I bought some LED lights online for use in buildings and I'm not sure what I need in order to wire them up to a 12v power pack without them burning out. I've linked a picture of the LEDs. Can anyone tell me what I need and how to wire it up so these work? Wiring has never been my strong suit. I'm tempted to go with one of the plug-and-play lighting systems but they're so expensive.
http://imgur.com/a/jN2g6
Thanks
You need to get a pack of 1K ohm 1/4 watt resistors. Connect one lead of the LED to one lead of a resistor (doesn't matter which one, but it pays to be consistent). For each circuit, wire these LED/resistor sets in parallel and feed them around 12V DC. Polarity matters, but the LED won;t blow up if hooked up backwards, it just won't light. If you preassemble the LED/rsistor pairs at the bench and always solder the resistor to the negative side of the LED, it will be easy to keep straight once installing them.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Dave,
You can do two things here. You can run them on 12 volt and add a 1,000 ohm (sometimes written as 1k ohm) to each LED to protect it against the high voltage compared to the standard operating voltage (noted as 3.0 to 3.4 volts).
Or you can step down the 12 volt power supply and use a much lower rated resistor (20 to 100 ohms) to protect the LED at the more copacetic voltage. One way to do this step-down is to buy a "buck transformer." This is an example I started using:
http://www.ebay.com/itm/282049730712?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The specs:
Mike Lehman
Urbana, IL
Hi Dave:
Wiring the LEDs for 12 volts is pretty simple. The only other parts you require are some resistors (one per LED is the norm) and some wire.
First think to understand is that LEDs are polarity sensitive. In other words, you have to keep the + and - leads wired the right way. Nothing bad will happen if you reverse the polarity but the LED won't light. On your LEDs the + lead is the longer lead.
Second, you want to wire multiple LEDs in parallel, not in series. In other words, the + leg of each LED will be wired to the + wire of the power supply and the - leg of each LED will go to the - wire of the power supply. Note that you must install a resistor between one leg of the LED and one of the power supply wires. It doesn't matter whether the resistor is wired to the + leg or the - leg. Many people make a habit of always wiring the resistor to the same leg. That makes it easy to tell which wire is + and which is - after the LED legs have been trimmed.
For most purposes a 1000 ohm 1/4 watt resistor works well. You can get away with 1/8 watt resistors but they will be hotter when in use. You can go as low as 470 ohms but there is no advantage. The LED will be as bright with a 1000 ohm resistor as it will be with the 470 ohm one, and the disadvantage is that your LED(s) will be drawing twice as much power. If your LEDs are too bright with the 1000 ohm resistors then you can dim them down with higher value resistors. I have gone as high as 30,000 ohms in order to get the LED to just glow like a kerosene lamp.
One other suggestion I would make is to black out your structures' walls and roof. In other words, paint the interiors with black paint first so light cannot bleed through the walls. Nothing says 'toy' more than a glowing building. Make sure you paint any plastic door and window frames too.
Hope that helps.
Don't be afraid to ask more questions.
Regards,
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Thanks to everyone for the quick responses. I've also done some more research online since posting. If I'm understanding correctly, I can think of wiring my LEDs like wiring my DCC track. I can run bus wires around under the layout and run feeder wires to each LED as needed. Each feeder wire will need a 1k ohm resistor. Then each LED is getting the same voltage and the resistor will keep the LED from burning up.
Dave, a couple of more suggestions for buildings:
a) as noted above, you do not want the light to shine through the building walls. I usually spray the insides with a gray primer before assembly, then paint the inside wall with acryllic wall paint for the interior color I desire
b) Be sure your power supply is protected against overload. For instance, on my small layout I have three simple 12v, 1A DC regulated walwort type supplies. If overloaded they would fry internally and I would have to replace. So I install a fuse holder and a 3/4 amp quick blow fuse in the output bus. I keep a log of each circuit so I know how many milliamps draw total I am adding so I stay within my fuse rating.
c) If you have larger building and want more light than several LEDs may provide, you may want to try the warm white strip LEDs that operate in segments of three or multiples of these (together or separated by a bit of wire). The resistors are on the 3-segment strips. You just cut the 3-LED segments from the long strip with a scissors. You can find these readily on Ebay.
Paul
Modeling HO with a transition era UP bent
88gta350If I'm understanding correctly, I can think of wiring my LEDs like wiring my DCC track. I can run bus wires around under the layout and run feeder wires to each LED as needed. Each feeder wire will need a 1k ohm resistor. Then each LED is getting the same voltage and the resistor will keep the LED from burning up.
You have it right about the wiring pattern. However, as Paul mentioned, there is a limit to how many LEDs you can put on your power supply. The specific number depends on the output of the power supply. As a general rule you should only go to about 75% of the rated power output. Running a single bus for structure lighting will work up to a point, but once you start to exceed that 75% rule you will need a second bus, and maybe a third etc. etc..
How much power each LED draws depends mostly on the size of the resistor. Your particular LEDs may specify a draw somewhere around 20 - 30 ma (Milli Amps, or 1/1000th of an amp). However, that draw is reduced as the resistance is increased so, for example, if you are using a 1000 ohm resistor the draw will only be about 10 ma.
