When it comes to noise and
When it comes to noise and spike suppression caps, there aren’t really any concrete rules.
The last project I used the above H-Bridge for had quite small motors, and a very solid power supply. That meant that motor noise was very mild, and the current never spiked dramatically. The 10μF cap I used across the motor was a non-polarised electrolytic (I’m lazy with my cap symbols; a cap is either polarised or not - that’s all I care about apart from capacitance and voltage tolerance), and its only job was to reduce the ‘kick’ when the motor was abruptly turned on from a stalled start.
The controller was also quite immune to noise, so there was no need for noise suppression on the input lines or anything else. I put a large (1000μF) polarised electrolytic across the power supply lines just in case, but as the power supply was so solid compared to the light current draw of the circuit this probably wasn’t necessary.
I recommend you pick up a few electrolytic caps of varying sizes, maybe a few each of 1μF, 10μF, 100μF and 1000μF, plus a few small ceramics in the pF and nF range. Often you can buy bags of an assortment of small ceramics which is quite handy. Except for in very precise analog filters or in capacitive timers you don’t normally need great precision in your capacitors so it’s good to have a nice range of basic units. Ceramics are usually pretty robust anyway, but make sure your electrolytics can handle 16V or more, even for a 5V circuit, since the motor back EMF can spike quite a lot higher than the supply.
