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Stepper motor!!
Stepper motor!!
8/1/08 6:08 AM
Hi,

Iam supposed to use a stepper motor for my design which will drive a lock( Home door locks ). I already have a piece which i had used for the project earlier. But the problem is that it needs an external driver circuit. Now since i haven't got any data sheets iam not sure about the current rating. Neither was anything mentioned in the motor. I simply new the four set sequence to get it rotating. Unfortunately i had borrowed the driver circuit, which i can't get hold of now.

1. Is there a possibility that PIC will be able to drive it ?

2. If incase the above doesn't workout ( which is likely)- what are some cheap alternatives? I found some parts at the Digikey website, but they require a driver too.

I don't mind using a driver circuit- but the problem is that it increases the hardware size. I need to keep it to a mimimum as the entire design should fit into a tiny lock.

Regards,
Kauser.
RE: Stepper motor!!
8/1/08 1:22 PM as a reply to kauser.johar .
A common solution is not to open/close the lock itself, but make the strike plate open up instead. The first search example I could find is Electronic Door Strike Latch where you simply energize a solenoid in the unit to open to door.
RE: Stepper motor!!
8/1/08 1:24 PM as a reply to kauser.johar .
Depending on the current rating for the motor, you can use readily available H-Bridges from digikey, such as the LMD18201T-ND H-Bridge, use 2 of these to interface the stepper to the Pic, requires only 2 external .01uf caps to operate, and have the pic do the sequencing..... I have used the UDN2998W dual H-Bridge, which is no longer available from digikey.... I've used these H-Bridges in many of my projects, and had a Pic16F84A do the step sequencing.
RE: Stepper motor!!
8/2/08 1:41 AM as a reply to kauser.johar .
Have you considered solenoids? With many of them, you can remove the spring (if there was one at all), and use two; one to push and one to pull. You might even be able to use it similar to a key tumbler; one pushes from the door into the jamb (lock); one pushes from the jamb to flush with the door (unlock). Solenoids tend to pull instead of push, so it may take some linkages.
RE: Stepper motor!!
8/2/08 12:56 PM as a reply to kauser.johar .
well maybe instead of "re-inventing the wheel", you should probably just use an electronic door strike plate like Darell mentioned. That is how all electronic door locks work that I know of and the security issue has already been figured out, so all you would have to do is activate the solenoid in the strike plate, much easier to accomplish. You would have to use quite a large stepper (NEMA 23 atleast) to push or pull a deadbolt into the door jam, which I doubt you can fit in a small enclosure in the locking mechanism.
RE: Stepper motor!!
4/22/10 4:40 AM as a reply to bmorse .
Can I use the udn2998w to drive a simple motor and reverse the polarity going to the motor with one of the input pins on the udn2998w ?
RE: Stepper motor!!
4/22/10 10:50 AM as a reply to Harold .
Harold:
Can I use the udn2998w to drive a simple motor and reverse the polarity going to the motor with one of the input pins on the udn2998w ?
]

Your choice for a UDN2998W, is excellent choice for your project.
The device can be used to drive solenoids, small DC motors, bell
circuits, steppers, ultrasonic generators and the like.

And as you get more experienced, you will find many more
unique applications for the device.

As to the specific implementation take a detailed look at page
4 of the Allegro Data Sheet and study the phase and enable
diagram.

Good luck with your creation.

Alfons:

UDN2998 A fine Allegro product, the very best from USA.
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