Hello,
I am looking for a quiet stepper motor with a lot of torque that would be compatible with arduino. I am new to stepper motors and have only played around with servos. From what I have read you need some sort of "driver" to interface between an arduino and stepper motor, is this correct? Which means I can't just pick out any stepper motor and hook it up like a servo and it would work? I was looking at these stepper motors Stepper Square High Torque more specifically something around the 24Y3, but am open to ANY suggestions. This motor would be used on a pulley system to unlock/open a door. If there are any better ways to do this I am also all ears.
Thanks,
-Falven
Choosing a motor, motor driver, and motor controller is not a simple task. You say that you need a motor to drive a pulley system to open a door? How fast must the door open (hence, how fast must the motor turn)? How much torque is required? Is there something about this pulley system that requires the precision of a stepper motor or would a (simpler) DC brush motor work just as well (perhaps with some limit switches?)
--
The MegaRAM shield: add 128 kilobytes of external RAM to your Arduino Mega/Mega2560
Yes, you are correct,
I have a system where there is a pulley on the top of the door on the opposite side of the door hinge.
I run fishing line form the door knob, through this pulley, to the setup (servo/motor).
The setup pulls the line causing the doorknob to turn and then begin to pull open the door.
The door measures 80"x35"x2" (Height x Width x Depth/Thickness) and is made of, I believe, pine wood? I would like the door to open relatively fast, but overall I am looking for a compromise between speed and quietness. I worked on a project just like this a while ago in college where me and some buddies automated our dorm door, using a 15 kg * cm servo with metal gears. The problem with that setup was that the servo made terrible loud noises and also grinded the plastic gear-fitting so they had to be replaced a lot. This is why I am looking for a better setup.
I experimented opening the door with a drill I have that has approximately 40 kg * cm of torque. This is too much, I would say the right number would be between 20 - 30 kg * cm of torque. I could be completely wrong. But I also have to take into account the speed and quietness because a slow system would be pointless 
Thanks for the quick response,
-Falven
Edit:
Something that could be even better would be a system using hydrolics since they are quiet, yet powerful. What I am meaning to say is: feel free to change up the design if you think of anything better. My inner amateur told me to go with this one. 
Weight of the door:
Vol = 80"x35"x2" = 5600 in^3
Dens = ~.50g / cm^3
Mass = 5600 in^3 * .50g /cm^3 == 45.860 kg (~101 lbs)
Have you thought about a DC linear actuator; not the cheapest option - but certainly cheaper than hydraulic or pneumatic would be.
You probably don't really want a true hydraulic system; should a hose or fitting blow, the last thing you want is hydraulic fluid/oil everywhere. One option might be something homebrew, and the working fluid is water with anti-corrosion chemicals mixed in - but that still could be a messy situation.
I agree. A hydraulic system would be a mess.
I did think about using a Linear Actuator, I just couldn't think how the design would work. Here is a terrible paint illustration of how I currently have my design set up:
The black box on the top left is where my arduino along with a power supply and the servo/motor would be housed. The whie line is the fishing line going to the pulley, which reroutes it to the doorknob. The door opens in.
How would you implement a linear actuator into this scenario? 
Thanks
-Falven
No problem,
The photo is of the actual door I am going to be opening. It is a photo of my apartment's entrance, from the inside of the apartment. I only need to worry about opening the door, because it closes on its own; therefore I am just trying to open the door. When the servo or motor (in the black box on the upper left of the image) begins spinning, it will roll up the fishing line, pulling on it and causing the door handle to rotate. When the door handle fully rotates, the door will be free to open, and will begin doing so.
I do not know how to measure how much torque it takes to turn the knob and open the door, but my rough estimate/guess is between 15 (absolute minimum) to 30 kg * cm.
The diameter of the doorknob is ~ (approximately) 2" (inches).
The reason I chose fishing line is because it is nearly transparent, and as such will not be visible, and because it can be very strong, fishing line can go upwards of hundreds of pound test (how many pounds you can lift), which is above the total weight of the door (more than necessary). If this becomes a problem Ic ould always find a viable solution (strong wire, etc..).
But again, if there are better ways to do this that don't require such a rube-goldberg approach please let me know. The goal, again is not only to unlock the door by turning the knob, but also to open the door, as quickly and silently as possible.
