help: need 60-300 rpm motor

I need a small low rpm variable speed motor/controller. the speed must be variable be able to go from 60 to 300 rpm. I don't know anything about
motors, so I don't know if it should be dc or ac,etc
All I know that the rpm must be pretty exact and it must be variable.
suggestions? urls?
tia shockie B)
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How much power/torque do you need? Does it need to be continuously variable, or would pulleys work? How much can you afford?
My first thought is a variable-speed drill.
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dan:
power and torque i think are irrelavent in this case. what I want to do is attach some rotor blades to it and the motor needs to variable from 60/120/180/240/300 rpm or more.
shockie B)

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You've had some good suggestions by other posters. A stepper motor with drive is available from All Electronics for $25. It's a kit, but I've built other stepper driver kits (not this one) and they're [retty simple. If you need *exact* speed control, you're going to need some sort of controller that has a feedback mechanism - a tachometer or encoder attached to the motor shaft. If "close" is good enough, if it doesn't matted if the motor slows slightly under load, then a simple controller would work. How do you determine speed? The old-fashioned way was a stroboscope. There are also non-contact optical tachometers. If you want cheap-and-dirty (hey! a CHAD tach!), you could print out either a wheel or a strip with properly spaced lines. Under a fluorescent light (or neon bulb), with the right dimensions, the lines will appear to stand still.
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I had considered a 0-1400 rpm variable speed drill, but how would I be able ensure that I am at a specific rpm? and stay at that rpm?
shockie B)

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how about this one or similar:
http://www.smartbargains.com/go.sb?pagename=prod&deptidt&isrw=2&catid 8&prodidp10275257&aidu
says ;
Two-finger trigger and lock-on switch
does that mean I can rev it up to a certain rpm and click a swicth to keep it at that rpm?
shockie B)

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Only if you don't care about repeatability. That is just a friction lock on a slide potentiometer.

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I need repeatability...
shockie B)

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Ok here is a couple of eBay hits.
This will be a good control ~ http://tinyurl.com/98gt4
This should do the trick for the motor ~ http://tinyurl.com/9s3qw
From this point you need a 24v supply, and an enclosure to mount the drive. Then power the thing up, Pick a point on the potentiometer, measure the RPM and mark the setting.
Hope this helps

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Oops, goofed on the speed, but I'm pretty sure you get the idea.You just need to find a motor that has a max speed of 10-15 percent higher than your need.

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thanks Al, thats the kind of stuff I am looking for..
shockie B)

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Ok, that one is wide open.
How much torque do you need? How repeatable/accurate do you need to be on the speed? Do you need constant torque across the speed range? Do you have a weight limit?
And most importantly, how much do you want to pay?
Here is a couple of ideas
Search eBay under the string "servo motor" I just did and there are several motors and amplifiers available.
I also checked McMaster and there are several motor and controller combinations you can assemble. Although I was not able to get any workable combination for under $300.
Or you can buy a electric RC drive motor and a variable speed drive and then hack a circuit to replace the receiver.
Along the same lines as the RC solution, I understand some model train enthusiasts use PWM (pulse width modulated) speed controls you can control a tiny DC motor with.

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--
Jim Yanik
jyanik
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al:
I found this page about little LEGO motors and they seem to have the rpm range that I am looking for...
Can I assume that by altering the voltage I can control the rpm? Or is that what a motor controller does?
shockie B)

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In some cases altering the voltage changes the speed. I won't go into the theory, but if all you do is simply reduce the voltage you will reduce the torque the motor can deliver. at some point the torque available will drop below what is required to turn the unloaded rotor.
The controller uses full voltage all the time and, keeping it simple, switches on and off real fast, thus lowering the voltage the motor "perceives". This is called PWM or pulse width modulation.
The rapid on/off cycling can often be perceived as a whistling sound.
Hope this helps.

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www.google.com your hindass.
On Thu, 04 Aug 2005 01:09:22 GMT, "shockwaveriderz"

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