Hard disk motor gyroscope and SATA pins

[rput]

Hi,

I am looking at making a gyroscope from a hard disk motor and am having some problems powering up the motor. After a few nights of internet searching and testing I still have no solution and am feeling quite stupified..

The issue I don't understand is that the motor spins when I plug in the 15 pin SATA power connector from the PSU. However, when I apply the 12,5, and 3V dc on the SATA pins directly, there is just a clicking sound but no spinning.

I also tried directly applying a RC speed controller on the motor (it has 3 leads) with the pcb removed, but get the same clicking sound.

I read about the SATA pin 11 being an open collector signal that controls spin up, but am not sure if this plays a role, and how I should deal with it. If anyone is able to help me, that would make my day!

Hard disk: Seagate Barracuda 7200.9

 

[CocaCola]

The issue I don't understand is that the motor spins when I plug in the 15 pin SATA power connector from the PSU. However, when I apply the 12,5, and 3V dc on the SATA pins directly, there is just a clicking sound but no spinning.

Are you connecting it correctly? All the rails including ground attach to multiple pins, each voltage is carried on 3 pins, and ground is also carried on 5 pins because the connector is too small to carry the load...

I read about the SATA pin 11 being an open collector signal that controls spin up, but am not sure if this plays a role, and how I should deal with it. If anyone is able to help me, that would make my day!

Pull this pin low (tie it to ground with say a 10K resistor) if you want the motor to spin up without being told to by a host to do so... If you leave this pin floating the drive is in stand by mode and waiting for the host to tell it to fire up... This allows a smart power supply to stagger the start time of drives so there is no huge simultaneous initial power surge when booting...

 

[rput]

Thanks for the quick response!

I use a cut-off SATA connector to connect the voltages and ground. I havent tried the resistor yet, but that sounds it may help. Does the PSU apply this as well?

 

[CocaCola]

Thanks for the quick response!

I use a cut-off SATA connector to connect the voltages and ground. I havent tried the resistor yet, but that sounds it may help. Does the PSU apply this as well?

The spin up pin can be controlled by the power supply (usually it's this way) or the hard drive itself, either or, or both... If the power supply doesn't supply the spin up signal (grounding this pin) then when the drive is actually asked by the host to do something it will ground the pin itself and spin up...

 

[rput]

Unfortunately that did not work. I added a resistor between the ground and the 10-11-12 pins. Should it be only to the 11? But then the psu should not be able to make it spin as it is connected in the same way.

 

[CocaCola]

Try grounding pin 11 directly to 10 or 12 without a resistor...

Pin 1 2 3 = 3.3v
Pin 4 5 6 = Ground
Pin 7 8 9 = 5.0v
Pin 10 = Ground
Pin 11 = Spin up, pull low to ground
Pin 12 = Ground
Pin 13 14 15 = 12.0v

If it spins up when connected to the power supply with only the power cord (as you stated) without the data connection cable plugged in, then doing the above hookup will 100% mimic the power supply and it should act the same exact way...

 

[rput]

Ok, after some more trial and error I seem ot have isolated the problem: my alligator clips.....

When I hook the power directly to the PSU to the SATA pins it works, but when I use alligator clips it doesn't. My conclusion is that they are too small to pull the required current. Would you agree with this, or can there be an other explanation?

 

[CocaCola]

There could be an issue with your connection yes, what I posted above will act just like the power supply when done, the fact you claim it isn't suggest that yes yo have a faulty connection or some other issue...

 

[rput]

Thanks CocaCola for your help, I was able to solve the issue!

A final update:
The alligator clips were not sufficient to provide the required current to the motor. When I added second clips to the 5V line and GND it worked as expected. The 3V line was not necessary to get the drive to spin up. Since I did my R/C speed controller also with the clips, I repeated that with proper wires and it works like a charm.

The only issue I have now is that I just realized the motor is integrated with the drive chassis. This means I can not take the motor out other than cutting the chassis around. Oh well, I will not bother you with this issue.

Thanks again, and good night!