I have been working with little PIC LED kits, and they need ZERO caps to keep them working well.
Often circuits will work without decoupling caps, especially if the voltage source has a very low impedance and is decoupled.
To ensure a circuit will work under all normal conditions, decoupling is recommended.
I know this is "on the cheap, and if it works why not?" but I'd like to know a bit more about "best practice" when using caps for noise suppression, etc.
The best practice is to fit decoupling on the power rails.
I know that switching outputs can put a load on power sources, so maybe it is a good idea to just stick a cap across the power going to a pic (is 0.1 a "good choice?")
I would always add a medium value cap across a power input, say about 47uF thru 470uF, depending upon the type of circuit and psu. Also at least 100nF cap
I once made my own scratch built computer board, and the power was oscillating like crazy, until I stuck a very very tiny cap across the input (I think it was) of the 7805 regulator, so I learned by experience a cap can help...
The datasheet for the 7805 states that they can be unstable and a cap should be fitted on the input and output. Low value caps say 10nF thru 100nF.
Thanks very much, from a very experienced programmer, pretty good digital hacker, but very green "general electronics" person. I just bought my first handful of transistors and diodes and etc to start experimenting, and so far have only done some "Joule Thief" type boost circuits with various inductors I could find. I would LOVE a 'scope to watch what is going on at various points, see what frequency it is running, see at what voltage the transistor conducts, etc. Real basic stuff!
Take care.