The robot will have 3 actuators:
2 dc motors for locomotion, which will need between 6v and 9v
1 stepper for rotating an iPhone with a lidar type sensor. This sensor has its own battery so power for this one is not an issue at this stage.
A stepper motor requires a lot of current. They are rarely the correct choice for mobile projects that need to carry their own batteries. A servo motor can probably wave the phone around just as easily, requiring far less current.
- What minimum stepper specs would get the job done?
As in, rotating the phone + light sensor + case which attaches both.
The pink one. Which model iPhone? Which case? What does the whole thing weigh? How will it be connected to the stepper?
I looked up steppers but did not see a stall torque spec
Guess I should read ahead before typing, since you did list the weight. But, the torque that a stepper motor can generate depends on many factors - voltage, current, and speed, among others. Stepping slowly uses less current than stepping fast.
- Are my estimations for the robot wheel's DC motors correct?
I estimate the total weight of the robot (excluding the stepper since I don't have the answer to question 1 as of now) to be 607.6g
Interesting to see an estimate to the nearest 10th of a gram when you don't know a critical component's weight.
- And related to the above, if I were to use the other chasis with the 9v motors:
would I need to do the oposite in terms of regulator? meaning a step down from some 9v source to aprox 7 for the Arduino and Shield or would it make sense to use less than the motor voltage (i.e. still 6 or 2 18650's at aprox 7.4 and step up to 9v?)
The Arduino has a builtin regulator. You can supply up to about 12V to the regulator, and it will output the required 3.3V to power the Arduino. The rest it will waste, as heat, which could be a problem. Having the Arduino-controlled robot stop doing anything because the robot batteries went dead is probably not a good thing. A separate power supply is.