...attached please find the circuit diagram of my current project. As it is my second diagram at all and I want to do a PCB with it, please let me know if you think I should change or add things.
The circuit will be used to control the speed of seven brushless fountain pumps (with integrated electronics). To drive the pumps I'm using a PWM signal which is amplified (to 12V) by a darlington array, then connected to a low pass filter and an adjustable voltage regulator (input: 12V).
With the help of a schottky diode I'm "converting" the tacho signal from the pumps to 5V.
The above part of the circuit has been tested on a breadboard and works fine.
To be able to drive the pumps' speed according to the surrounding sound level I added a lm386, which I did not test together with the rest of the circuit, but some time before. The input of the lm386 is connected to an electret microphone and the output is connected to an analog input pin of the arduino. The noise level will be high, as digital and analog signals are mixed. As the lm386 gets its power from the Arduino micro which again is powered from a 12V source I wonder if it will draw too much current for the regulator!?
I got recommendations to use high side instead of low side switching with the mosfet (which is used to be able to switch of the power completely, as the lowest possible voltage of the regulators is ~1,5V), but low side switching works fine.
I never used an acs712, but I want to try to use it together with the tacho-signal of the pumps to be able to find out if a pump is blocked, not connected or sucking air.
Regarding the safety of the circuit I'm fine with using only a polyfuse, no reverse current protection and no voltage protection (regarding the latter I count on the power supply)! - Thanks for the answers in advance!
please let me know if you think I should change or add things.