Adjustable speed motor

[Leonord]

Hello everybody,
Im a total newbie in electronics but I have a cool project idea that needs a special motor.
I need a motor with an adjustable speed.

Any ideas or help to build one?

Edit:
Seems like I forgot a lot of details.
I need a motor that can run all the time at a realy precise constant slow speed.
The motor will run a mechanical clock. Is must move a 2 meters long belt.
I want to be able to change the speed of the motor whenever I want because I dont know the final exact lenght of the belt or the dimensions of my clock.

 

[donkey]

all motors can be adjusted in speed. using pwm.
if you give us power requirements then we could possibly show you a circuit.

oh and welcome to the forums

 

[duke37]

There are many motor types which can be varied in speed, they go from cassette recorders to locomotives.

You need to specify power, speed, speed regulation, torque, voltage supply etc.

Building a motor would be very difficult.

 

[Leonord]

Is it possible to adjust precisely the motor with pwm? I need it for a mechanic clock.

Edit: I mean building the circuit not the motor xD

 

[CocaCola]

Building a motor would be very difficult.

Better stated building a reliable, high performance and high quality one is difficult...

I built one as a teen in high school for general shop, nothing to write home about I was just some hunks of steel and some winding wires, but it did spin...

 

[Leonord]

I just added the project details to the first post.

 

[CocaCola]

You need a stepper motor and a controller to run it...

 

[donkey]

if its for a clock then the simplest idea is to get a normal motor and gear down the speed, in most cases this increases torque as well.
power requirements is still not added here

 

[donkey]

you don't NEED a stepper motor, it is easier that way. but if you goto nearly any basic craft store they will have a cheap clock you can pull apart to get the basic concepts.
anyway what sort of power you looking at running it on?

 

[Leonord]

I want to plug it to 220v
I'll need a transformer of course.

 

[donkey]

a plug pack would suffice. as coca cola said the easiest way is a stepper motor. to keep it accurate you could simply put an IC in to give digital time an when the second hand or minute ticks over inside the stepper motor will move an increment. this will provide an accurate timer. I would off course put in a secondary system in case you need to adjust the time. gear ratio and torque requirements I can't give you because of 2 very important factors
a) you haven't told us size or weight yet
and b) I wouldn't have the foggiest idea of how to calculate it unless i refer to the wise old google.

also i understand you want a clock, and a belt. does the belt drive the clock or does the clock drive the belt? and if it is the latter. for what purpose?

 

[donkey]

I also had an idea regarding keeping the motor speed in check is you could use something very simple like a magnet on the side of a gear and a reed switch, whenever the gear rotates it will close the reed switch. if you use the signal to calculate how fast it SHOULD spin you could adjust speed accordingly

 

[Leonord]

Thank you very much guys. So a steeper motor with an IC (no a idea what that is).

I'll do some more research an come back when I have more details about the needed power.

To start thinking about the control unit.. Should I get first the apropiate motor or the motor specifications don't matter?

 

[donkey]

ok leonord just a quicken, an IC is an integrated chip. there are ones that are used for timing. for exmple the 555 timer. you can set these to output a signal every second (pretty precise too) and that will give the stepper motor the signal to move 1 increment.
number 2 I may be a vip on the forums here but that in no way means I am the smartest, in fact I would say I just know a few words that sound good. My idea is sound, but putting it into practise is another issue.

 

[CDRIVE]

Long before digital clocks came along just about every electric wall clock found in home and industry were driven with synchronous motors. They're designed to be RPM accurate and not intended for high HP/Torque.

http://search.yahoo.com/r/_ylt=A0oG...rop=image&fr=yfp-t-701-s&va=synchronous+motor

http://search.yahoo.com/r/_ylt=A0oG...ttp://en.wikipedia.org/wiki/Synchronous_motor

FYI, a statement made earlier in this thread is false. All electric motors can not be speed controlled with PWM.

 

[donkey]

very good observation. I meant all motors speed can be adjusted, and pwm is one way. gear ratio is another