# Cheap Power for LED Lights



## jimben (Jun 27, 2018)

Most auxiliary lighting uses LEDs. Street lights, traffic lights, various lighted signs and buildings. Many train transformers have only AC as the auxiliary voltage and many are at 17-18 volts. This is ok for 15-20 volt incandescent lamps, but as mentioned most newer items use LEDs that require DC voltage.

For lighting a building various 12 volt DC LED lighting is available. More expensive LED strips or the ultra bright 20ma (current) 12 volt DC LEDs. The 20ma LED are available for under $10 for 50 LEDs with 8-10" wires. One 20ma LED will light up HO gauge and smaller buildings brightly. G and O gauge are well lighted with one LED, but due to size two equally spaced LEDs are better for more even lighting in the larger G and O gauge buildings.

LEDs are usually 12 volts DC for single LEDs with wire leads and 3 volt at 10ma for traffic lights, railroad crossing signals, street lighting and many lighted signs. Note that some street lights are 12 volt.

3 volt 10ma LEDs must use a 1000 ohm 1/2 watt resistor in series with the LED wiring to lower the voltage from 12 volts to less than 3 volts. You can light up many 3 volt same current draw LEDs using one lower value resistor. Just divide to resistor value of 1000 ohms by the number of LEDs.

Now, having an auxiliary AC voltage will not work. The answer is to purchase a wall wart for auxiliary lighting. Many are available on ebay for $5 and rated at 12 volts at 2 amps. Two amps can operate one hundred 20ma LEDs. Below is an example of a wall wart for sale on ebay. Doing a search on ebay, use 'wall wart', '12VDC' and '2A' to find 12 volt 2 amp wall warts.

https://www.ebay.com/itm/AC-Power-A...095241?hash=item41a4a425c9:g:vDEAAOSwk6dbkJ33


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## gunrunnerjohn (Nov 10, 2010)

Actually, if you want LED's to be lit at full intensity, the resistor for a white 3V LED from 12VDC would be 450 ohms or probably a standard value of 470 ohms. Be careful paralleling LED's, if they're not identical, you'll get uneven lighting, or some won't light at all. 

If you parallel different colors, you will find that most likely only the ones on the low scale toward red will light as they are the lowest voltage units.


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## MichaelE (Mar 7, 2018)

DCC track voltage works fine for resistor limited HO scale lighting from any manufacturer. And those manufacturers include the resistor in-line on one lead or the other. It makes no difference to an LED if it's AC for which ever lead you use. That's why it's called _A_lternating voltage. the sine wave goes both ways and the LED will take advantage of one half of the wave or another depending upon whether you picked the anode or the cathode for positive or negative. The eye can't see 60 Hz cycle so it shouldn't make any difference in your viewing enjoyment of your layout.


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## gunrunnerjohn (Nov 10, 2010)

One issue with LED's on AC is that they typically have a very low reverse voltage tolerance. about 5V peak is typical for garden variety LED's.

I used to wire my TMCC stuff with just a resistor and the LED. I couldn't understand why after about 6 months to a year, I'd start losing LED's. Added a protection diode and that issue was resolved.


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## MichaelE (Mar 7, 2018)

Veissmann supplies their LED signals and semaphores with a diode for that purpose.


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## gunrunnerjohn (Nov 10, 2010)

A wise precaution.


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## Stan D (Feb 1, 2019)

Wall warts come in many voltages. I never throw them away, and the smallest one I have is rated at 1.9 volts. Most phone chargers are rated at 5 volts.

The thing you should be aware of is "rated" versus actual. Actual is almost always more, without a load. And LEDs don't draw much of a load. I've seen ones rated at 12 volts that measures out at 16 volts. So even with resistors, you could overdrive LEDs, so measure before you wire it up.

Another thing you should know is there are two types of wall wart. Those that have a transformer in them (old tech), and switching type (newer tech, and more regulated). A switching type is more likely to have the actual voltage closer to the rated voltage. You can tell the difference by rating and weight. Easier with the higher rated (1 amp or more). A transformer type will feel noticeably heavier and be larger than a switching type of the same or similar current rating.


