work for some limited number of LEDs in series. It should also work with parrallel strings of LEDs in series.
i believe you can add a dimmer control by putting a potentiometer in series with the fixed resistor in order to increase the total resistor and therefore decrease the current.
greg - Philadelphia & Reading / Reading
gregc HObbyguy To run the LED in the safe operating area (shown in red in the graph) you need an LED driver, a special type of power supply that regulates the output current rather than the output voltage. A simple current regulator is needed. This should work for any input voltage less than the max of the lm317 plus the LEDs. This should work for some limited number of LEDs in series. It should also work with parrallel strings of LEDs in series. i believe you can add a dimmer control by putting a potentiometer in series with the fixed resistor in order to increase the total resistor and therefore decrease the current.
HObbyguy To run the LED in the safe operating area (shown in red in the graph) you need an LED driver, a special type of power supply that regulates the output current rather than the output voltage.
The LM317 is only good for around 200ma load, which would only be 10 leds - and at that load it would need a heat sink. Your power supply should at least match the load you plan on driving. A ribbon that contains 100 LEDs will require at least a 2 amp driver.
Mark R.The LM317 is only good for around 200ma load, which would only be 10 leds - and at that load it would need a heat sink. Your power supply should at least match the load you plan on driving. A ribbon that contains 100 LEDs will require at least a 2 amp driver.
but the current remains the same for one LED or multiple LEDs in series
If a single LED draws 20 ma at 3V, 10 LEDs in series would require 30V but would still only draw 20 ma. More that 30V would be needed. 5V across the LM317, if a 35V supply was used, passing only 20 ma and dissipating 2W 100mW.
A ~120V would be enough for a single string of ~40 LEDs drawing only 20 ma. Again only some small voltage across the LM317 passing only 20 ma.
not sure about strings of LEDs in parallel.
gregc Mark R. The LM317 is only good for around 200ma load, which would only be 10 leds - and at that load it would need a heat sink. Your power supply should at least match the load you plan on driving. A ribbon that contains 100 LEDs will require at least a 2 amp driver. but the current remains the same for one LED or multiple LEDs in series If a single LED draws 20 ma at 3V, 10 LEDs in series would require 30V but would still only draw 20 ma. More that 30V would be needed. 5V across the LM317, if a 35V supply was used, passing only 20 ma and dissipating 2W 100mW. A ~120V would be enough for a single string of ~40 LEDs drawing only 20 ma. Again only some small voltage across the LM317 passing only 20 ma. not sure about strings of LEDs in parallel.
Mark R. The LM317 is only good for around 200ma load, which would only be 10 leds - and at that load it would need a heat sink. Your power supply should at least match the load you plan on driving. A ribbon that contains 100 LEDs will require at least a 2 amp driver.
But that's the difference. Those reels of LEDs are compromprised of groups of LEDs wired in series / parallel. There are groups of 3 LEDs wired in series with their own resistor and all those groups are wired in parallel with each other. That's how they are able to run the whole ribbon on 12 volts. It's all the parallel groups that add up the current draw.
Power supplies need to be matched with the number of LEDs to be used ....
https://www.flexfireleds.com/content/LED%20strip%20light%20power%20supply%20calculator.pdf
Power supplies are available in a number of amp ratings depending on how long your reel is ....
http://www.flexfireleds.com/non-dimmable-led-light-power-supplies/
For what it's worth, the industrial grade LED ribbons from the above company are the brightest you will find. Not cheap, but well worth it.
Mark R.But that's the difference. Those reels of LEDs are compromprised of groups of LEDs wired in series / parallel. There are groups of 3 LEDs wired in series with their own resistor and all those groups are wired in parallel with each other. That's how they are able to run the whole ribbon on 12 volts. It's all the parallel groups that add up the current draw.
i didn't realize this is how the strings were put together. This would explain how if one LED blew out, the whole string wouldn't stop working, just the 3 LEDs in that group. Is this the only way LEDs strings are put together?
Since each group of 3 LEDs in series still only draws 20 ma, 30 LEDs would require 200ma, and 300 LEDs 2A.
With 3 LEDs and a current limiting resistor in series, I see no need for a regulator at all. Why would you need a driver?
Driver / power supply .... same thing ....
Here you can see how the ribbons are configured in the 12volt system. You can cut the ribbon at any of the indicated marks and not affect their operation ....
I can see where the sophistication of the driver is preferable over an oridnary power supply when running LEDs at or close to the full design light output.'
But I never run them like that on the layout itself. All the LEDs in my rolling stock and structures have been throttled down with resistance to one degree or another. I use both ordinary discreet LEDs, SMD LEDs, and section of 12V LED strip lighting. Runnig them on dim extends their life and looks better, too. I doubt a driver would make much difference for such applications and certainly wouldn't be necessary for good operation.
The other advantage of the series/parallel arrangment theyt use on those strips is that it keeps the resistors manageable. With 3 in series they need over 10 volts, so for a 12V power supply, they don;thave to drop much - and at the high current levels those LEDs operate at, if they had to drop 12V down to 3.5V or so, you'd need a pretty hefty resistor to handle the power, a little 1/4 watt or 1/2 watt wouldn't cut it.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Based on discussion I think my original thinking is right. For our purposes using the LED movie reel strips, the "driver" just needs to be a constant VDC power supply. And as long as it is rated with enough capacity to feed all the LEDs in the circuit then all is well with the world. The term "driver" is probably creeping into the consumer LED market from large-scale commercial systems where special power supplies are used.
I think the term driver and power supply do refer to different types - although the end result is the same. A power supply relies on the brute force of a large transformer to provide sufficient current. A driver uses technology like that of a computer / laptop power supply in that it uses a switching power supply to gain the currents, requiring a much smaller transformer.