Automatic sliding bathroom door in aluminium

[eggi]

Hi to all, this is my first post here so be gentle with me :roll:

I have made a new bathroom door in 5mm aluminium and it slides very easy with ballbearings. Since I am a scifi fan I was thinking of making some sort of automatic open and closing of the door.
Requirements:
- open/close from both inside and outside
- be able to lock it from the inside
- a function that shuts the mechanism off if something/someone is
blocking the door

What I think would be cool:
since the door is aluminium, would it be possible to make the open switch to be the door itself, like those touch switches used in some different lightswitches?
So one little touch to the door and it opens and perhaps have a automatic close function, delay of about 5 sec. and then have a switch inside that turns of the power to the circuit, then the door would be locked.
I will try and attach some picture of the door.
(no comments on the wiring )

 

[rukid88]

When u are done with this please give me the schematics
Thanx in advance
:lol:

 

[gtrman1992]

This sounds like a dangeous project to me. The chance of getting electricuted is too risky. Water and electricity DO NOT mix.

If it was anywhere else in the house the project is not too difficult.

 

[mattg2k4]

It's just about as dangerous as putting lights and electrical sockets in the bathroom when properly done.

You'll need an h bridge to so you can get biderectional control of the motor. Look in the robotics forum if you need to find a schematic. I would use mosfets instead of transistors because you'll probably be using somewhat high powered motors.

To stop if something is obstructing the door I would put a low value high power resistor in series with the motor for current sensing. As current increases, voltage drop across the resistor will increase. When the voltage drop gets too big, meaning the motor is working too hard because the door is obstructed, it turns off.

To control the h bridge and interface with the buttons for opening, closing, and locking the door, I would personally use a PIC microcontroller, because then it's just a quick coding job. You'll want some sensor, probably a pushbutton switch to sense when the door is fully open or closed, so you know when to stop the motor. Or you could utilize the metal door to complete a circuit when it is fully open or closed.

If you don't want to use microcontrollers then you'll have to work out some logic circuits and stuff to use. It would be cheaper and easier for mass production that way, but for making just one door controller a microcontroller I really think would be best, and if you're interested in home automation and control, you'll want to be good with microcontrollers.

 

[eggi]

This sounds like a dangeous project to me. The chance of getting electricuted is too risky. Water and electricity DO NOT mix.

If it was anywhere else in the house the project is not too difficult.

I hope the project can be done with using low voltage,6-12V, and it wont use much power so the chance of getting electricuted will be small, but thx for the concern.

The first thing I need help with is to find a way to control the DC motor . To prevent people of being trapped by the door it needs to have some safety switch of some sort.
I imagine that there exists a "chip" that can survey the motor's power usage and when the engine meets resistance it would send a signal to reverse it to open position.
There are a few circuit diagrams for human touch switches on discovercircuits, but will they work with the large aluminium plate as sensor?

 

[bmcculla]

Motorola makes a neat e-field sensor that can detect changes in capacitance. This would let you detect a person touching the door (the capacitance of the door to ground would change). If you turn the sensitivity up you might be able to detect the person as they get close to the door. I forget the part number but Circuit Cellar magazine ran a design contest on them a couple months back.

Brent

 

[Nigel Goodwin]

It's just about as dangerous as putting lights and electrical sockets in the bathroom when properly done.

You don't have your location filled in, but presumably you may be in the USA?. In the UK it's illegal to have mains sockets in bathrooms, but electrical standards are far higher over here - I can't believe the USA still allow 'screwit' connectors (I think you call them plastic nuts?), these were banned back in the 1960's over here.

I love watching 'This Old House', I think Norm's great :lol: but I'm just amazed by their wiring practices!.

 

[Oznog]

You can do a touch sensor with a 555 and use the PIC to count the frequency. Easy, but the freq difference between free air and touched is not going to be nearly as large since the panel's inherent capacitance is quite large.

Unlikely the touch sensor will be able to tell the different between a person's touch and just being wet. That water running down may connect several sq feet of surface together.

Besides, do you really want the door to open whenever you touch it? What if you've just got soap over your eyes and you're just reaching around with the water still on full blast?

You would just put a small, high wattage shunt resistor on the ground leg of the H-bridge and use the PIC's ADC to read the current. If it's above an expected value, you back up. If you're already backing up, the decision is more complicated, maybe a towel got caught in the jamb. Maybe back out a few inches, stop and reawait triggering?

 

[IRQ57]

Sliding door

Hi Eggi,

Just a different idea : Use a hydraulic linear actuator (HLA)controlled by a low voltage three way valve.

