francis24:
I want to move the motors either simultaneously with the same speed, or simultaneously but with differing speeds (e.g. Motor A: 100 rpm, Motor B: 60 rpm). Would you count the Big Easy as a "proper stepper driver board"
Yes, the BigEasydriver is a proper stepper driver board.
Driving the motors at different speeds or at the same speed is pefectly feasible with AccelStepper provided (in the case of different speeds) you don't need them to be precisely synchronized at the level of individual steps.
You would need them synchronized if, for example, you want the X and Y axes on a machine to cause the tool to follow a diagonal path or a curve.
Can you describe the machine in which you are thinking of using the motors?
Sorry, I should have done this earlier actually! I am a Psychology student (and a complete n00b in terms of electronics and robotics..) and for my Phd I am building a stimulation device for inducing the rubber hand illusion (The Rubber Hand Illusion - Horizon: Is Seeing Believing? - BBC Two - YouTube). My plan is to attach a paint brush to each stepper motor, and I will have two different conditions- (1) simultaneous stimulation with the motors running both with the same speed , so the brush touches both, the rubber and the real hand at the same time and (2) each motor rotating at different speeds so the touch to the rubber hand occurs at a different time point than the touch on the real hand.
So basically, what I aim to do is to drive two motors simultaneously, with the ability to vary the speeds individually, with maximum rpm of 200 and enough torque to not slow down because of the paint-skin contact.
Considering this, is using Accel Stepper and a setup with an Arduino UNO, two Big Easy drivers, two of the aforementioned Adafruit NEMA 17 stepper and a power supply of 12 V suitable?
Thanks for your help and patience in explaining, you are saving me here!
francis24:
(1) simultaneous stimulation with the motors running both with the same speed , so the brush touches both, the rubber and the real hand at the same time and (2) each motor rotating at different speeds so the touch to the rubber hand occurs at a different time point than the touch on the real hand.
I suspect from what you say and from looking at the video that you don't need the fine synchronization that would be required in a CNC machine and, if so, AccelStepper should be OK.
I suspect that a higher voltage (than 12v) will be needed to give adequate torque at higher motor speeds. But so much depends on the application that you need to run some tests.
How are you planning to link the brushes to the motors?
By the way (and I know it is rather late in the day) but have you considered using servos rather than stepper motors. Everything about servos is sooooooo much easier. The price, the control, the mechanical connections ...
Great, ok. They will be attached in a right angle to the shaft, so they rotate radially, I was thinking of getting a little propeller or something and just sticking the brush to that. Totally appreciate better ideas though. In terms of servos- What would I need for a setup like that? I have just focused on getting information about steppers so far since a friend of mine suggested them to be the best choice but reading up on servos now- they do seem like a good option but as far as I understand continuous servos do not have position feedback, thus, steppers would be easier to get to the same position again, after I rotated them not in sync but individually. In case this concern is wrong, what driver etc would I need to get and what servo motor would be best?
Ps. I have the Adafruit Motor shield already (unfortunately only version V 1 .1), if that is any help in terms of a servo setup.
The video gave me the impression that you want to and fro brush strokes on the person's fingers. A regular servo seems far more suitable for that than either a stepper motor or a continuous rotation servo. After all, the technician manipulating the brush in the film was not swinging his arm in a circle. Also think how much space will be needed to allow a brush to rotate though a full circle compared to a short to and fro action.
You are correct to say that continuous rotation servos do not allow the position to be defined and if you do need full rotation and position control a stepper would be better.
Ah yes, sorry.We are slightly changing the brush strokes, the brush will only have to go in one direction all the time. I have ordered the stepper motors and the big easy drivers. Thanks a lot for all your help and advice!