Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Auto/Motor Need help choosing the necessary motor for my first ever DIY project

  1. Aug 12, 2018 at 4:25 AM #1

    I have decided that no matter how many times I ask, people will always leave my bedroom door open. Therefore, I have decided to try my hand at a DYI project to create an automatic door closer. I'm aware these already exist but I'm also doing this because I've always been interested in robotics and figured this would be a fun way to get my foot in the door.

    The main things that I am struggling with is deciding how much voltage my motor will need, and what type of motion my motor will need to use. My door weights about 60 pounds and the motor will only need enough force to close it close it shut. I do not need it to open the door. How can I calculate this? Will the angle in which the door is open affect the power needed?
    Last edited by a moderator: Aug 14, 2018 at 9:04 AM
  2. jcsd
  3. Aug 12, 2018 at 6:51 AM #2


    Staff: Mentor

    Welcome to PF.

    You will need some clever mechanical design not just motor design. The angle changes very much and that's important. You also need a way to stop the motor when fully closed, and a way to sense when it should turn on.

    I suggest that you start by studying the pictures of the very many existing electric door closer. This search in google images will show you many.
  4. Aug 13, 2018 at 5:22 PM #3


    User Avatar
    Gold Member

    I would suggest a cheap alternative, but it might be too subtle. I'd look at adjustable spring hinges. If there were three on a well hung door, they will probably close it, or at least pull it very close to latched. I usually put one on doors that aren't level and want to stay open if I can't level the door any other way.


    If you install a motor to close a door, there should be some kind of safety or torque limit that prevents the door from closing on a person, pet, etc...
  5. Aug 14, 2018 at 4:00 AM #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The max force required is likely to occur when compressing the latch. Perhaps measure that
  6. Aug 14, 2018 at 7:20 AM #5
    I would just try to adapt a tray servo from a CD drive. That is made with slipping allowed, is slow, has some push but not much, also there are the endpoint switches ready...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?