Help me design a cheap automatic door opener

I've been spending lots of time researching automatic door openers over the last several months and have come up with a couple thoughts:
1. There aren't many manufacturers that make them
2. They cost an awful lot of money
3. I could probably make one myself for much cheaper

There seems to be two types of automatic door openers used in the commercial world; those which use a pneumatic cylinder and those which use a electromechanical device. The pneumatic operators seem to be used in more large scale operations where a large number (10+) of automatic doors are spread throughout an establishment. An air compressor/tank and the pressure valves/manifolds/controls are located in a centralized place and then routed to each individual door. Electromechanical operators are more self-contained, and although costing more, have everything packaged as an operating unit right at the door. For simplicity it seems like an electromechanical system (possibly with a battery backup) is the way to go to seamlessly integrate everything into my home automation system.

For pricing, commercial style electromechanical operators like the ones you see in grocery stores/businesses across town are more than $3,000 apiece. I've found a company, that makes a very good residential electromechanical operator for about $1,500, which seems like a better deal, but is still an awful lot of money; especially when you consider I need 3 of these.

So I think I want to design my own, and would appreciate any help you guys might have with coming up with a solution.

Linear Actuator
My initial thoughts were to use a simple 12/24VDC linear actuator. Energize the actuator in one direction and it would expand/open the door, energize the actuator in the other direction and it would compress/close the door. Would definitely work, but it has a few failure modes/safety issues that make me very nervous.
1. When you energize a linear actuator it is moving. It doesn't care if there is a finger, foot, or whatever in the way. This is definitely a major safety issue and not something I'm okay with.
2. What happens if you lose power? There is no manual operation of a linear actuator, so without power the door stays close. Another major safety/access issue I'm not okay with.
So the linear actuator is out!

Pneumatic Cylinder
From there, I started thinking about using a pneumatic cylinder to open/close the door. You could attach a pneumatic cylinder almost like they attach one to a storm door to control it from closing too fast. With a 12/24VDC solenoid on each side of the cylinder you could open/close the door depending on which side you pressurize. Energize the solenoid on the low side of the cylinder and you'd extend the ram/open the door; energize the solenoid on the high side and you'd retract the ram/close the door. By regulating how much pressure is in the system you could regulate the power of the device and prevent the safety issues caused by the linear actuator. You could also get creative with depressurizing the system after operation so that you could still have manual, unimpeded operation of the door.

Seems like a much better option, but still has the complexity of routing air/pneumatic tubing to the doors in the house.

12/24VDC Motor/Electromechanical Clutc
My last brainstorm/epiphany/which way I currently think is best is to use a combination of a DC motor with a electromechanical clutch. For automatic operation you would run the motor/engage the electromechanical clutch in the forward direction which would open the door. Then switch polarity on the motor/still engage the clutch to close the door. Full manual operation would still work because the electromechanical clutch would normally be disengaged and allow the door to open/close as though no operator was attached. The electromechanical clutch could be sized such that it would slip when obstructed by a person, foot, or finger mitigating the safety issues of the linear actuator.

I think this is definitely the design route I'd like to go, but I have no idea how to size the motor/electromechanical clutch. What RPM motor do I need? What torque value clutch? All kinds of questions! What stuff do I need?

I've got some very talented fabricator friends that can make me any sort of linkages/whatever I need. I just need to figure out what pieces to give them to make this work.

Any thoughts guys? Appreciate it!
-Mike

Most of the quality commercial operators I have seen are hydraulic or belt drive depending on the door type.

I think if you are concerned about safety, lawsuits, and reliable operation you would go with the available options. They cost a lot of money for a reason. They a have numerous safety components, internal and external, that stop people from getting hurt. They are also designed for 24/7 operation.

Unless you are going to market with this device and you plan on getting the proper certs and UL approval, I would stick with something that is commercially available.

gatchel said:

Most of the quality commercial operators I have seen are hydraulic or belt drive depending on the door type.

I think if you are concerned about safety, lawsuits, and reliable operation you would go with the available options. They cost a lot of money for a reason. They a have numerous safety components, internal and external, that stop people from getting hurt. They are also designed for 24/7 operation.

Unless you are going to market with this device and you plan on getting the proper certs and UL approval, I would stick with something that is commercially available.

