# Reverse rotation twice a second

Discussion in 'Homework Help' started by Danny Vain-Nielsen, Oct 26, 2015.

1. ### Danny Vain-Nielsen Thread Starter New Member

Oct 26, 2015
4
0
Hi all!

I'm a an engineering student, and I don't know a whole lot about DC motors. Is it possible for a DC motor to reverse rotation twice a second? We need that kind of movement for a shaft. We might also have to make the rotational angle adjustable, meaning sometimes 180 degrees, other times 150 degrees. Is that possible and easy for a newbie to program?

Jul 18, 2013
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Depends on the inertia of the armature and the load.
Do you intend accurate positioning?
If so you either need PID feedback or use a stepper motor.
Max.

3. ### Danny Vain-Nielsen Thread Starter New Member

Oct 26, 2015
4
0
The torque is quiet heavy. 57 NM. Do you know an easy and inexpensive way to doing this?

4. ### joeyd999 AAC Fanatic!

Jun 6, 2011
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A linear actuator?

Jul 18, 2013
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57N-m, That is a considerable load, I envision some kind of gearing to use an small motor.
Is it possible to use a linear actuator to operate a small rack with a pinion on the shaft.
You may want to employ one of the free sizing programs to get an idea of sizing.
Such as Kollmorgen graphical motor sizing.
Max.

6. ### joeyd999 AAC Fanatic!

Jun 6, 2011
2,757
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Why rack and pinion? Sounds like he just wants to move a shaft. Direct drive from the actuator.

7. ### Danny Vain-Nielsen Thread Starter New Member

Oct 26, 2015
4
0
I asked a big company doing linear actuators and they had none, that could move so fast.

Jul 18, 2013
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Smaller linear actuator with extra gearing, there has to be some kind of linear to rotary connection anyway.
Max.

Jul 18, 2013
10,858
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How did they assume you were transferring to rotary?
Max.

10. ### crutschow Expert

Mar 14, 2008
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Here are some high torque stepper motors (up to 50 Nm), but I don't know their cost.
You could likely use one of those with a gear reduction to increase the torque.

11. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,791
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What about a mechanical solution like a crank so you never need to change direction but get the same motion effect..

JohnInTX and shortbus like this.
12. ### Biff383 Member

Jun 6, 2012
49
19
30hz for any motor seems to be asking a lot. Maybe better to think about a solinoid? Way simple in the US. Not all that difficult in the rest of the world.

Sep 20, 2005
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14. ### crutschow Expert

Mar 14, 2008
13,505
3,382
Where did you get 30Hz?
The OP wants twice a second or 2Hz.

15. ### kubeek AAC Fanatic!

Sep 20, 2005
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Probably mistaken for 30 RPM.

Jun 6, 2012
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Yup.

17. ### Biff383 Member

Jun 6, 2012
49
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Oops.

Jul 18, 2013
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I have a large NEW unused Bayside precision planetary through-hole gear box 15:1 with 180Nm output.
The original cost was around \$2000 yours for \$150.00 + shipping.
Max.

Last edited: Oct 27, 2015
19. ### Danny Vain-Nielsen Thread Starter New Member

Oct 26, 2015
4
0
We will look at it... our budget is around 6500 € for everything the machine needs. But the school want us to buy only from wellknown companies.

I think the solution is to choose a 400 W DC motor and install to a constant speed at 60 rpm and then making a crank to get the forward and backwards movement.