In other words (geez I keep using that phrase. You must be sick of it by now), if you have a 1 amp power supply @ 12 volts, and you want a maximum of 3/4s of that rated load, you can safely draw 750 ma, or about 75 LEDs with 1000 ohm resistors. Keep the size of the resistors in mind always. If you were using 470 ohm resistors you would be limited to about 30 LEDs on the same power supply. If you were using 3000 ohm resistors you could get about 150 LEDs on the circuit. Ed's suggestion of a fuse in line with the LED bus is a good safety feature in case you accidentally connect too many LEDs to the power supply.
If you are going to use a lot of LEDs, i.e. several hundred, you might consider buying a larger power supply with multiple channels. These are typically used for closed circuit TV cameras. You can get them with built in resettable fuses, one for each channel. This one is probably larger than most modellers would need, but having a few extra 12 volt circuits available could be handy for animation etc.. Ignore the Canadian pricing. They will be much cheaper in the US:
https://www.amazon.ca/Q1C1-Security-Power-Distribution-10Amp/dp/B007A738LY/ref=sr_1_16?ie=UTF8&qid=1485751642&sr=8-16&keywords=12+volt+10+channel+power+supply
peahrens Dave, a couple of more suggestions for buildings: a) as noted above, you do not want the light to shine through the building walls. I usually spray the insides with a gray primer before assembly, then paint the inside wall with acryllic wall paint for the interior color I desire b) Be sure your power supply is protected against overload. For instance, on my small layout I have three simple 12v, 1A DC regulated walwort type supplies. If overloaded they would fry internally and I would have to replace. So I install a fuse holder and a 3/4 amp quick blow fuse in the output bus. I keep a log of each circuit so I know how many milliamps draw total I am adding so I stay within my fuse rating. c) If you have larger building and want more light than several LEDs may provide, you may want to try the warm white strip LEDs that operate in segments of three or multiples of these (together or separated by a bit of wire). The resistors are on the 3-segment strips. You just cut the 3-LED segments from the long strip with a scissors. You can find these readily on Ebay.
Thanks for the tips. I had already founf out about those light strips after posting my original comment and then watching some YouTube videos about using them. I've ordered some off Ebay but will also be using up my single LEDs. I'd like to finally learn some basic wiring so using my own LEDs will help witht hat, too.
hon30critter 88gta350 If I'm understanding correctly, I can think of wiring my LEDs like wiring my DCC track. I can run bus wires around under the layout and run feeder wires to each LED as needed. Each feeder wire will need a 1k ohm resistor. Then each LED is getting the same voltage and the resistor will keep the LED from burning up. You have it right about the wiring pattern. However, as Paul mentioned, there is a limit to how many LEDs you can put on your power supply. The specific number depends on the output of the power supply. As a general rule you should only go to about 75% of the rated power output. Running a single bus for structure lighting will work up to a point, but once you start to exceed that 75% rule you will need a second bus, and maybe a third etc. etc.. How much power each LED draws depends mostly on the size of the resistor. Your particular LEDs may specify a draw somewhere around 20 - 30 ma (Milli Amps, or 1/1000th of an amp). However, that draw is reduced as the resistance is increased so, for example, if you are using a 1000 ohm resistor the draw will only be about 10 ma. In other words (geez I keep using that phrase. You must be sick of it by now), if you have a 1 amp power supply @ 12 volts, and you want a maximum of 3/4s of that rated load, you can safely draw 750 ma, or about 75 LEDs with 1000 ohm resistors. Keep the size of the resistors in mind always. If you were using 470 ohm resistors you would be limited to about 30 LEDs on the same power supply. If you were using 3000 ohm resistors you could get about 150 LEDs on the circuit. Ed's suggestion of a fuse in line with the LED bus is a good safety feature in case you accidentally connect too many LEDs to the power supply. If you are going to use a lot of LEDs, i.e. several hundred, you might consider buying a larger power supply with multiple channels. These are typically used for closed circuit TV cameras. You can get them with built in resettable fuses, one for each channel. This one is probably larger than most modellers would need, but having a few extra 12 volt circuits available could be handy for animation etc.. Ignore the Canadian pricing. They will be much cheaper in the US: https://www.amazon.ca/Q1C1-Security-Power-Distribution-10Amp/dp/B007A738LY/ref=sr_1_16?ie=UTF8&qid=1485751642&sr=8-16&keywords=12+volt+10+channel+power+supply Dave
88gta350 If I'm understanding correctly, I can think of wiring my LEDs like wiring my DCC track. I can run bus wires around under the layout and run feeder wires to each LED as needed. Each feeder wire will need a 1k ohm resistor. Then each LED is getting the same voltage and the resistor will keep the LED from burning up.
Thanks for the info. At the moment I just have a small layout as I try to relearn the skills after a long time out of the hobby. But I'll be sure to keep track of the number of LEDs.