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## jimben (Jun 27, 2018)

MichaelE said:


> DCC track voltage works fine for resistor limited HO scale lighting from any manufacturer. And those manufacturers include the resistor in-line on one lead or the other. It makes no difference to an LED if it's AC for which ever lead you use. That's why it's called _A_lternating voltage. the sine wave goes both ways and the LED will take advantage of one half of the wave or another depending upon whether you picked the anode or the cathode for positive or negative. The eye can't see 60 Hz cycle so it shouldn't make any difference in your viewing enjoyment of your layout.


LEDs will fail within days to a few months on AC. DC will have LEDs last 100 years. A diode can be used on AC to make 60Hz pulsating DC.


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## jimben (Jun 27, 2018)

Stan D said:


> Wall warts come in many voltages. I never throw them away, and the smallest one I have is rated at 1.9 volts. Most phone chargers are rated at 5 volts.
> 
> The thing you should be aware of is "rated" versus actual. Actual is almost always more, without a load. And LEDs don't draw much of a load. I've seen ones rated at 12 volts that measures out at 16 volts. So even with resistors, you could overdrive LEDs, so measure before you wire it up.
> 
> Another thing you should know is there are two types of wall wart. Those that have a transformer in them (old tech), and switching type (newer tech, and more regulated). A switching type is more likely to have the actual voltage closer to the rated voltage. You can tell the difference by rating and weight. Easier with the higher rated (1 amp or more). A transformer type will feel noticeably heavier and be larger than a switching type of the same or similar current rating.


I recommended switching type as shown on the ebay link.


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## gunrunnerjohn (Nov 10, 2010)

It's actually harder and harder to find a transformer wall wart nowadays, it's actually much cheaper to make the switchers. Add to that all the modern electronics that gets really annoyed when you feed them the wrong voltage, and regulated switchers are the norm.


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## jimben (Jun 27, 2018)

gunrunnerjohn said:


> It's actually harder and harder to find a transformer wall wart nowadays, it's actually much cheaper to make the switchers. Add to that all the modern electronics that gets really annoyed when you feed them the wrong voltage, and regulated switchers are the norm.


I do not find new transformer type on ebay now. Transformer type produce dirty DC power- avoid.


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## jimben (Jun 27, 2018)

gunrunnerjohn said:


> Actually, if you want LED's to be lit at full intensity, the resistor for a white 3V LED from 12VDC would be 450 ohms or probably a standard value of 470 ohms. Be careful paralleling LED's, if they're not identical, you'll get uneven lighting, or some won't light at all.
> 
> If you parallel different colors, you will find that most likely only the ones on the low scale toward red will light as they are the lowest voltage units.


You are correct 3 volt standard LEDs can use 470 ohm for maximum brightness, but items such as railroad crossing lights are unnaturally bright with 470 ohm resistor IMO. However, I should have mentioned 3 volt street lights would benefit from 470 ohm resistors. On the other hand, just order the 12 volt DC street lights. About the same cost, no resistor needed. Mouser Electronics is a great source for resistors and have no minimum cost order.


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## Lee Willis (Jan 1, 2014)

What I use - I have about eight staeioned around the layout feeding locally, are small 7 W DC power supplies made for RTR HO and N scale sets - small black boxes with a voltage adjustment knob with names like Lifelike, etc. - all the same. I find them at shows and swap meets used for around $2 each. They are adjustable 0 to 16 VDC, so i can vary the voltage a bit to get just the brightness I want. One or two would probably power all the LEDs on the layout but it is more convenient to have several at points around the layout for just the lights nearest each.


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## jimben (Jun 27, 2018)

Lee Willis said:


> What I use - I have about eight staeioned around the layout feeding locally, are small 7 W DC power supplies made for RTR HO and N scale sets - small black boxes with a voltage adjustment knob with names like Lifelike, etc. - all the same. I find them at shows and swap meets used for around $2 each. They are adjustable 0 to 16 VDC, so i can vary the voltage a bit to get just the brightness I want. One or two would probably power all the LEDs on the layout but it is more convenient to have several at points around the layout for just the lights nearest each.


7 watt will produce about 1/2 an amp current. That will operate 25 20ma lights for buildings or 50 small 3 volt 10ma LEDs in traffic lights, lighted railroad crossings, etc.


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