If you ask 10 electrical engineers how to solder two wires together, you will get 10 different answers -- and possibly
a fistfight if all 10 engineers happen to be in the same room at the same time. So just because I'm telling you how
to solder two wires together doesn't mean I know the only way, or even the best way, to do it. I just know my own way,
which has worked well for me in the past.
Of course one can't have a soldering tutorial without the standard disclaimer, so here it goes. Soldering irons get
very hot, and will burn the heck out of you if you touch them. Don't ever touch the metal part of the soldering
iron! Don't solder on your coffee table, or you will burn it. Don't solder on your formica kitchen counter, or
you will melt it. If you solder on a wooden table, you run the risk of making big burn marks on the table, and perhaps
even torching it. Never leave a soldering iron unattended.
So having said that, how do you solder two wires together? Well, I'm glad you asked.
Here's what you'll need:
- Soldering iron
- Electrician's solder
- Flux (no-clean flux is good, rosin flux is good, acid flux is bad)
- Wire cutters
- Wire strippers
- Heat shrink tubing (the kind with heat-activated adhesive is nice)
- Cigarette lighter or heat gun
- Wet rag to clean soldering iron tip
Here's what to do:
- First you need to get your wires ready. Make sure you have enough wire to make your connection and have
at least 3 inches of slack after the wires are routed the way you want. Once you've got this, strip about 1 inch
off the end of each wire. Resist the temptation to twist the stripped portion of wire so that it's neat. You
should have something like this:
![](images/solder1.gif)
- Now get a bit of heat shrink tubing, at least 4 inches long. I like to use heat shrink tubing with a
heat activated glue in it -- this when heated, it shrinks and glues itself to the wire, which creates a tight,
water resistant seal, which is what you want. Anyway, get your heat shrink tubing (it should fit easily over
the wire, with enough room to fit over a solder joint!) and slip it over one of the wires. Get it as far
from the joint as possible, so that it doesn't shrink while you're soldering.
- Don't forget the last step! You'll feel pretty silly if you go solder the wires and then realize that your heat shrink
tubing is not on the wire.
- Now is a good time to plug in your soldering iron, if you haven't already.
- Now stick the stripped ends of the two wires together, as close as they go:
![](images/solder2.gif)
- Twist the stripped part a bit: grasp one end of the connection with your thumb and forefinger, so that you have
a good grip on one wire and about 1/4 inch of the stripped part end of the other wire. Grab the same bit of the other
wire with your other hand, and twist the two. Get one or two full twists.
- Bathe the stripped part of wire with flux. I recommend rosin flux or a 'no clean' type flux. Flux pens are handy.
Get lots of flux on it; it should be dripping. Don't do this on your coffee table; do it on the workbench or the
garage floor, or something.
- Make sure your soldering iron is tinned -- there should be a bit of clean solder on the tip of the iron. If there
is not any solder there, or there is but it is not clean, you should clean off the tip and put some more solder on it.
To clean the tip, get a wet rag, bunch it up so you don't burn yourself, and wipe the tip of the iron.
- Solder! Have the end of your piece of solder touching the wire, and heat the wire next to it rather than the solder
itself. The flux will steam and bubble and might splatter a bit -- be careful! If your wires are well fluxed, the solder
will get sucked into the wire. Keep applying solder until the entire 1 inch connection is totally coated. Don't use too
much solder, or you will have trouble getting the heat shrink over it. If the solder bubbles on the surface of the wire
instead of getting sucked in, you either don't have enough flux, or the wire is dirty. In either case, dump on more flux.
This isn't the most efficient method of cleaning wires but it seems to work. You can also try heating up the wires a bit
more with the iron, but be careful not to melt the insulation or whatever surface you're working on.
- When you're done, and you have a nice neat connection, unplug your soldering iron and let the wires sit until the
connection cools. This is important because if the connection is still hot when you try to slide the heat shrink tubing
over it, the tubing will shrink and make life difficult.
- When the connection is cooled, slide the heat shrink tubing over it so that there is at least 1.5 inches of tubing on
each side of the connection:
![](images/solder3.gif)
- Now get a cigarrette lighter or heat gun and heat the tubing. Always heat the tubing from the center and work out,
never start from one end and work to the other. If you are using a lighter, don't let the flame touch the tubing or
it will melt.
Done! If you have multiple wires to connect, do one wire at a time. Also, don't cut all of the wires at the same spot; 'stagger'
them so that where one joint ends, the next begins. This way, if something goes wrong and one of your connections becomes
exposed, there will be less chance that it will arc and short with another one.
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