To avoid accidental breakage or pulling apart of bulb wire from a resistor are there any suggestions on how to best make the soldered connection?
Also, is it possible to damage the resistor by overheating from the soldering iron?
I’m using 30 gage wire with resistors in the 360 ohm to 1 K ohm range.
Use a heat sink between the iron and resistor or get in and out quickly. Make sure the tip is clean
Well, in my learning experience, you should “tin” the wire and the resistor, then your not exposing either to a prolonged contact to the soldering iron. You only need to touch the area with the soldering tip until the tinning “flows” together.
Iv’e been learning some soldering techniques, as, sometimes you need to solder wires to decoder boards, for different lighting options.
Mike.
EDIT: When soldering my track sections together, I used a small piece of damp rag on each side of the soldering joint to act as a heat sink.
Many times I have used a pencil iron and dab of solder. Little flux. If the resistor has been laying around for a while, I use 150 grit sandpaper on a sanding block to shine it up. I have had a large junk box of electronic components for many years.
I have been soldering since 1954 and do not recall ever overheating components.
If you have never soldered, practice with scrap wire.
Rich
Hi Jerry:
I don’t think you will pull the bulb wire out unless you really apply a lot of force. Normal handling shouldn’t cause any damage.
You can smoke a resistor by keeping the iron on it for too long, but that would be much longer than it should require for the solder to flow.
If you are worried about heat build up, do as Jim suggested and use a heat sink. I use a small pair of needle nose pliers with an elastic band wrapped around the handles to keep the jaws closed. If practical, I mount the pliers in my bench vise.
If you prepare the work properly heat build up shouldn’t be an issue. I always apply a little bit of flux to the joint even if I am using rosin core solder. Some will call that overkill but it guarantees a fast, solid connection. Pre-tinning the wire is a good idea. It takes less than a second to make a joint with small wires when things are set up properly. I clean the tip of the iron every couple of joints.
One other suggestion I would like to make is to use LEDs instead of bulbs. Bulbs will eventually burn out whereas LEDs will last for 1000s of hours. LEDs are just as easy to install and they are cheap. The only thing you have to observe is the polarity of the LEDs. Use 1K resistors with the LEDs.
Dave
I have been using 12v LEDs. No resister required. No special wiring or making changes to DCC decoders. I found them at http://www.led-switch.com/
Resistors are hard to burn up, but you can do it. You’d have to really break ever rule in teh book on soldering to do it.
The LEDs, on the other hand…
The key to a good solder joint is a CLEAN SHINY TIP. A dull oxidized tip doesn;t transfer heat very well, causing you to have to keep holding it on longer and longer - this is what damages components. A clean shiny tip, with a 40 watt or so iron, will heat up fine decoder wire and a resistor lead such that it shouldn’t take more than a second to get the solder to melt and flow, flux or no flux.
Depending on where the LED has to go, I often solder the resistor right to the LED, cutting both wires short. For LEDs you can use 1/8 watt resistors, and shrink tubing that fits over a 1.8 watt resistor will shring dairly tight to the led/resistor lead junction as well.
–Randy
Jerry,
As others have noted, “clean and shiny” is what you want from both your soldering iron tip (before soldering) AND your solder joint (after you’ve finished). And, if your solder joint is done properly, the 30 AWG wire will break waaaay before the wire will pull away from the resistor.
So, a clean and shiny (silvery) joint is what you’re after. If the joint is gray and dull in appearance, more than likely it’s a “cold” solder joint, which doesn’t conduct current very well at all and should be avoided at all costs.
Tom
Are you saying you use LED’s and DC, or do your LED’s not require resistors. As a DCC wannabe, I am confused.
The “12 volt” LEDS are just regular LEDs that have had resistors pre-attached.
Joe
Doh! The warm white 3v led’s put out 7500 MCD millicandellas and the 12 v 3000 MCD’s. Do the resistors reduce that on the 3v or are they still brighter than the 12v?
There are no resisters that can be seen. Maybe they are inside the LED, but I doubt it.
I connect them directly to the light output of the DCC decoders. No cutting a foil strip on the decoder, no resisters. They operate at 12v DC like a standard light bulb.
A handy tool to have around for soldering LEDs is a hemostat, they make a great heat sink.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
12V is 12V. Current doesn’t care if it’s incandescent or an LED. Therefore, you shouldn’t need a resistor if the LED operates on 12V.
The only way it won’t light up is if you have the LED hooked up backwards. Diodes are uni-directional and current will only flow through it one way. If it doesn’t light all you have to do is swap the wires.
Tom
The light output of an LED depends on several things. That material and design, and how much current is flowing. The ratings given for LED usually are max light output when run right to the maximim current, usually around 20-25ma for a white LED. Using a 1K resistor with typical DCC HO track voltage results in around 9ma through the LED, so if they are 3700mcd at 20ma, they won’t be that at 9ma (but not half, either, they aren’t linear).
The 12V LEDs MIGHT be giving their output in mcd at 12V, but the key thing is the current. Light output in a straight LED(no resistor) does vary a bit with voltage but it’s a rather narrow band between not lighting, dim, and bright. The current is a better control.
–Randy
OK now I’m confused. The 12 volt LEDS that I am familiar with have a resistor attached and it appears that the ones mentioned above don’t. Are they fabricated with an internal resistance?
Joe
I just sent Bill at LED-Switch an email asking if he can explain how the 12 v LEDs work. Might not get an answer until Monday.
Dave
There’s a resistor inside, guarantee it. Do you have a macro mode on your camera to take a good clear closeup of the inside? I’ve found a few pictures via Google image search, one of a clear white one that very obviously shows the resistor inside the package but it’s one of those ridiculously long file names from a blog that does not end in a normal jpg or other image file extension.
There’s this red one from Digikey:
http://media.digikey.com/photos/Lumex%20Photos/SSL-LX3044ID-12V,SSL-LX3044HD,SSL-LX3044ID-5V.jpg
If you look on the right hand lead after it enters the LED case, you cna see a black vertical line in there, then another piece of metal, then finallt the larger piece of metl with the slight cup in the top of it which is where the diode junction is. Because it’s a diffused red case you can;t see the bond wire but that black line is the resistor.
Ah, here’s a clear case white one so you can see the insides:
Notice the gap on the top side and what looks almost like a third leg that doesn;t actually go outside the LED case. That diagonal gap is where the resistor sits.
It’s a property of the semiconductor material that makes up an LED that it has a coltage drop of 3.2-3.5V for white, usually les, like 2.3-2.7 for red/yellow/green ones. It would take the development of a completely new kind of material to make an LED with a native 12V forward voltage. ANd to run it at above 12V at all would still need a resistor or some method of current limiting lest it fall victim to thermal runaway which is what happens when you take an ordinary LED and connect
Thanks Randy.
Do you know if there is any significant heat build up from the resistors?
Dave
Shouldn’t be, without knowing the exact specs it’s hard to calculate but if the reistor is saw 1K and the LED is a typical white one, it’s about 9ma, I^2R gets you less than .1 watt. The actual LED junction inside them gets fairly hot, it’s just such tiny point source of light and heat that it is easily dissipated and the LED never gets warm. The RGB LEDs on the strip lights I have definitely get warm after they’ve been on a for a while.
–Randy