Thanks,
-Falven
In order to free the latch of the doorknob I must spin it between 70 - 90 (absolute max) degrees any direction.
I just tied a string around the doorknob and taped it to secure it, I then wrapped the other side of the string around the tip of an electric screwdriver that I have laying around. The screwdriver spun and pulled the string and the doorknob spun the required amount before opening.
The amount of force it took to spin the knob increased when I tied the string around the "neck" of the doorknob (the thinner section between the door and the knob). It would be ideal for me to use that section so the handle of the doorknob is free of fishing line(or wire) and tape and could therefore be used normally. I cannot say for sure how much torque it took. I can say however that the screwdriver is rated for 50 kg * in of torque, and that if it was secured to something and if it kept running there was a probability it would have ripped the doorknob off the door. This is why my guesslays between 20-30kg * cm.
I tied a half gallon of milk to the doorknob and it didn't turn, I then tied a gallon of milk to the doorknob and it turned more than easily, so the answer lies between a half gallon and gallon of milk (approximately between 4.4 and 8.8 pounds). Keep in mind this is only to turn the knob, the motor then needs to be able to pull the door open.
I do agree that this system seems unreliable. This is why I started this thread, so i could gain various input on how to make a reliable system, and otherwise to find the right motor to use for the job.
While I do like what people have done with the secret knock door lock, this is not the kind of thing I amgoing for. The system I am trying to implement will unlock the door and pull it open. If I just wanted to unlock the door I would have used an electric lock like the one below.
http://www.ebay.com/itm/Door-Fail-Safe-access-control-Electric-Strike-v5-NC-/350256744192?pt=LH_DefaultDomain_0&hash=item518cedc700
How do one of these motors look (30RPM version)? They don't mention how much torque they actually output, they just say quiet and high torque...
Another possible design would be something like this:
http://www.smarthome.com/73105/Skylink-DM-150-Swing-Door-Opener-with-Electric-Strike-Automatic-Door-Security/p.aspx
It's just another motor that turns to push the door open.
What I liked about the first design is that it both unlocked and opened the door.
In the end I am going to need to end up with a quiet, decently high torque, and fast DC Gear motor.
Any recommendations?
falven:
I agree. A hydraulic system would be a mess.
I did think about using a Linear Actuator, I just couldn't think how the design would work.
Well, the linear actuator (whether electric, hydraulic or pneumatic) would only allow for opening and closing the door (take a look at how gas springs work to hold open a hood, trunk, or hatch back on a car - same idea, except the actuator takes the place of the gas spring, and its mounted horizontally at the top of the door, connected to the door and the wall - extension of the actuator closes the door, retraction opens it).
Now - you would need something separate to turn the knob; you could probably get away with a standard servo there, attached in some manner to the doorknob. A better solution (though more expensive) would be to use an electromagnetic door strike (this would require modification to the door and jamb, most likely - but it'd be much more professional looking - although most of the time such strikes are meant for thicker non-interior doors).
BTW - if you use a linear actuator, make sure you take plenty of measurements to get the right stroke length; you won't be able to get the exact stroke length (unless you're really lucky!) - you'll need an idea of the maximum lengths; get an actuator that will be at least this long or longer when extended. Some linear actuators have limit switches (end-of-stroke), others have pulse encoders, and still others have potentiometers. If you can, get one with a potentiometer. Otherwise, you'll want to install limit switches (might be a good idea even with the potentiometer!).
Check out the force rating of the actuator, too; I just recently bought a "small" 24 VDC linear actuator off of ebay, which can supply up to 4000N of force pulling or pushing! This is equivalent to 800+ lbs of force; if yours has such an extreme rating (actually, not extreme at all - there are plenty out there much more powerful than that!), you'll want limit switches and other precautions, unless you like replacing busted doors, jambs, frames, etc.
Crosh, thank you for your valuable feedback!
I was just about to buy the actuator when I realized... what would happen if my system failed. Like for example, if there is no power.
The door would be forced shut? Do you know if you can custom order actuators that are "loose" when no power is running through them in either polarity? Or is that default behavior?
