simple motion control solution

pmdavis300 · Aug 21, 2010

I need an inexpensive solution to my problem. i want to connect a motor to a chain drive that will rotate a load, basically it will be a little vice contraption that will rotate a 17lb box 180 degrees. the probelm is i need it to stop within a half of an inch of that 180 degree mark everytime. my intial thought was to just put a prox switch on there to detect when the 'vice' was in the correct position, but obviously there will be some over travel and even with slightly offsetting the prox switch to compensate for the over travel i dont think i would get consistant results every time. my thought was to do a servo motor and it would just correct itself after it stopped, but thats going to cost me thousands of dollars i think.... i dont want to spend more then $500 or so. any ideas?

rev667 · Aug 21, 2010

Use a braked motor perhaps?
Fit an inverter drive?
Servo is overkill for 1/2" accuracy.

Rev

bernie_carlton · Aug 21, 2010

That 1/2 inch is how many degrees?

OkiePC · Aug 21, 2010

Unless it needs to be able to continuously rotate, a simple linear actuator might suffice.

Ron Beaufort · Aug 21, 2010

can you slow the drive motor down to a "creep"? ...

if so, consider TWO prox sensors ... the first one puts the motor in the "creep" speed as it approaches the correct position ... the second sensor actually stops the motor ...

another possible solution:

provide a simple mechanical "stop" that you can actuate to move it into position as the table is rotating - and then retract the "stop" out of the way whenever it's not needed ...

JeffKiper · Aug 21, 2010

Where are you measuring 1/2" at ? 25" from the pivot or 0.25" from center?
No servos don't auto adjust you have to program them just link you do anything else.
Do you have all the motor, gear box, & mechanical systems? $500 dollars is not going to buy you much of a system.

pmdavis300 · Aug 21, 2010

rev667 said:
Use a braked motor perhaps?
Fit an inverter drive?
Servo is overkill for 1/2" accuracy.

Rev

ya i figured so. ive never heard of an inverter drive... what is it? and ive yet to find a braked motor... what search terms should i be using to find an example of one?

pmdavis300 · Aug 21, 2010

JeffKiper said:
Where are you measuring 1/2" at ? 25" from the pivot or 0.25" from center?
No servos don't auto adjust you have to program them just link you do anything else.
Do you have all the motor, gear box, & mechanical systems? $500 dollars is not going to buy you much of a system.

1/2 from about 8in from center... im just talking about a motor for $500. i dont care about the other equipment so much its cheaper.

pmdavis300 · Aug 21, 2010

Ron Beaufort said:
can you slow the drive motor down to a "creep"? ...

if so, consider TWO prox sensors ... the first one puts the motor in the "creep" speed as it approaches the correct position ... the second sensor actually stops the motor ...

another possible solution:

provide a simple mechanical "stop" that you can actuate to move it into position as the table is rotating - and then retract the "stop" out of the way whenever it's not needed ...

cant creap, the process will need to be relativly fast. i did think of mechanical stops but i was hoping for a more practacle solution like a braked motor or something as mentioned above

pmdavis300 · Aug 21, 2010

OkiePC said:
Unless it needs to be able to continuously rotate, a simple linear actuator might suffice.

it will keep rotating in 180 degree increments, 360 per cycle then start cycle over again from that point

bluebyu · Aug 21, 2010

How about a brake clutch in the drive train?

See this link for one brand of many;
http://www.southernpower.com/nexen/nexen.cfm

Alot of info is missing to get good answers:
How fast?
HP of current/proposed motor?
How many start/stops per min?

pmdavis300 · Aug 21, 2010

bluebyu said:
How about a brake clutch in the drive train?

See this link for one brand of many;
http://www.southernpower.com/nexen/nexen.cfm

Alot of info is missing to get good answers:
How fast?
HP of current/proposed motor?
How many start/stops per min?

not sure yet of any of those... i would like to get a 180 degree rotation in maybe .5-1second
thinking maybe 1/2 hp??? load is 17lbs.

pmdavis300 · Aug 21, 2010

by the way thanks for all the good ideas, im not really sure of what is out there since im relativly new to all of this. thanks for you help so far.

DickDV · Aug 22, 2010

Do a google search for "brakemotor". It's your best and simplest answer.

Do not use an inverter drive. You will have to add braking resistors after buying the drive and then you have to program the drive. Way more complex than necessary.

If wearing out the brake disc on the motor is an issue, you might want to consider a DC injection brake. This is an inexpensive electronic device that connects to your starter and shoots DC into the motor when the starter opens. The DC makes the motor stop turning almost immediately without anything wearing out. Braking intensity and brake on time is adjustable.

gas · Aug 22, 2010

I would think "mechanical" and not "control".
A 180 deg pneumatic actuator and valve should cost less than 200 bucks. That will still leave you 300 bucks for machining and maybe enough left over for beer.

simple motion control solution

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