The basic idea is to replace the deck with one another deck with rotational mechanism.
Please see the attached pictures. They are the side and front views of my design.
R1 = Distance from the center point to the edge of Cradle
R2 = Distance from the center point to the edge of Platform
Center point of R1 and R2 should be same.
Thickness of gap = R2-R1
I have to use a timing pulley on the motor and one on the deck shaft, connect these two with matching timing belt.
I can hide the timing pulley from the deck shaft in the side of the box.
Requirements for the motor:
constant speed
really accurate (200 steps/rev or 400 steps/rev)
very quiet
powerful enough (Holding Torque)
Do you think that Nema 17 and Adafruit Motor Shield V2 are the good choice??
The "cradle" will most likely be made ??of wood or metal..
Note the voltage rating of the motor (3V) . Adafruit motor driver,
instead of a L293D darlington driver, we now have the TB6612 MOSFET driver: with 1.2A per
Since you have mosfets on the Adafruit motor driver, you can use a motor supply voltage of 4.5V.
You can use one of these for your motor voltage and power it with a 12V rechargable gel cell battery.
You certainly CANNOT power your motors from the arduino 5V regulator so you will need a separate motor power suppy anyway.
The advantage of a dc to dc converter like this is that it allows you to use a commonly available voltage (like 12V) and reduce it with the voltage adjust pot on the dc to dc converter.
I am not commenting on whether that motor is suitable - it may or may not. Have you measured how much torque you need?
It is very important to realize that the voltage rating for stepper motors is largely irrelevant - it is normal to run motors at a much higher voltage than the nominal figure. What matters is the coil resistance and the maximum current.
A motor shield or an L298 is a poor choice for controlling a stepper motor. You should use a proper stepper motor driver shield such as the Pololu DRV8825 which should be suitable for that motor. Using a proper stepper motor driver board will allow you to power a nominally 3v motor with 12, 24 or even 36volts to get much better torque at higher speeds. The stepper motor driver board can be set to limit the current to prevent the high voltage from frying the motor. The proper stepper motor driver board also makes programming much easier.
Stepper motors tend not to be quiet.
Also note that the holding torque only applies when the motor is stationary. The torque decreases as speed increases.
The only parameter available to me is the load. I have to control the load of max 0.7 kg (cradle with decks).
I intend to rotate the mass, not lift, neither slide it.
I have to hide the motor on bottom of the box and therefore use timing pulley and timing belt to connect them.
I don't know yet the values of diameters.
The speed of rotation would be constant and low (for a full revolution cca 5s) and without acceleration.
For this stepper motor the torque is:
HOLDING TORQUE: 48 N.cm Min
DETENT TORQUE: 2.2 N.cm Max
Does this torque would be enough to rotate the load?
potter3366:
The only parameter available to me is the load. I have to control the load of max 0.7 kg (cradle with decks).
I intend to rotate the mass, not lift, neither slide it.
Does this torque would be enough to rotate the load?
The data you have given is not sufficient to answer that question.
For example, if the load was mounted so it was perfectly balanced and you have very low friction bearings you would only require a tiny amount of torque once you have the thing up to speed.
On the other hand if most of the 0.7kg is on one side it would be like lifting and dropping the mass repeatedly.
And you might have crude high friction bearings.
Make a reasonable mock-up and measure the torque.
My GUESS is that the motor would be adequate - but don't come to me for your money back if I am wrong.
Measure it. Perhaps google "measuring torque"? drum, thread and small weights-basket
is one way. Once measured, double the value to give a good margin of error.
Also the MoI (moment of inertia) would be good to know, it will affect the max acceleration rate. Torque = MoI x angular-acceleration
