Suggestions / Help for Project

RE*AC*TOR

OK, I hope this is the best forum to ask this question - if there are better please move etc. I couldn't find one more suited...

What I want to do:
I have 1 screw (flat) that I want to make very precise timed manipulations to.

For example over a 30s time period. 5s 2 cw revolutions - 15s 1ccw revolition - 25s 1cw revolution.

Apart from doing this by hand, I'd like some suggestions on how this might be possible to do mechanically (by someone with minimal electronic experience).

I'm thinking there must be some sort of motor / control board configuration.

Hope this makes sense.

coolwings

You don't give much idea as to how much torque is required.
If the screw you wish to adjust is "friction free" then a longer screw can be installed in it's place, with the extended length carrying a pulley, locked both sides by a hex nut, and then the lower sections doing the work of the existing bolt.
Then it's easy to put a drive band on from the relatively large pulley, driven by a motor turning a low torque tiny pully.
Alternatively the meccano contrate gear could be put on the screw top, and a motor driven meccano worm gear would rotate it slowly. Control could be by variable voltage power supply, or an electronic speed controller controled either by servo tester or RC and receiver.

A potentially useful ready made part is a modified RC servo designed to be used for rotating radar arrays in RC scale boats. Ordinary RC servos swing 60 - 180 degrees and must turn back, but the type I am referring to rotates at a slow speed indefinitely.
In effect an easily controllable slow rotating motor.

In Dublin Greenhobbymodel.com do those kind of parts.

A servo testing unit connected by a cable of whatever length would control rotation rate and direction. A 4 cell battery pack gives the correct power to make such parts work.

RE*AC*TOR

Torque... hmmm

The screw can't move freely, nor actually is the screw a screw, moreso a screw head on a valve adjustment.

The screw-head can be adjusted by hand with moderate-low effort by an adult. That doesn't give much indication of a precise amount of torque, but it's probably considerable.

I was thinking a stepper motor, perhaps some kind of usb control board... but as you may have gathered I'm quite ignorant of the area.

Ideally these adjustment would be automatic, so for example at the push of a button, a timed sequence would occur. This is what got me thinking of USB control - do some programming on the computer side of things.

Further thoughts? Would the motors you mentioned have sufficient torque (I'm thinking no)?

loopingfred

Hi,

Servo motors are not precised enough for what you are trying to achieve I think.

The best thing as you said, is to use steper motors.
They can be easily software controled, but you will need an electronic card between the PC and the motors.

To give you some ideas, have a look here :

CNC cards :
http://www.axemotion.com/eng/index.php
http://www.techlf.com/ (I have a CNC4AX from them.. Very good stuff!)
http://www.driver-motor.com/
http://www.cnczone.com/

And google will gives you zillions more !

Softwares :
Depending of what you want to do, you may have to make your own (most of the cards works in G-Code) or use an existing software to adapt it to your use.
I use Ninos myself (can control the steper manually if you want...) but you have loads more ! Galaad have a programing option integrated...
Same, a google with what you want to do will give you loads of options I believe...

Hope this help.

Fred

coolwings

You can use a stepper with programming card and software.

You might also consider an analogue motor (or servo) with mechanical block/stops and a power stall current detector shutoff (how the window motor shuts down in an automobile when the top is reached). This is a basic circuit with no software. Less elegant but would also get the job done.

RE*AC*TOR

Thanks for the suggestions and tips guys. I have some research to do.