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Anonymous Poster

Automatically change the rotation of the miniature motor

01/09/2007 3:18 PM

hi all,

I am wondering if there is a way to change the direction of motor rotation (DC miniature) automatically? I am trying to set up a tube the dips reapetedly (up and down) into a solution by motor action. what would be the easiest way to do that?

thanks much for the help

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Anonymous Poster
#1

Re: Automatically change the rotation of the miniature motor

01/09/2007 6:33 PM

if you dont need it to dip at some exact time, just use a cam.

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Associate

Join Date: Dec 2006
Posts: 26
#2
In reply to #1

Re: Automatically change the rotation of the miniature motor

01/10/2007 12:44 AM

yeah, use a reciprocating mechanical arrangement. thats far simple and easier.

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Anonymous Poster
#3

Re: Automatically change the rotation of the miniature motor

01/10/2007 1:34 AM

As an alternate, you can use pneumatic cylinder arrangement with solenoid valve and timers.

But mechanical cam arrangement would be low cost solution.

LIMBKAR

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Power-User

Join Date: Dec 2006
Posts: 441
Good Answers: 20
#4

Re: Automatically change the rotation of the miniature motor

01/10/2007 9:50 AM

Think of a square wave power supply. You can adjust the amplitude symetrically for negative and positive as well as the frequency. Seems to me I remember an old Wavetek oscillator we used in school. It was capable of 10 second periods with amplitudes of 10 volts at 300ma. I think the model number was 175. Surely by now some IC mfr has reduced this to a chip.

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Guru

Join Date: Dec 2005
Location: Wisconsin USA
Posts: 824
Good Answers: 37
#5

Re: Automatically change the rotation of the miniature motor

01/10/2007 9:56 AM

Old toy trains (Marx. Lionel, etc.) that had a three-rail track system (1950s vintage) used a mechanical toggle that switched polarity every time the train stopped. This was needed because they ran low-voltage AC motors, with the two outside rails as "ground" and center as power. The next start would always be in reverse, if you had been going forward. To go forward again, you'd back up for a second, then stop again. The arrangement was sort of like the ball-point pen action, with alternate clicks to extend and retract. In a Rube Goldberg set-up, you could wire a solenoid into the motor's power supply, and have it operate a ball-point mechanism, with the ball contacting a switch. But there are push-push switches that would do that part for you more reliably, and I think you can find relays that will accomplish the same alternating polarity output.

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Anonymous Poster
#6
In reply to #5

Re: Automatically change the rotation of the miniature motor

01/10/2007 4:19 PM

thanks much for the help, great forum you have here

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Guru
Australia - Member - New Member Fans of Old Computers - H316 - New Member Hobbies - Model Rocketry - New Member

Join Date: Jun 2006
Location: Port Noarlunga, South Australia, AUSTRALIA (South of Adelaide)
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#7

Re: Automatically change the rotation of the miniature motor

01/15/2007 8:16 AM

One solution is to use a stepper motor. The circuitry is more complex since you need to step between four phases one at a time but there are advantages. Firstly the speed is controlled by the speed that you switch between phases so there is no complex current control circuitry. Secondly if you keep count of the number of forward or backwards steps you know the position of the motor which means you don't need any positional feed back circuitry. You can buy chips that have everything built in to control stepper motors off the shelf so you can actually achieve the end result with buy off the shelf electronics, all you need to do is wire it up and program the controller.

Sorry for the slow response, I have gotten a bit bogged down with a couple of other threads and am now only catching up with last weeks mail outs.

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