Dave M,
Just remember that 1000ma equals 1amp and it is usually best not to go over 75% of the rated power supply You are using and You won't have any problem's.
Take Care!
Frank
88gta350At the moment I just have a small layout as I try to relearn the skills after a long time out of the hobby. But I'll be sure to keep track of the number of LEDs.
Starting out small is good! (or in your case, re-starting). It limits the number of mistakes you have to correct!
Sorry about my long winded answer. I seem to always do that when fewer words would suffice. As you can see, brevity is not one of my strong points.
Good luck! Keep us informed!
rrinker Connect one lead of the LED to one lead of a resistor (doesn't matter which one, but it pays to be consistent).
Connect one lead of the LED to one lead of a resistor (doesn't matter which one, but it pays to be consistent).
Rich
Alton Junction
Hi Rich:
What happens in most installations is that the LED leads end up being trimmed off. That eliminates the ability to identify the long leg as being the positive lead. If you always attach the resistor to the negative lead (or the positive, it doesn't matter as long as you are consistent) then you can always easily identify which lead is which. If every installation went perfectly and never had to be touched again it really wouldn't matter, but that's not how the real world works, Murphy's Law and all.
Besides, it doesn't cost a penny to be consistent, and the one time in 100 (or 1000) that you need to figure out which lead is which the answer is right in front of you. Is it a big deal? No, absolutely not. It is just a personal preference.
Just to prove how anal I am, I always paint the + lead red too if the wires aren't already colour coded. That saves mix ups before the resistor is attached.
richhotrain rrinker Connect one lead of the LED to one lead of a resistor (doesn't matter which one, but it pays to be consistent). If it doesn't matter, why does it pay to be consistent? Rich
If it doesn't matter, why does it pay to be consistent?
What Dave said plus if you've built them all consistently, when it's time to actually install them you can do so fairly mindlessly, always knowing the resistor goes to the black wire because all resistors are on the negative side of the LED, or similar.
This is another one of those things I would tend to batch build, once I get that far. I will probably just sit down one evening and wire a hundred LEDs to resistors and throw them in one of my organizers so that when I get to installing building lights, I won't have to keep stopping and soldering resistors on. Like I do with my joiner feeders, I make up dozens of pairs and put them in a drawer so when I get into a rhythm of tracklaying I don't have to stop and make more.
It does not matter to the LED. It does matter if you have to troubleshoot your circuits.
LION uses a common ground throughout the layout of him. A HARD ground connected to the building's electrical ground system. (Buy a regular replacement plug, connect ONLY the ground pin, and attach that to your ground----Failure to do this will give you a "floating common" which will be home to all sorts of stry voltages)
Having such a common or hard ground I connect the NEGITAVE pole of the LED to this ground, and so I do not want the resistor there just because.
LION has a +12v dc bus (labled Hotel Power) [Him swiped an old computer power supply for this purpose.] I connect the resistor directly to the LED and then the drop wire to the Hotel Bus. This is important to me, because if you put the resistor elsewhere such as at the bus itself, you run the risk of connecting an unprotected LED to the voltage.
Below, you can see power bus consisting of two bare copper wires. The NEG lead from the LED connects to the ground bus, the POS lead from the LED connects to the 1K Ohm 1/4W resistor and that to the Hotel Bus.
LION uses 1/4W resistors because they are less that half the price of 1/8W resistors, him buys them in boxes of 1000 pcs.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
I am not sure where the 1K ohm value came from, Both my own calculations & the use of a LED resistor calculating app http://ledcalc.com/ to confirm, has come up with a value of 390 ohms
correct me if I am wrong
make sure that your power supply is 12 volt as a lot of older train set ones are unregulated up to 18 volts and are pron to voltage spikes get a well filtered DC supply if you can in the 3.5 to 5 volt range.
Rich,
I attach my resistors to the cathode (-) side of an LED for consistency purposes, as stated earlier by Dave and Randy. From a troubleshooting standpoint, it visually makes diagnosis and/or replacements easier.
You could liken it to wiring your layout: Your track doesn't care what color wire you use to ID the power bus or the feeders to left and right rails. You may, however, care if you have to diagnose a short or replace a turnout and you're trying to trace where a certain wire goes and it keeps changing color on you.
Liken it also to putting tools back in the same drawer: You spend less time trying to find it the next time you need it.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
dbduck:
Your calculation is correct. All you really need is 390 ohms. However, if you use 390 ohms the LED will be drawing close to its maximum amperage, usually in the 20 - 30 ma range. If you use a 1000 ohm resistor you will be drawing about half the maximum amperage but the LED will still be bright enough for most purposes. In fact the difference in brightness is hard to determine with the naked eye. The advantage to using 1000 ohm resistors comes into play when you are powering multiple resistors from the same source as is the case with structure lighting. The larger resistors allow for more LEDs on the same circuit. Simple as that.
Higher value resistors also come into play where you want to dim the resistor significantly, like when you are trying to mimic a lower wattage incandescent bulb or a kerosene lamp. I have used resistors as high as 30,000 ohms to get the LEDs to just glow.