I have assortments of resistors and capacitors, and even bipolar transistors (https://www.aliexpress.com/item/Free-Shipping-18valuesX10pcs-180pcs-2N2222-S9012-S9013-S9014-A1015-C1815-S8050-S8550-TO-92-Transistor-Assorted/32323342275.html).
But what would be useful for MOSFETs?
I would foresee using them mostly for turning power on and off to circuitry and sensors (so fairly low current, either a couple/few mA up to a couple of dozen mA), enabling/disabling flow of charging power to batteries, motors for a volt or two up to a 12vdc, sprinkler valves, and possibly for actual appliances (such as hothouse heaters, but I assume that optically isolated relays are a better idea for that . . .)
While I managed to learn their theory ears ago in my physics degree,I remember very little, and am slowly picking up and reabsorbing bits and pieces.
As I understand it at the moment, p-channels would turn on/flow from a high signal from the avr, while n-channel would trigger with a low.
And until I configure a pin as an output, the internal pulp resistor applies?
In turn, does that suggest n-channel as the more frequent choice if I don't want any momentary activation before the sketch gets to configuring the pin?
And should I have an inline resistor between the pin and the mosfet gate? if so, how much?
I'll be dealing almost entirely with 3.3v avrs, although they will frequently switch higher votages.
So which are worth stocking? Which should I avoid?
So which would be useful to keep around?