Hello everoneI have an LED question. This is my first install. I had the motor control working very well and now I want to install the LEDs. 1. Can I put a dab of glue on them to hold them in place or will that cause them to overheat? 2. I would like to shorten the LED wires and the resister leads. How short can I make the leads if I put a clamp on the wire for a heat sink?Thanks in advance for any help you can give.
Lee
No, the LED won't overheat if you use a dab of glue on it. You can glue them right in a palstic loco shell and it will never melt it - I've used plain old white glue for this, sinc eit dries clear and doesn't form a real solid bond with the epoxy case of the LED, but it keeps them from falling out and if I should ever need to remove it, slight pressure will pop it lose.
You can cut the leads as short as you can manage to solder to. I don;t even use a heat sink, but I am also only using a tiny 15 watt iron for work like that. Haven't cooked one yet. Before you clip the leads short though, make sure there's some other identifier as to which terminal is which. Many LEDs have a flat in the side of the case nearest the cathode lead, but some just go by the lead length - obviously that distinction is lost if you clip them both short. No harm if you hook one up backwards - it just won't work. If you are cutting the leads short, swap connections at the opposite side rather than risk desoldering and then soldering right against the LED again. It does not matter which lead the resistor is connected to, so long as it's there. If the LED is not completely opaque and you know what you are looking for, you can actually hold it up to a light and see the insides and determine which terminal is which.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
RandyThanks a bunch. I've been playing with this SD7 so that I can learn the is and outs of installing decoders. This is not a sound decoder so if I blow it theres not much lost. I may still put sound in it but there is very very little room in it. Thanks again.Happy railroading.
Which SD-7? Proto 2000? I have pictures on my web site..or I think I do, of an SD-7 decoder install I did.
You can shorten the leads. I did this for my beacon light:
At first I soldered the feeder wires. But be carefully, the LED could melt. Don't ask me.
Then I shortened the wires, you see the LED together with a Details West RB-106 Flasher Beacon.
Now, I've only to install.
Wolfgang
Pueblo & Salt Lake RR
Come to us http://www.westportterminal.de my videos my blog
rrinker Which SD-7? Proto 2000? I have pictures on my web site..or I think I do, of an SD-7 decoder install I did. --Randy
If you look closely at the LED itself, you will be able to tell which lead is the cathode or anode even after you cut them.
http://en.wikipedia.org/wiki/Image:Uvled_highres_macro.jpg
TONY
"If we never take the time, how can we ever have the time." - Merovingian (Matrix Reloaded)
The shorter lead, and/or the one with the flat in the case, is the cathode. This is the negative terminal. For a decoder installaton, the cathode goes to the function wire - white, yellow, etc, and the anode goes to the blue wire. The blue wire is common to all functions, but it is the positive lead, NOT the negative.
If you have the proper resistor installed in series with the LED, and it doesn't turn on when you turn on the function, you haven't blown it up. It's probably just backwards. Swap the leads and try again.
jasperofzeal If you look closely at the LED itself, you will be able to tell which lead is the cathode or anode even after you cut them. http://en.wikipedia.org/wiki/Image:Uvled_highres_macro.jpg
Note the fine whisker of wire coming from the anode (+) sire into the top of the cathode area - that more than anything is a pretty foolproof way to know which is which. The base substrate of the semiconductor in the LED is the cathode, and the anode contacts it with a very fine whisker - pretty much like an old crystal radio where a chunk of germanium was held in a clamp and you probed it with a fine whisker til you got reception. If you have an LED that isn't super bright (the white ones are out for this), you can look closely at it, with a magnifier if necessary, and you'll see that the light comes from right at that point of contact. Pretty neat, even if you're not up on the physics of semiconductors
Dunno if this will work, if not you can go to my web site in the signature block below and go to the DCC section and find the SD-7, but here are the pictures I took installing a TCS T-1 decoder and LEDs in one. PLENTY of room inside. Those LEDs are ones I think I got in bulk from either Litchfield or Empire Northern - Miniatronics Yelo-Glo LEDs are available at most hobby shops and work equally well. Resistors are 1K.
http://community.webshots.com/album/271252792dMRNdN
Randy, Tony.Thanks I downloaded a picture of an LED so I can remember, great site. This old dog is learning a few new tricks. Now I have to learn how to make the wire connection and solder those tiny wires. Anyway thanks to both of you.
yankee flyer Randy, Tony.Thanks I downloaded a picture of an LED so I can remember, great site. This old dog is learning a few new tricks. Now I have to learn how to make the wire connection and solder those tiny wires. Anyway thanks to both of you. Lee
SMALL soldering iron. With a very fine tip. I usually use a 15 watt for electronic work - I think Radio Shack still sells the same one, it's the only oen they have that's grounded, so it also keeps away static. Keep the tip clean. And use fine diameter solder, that 0.062 stuff might be fine for use with a 200 watt soldering gun and attaching feeders to the bus wires, but for soldering LEDs and decoder wires you need the small stuff and a small iron. And the best way I've found to strip the fine wire on decoders is my fingernails. Oh yeah - if you use heat shrink to to insulate connections (it's way less messy then electrical tape), put the piece of shrink tube on BEFORE you solder the connection.
rrinkerOh yeah - if you use heat shrink to to insulate connections (it's way less messy then electrical tape), put the piece of shrink tube on BEFORE you solder the connection.
Find that out the hard way, did ya?
Jay
C-415 Build: https://imageshack.com/a/tShC/1
Other builds: https://imageshack.com/my/albums
modelmaker51 rrinkerOh yeah - if you use heat shrink to to insulate connections (it's way less messy then electrical tape), put the piece of shrink tube on BEFORE you solder the connection. Find that out the hard way, did ya?
I'm taking the 5th on this