I've run out of 100nF capacitors, but by chance have a stash of small values of which the highest is 68nF. Are they suitable to use where where a 100nF capacitor would have been, adjacent to the picaxe power pins?
Correct. The small capacitor absorbs the high energy, low duration spikes, often caused by digital switching (both inside and outside the nearby chip). The larger one acts more like a storage "tank" of energy to handle surges in demand.I think it has to do with frequency response. The small capacity value responds to/absorbs high frequency voltage spikes, while the larger capacity responds to/levels out lower frequency ripples. Thus they represent high and low frequency noise filters on a DC voltage. Well, that's somebody told me.
I've mentioned this before, but it won't harm to say it again ...... The recommended power supply with the 7805 regulator has two capacitors in parallel on both the input and output sides. One is only 1/1000 of the other, so adding them in the normal way for parallel capacitors makes only 1/10 of 1% difference ...
Yes, Polyester is one of several plastic dielectrics used in the "typical" style of capacitor I described above. Other names/types are Mylar, Polycarbonate, PTFE and Polyethelyne, etc.. IIRC Polycarbonate was used in some of the "better" (industrial) capacitors and Polyethylene has very low dielectric losses so is typically used at GHz frequencies. However, as I described above, they may have a rather higher inductance, particularly if the connecting wires are simply slipped into the winding whilst the capacitor is being "rolled up".I also like the neat look of the polyester type, and they seem to have plenty of voltage rating. Are they also ok?