I want my Arduino to control 6 different small electronic motors. They are from battery powered fish tank air pumps that run off 2 AA batteries. I only need 1 of them to run at a time so I figured a Demux would work nicely. in reading through other peoples demos and ideas it was apparent that the arduinos ports did not put out enough current to power the motor. so I put together this schematic. My problem is selecting the correct transistor. my guess is that 100mA is enough current to get these guys running, they are you''re standard can shaped motors that get used in every basic project.
Is there any good way to measure the current draw? What transistor should I select?
Once that is selected, I figured I could use PWM to control the speed of the motors, essentially my program would select a particular pump and the pwm would control the speed. This seems reasonable to me if its only getting high pulses for 80% of the time, it will run slower (probably not 80% speed, but precision is not an issue here). any problem with that logic?
any issues with my schematic?