This is the actuator I was looking at:
Thanks
-Falven
KE7GKP,
As I stated in my first post I am open to many ideas, the overall goal here is to build a cool, fast, efficient and reliable system that will both UNLOCK and OPEN the door.
I realize 18 inches are not enough to turn the knob AND open the door. The Linear Actuator is just meant for opening the door. I went with 18 inches because that is the length from the wall to the horizontal center of the door at an angle.
For the door lock, I was planning on either:
A. getting a proper motor for turning the door knob and/or possibly the deadlock at the same time.
B. Finding a very small electric strike lock that would fit well into my small doorframe (I do not want to accidentally crack the wood of the frame by drilling it bigger).
C. Whatever solenoid operated latch plan you mention, could you describe in more details?
The problem I am facing right now is whether the Linear Actuator will prevent me from opening the door if there is a power or system failure. Can you get these custom made to slide in and out if there is no current in either polarity? Or is this the default behavior?
Thanks,
-Falven
While it may be easy for someone with your experience and resources to make a linear actuator of the such, someone with limited mechanical engineering experience such as myself would have a hard time making such a device. I am more of a computer guy.
Is there any Linear Actuator of the sorts that provides the functionality I am looking for?
Or some way to provide that functionality to an existing linear actuator? This "breakaway" mechanism you speak of...
Like for example, automatic doors in all sorts of corporate buildings use what looks like a linear actuator to open the door, but the door is still able to open and close non-electronically.
Regarding the latch/doorknob. I can make whatever modifications I like as long as I can always revert back to the original way it was. I am in an apartment complex and I do not believe my landlord would be happy if I permanently broke the door/frame
I have been looking for a really small electric strike lock as his would be ideal.
Measurements: 2 1/4 " tall (minimum with room to spare) x 1" deep (max) x 1.25" width (max).
Thanks for the help so far
-Falven
KE7GKP:
There is no electronic linear actuator that behaves like you are asking for. That is one big reason why I think it isn't an appropriate solution for your project.
Don't get discouraged, there are always mechanical ways around this.
KE7GKP:
As for resources and experience, it could hardly be simpler to attach a $3 threaded rod to a DC gear-motor shaft and use one of dozens of different kinds of nuts to run up and down on the shaft. That is all that is inside the fancy Firgelli case. It really is a lot simpler than you seem to be making it out to be.
This may be so, when I reach that point I will ask you for more specifics on creating my own.
KE7GKP:
Of course, there are some latches that have mechanisms that prevent that (to make them harder to break into).
Unfortunately, my latch exhibits this behavior. Nothing that can't be fixed with a new latch or electric strike.
As far as the plan goes, I came up with a pretty nice possible solution (at least on "paper").
Here's the explanation:
The box on the top left will contain the arduino and power supply powering this project. The power will come through the wall directly behind the box. I have already done the measurements and there are no issues with this part.
The measurement tape on the Image will represent the Linear Actuator (Custom made or bought is irrelevant at this point) with it's hinges clearly demarcated. Behind the Linear Actuator, on the door you will see an elongated rectangle. This rectangle represents a "Rail" where the linear actuator can slide when it's not operating. By operating I mean attempting to open or close the door. The arrows indicate that the Linear Actuator can slide on this "rail" when it is not "operating", or powered on.
Here is the process I would go through for opening the door:
-
User scans rfid card to the door (already set up and working. I have an ID12 hooked up to my arduino reading and recognizing RFID cards into it's EEPROM memory) or some other sort of biometric validation.
-
The Arduino signals a "locking mechanism" that will lock the Linear Actuator in place so it doesn't slide along the rail, and can therefore pull the door open. How this mechanism could be implemented is still up in the air.
There are many ways to do this, it could be electrically-mechanically initiated from the arduino or it could be some inherent mechanism on the rail (one good example is what this fellow did with the latch on his chicken coop device at 2:00
- The Linear Actuator is then powered on and begins pulling the door open.
I really like this plan. I can already foresee your agrument, it is complicated, yes. I knew what i was getting myself into when I decided to improve upon the mechanism I originally devised my freshman year in college (Using the servo and a string to pull the door open). While this mechanism would be harder to implement, it would present a much faster way to open the door, a much quieter way, and a much more reliable way of performing these functions in general.