Click to expand...

Definitely get what you're saying about safety/certifications, and think that's of the up most importance, but not planning to go to market with this, just planning to use it in my personal residence. Even so, I want this to be safe and couldn't live with myself if somebody got hurt because of my design.

I just can't see myself paying $3000 for something that doesn't have much more than $2-300 worth of parts.

Assuming it's a standard swing open door... have you looked at the Otodor opener from Skylink?

http://www.aartech.ca/otodor-door-opener/
http://www.skylinkhome.com/can/products/sd...oor_opener.html

Cheers
Robert

aartech said:

Assuming it's a standard swing open door... have you looked at the Otodor opener from Skylink?

http://www.aartech.ca/otodor-door-opener/
http://www.skylinkhome.com/can/products/sd...oor_opener.html

Cheers
Robert

Click to expand...

Hey Robert,

Looks like a great product, and definitely at a reasonable price. I don't know why all the other manufacturers charge 5-10 times more. My only problem is it doesn't offer manual operation. The solution would work great for me, but I doubt the able-bodied folks in the house would want to be forced to use the automatic door opener every time they enter/leave the house.

Do you know of any other product that would still allow manual operation?

Thanks so much,
-Mike

Why not go with the pneumatic option, but only pressurize on open. On close, you could open the relief valve and rely on some sort of spring pressure to pull the door shut and force the air out of the cylinder. Powered closing seems like a bad idea.

Where have you looked for commercial products?

I've seen Stanley Access Technologies workmen working on automatic doors where I work. Call up a rep, and ask for a quote on a budget and/or used system.

I'd hate to say this..but i think you're much better of paying to price and moving on..you'll have so many other things to worry about that you don't need this extra one. Inspection issues, coordination with your builder, get you it all to fit in a esthetic pleasing package...etc..etc.

The pneumatic open and standard spring hinge closure sounds like it might be fun to design and build. Do you have a machine shop? Seems like some custom fabricated parts and welding might be involved. If you had the pneumatic setup at high power the door could swing with such force as to hurt someone, so just don't do that. I can see the cartoon now of the door jettisoning open and whacking you in the face. I'm thinking BBC kind of stuff. Pneumatic pressure relief valves would prevent the door from pushing with force in excess of whatever relief pressure you install.

Lou Apo said:

The pneumatic open and standard spring hinge closure sounds like it might be fun to design and build. Do you have a machine shop? Seems like some custom fabricated parts and welding might be involved. If you had the pneumatic setup at high power the door could swing with such force as to hurt someone, so just don't do that. I can see the cartoon now of the door jettisoning open and whacking you in the face. I'm thinking BBC kind of stuff. Pneumatic pressure relief valves would prevent the door from pushing with force in excess of whatever relief pressure you install.

Click to expand...

I don't have a machine shop.... yet. I have welders and a drill press right now. My wife told me that once I get the deck on the house, I can buy "whatever the hell I want." A mill and a lathe are towards the top of the list, along with a RepRap. I tried some light milling with the drill press, don't try it unless you're milling Jello.

You can probably buy most, or all, of the parts you need from McMaster-Carr. Grainger has stuff also, but McMaster had a better selection of pneumatics a few months ago when I was looking for something. I think they also have pneumatic cylinders that auto retract when they are not under pressure. In that case, you'd need:

- Adjustable relief valve
- Cylinder with auto retract
- 2 ball pivots
- Air solenoid
- Flow regulator to adjust open speed
- Air hose and fittings

You probably wouldn't need to machine anything. If you need more strength where the ball pivots mount to the door and frame, you can just use some stainless angle stock and drill some holes in it. McMaster also has a selection of brackets for the pivots that would work.

I looked at all of this stuff for another project a few months back. They should have all of it. You'll need to mount the ball pivot to the TOP of the door frame at least 3 inches out from the hinge side of the door (assuming you are pushing the door outwards), and also move it back from the door a couple of inches so it can start the door moving outward. The reason you need to mount 3 inches out from the frame is because when the door gets all the way open, the side of your cylinder will bind on the inside edge of the door.

Using air is definately an easier option but you then need to plumb th air lines around, air compressores are noisy and its another device to run and waste power on.

What type of door are you looking at?

