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Topic: Roll and Unroll motion with a stepper (Read 190 times) previous topic - next topic

fanny567

Hello, i'm making an art project with a Nema17 stepper motor, a Big Easy Driver, Arduino UNO and a battery holder for the Driver of 12v 2A.

What I want to do its attach a chain on the shaft of the motor (with the proper attachment) want make it roll and unroll.

That chain will be around 3 feet and will go a bin full of a liquid. It's will "unroll" in the liquid for about 1 foot, than "roll out" of the liquid for about 2 feet. It will stop for some time, for looking at the dripping from the chain. And do it again. Over and over.

All the code Ive found for the Nema and the big easy driver are for micro steps (like printer). Me I need full rotations.

The sequence should be:
Unroll -> Motor turn in one way for an amount of time
Stop ->  Stop for an amount of time
Roll -> Motor turn the other way for an amount of time
Stop -> Stop for an amount of time
----On a loop----

Do you think a Nema 17 is tough enough to carry a 3 pounds chain?

Also is this the best motor (Nema17) for it? I need something not to big and efficient to hide it in a sculpture.

Any help would be very appreciate after 2 weeks of research and nothings work :(

edgemoron

#1
Jul 14, 2017, 06:26 pm Last Edit: Jul 14, 2017, 06:29 pm by edgemoron
What will the diameter of the sprocket on the shaft be? How much will the chain in the liquid weigh? Will there be excess chain hanging on the other side of the sprocket that will counterbalance the part in the liquid? How fast will it go up and down (cm / second)? Will the speed be fixed or variable?
Might be better to use a gearmotor depending on speed and torque required.

fanny567

What will the diameter of the sprocket on the shaft be?
I was thinkin of making my own spool at the metal shop at school. The chain i use is not a gear chain but a classic link chain from hardward store.

How much will the chain in the liquid weigh?
It's hard to tell... This is motor oil. I will start with  the chain i got (3lbs) and try smaller gauges of chains until i find the good one i guess. :smiley-confuse:

How fast will it go up and down (cm / second)?
Kind of slow. About 1cm/sec. Maybe a bit less, I need to fine tune.

Will the speed be fixed or variable?
It would be nice to be a tiny bit variable in the sequence to create dynamics. Like it does the same patterns for 3 times and the fourth time it will be a bit faster. and than restart the full pattern. But if its too complicated, i prefer have something solid than dynamic...

Might be better to use a gearmotor depending on speed and torque required.
Gear motors are more "solid"? And only use around 6-24v not 120v? Do i need a driver or something for using it with arduino.

Thank you!!

Paul_KD7HB

Interesting project. I have never heard of cyber art!

I think it's time to show us a diagram to what you are making. Also, winding chain on a shaft is problematic. You need a shaft with a diameter of 4 to 6 chain links in size. Otherwise you will get abrupt winding/unwinding because of the solid chain links won't bend around the shaft.

Are you making a "loop" of chain, or is gravity pulling the chain as it unwinds?

Paul

Robin2

All the code Ive found for the Nema and the big easy driver are for micro steps (like printer). Me I need full rotations.
Stepper motors move in steps. You just need to work out how many steps you need. Most motors do 200 full steps per revolution

This Stepper Motor Basics link includes some simple advice for figuring out how much torque you need from a motor

...R
Simple Stepper Code
also look up the AccelStepper library
Two or three hours spent thinking and reading documentation solves most programming problems.

promacjoe

the problem I see with this approach is, When the stepping motor loses power, the weight of the chain will cause the stepping motor to start to turn. So you will never be able to turn off power completely for any length of time. You might consider a worm drive stepping motor. This will give you an automatic gear reduction and prevent the chain from spinning the motor if it ever loses power.

promacjoe

Another thought, You could use 2 chains instead of 1. Each moving in opposite directions. They would be controlled by one stepping motor but connected through gears. This would reverse the rotation. when 1 chain goes down the other would go up. They would be in balance. And when power was turned off, the chain would not move.

MarkT

Quote
All the code Ive found for the Nema and the big easy driver are for micro steps (like printer). Me I need full rotations.
That makes no sense to me - given enough steps or microsteps you can move as far as you like.

Quote
Do you think a Nema 17 is tough enough to carry a 3 pounds chain?
That is a question about dynamic torque rating of the motor, and requires knowledge of the mechanical
set up to calculate, specifically the width of the chain and the diameter of the drum.

Quote
Unroll -> Motor turn in one way for an amount of time
1 millisecond? 1 minute? 1 month.  "an amount of time" is not useful to us.

What speed do you want the chain to move?  (in m/s preferably)
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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