DC motor power supply

[dsesmg]

Hi, I am trying to turn on 15 DC motors at the same time.
The specification of each DC motor is 6V and 120mA.
I have a power supply which is 24VDC, 1.25A and I used this power supply to turn on at least 10 of these motors. When I connect one motor to this power supply and test it, the motor spinned(very fast).
But, when I connected two motors to this power supply, the motors are moving but it spinned and stopped and goes like this on and on. When I connect three motors, the motors won't spin.
Could you advise me what do I have to do to get all of 15 motors to be spinned?

[Soeren]

Hi,

Are the motors identical?
Did you connect them in parallel or serial?
Do you think it's a good idea to run 6V motors at 24V?

More specs if you want useable answers, please!

[dsesmg]

Hi, Thanks for your reply.
Yes, the motors are all identical.
This is the link to their specification.
http://www.eleparts.co.kr/epdf/others/ES-311DCGn.pdf
I used two copper plates(700mm x 10mm, 0.2mm thickness). One for positive pole and the other for negative pole. I attached all the motor's positive wires to copper plate(+) and attached all the motor's negative wires to coper plate(-).

 M(+)     M(+)      M(+)     M(+)     M(+)    M(+)
-----I----------I------------I----------I-----------I----------I-----   copper plate(+)
-----I----------I------------I----------I-----------I----------I-----   copper plate(-)
 M(-)      M(-)       M(-)      M(-)      M(-)     M(-)

I guess I should call this a paralllel connection.
No, I don't think it is a good idea to supply 24V voltage to 6V motors, but I wanted to check for just a few seconds whether all the 15 motors are spinned or not. 

[Conscripted]

What you have there is indeed a parallel circuit. You stated that your motors drew 120mA at 6 volts. I didn't see that on the spec sheet you supplied so I'll assume that's the stall current. If you ran all 15 motors at stall they would need 1.8A. Running them at four times their rated voltage is going to make their current requirements much higher. If my math is correct each of your motors has about 50 ohms of resistance. If you were to run them all at 24V you would need about 7.2A. Of course the motors shouldn't be at stall all the time. When a motor is first powered up it isn't moving so it is "stalled".

Conscripted

[dsesmg]

Hi, thanks you for your advise.
Then, do I need to use 6VDC, 1.8A power supply?
Is this type of power supply commercially available?

[Conscripted]

Your power supply would not need to be exactly 1.8A it could be 2 or 2.5A. What is your application? Those motors would probably work fine at 5V and would probably run at 9V for a while.

Conscripted

[dsesmg]

Hi, my application is like this.
I connect 15 motors as I've described ealier and I also put switchs(total 15pcs) on each motors.
So, that I can turn on those 15 motors as I like(like playing a piano or something).