Is stepper motor self locking?

[georgio17]

When a pulse given to the stepper motor it will move to a particular position, on reaching that position if i do not pass any current will the motor move due to the weight it is supporting or will it remain in the same position?
Or do i have to continuosly pass current to keep it fixed in that position??
Thanks..

 

[alexan_e]

If you try to rotate the motor by hand you get a feeling of steps but doesn't take much effort. In order to actively lock the motor in place you have to provide constant current to the coils.

 

[Analog Ground]

Here are some comments often related to your question. Some stepper controllers and drivers have a feature which reduces the motor current when holding a fixed position. Often the current required to accelerate the load is a lot more than required to hold the load. Sometimes a separate electro-mechanical brake is used to hold the load using no power then energized to release the load during motion.

 

[electronicsensation]

Stepper motors requires holding current to stop in fixed position. If you remove that holding current or put excessive amount of weight then it will rotate. Disconnect it from controller and try to move it, you will get the answer.

 

[georgio17]

Thanks.. is there any method i can make it self locking without pasing current as i want to make it efficient..
I am designing a dual axis solar tracker and my fear is that the losses will be more that what i can acheiveon implementing the dual axis tracking..

 

[electronicsensation]

I am personally not aware of any such method because stepper motor in principle is an electromagnet which means if there is no current then motor will rotate freely. Can you give some information on motor, driver and weight?

 

[thylacine1975]

Permanent magnet type stepper motors can be made a lot "stiffer" at rest by simply shorting the windings together, which is a nice zero-quiescent-current solution that might work for you. Currents induced in the shorted coils by attempting to rotate the armature oppose the applied rotation.

The alternative suggested by AnalogGround is often used in electric wheelchairs & mobility scooters - an electromagnetic brake (which is usually a solenoid/clutch type mechanism) is applied when the motors are de-energised. The braking mechanism is incorporated into one end of the motor assembly. Some begging around a wheelchair repair shop might turn up a bargain or two