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Discussion Starter #1
I have two Tyco transformers. I want to use them for lighting. The AC side for street lights in parallel. Using both LED and bulbs (12V and 16V) for the different colors. I have 10K ohm 1/8 watt resistors to use with 3.3V LEDs. Will this work on AC terminals ? IS the resistor to small for AC ? I will use the DC terminals for the inside structure lighting as a dimmer using both bulbs and LED in parallel.
 

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With the LED's you may find only one transformer is needed.
10K ohm seems too big to use for 3.3LED on 12-16 VAC. Start with 1K or 2K.

AC can be used, but you have DC, put everything on the DC terminal so you can lower lighting easily.
 

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Discussion Starter #3
Dennis I must be confused. I thought 10K would restrict more power causing a dimmer light. 10K is so much smaller than a 1K in actual size.
 

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I have no idea how bright/dim you want. Try both see which is better for your intentions.
 

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LED's are current devices and as such using resistors to dim them works over a very limited range before the LED just plain shuts of. If you want real dimming control, you need to generate a Pulse Width Modulation, then you can adjust from 100% down to zero %. Try the 10K before you install any. I always found that using just resistors for dimming LED's unfulfilling! You might try something like this to dim your LED's/
https://www.amazon.com/SUPERNIGHT-1...+led+color+controller&qid=1583691248&sr=8-113
Connect a 12v DC power supply and then the output would go to you array of LED's connected in parallel (each LED would need a 1k resistor connected in series. Then you could dim from full bright to off.
 

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Discussion Starter #6
Here is an example the best I can give. I got a 0402SMD wired with a resistor for the headlamp in a bowser TCSWOW conversion. I cut off the resistor (at the direction from TCS) and then checked using a color code chart. It is a 15K. I will guess by the length of the case it is a 1/4 watt(blue). The 0402SMD is very bright and very white( not so warm). I have 29 more of these. I am waiting on tamiya clear and clear yellow paint. I tried orange clear, not happy with that. The idea is to try for a more incandescent color. I read that dimming with a resistor would help to lesson the white effect. Ok so I will get a pack of 1K to try out. What watt 1/4,1/2 ? Using ac terminals for street lights only. No need to dim those.
 

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LEDs draw very little current...the 1/4 watt resistors
are all you need.

Use the DC TRACK terminals on the power pack for your
LEDs. Note: Long wires on LEDs are +. Vary the speed control even tho resistors are in the circuit...you might get the
'color' you want.

Don
 

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Just for clarification, blue resistors are typically 1% tolerance and will have five color bands on them. Did you use a chart for all five bands, or did you arrive at your 15K value using only the first four bands? Honestly you would be better off just using a meter to measure the actual value of the resistor, because there is a huge variation in the color bands depending on manufacturer (for example, red can look exactly like brown or orange of another manufacturer).

If you want a warm-white color output, you need to buy warm-white LED's. Trying to dim them or paint them another color is just making more work for yourself. Warm-white LEDs have a nice yellow glow that is ideal for old steam engines. Also, as mentioned, you want to use DC with LEDs, not AC. It may work for a short time, but I would be worried that the AC would burn them out eventually?

Regarding the exact value of resistor... if you can provide a link where you bought the LEDs from, and what voltage you intend to use to run them, we can tell you the exact resistor value to give a bright output, or suggest alternate values for a lower output. The specs of the LED, along with the supply voltage, all work together to determine what resistor values are appropriate.
 

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Discussion Starter #9
I don't have a meter. Yes I used the 5 band chart and Jack at lichfield station verified the resistor. 15K 1/4 watt. However warm white is at 3000 Kelvins. Still white like fluorescent. I am looking to reduce( using a resistor that won't over heat) that closer to 2700 Kelvins. Which would be close to an incandescent 75 watt bulb ( color ). I did find 12V 40mA bulbs on ebay 100 for 12.00. I may use these for all inside lights controlled by the Tyco DC terminals so I can dim them. But all outside lights doorways, porch lights are 0402 SMD's I don't want to dim them just get the yellow incandescent glow ( Tamiya clear paint, clear yellow mixed 50/50 ). Street lights and yard tower lights are a combination of warm white 3mm I got 100 for 5.50 on Ebay 3.2V 20mA and 12V,16V bulbs and I don't want to dim these. That is why I asked about using the AC terminals. Golden white LED's are orange clear plastic. Just ugly. I found these to be cool as well A Power Distribution Board for LEDs. It has a pentameter built in to dim lights as an option. The correct resistor will still be needed.
 