What do you think of this plan?
Any ideas for the latching mechanism?
Again, I am kind of unexperienced with the many options available to Arduino...
KE7GKP:
A very clever "regenerative" pneumatic door opener. It stores up compressed air from people opening the door in the conventional manner, and then when you want it to open by itself, it uses the stored-up compressed air to open the door. It converts the linear motion of the air cylinder (made from a clear plastic tube) into a rotary motion of a shaft which uses a lever to open the door. Of course, you don't have to use the regenerative feature if you have power (electric or pneumatic) available....
That is rather clever. Very cool. Unfortunately our goals are dissimilar, and he utilizes pneumatics, which, was we discussed with Crosh at the begining of the thread, can get very difficult, messy, and hard to maintain.
KE7GKP:
Here is another pneumatic design controlled from an iPhone app. In particular, note the doorknob turning scheme at around 20 seconds. It uses a little plastic toy servo to do the turning...
Again, another clever idea, but it still utilizes pneumatics.
KE7GKP:
Here is a compact electric version. The video is terrible, but around 0:48 you can see how it works...
That electric version is what I would use. I would get something like this gear-motor...
http://www.allelectronics.com/make-a-store/item/DCM-434/12-VDC-GEARHEAD-MOTOR-3-SPEED/1.html ($20)
Since it runs on 12VDC, I would use a small motorcycle battery to power it so that you can open the door even during a power failure.
The motorcycle battery is a nice Idea, I will definitely have a backup plan like this where the unit will run off the power supply and if there is a power failure it will switch over to the motorcycle battery, which should give me enough time to open the apartment back up and make necessary adjustments. Unless I go with my design, in which case the door would always be able to open normally. Also, I don't think you realized, but by using the Electric Strike I circumvent having to use a servo to turn the doorknob. The door would remain locked, but would still be free to swing open whenever the electric strike opens/unlocks.
I think i'm pretty close to the correct solution, the one problem that is preventing me from achieving this is how to "lock or latch" the Linear Actuator onto the "Rail" so it doesn't slide left or right on the "Rail" when I want it to actually open the door. Still open for ideas.
Thanks,
-Falven
Edit: what if I use two very small, but powerful solenoids that pop out through two holes on the rail and hold the Linear Actuator in place while it pulls the door open?
KE7GKP,
Again, thanks for all your help so far. I just need a little bit of more information so I can work on this cool project.
Do you know where I can get small, powerful solenoids that wil work with my projecT?
Thanks,
-Falven
Edit: Trying to find stuff on my own I came across this: "Double acting Solenoid" is this what I am looking for?
KE7GKP:
Here are some solenoids from some of my favorite sources...
http://www.allelectronics.com/make-a-store/item/SOL-102/MINIATURE-12VDC-PUSH-TYPE-SOLENOID/1.html
http://www.allelectronics.com/make-a-store/item/SOL-58/24-VDC-PULL-TYPE-SOLENOID/1.html
http://www.bgmicro.com/ACS1304.aspx
http://www.bgmicro.com/ACS1408.aspx
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16036
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16822
http://www.goldmine-elec-products.com/prodinfo.asp?number=G18001
Thank you for the suggestions,one thing I noticed is that all of these are normally expanded, and pull in. We would like the opposite behavior no? Because I would want to be able to manually open the door all the time unless the solenoid and linear actuator recieve the signal to open. Also, another thing is the duty cycle on these guys. Will these be able to widthstand being expanded for so long (because of their duty cycles)? And will they, quality wise, be able to withstand the force of the linear actuator using them to pull teh door open?
Thanks
-Falven
Hmm, I just had an Idea.
Since the Linear Actuator would only slide to the right when the door is opened manually, am I correct? (The door only opens inward.)
Then I could use a ball-bearing drawer glide/rail like these:
so when the Linear Actuator is pulling on the door, they lock up since they only extend to the right, and allow the actuator to pull the door open. And when the door is manually pulled open (the linear actuator is fully expanded) the glides/rails expand with the actuator so it doesn't break...
This would rid me of needing to hook up a solenoid (and another component that could break/present problems).
I hope I got my point across correctly
Thanks
-Falven