how to make a motor vibrate ? for silent alarm

I've searched the net, for help on this, and was wondering if anyone can point me in the right direction as to where i might read up on making a motor vibrate/oscilate(is it ?) will be using hopefully a standard 9v battery in line with the rest of the circuitry i have.

Any help, advice and pointers are appreciated.

Probably be best to use an existing vibrating motor out of a control pad or mobile phone??

The vibro-motor have an half-disk as unbalanced weight.See my primitive pic...

I agree with Sebi, if you already have a motor, the way you make it vibrate is by adding a weight that's off center, usually either a bar, or a semicircle.

If you don't already have a motor you can pick up a pager motor for under $5 from most online stores.

I made one of these recently. They wanted a vibrator with a variable frequency output for research. I used a little DC motor and fitted a disk to the shaft. The disk had a hole drilled at one side to unbalance it.
Touching a spinning disk accidentally does not hurt as much as a spinning bar or anything else not round .
This was fitted inside a block of plastic so it could be handled easily.
The frequency of the vibration is changed by altering the speed of the motor which is done simply by varying the voltage.
Its only 'silent ' when held in the hand, if put down on a desk it will hum loudly.

Klaus

P.S. Don't un- balance it too much, those little motor shafts and bearings are not designed for that sort of abuse :wink: