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I am in need of assistance regarding electric motors.

I am planning on making a electric powered vertically sliding pet door.  I have all the mechanical and pulleys etc worked out but am ignorant regarding small electric motors. I am very competent regarding wiring and circuits/relays etc, only issue is the power for the unit.  I know they sell units like this but i want to build my own.  I need the motor to move slowly one way and stop when i cut power using a switch and when next powered to reverse until the switch cuts power so on and so on.  Any ideas as to where I can purchase a motor such as this?  Radioshack has zilch, so i assume I am going to need to go online.  Any help on this would be greatly appreciated. I have been planning this in my mind for quite a while, generally right around the time the dog door breaks in the dead of winter.  Thanks for any help!
Joe

Here's a circuit that will do what you want. Add a "door edge" limit switch too, in series wityh the lower limit switch
Hen door.jpg
frollard5 years ago
A simple dc gearmotor can do the job for you...

See image: If you put a limit switch on one A wire and one C wire (top limit and bottom limit) you have a reversible motor that won't go too far.

Add an extra limit switch on the bottom of the door to stop it cutting your pet in half (on the down circuit)
dpdt.PNG
For linear actuators there is this trick popularly used by persons building homemade CNC machines, and that trick is to make a jackscrew
http://en.wikipedia.org/wiki/Jackscrew
from a piece of bolt stock, and drive this to move a sliding tray (in your case a door) which is attached to a nut that rides on the jackscrew.  An example of this trick is shown in the 'ible linked below.
https://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Milling-Machine/#step3

For the motor which drives this jackscrew, I recommend an gear-motor pulled out of a car.  For example, most cars, both modern and ancient,  have a geared-down motor which drives the windshield wipers.  Also, depending on the car, you might motorized actuators that move the windows up-and-down, or adjust the seats back-and-forth, etc.   You can buy these gear-motors from surplusmongers, like:
http://www.electronic-goldmine.com/
or used on Ebay, or from U-pull-it type partsmongers.
http://en.wikipedia.org/wiki/Wrecking_yard
  Better yet if it just so happens that you own a car, or have a friend with a car,  then can just extract one of these gear-motors from your, or your friend's car.  You might think that your friend might get mad at you for stealing a window actuator from his or her car.  But once you show your friend the really cool motorized pet-door, I am sure he or she will understand.
;-)

Oh I almost forgot the best part.  A while back, in the Answers forum, I noticed that Steveastrouk uploaded a really plausible looking diagram for driving a motorized door up-and-down, using a 12 volt DC motor, 2 limit switches, 2 relays, and two normally-open push buttons (i.e. one button makes door go up then stop, and the other button makes the door go down then stop.)
https://www.instructables.com/file/F6GADCMG825CSAV/
https://www.instructables.com/answers/Limiting-Switch/
Try a model shop and find a chunky servo motor