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Topic: new to arduino, wondering about a motor control/dc motor (Read 607 times) previous topic - next topic

crankyjanky



two arms, each about 12-18in long with a 5 oz weight connected to the end.


Are you going to have some sort of containment system? Those weights are going to have a heck of a lot of energy and if anything goes out of balance or gets detached this could be very dangerous.


I don't think it will be that dangerous at the speeds I'm imagining. I understand balance is going to be really important though.

MarkT


I knew physics class would come in handy someday.  :)

I was looking at stall torque to choose that motor, the other ones on that site seemed to weak to get the arms up. I don't seem to see that specification on most of the other motors I looked at.



Torque isn't important for the arms to raise (assuming low friction), only angular velocity.  To get up to speed quickly you do
need more torque - so how quickly do you want to change angular velocity?

Multiply that rate by the moment of inertia and you get the torque required (all SI units
of course).  Little maths refresher might be required for those MoI calculations of course ;)

Oh and whatever routine torque you want the motor to supply should be quite a bit less than the
stall torque of the motor, perhaps a third or less, in order to prevent it struggling (or excess strain
on the gearing).
[ I won't respond to messages, use the forum please ]

PeterH


I don't think it will be that dangerous at the speeds I'm imagining.


What speeds are you imagining?
I only provide help via the forum - please do not contact me for private consultancy.

crankyjanky



What speeds are you imagining?


What mark said about 45RPM seems about right to me. I don't want it spinning so fast that the arms are parallel to the ground, which I assume would happen before things started flying off.



Torque isn't important for the arms to raise (assuming low friction), only angular velocity.  To get up to speed quickly you do
need more torque - so how quickly do you want to change angular velocity?


I think 0-45PM in 3-5 seconds is about what I'm aiming for. I'm quite certain I will screw this up somehow so I am assuming I may try more than one motor. So my Arduino will send a PWM signal to the motor shield, and that controls the speed of the motor?

For my purposes, a geared motor just means more torque, right?

Are there any retailers you'd recommend for parts like this? The amount of specifications given for little DC motors seem all over the place.

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