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Discussion Starter #10
I watched a video on YouTube of a resistor catching on fire using a 12V battery, pretty cool. I don't want to do it myself. I made my own control panels based off a YouTube video. I thought I ordered the correct resistors. After getting it all wired, turned it on the leds started burning out. I got smaller ( I think ) resistors 10K 1/8 watt using 5V phone charger for power to the panel. This is why I am looking for help with the right resistor the first time. LOL.
 

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I think you're missing something here. Dimming an LED does not change it's color (like you might see with an incandescent bulb). LEDs put out a light at a defined color until the current drops too low and they stop working at all.

If your LEDs are actually 0402 SMD size, they are going to use an incredibly small amount of current. We're talking probably even less than 1/10th of a watt (which is around where SMD resistors are rated at). Also the wattage of a resistor has no bearing on how much current it allows the LED to pull. It is the resistance that controls how much current the LED receives.

How did you determine what the 'proper' resistance was to match the LEDs you are using? There is a formula based on the power supply voltage, the LED's voltage, and the LED's amperage. You need to know all three values in order to determine the right resistance to match with the LED, and once you know that then you will also know how much wattage will be drawn by the circuit, and you can get a resistor of the appropriate wattage (and resistance). These values are not something you can just grab from a youtube video and assume they will also work with whatever LEDs you purchased. That's why I said we could help you find the right info if you provided a link to the exact LEDs you have.
 

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Discussion Starter #12
I don't know how to post a link. I use - Dropping Resistor Calculator at GTSparkplugs.com. I plug in the info then round up the answer. The 0402SMD does not give any specs. it is prewired with a resistor 9V-12V use. I think the Tyco transformers are 12V no idea how many amps. The 3mm LEDS are 3.2V 20mA. I did think that a resistor would dim/limit current. It was explained to me that watts create heat, using a larger watt rated resistor allows the resistor to operate cooler. As far as dimming LEDs I picked up a 1K trimmer pot for the LED strips in S scale pass cars to dim the lights. The resistors are built in the strips. I do know from my past mistake that the wrong resistor will make a LED brighter. Then it burns out. I changed to a 10K and a new light now they work and are dim. But that's at 5V input. Is a phone charger AC or DC ?
 

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Which Tyco power pack do you have? If it's the most common gold one (for an HO train) then it puts out 18VDC, not 12V. If the power pack was for an N scale train then it might only put out 12V.

OK do your LEDs look like this? The specs say about 3.3V and 15mA, which seems incredibly high for such a tiny device. Assuming you have the same Tyco packs that I have (18V), that would mean the LED takes a 1.0K ohm resistor rated at 1/2 watt!

If this is true, then you would be better off wiring several LEDs in series so you can use a more reasonable resistor. For example, if you used three LEDs in series you could safely use a 540 ohm, 1/4W resistor. Adding more LEDs in series brings down the load that the resistor carries.
 

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Discussion Starter #14
OK they are 18V that changes alot. Can't read them. I can see the gold and the style means Tyco. I assumed they were 12V both AC and DC. Yes, those are the 0402's I have with a resistor for 9-12v. How ever now that you said I have 18V I need to rethink everything so I don't blow out all the lights. Thanx for the help so far.
 

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Honestly it is probably easier if you just pick up a cheap wall-wart style DC power pack. At least for your LEDs, a small 1A supply would run around 66 of them. Then you could run your incandescents separately from the Tyco pack (note it puts out 20VAC if you choose to work from that side).

You asked about using a phone charger... If you're referring to a cell phone charger, that puts out 5VDC and could be anywhere from 0.5A up to several amps. The resistor values would be different, but yes it could be done.
 
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