20x4 LCD stops working sometimes, caused by power drops?

hi, first of english not primary language description may not best. anyway, have arduino uno (china version) has lot of stuff connected it, example real time module, buzzer, xyz-axis module, mosfet , on (all analog , digital ports ocupied), , ofcourse actual lcd.
my problem lcd stops working example when buzzer beeps or when relay switched. happens when stops working characters moves around , when pressing whole lcd filled random characters (/0?<_ etc.) . pressing reset on arduino lcd starts working normal again.

my guess relays or buzzer uses power short amount of time lcd lacks enough power. how can solve this? can place capacitor somewhere? , how many f?

thanks in advance

yes in deed... need conect external power supply , there feed including arduino, power comnsumtion stay in limits of arduino pins.

try use buck converter @ proper voltaje, , there send vcc , thr gnd each of components, when relays need more power, take converter, not arduino pins.

cheers.
-alex.

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