I am wanting to create a system that supplies approximately 24V and 1A to a load (essentially a resistor) for up to 1 second. The process will not be repeated for any one load and there would be no continuing current flow after about 1 second. The positive wire will be switched by a momentary SPST switch but I also want to use an arduino output to have the option of solid state control (Arduino) or manual control (SPST switch). I wish to use 16 SPST switches to control 16 separate loads but I will also need to use switched grounds as I want to use an 8-core conductor from the circuits to the loads to control all 16 of them independently (i.e. the loads will be "matrixed").
My question is can I use NPN transistors as in my below diagram to allow switching of the POS and GND to a particular load via the use of a single SPST switch (i.e. mimicking a DPST switch through the use of transistors)?
If so, I will be needing a total of 192 transistors (aiming for 6 "banks" of 16 loads) so which transistor would you guess would be the cheapest and could handle this sort of current for the brief period intended (1 second)? I was thinking TIP120 / TIP 125.
Lastly how would I calculate the correct resistance of the resistor so that only enough current flowed from the SPST switch to the base of the 2nd NPN transistor to activate it while maintaining maximum current to the load.
Thanks for your help Aaron. So you suggest this arrangement?
So the resistor between the SPST switch / drain of the P-FET to the gate of the load-negative N-FET isn't needed? (as in no current would flow through the gate as it would all go from the drain to source of that N-FET)