Hi i have a project that use 12V DC motor and PHmeter.
PH meter is connected to the analog input of Arduino, voltage the phmeter output correspond to the measured PH value. I also need to run 12V DC motor in this project, i want to use a transistor to handle this motor, unfortunately when I run motor voltage on PH Arduino AI rise about 1V, i try to connect motor excluding transistor directly to the 12VDC power source (the same source powers Arduino on DCIN pin) in parallel to the Arduino, but effect it the same, when the motor starts voltage on arduino analog pin corresponding to the PH rise about 1V.
This is not a Arduino measurement issue because I measure voltage between Arduino AI and GND by multimeter and it actually rise about 1V, voltage between + and GNS remains constant. I connect a quick diode on a + line and 2 capitators (100µF and 100nF) between + and GND before Arduino DCIN and GND, then I run DC Motor in parallel before my filter and this not help, 1V variation still occurs.
When I replace a DC motor with a resistance load problem does not occurs, so DC motor must generate disturbances on phmeter please help :(