Cavity sliding door (CSD), or swing door.

If a CSD, how about a motoroised curtain track and motor. Instead of sliding the curtain, its attaced to the door somehow. Limit switches allow adjusment of movement, and they should have an overload stop (not sure on this one) for an obstacle.

I dont have a motorised curtain track, but I would hope that you can manually open and close your curtains, and if so, then this will allow manual operation of the door - only good for internal use though.

As for a swing door - gate openers or the one linked too.

Mick

I wonder if you couldn't work some of those cylinders they use to open auto trunk lids into the scheme. They are not terrible expensive and push the turnk lids open nice and smooth like. Perhaps you could stop by a junk yard and find one of those mini-vans with the powered tailgate.

I have to say, znelbock has a point about having to run airlines from your garage or whereever you keep the compressor. Maybe you could use your natural gas lines to power it. (I don't really think I need to point out that that is a joke but I will anyway just to make sure some yahoo doesn't take my advice and file a suit against me when he burns down the house).

Wow!

You guys have definitely been busy while I've been out running around all afternoon meeting with the builder, finalizing the window selection, and confirming the placement of the island in our kitchen.

If all goes as scheduled I should see the earthwork people up there early next week, and then the concrete guys shortly thereafter. To answer any questions about plumbing airlines around... this is new construction and the walls will be completely open so that should be a rather simple thing to do.

Neurorad, the product that has most caught my eye is a residential automatic door opener made by a company called Open Sesame Door Systems. It works with a small 1.5A 12VDC electric motor and a 15 in-lbs constant torque slipping disc clutch all run by a 12VDC battery which is trickle charged from a 24VAC wall transformer. The device allows full, unimpeded manual operation, still works on power failure, and will allow a dry contact to operate it so it would be very easy to tie into my HAI OmniProII. Only problem is that it's $1,600.

MavRic... you are absolutely right! I'm far too busy to be screwing around with designing my own door opener, but the budget is very tight and my imagination is running wild and for whatever reason this seems like a really neat project to tackle that might be very interesting to a lot of people.

Everyone else... Keep the great ideas coming!

I've got a very talented friend who owns a farm tractor equipment machining/fabrication shop and has every piece of equipment known to man. CNC milling, large hydraulic presses, whatever we might need and he is very willing to help.

My initial thoughts were that a pneumatic setup might be the easiest to accomplish this as well. I've already got nice pneumatic tank that will be plumbed to the garage because my dad is a road/mountain bike mechanic, so a little extra tubing to some other areas of the house should be no problem.

The doors I'd like to automate are two 42" inch swinging doors, one 48" sliding glass door, and one 36" sliding glass doors.

The sliding glass doors should be very easy, with just an appropriately sized pneumatic cylinder. In my mind the other doors shouldn't be that much more challenging.

Do you think if I were to pressurize the system properly I can make it operate safely? I.E if somebody got in the way it would be low enough pressure so that it wouldn't smack them too hard.

If you guys think I can make this safely... let's get planning. Throw in a few 12/24VDC solenoids fired off a form C relay connected to my HAI and we should be in business.

znelbok said:

Using air is definately an easier option but you then need to plumb th air lines around, air compressores are noisy and its another device to run and waste power on.

What type of door are you looking at?

Cavity sliding door (CSD), or swing door.

If a CSD, how about a motoroised curtain track and motor. Instead of sliding the curtain, its attaced to the door somehow. Limit switches allow adjusment of movement, and they should have an overload stop (not sure on this one) for an obstacle.

I dont have a motorised curtain track, but I would hope that you can manually open and close your curtains, and if so, then this will allow manual operation of the door - only good for internal use though.

As for a swing door - gate openers or the one linked too.

Mick

Click to expand...

Motorized curtain track and motor... super idea! There is actually a very good commercially available sliding glass door opener that doesn't break the bank to bad... think it's around 800 bucks or something. I'll track down the link sometime what I've got a bit more time.

But yeah... I think pneumatic might really fit the bill, although I will admit if I DO think an all electrical system would probably be a little more clean/seamless.

I've got an open mind though. Thinking this is very cool to see all the responses. Thanks guys!

http://www.mcmaster.com/#pneumatic-cylinders/=869t2o

The spring return cylinders are listed on this page.