Reverse polarity

[Secureit]

How do I make a motor to alternatively reverse its action everytime power is switched on  i.e. if clockwise on first switch, anticlockwise on second switch and so on. The motor (taken out of a chordless hammer drill) runs on a 12V dc.

[Hero999]

Do you have access to a permanent 12V power supply?

If not this won't be easy because it needs to remember whether the shaft was spinning clockwise or anticlockwise when the last time the power was applied i.e. it needs to be non-volatile.

How much current does the motor need?

[Secureit]

Access to 12 V -  Yes I am using the same battery pack as a power source, which was part of the drill, which is rechargeable.
The drill also has a manual button that reverses the motion, ie used to screw/unscrew, but this is a manual button. Can this be controlled with any sort of an electrical gadget which will basically do the work of manually pushing this button. Will a contactor relay help at all?

[Hero999]

Yes it's possible, the power can be reversed using a circuit known as an h-bridge.

To alternate between forward and reverse, you need a divide by 2 counter.

You need to know the current consumption of your motor to select components for the h-bridge.

[ARUN CHOWDARY]

it will only happen when the polarity changed in the dc mortor

by using stepper motor you can do this


have you a nice day

[bobleny]

Correct me if I'm wrong, but if you reverse the polarity at the motor, won't it spin in the opposite direction? That is, if the motor runs clockwise while positive is connected to positive and negative is connected to negative, won't it run "anticlockwise" while negative is connected to positive and positive is connected to negative?

If that's the case, then a set of relays should be enough to make it run forwards and backwards. However, as mentioned before, you don't just want to slam the motor in reverse while it is going forward at full speed. You may need to add a timer to the circuit to give the drill time to slow or stop before changing it's direction.