Advice page for lab 2a

Sharing equipment

There aren't enough screwdrivers for everyone to have one to themselves, so please return screwdrivers to the common pile once you're done with them, so that your classmates can use them.

Use stranded wire, not solid core wire.
The stranded wire we have comes in twisted pairs. You don't have to keep them in twisted pairs, but it might make your wiring neater =)
Wire length is assessed. Try to cut your wires to the right length: long enough that you have a little bit of freedom, but not so long that you have them winding around like a snake. Here’s a tip: it’s generally easier to make wires shorter than longer, and it’s often easier to judge wire length with one end of the wire in place. So it can help to cut an overlength wire, solder one side, then cut the other end to length.
In fact, having wires that are too long can cause one side of your lid not to close properly, or might counteract gravity enough that your arm won't turn off your switch.
Plan which direction your wires will point before you solder them, especially with the DPDT switch. The box is small enough that some directions just won’t work.

One of the biggest determinants with how clean a solder joint ends up looking, is how cleanly the wire is wrapped around the switches. The switch’s pins are quite close together, which makes neat wire wrapping all the more important.
It's easier to make the wrapping clean if you tin the wire before you wrap it, and don't strip too much insulation off (you only need enough to get around the pin).
Don't be tempted to wrap the wire around the pin multiple times, or even one full revolution. A single “U” squeezed in will do. You might elaborate wrapping would make it neater, but the bulge of wire actually makes it harder to get a neat joint.
If you're using the breadboard, you'll need to tin the wire so that it has enough structural strength to go into the breadboard. Tinning a wire is a bit different to soldering a joint. First, twist the wire so that it doesn't fray. Then, surround the wire with a blob of melted solder (soldering iron on one side, solder on the other), and drag it towards the tip. A coating of solder should stay on the wire as you move along. If you end up with a blob at the tip, just cut it off.
It'll sound obvious once we say it, but soldering irons melt plastic. So if you need to solder anything very close to your acrylic box, either be very careful, or unmount the motor or switch before soldering.

Some of the screws can be challenging to get in. This is because they're self-tapping: they cut a thread as they go in, in order to hold the plastic. Because they're so hard to screw in, it's particularly important to use the right size screwdriver. The limit switch screws take a Phillips size #2, or a #1 will work, but a #0 will make your life miserable.