Learning - Hardware

The “Learning” series of pages is a place for me to dump anything new I’ve learned while acquiring a specific skill. For example, I recently started working with hardware at a higher level than “connect this cable to this Arduino slot”, and started learning more about making PCBs, soldering and more details about how hardware works, so this is an account of all the things I’ve learned.

The purpose is to gather every titbit I’ve come across or been told after hours or days of looking and stick it here for an interested reader to read (or look up) all at once. The format won’t be very structured, it will probably just be bullet points into various categories, with sources (when possible).

Here they are!:

General

  • Always connect the grounds. All the grounds.
  • Use N-MOSFETs to switch ground, P-MOSFETs to switch VCC. That’s because N-MOS needs higher voltage on the gate than on the source and P-MOS needs lower.

Soldering

  • The reason your soldering iron goes up to 500 C even though solder melts at 180 C is that, if you have a fine tip, heat will very easily get transferred off the tip onto the solder, so you need more heat on the tip to actually transfer enough energy to the tip. (source)
  • Flux in your solder cleans away the rust from your metal pads so the solder can adhere to the pad. (source)

PCB design

  • Take care to make your tracks wide enough to accommodate your current. The more current and longer the length of the track, the wider it needs to be. There are various handy calculators (including one in KiCad) that will tell you the exact width you need to use for each current and length.
  • Through-hole components are the ones that you need to add holes to your PCB for. They’re the normal, large components you’re used to seeing, with wires at each end. SMD components are soldered to the surface, on metal pads, and are tiny by comparison. SMD components are preferred, and they aren’t hard to solder at all, with proper technique (apply some solder to one pad, solder the component onto that to keep it from moving, solder the other pads, done).

Miscellaneous links

My shopping list

Stuff I bought on eBay that I found helpful, in no particular order.