Introduction: DIY Oscilloscope Leads - I Made It at TechShop
I picked up an old oscilloscope at a garage sale, and thought I would make some simple leads to go with it. In this instructable, I will show you how to build some decent and usable oscilloscope leads from parts you probably have laying around anyway. They're not perfect, but neither is my old oscilloscope, so it works just fine for me :)
I made these cool test leads at TechShop Pittsburgh, which is just completely awesome. They have several locations, and you should seriously consider paying them a visit and taking a tour if you want access to more powerful tools or want to take classes and learn new useful skills. Check out all the cool stuff they do and the amazing equipment they have at www.techshop.ws
Alligator clips (2)
Short pieces of wire, about 6 inches long (2)
BNC cable (or coaxial cable with BNC adapter, etc.)
Electrical tape or shrink wrap tubing
Soldering equipment and supplies
Wire cutter and/or knife
Step 1: Preparing the Cable
First we will prepare the BNC cable by cutting and stripping the end of it. We want it to be a reasonable length, so it your cable is very long you may want to cut it down to a more sensible length of 4 feet or so. Coaxial cable is a bit more difficult to strip than your average wire, so take your time and be careful.
First cut off about an inch and a half of the outer layer of coating using the knife or wire cutters. Be careful to only cut through the outer plastic coating.
Now use the wire cutters to cut off the braided wire and foil, if your cable has it. It doesn't have to be perfect, but try to keep it neat.
Next we cut off a section of the inner plastic coating.
We now have access to both conductors of the cable, so we can move on to preparing our clips.
Step 2: Preparing the Clips
Let's get the wire clips ready now. Take your short pieces of wire and strip about 1/4" on one side and 1/2" on the other. Attach the 1/2" of bare wire to your alligator clips. If your clips have screws for this purpose, you can use those. Otherwise, you will need to solder the wire into the clips or crimp them on, depending on what type of clips you have. If you are using the screws, bend the wire around the screws in a clockwise direction so that when you tighten the screws, the wire is pulled in and tightened, not pushed away.
Step 3: Putting It Together
Now we need to solder the clip wires onto the cable. Wire to wire soldering can be more challenging than soldering components to a breadboard, and you might want to use some other tools to help hold things in place while you work on them. I use a 'helping hands' holder that clamps the wires in place while I solder them to make is easier. Start with the inner conductor of the cable. This is your signal wire, and the outer mesh is the ground. If you are using two different colors of wire for your clips, make sure you know which color goes to which conductor. I chose black for ground and yellow for the signal.
Let's actually connect it now. To get a good connection, you should line up the end of the wire with the cable of the connector so they are touching and parallel to each other. Make sure you have a good solder joint by checking to see that the solder is covering the entire connecting length, not just a single point or blob.
The outer mesh is easier to solder to, but less pretty. Just make sure it is stuck on there really well, and avoid burning through the inner insulating plastic with the soldering iron.
Step 4: Finishing Up
Almost done. We just need to protect our solder junction. You can either use heat shrink tubing or electrical tape. Shrink tubing looks quite nice and professional, but you need to plan ahead and slide it over the cable and wires before you solder them. Electrical tape may not look as nice, but we are going for function, not fashion here. I just taped over it so it wouldn't come apart and I made sure the conductors of the cable would not be able to short themselves together, making the cable useless.
Now just test it out to see if it works!