Hey!

I am trying to make an automatic door, and I am looking for attachments for a servo motor. Since I have never bought one, and ordering one will take a month to arrive at least, I would like to make sure I am getting the right kind of an attachment.

I have a MG955 at the moment, which is likely not enough to directly twist a door handle, but I will use it as a prototype. I am trying to attach an 8mm square door handle piece (the one that is actually twisting the mechanism inside the door) to the servo. The issue here is, that I can find 8mm attachments and so on, but I am unsure whether they will fit for certain, since I don't wish to wait for a month for a piece I will never use, and then try my luck again and wait more months.

What type of an attachment should I get? I use AliExpress since I am poor.

Also, if you have some experience in this sort of thing, I could use some pointers on what type of a motor I should get, and the attachments to that.

Thanks!

 

What is the mechanism for the door?
A servo motor requires a feedback device of some kind, a stepper motor of the right power may do the job?
You need to find out the torque required to operate any method or mechanism in place.

 

What is the mechanism for the door?
A servo motor requires a feedback device of some kind, a stepper motor of the right power may do the job?
You need to find out the torque required to operate any method or mechanism in place.

The mechanism is a simple twist of a handle. I need to do it that way, since I cannot change anything with the door itself, except add a mechanism for the missing handle part.

I measured the required force but I wrote it down somewhere that's not here right now.

I am in more need of knowing what type of an attachment to look for for this particular motor, so that I know how to look for attachments with the correct terms and the correct sizes and values and so on.

 

ADDITION:
By twisting the handle I mean there is no actual handle, but just the square piece of metal that goes through the handle mechanism. I think it's universal at 8mm, and the length of it depends on the thickness of the door and so on.

 

I would look at some thing like a geared DC motor with a high ratio gearbox.
I picked up some new-surplus automotive seat motors, that have a lot of power and fairly small, the action is only going to be one turn I assume?
So at that speed of operation, a simple limit switch each rotation limit may work.
Automotive wreckers are a good source of 12v motors.

 

I would look at some thing like a geared DC motor with a high ratio gearbox.
I picked up some new-surplus automotive seat motors, that have a lot of power and fairly small, the action is only going to be one turn I assume?
So at that speed of operation, a simple limit switch each rotation limit may work.
Automotive wreckers are a good source of 12v motors.

That might go for a motor yeah, and there are a few scrappers around I could go visit tomorrow.

The turn is going to be around 90 degrees I think, or if I am completely wrong it takes 180 degrees.

The motor with the highest torque I have at the moment is a servo that can do 10+ Newtons at around 1,3cm. I mistakenly put a piece of string onto the 1,3cm mark and no the 1cm mark for a more useful direct ratio. Not sure if that is enough but it was more than I thought. I have two of them, so gearing them up might even be enough and they are quite small.

The question still is that how do I attach a 8mm square piece onto a GM995 servo? Or onto any motor for that matter.

 

I don’t think you will find a standard part to adapt the 8mm square to your motor shaft. I would look at a knob that mates to to see if you can us some part of it to make the adapter.

Bob

 

The auto seat GB I mention have about a 5mm square hollow shaft. and the GB is right angle.
But you may have to fabricate a coupling method using square tubing for e.g.

 

The auto seat GB I mention have about a 5mm square hollow shaft. and the GB is right angle.
But you may have to fabricate a coupling method using square tubing for e.g.

I should probably mention, that even though my English is great, it lacks in certain professional lingo, so what I am basically asking is, what is an attachment to a motor called, and what values should I be looking for to find something that will fit a particular motor, and a particular shaft. The shaft in this case is the square 8mm one.

 

Called a coupling.
If you have round tubing available to you, if you get the right size, you can square it up in a vice etc, there are methods and calculations out there for the right size to start with.

 

You will not find an adapter/coupling that will fill your requirements for sale, anywhere.
You must create it yourself.
.
.
.

 

I assume you are looking for something like this?
This is UK source, but there maybe others out there, may require some final turning and drilling one end to fit?
Although I see it takes both round and square rod!

 

Looks like there is all kinds of options out there, https://www.aliexpress.com/item/32830901113.html
Search door handle spindle sleeve.

 

I assume you are looking for something like this?
This is UK source, but there maybe others out there, may require some final turning and drilling one end to fit?
Although I see it takes both round and square rod!

View attachment 264514

That must be fake! Post #11 says they don't exist anywhere!
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,
,
,
,

 

Called a coupling.
If you have round tubing available to you, if you get the right size, you can square it up in a vice etc, there are methods and calculations out there for the right size to start with.

Yes that's it, thank you.

The servo is surprisingly strong, and with two of them I think I could spin one well oiled handle for sure. The end of the motor though, the shaft? That is pretty small, and it fits a gear rather than a coupling, and it came with some lever type solutions but they are all plastic and don't really fit the part I would assume.

This is what I have. https://www.towerpro.com.tw/product/mg995/

For future reference, what kind of coupling could I get for this one? I think what you mentioned earlier about stepper motor being more suitable for this you might be right, although I would love to try it with this one too, since it is pretty easy to control.

 

Cordless drills are another possible source for a geared motor. Drills with dead batteries can sometimes be had for next to (or literally) nothing. I've acquired them at swap meets, scrap yards, yard sales in the "free" box, Habitat For Humanity's "Re/Store".

 

Cordless drills are another possible source for a geared motor. Drills with dead batteries can sometimes be had for next to (or literally) nothing. I've acquired them at swap meets, scrap yards, yard sales in the "free" box, Habitat For Humanity's "Re/Store".

I had this idea when I was going through my flat to see what I could use, but I forgot about it. I will go out and see if I could find a cheap drill at the local flea market, which is where I actually found the drill I use.

 

I would tend not to use a RC servo for this app, there are many small cheap DC motor out there, C/W gearbox.

 

I would tend not to use a RC servo for this app, there are many small cheap DC motor out there, C/W gearbox.

Is there a specific reason for not using one? I am learning so all bits of info are good.

 

I am just wondering about sturdiness and longevity?
I guess depends on the degree of usage.