BeerCannon wrote:Do you think I'd be better off leaving the unused outputs of the 74HC595 alone (high impedence), or holding them at +5V instead of holding them at GND via 10k series resistors? I checked the datasheet for the chip and it didn't say what to do with unused outputs.
It doesn't make any practical difference whether you connect to VCC or GND, but GND is the usual choice.
You can also leave the outputs floating (not connected to anything) and they'll be fine.
BeerCannon wrote:Also, does it matter if the .1 microfarad cap (between the VCC pin and ground) is a polarized type of capacitor, or not? I'd guess that it doesn't matter which kind is used as long as a polarized one is oriented properly.
You're right. Any cap that has the right value and is installed the right way will work.
Ceramic capacitors (non-polarized) are the usual choice. They tend to be smaller, cheaper, faster, and more durable than electrolytics. For circuits that need to move really fast, people tend to use tantalum capacitors (which are polarized) because those have very low internal resistance (and can therefore dump current quickly).
One of the "wish someone had told me that in school" bits of circuit design is that capacitors come in at least four significantly different flavors:
- Electrolytics: polarized, lousy tolerances, lousy resistance, lousy performance, slow, but cheap and large
- Ceramics: non-polarized, decent tolerances, good performance, fast, small (Farads), but cheap
- Tantalum: polarized, decent tolerances, excellent performance, really fast, mid-sized, expensive
- Film: non-polarized, excellent tolerances, excellent performance, fast, mid-sized, expensive
and there are more when you really get into the details. Electrolytics really are awful, but nothing else can match their capacity, and there are lots of situations when your requirements for a cap are, "meh, whatever".. a level of performance electrolytics can deliver.
When you void a product warrany, you give up your right to sue the manufacturer if something goes wrong and accept full responsibility for whatever happens next. And then you truly own the product.