Motor to Open a Door

Thread Starter

Lawrence H

Joined May 6, 2019
98
Hey! I have a few of questions, that might lead to more questions.

I am looking for a motor that could handle turning a basic 8mm x 8mm door handle shaft that goes into your average interior or exterior door. What type and model of motor would you suggest I get?

The other question is, that I might want an unintrusive retrofit system to turn a lock mechanism that is 4cm x 1,5cm in size. What motor would you suggest for this? I could use two motors to push on either end of this lock, or use just one to turn it.

My last question is, what are the things that secure something to the shaft of a motor so that you can actually use the motor? I would need some of those in order for this system to work, and I am having a hard time correctly googling what it actually is, and, if I find something, to know that it would actually work as intended.

I don't necessarily need a full set for this project since I like figuring things out, but if you have some examples you have made yourself or know to work, it would be nice to have a look at them to begin understanding what I need to know. Please remember that I am not a professional.

Thanks!
 

MaxHeadRoom

Joined Jul 18, 2013
25,229
A small geared DC motor should do it, it may not be intrusive though.
I recently picked up some surplus Automotive geared seat motors that would definitely do it.
 

Reloadron

Joined Jan 15, 2015
6,587
Rather than using a motor to turn the shaft all of which would be mounted on the door you may just want to consider an electric door strike. The strike is the part mounted on the door frame. The link is merely an example but such units are very common and come in a variety of voltages. Removing for example a door knob and mechanically linking a motor drive on the door will be a challenge.
My last question is, what are the things that secure something to the shaft of a motor so that you can actually use the motor?
Commonly called a coupling which won't be easy going from a square (door mechanism) to whatever motor shaft you have.

Ron
 

MrChips

Joined Oct 2, 2009
26,151
Agreed. If you want to unlock a door you need to rethink the locking mechanism.
You would use an electrically operated dead bolt as found in keyless door locks.
 

Thread Starter

Lawrence H

Joined May 6, 2019
98
Agreed. If you want to unlock a door you need to rethink the locking mechanism.
You would use an electrically operated dead bolt as found in keyless door locks.
The thing is, I can't touch the locking mechanism itself. At most I might be able to add a handle, but even that is probably not going to happen.

So this is why a simple bolt won't do unfortunately.
 

Reloadron

Joined Jan 15, 2015
6,587
The thing is, I can't touch the locking mechanism itself. At most I might be able to add a handle, but even that is probably not going to happen.

So this is why a simple bolt won't do unfortunately.
So yu can't use an electro mechanical door striker. You need to work off rotating a door knob mechanically linked and on the subject door?

Ron
 

Alec_t

Joined Sep 17, 2013
12,822
If you intend driving the handle shaft both clockwise and anti-clockwise, removing the interior centring springs from the door handle mechanism will reduce the motor torque needed.
 

Ya’akov

Joined Jan 27, 2019
5,683
Maybe instead of rotating the shaft with the motor, you could pull a lever attached to it with a solenoid or linear actuator.
 

MisterBill2

Joined Jan 23, 2018
11,927
The task is not as simple as you hope. And to add the motorized operation of an existing knob or lock-set will be either rater large or quite expensive. Small gear reduction motors with that torque level cost a lot, even as surplus.

Investigate the service manuals for hotel room door systems to understand the reasonable mechanisms. Those systems are quite different from normal hardware.
 

Reloadron

Joined Jan 15, 2015
6,587
Something to keep in mind. Figure the rotation of the shaft needed. Once your motor reaches that point it needs a stop mechanism in place. Once the door is open you need to reverse things to have the latch bolt return to the closed position and again with a stop. You are going to need a way to limit the motor travel be it limit switches or any mechanism of your choice. This project is not quite an easy undertaking.

Ron
 

LesJones

Joined Jan 8, 2017
3,712
How much torque is required to turn the shaft ? How many degrees of rotation is required ? (It does not need to be very accurate. For example our internal door handles rotate through about 45 degrees.) Do you need retain the option to still operate them manually ? Are you allowed to use screws to fix the motor assembly to the door ? Some pictures of the existing door lock / latch may be helpful.

Les.
 

MisterBill2

Joined Jan 23, 2018
11,927
A crank plus a tension element plus a ever are the simple scheme to operate a standard doorknob/lever scheme. That arrangement will still allow manual unlatching if any portion of the powered system fails. The down side is that it would not be hidden and it will not be pretty. A leadscrew arrangement mounted inside the door could be created to retract the bolt, but it would certainly not be simple, nor would it be easy,
A simple alternative that wi work well with non-pick -resistant doorknobs would be a mechanism to push the latch bolt back into the door so that the door would be released. That mechanism would be built into the wall and be hidden. The same concept will not work for any held-in-extension lockbolts.
So probably the TS wi need to spend a lot on some commercially made products. Most of them do have the advantage of still allowing manual operation in the event of power loss or product malfunction.
 

MisterBill2

Joined Jan 23, 2018
11,927
From post#7, it seems that the TS is not permitted to make modifications, such as the rules in a rental property will dictate.
Thus most of the suggestions thus far are not very applicable. More information, and possibly a photo will do a great deal towards clarifying the details.
 

Reloadron

Joined Jan 15, 2015
6,587
Well just maybe if the thread starter returns and provides more information including a picture and some dimensions better suggestions can be made. Till such time it's anyone's guess. They have no shortage of suggestions.

Ron
 

MisterBill2

Joined Jan 23, 2018
11,927
Well just maybe if the thread starter returns and provides more information including a picture and some dimensions better suggestions can be made. Till such time it's anyone's guess. They have no shortage of suggestions.

Ron
And now, one more thing: The title is motor to OPEN the door, no mention about unlatching the door.
 
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