The HLA, may be a simple piece of plastic (PVC) tube 1/2" in diam.,the piston/rod is another plastic tube (3/8") two O rings to seal, and one internal rubber band/tube to retract.

With a water supply at 80 PSI, the door is closed with 15 Lbs less the tension of the rubber retracter.

Electric washers use a very easy to modify water valves, to be actuated at 6 volts dc,very low current, to be operated with a little battery. An end of travel swicht will desactivate the feed valve which must have a limiting orifice to get a slow closing movement and not permit full pressure into the cylinder up to the end of travel. A safety pressure swicht will detect any detent before the end point, reversing the movement. A well water-proof-ed IR beam prevents any initial sliding. And in case of a emergency power failure (battery discharged) a manual discharge valve.

I think that is very difficult, if not impossible, to make a capacitive sensor system in a wetted metal construction, so... use simple push buttons to activate your " Electro-Hydraulic Sliding Door System" (EHSDS).

Regards

 

[eggi]

well the shower is isolated in a corner and has a fan above that starts when showering so the door never gets wet, and I was thinking of having a switch inside that turned of the power to the door so it would be locked.

did I forget to say that im a newbie to electronic circuitry?
so I dont know what a 555 is and all I know about PIC is that they are used in satelite cards. think maybe I have to read up on some of these things, would be nice to understand how it works and not just getting it to work. but thx for all the advice

 

[eggi]

IRQ57, new ideas are always welcome, but I dont like the idea of a water driven sylinder inside the wall right behind the main fuse box, but im sure it would work.

After googling around a bit I came across this,
touch sensor , it sounds like it might work since you can connect a external electrode and adjust the sensetivity by changing the Cs capacitor (not that I now what that is). I can order these from farnell.com, only cost 3US$ each.

But where do I send the signal from the sensor? need some kind of controller, is that perhaps what the PIC is for? :?

Oznog, thx for the advice on the shunt resistor, it sound like a good way to survey the motor's movement.

Now I need a good tutorial on PIC programming and free up some brain cells to learn it too.[/url]

Tag problems

 

[olly_k]

If you wish to make the door 'touch sensitive' for a start the door would have to be completely isolated from anything capable of either earthing, or changing the 'detectable' properties of the door.
Also as already pointed out I think it is too big a surface area to make such an idea work, or at least work reliably. The people to ask are Bang & Olufsen They make everything touch sensitive and in my opinion have mastered this particular area!

Why not use PIR? You could have a sort of square recess in the wall with a PIR or IR Tx / Rx built such that a hand wave within close proximity will activate the doors.
Or you could use a sensor/s in the floor? either optic or otherwise?
As for door obstruction, I think modern lifts generally use either small radar units or IR lights and detectors. You could use a 'beam' of light and bounce it off the edge of the door, with an appropriate sensor circuit. You would make this in conjunction with a current limit / detector circuit as a fail-safe maybe? I personally wouldn't rely on a current sense on it's own, especially where young children or older people could possibly end up in the wrong place!

You've potentially got a good project going there, just don't overcomplicate things and end up with a door that won't always open when you are in most need :lol:


off topic to Nigel:

I can't believe the USA still allow 'screwit' connectors (I think you call them plastic nuts?),

Obviously a bit before my time, Could you please elaberate?

 

[bmcculla]

You wouldn't have to isolate the door from everyting that would change its capacitance if you detect the Change in capacitance rather than absolute capacitance. Someone touching the door should change its capacitance fairly quickly compared to other events.

If you're a beginner you probably should start with an off the shelf component to detect thte touch. The evaluation kit you have looks like it might work.

Nigel: I think here in the US there is something in the Bill of Rights that protects people's right to be electrocuted however they see fit - including crappy household wiring :wink: .

Brent

 

[Nigel Goodwin]

off topic to Nigel:

I can't believe the USA still allow 'screwit' connectors (I think you call them plastic nuts?),

Obviously a bit before my time, Could you please elaberate?

They are cone shaped plastic devices, with coarse threads inside. You twist the bare live wires together (in the correct direction) and then screw this plastic connector over the top. It's an amazingly crude device, I can't believe they are still being used in the 21st century!.

I've seen them in very old electrical appliances, but as I mentioned previously, they were banned back in the 1960's.

 

[Nigel Goodwin]

Nigel: I think here in the US there is something in the Bill of Rights that protects people's right to be electrocuted however they see fit - including crappy household wiring :wink: .

Yes, it's just the opposite over here - you're not allowed to do loads of things - some are fairly sensible (like the electrical regulations). But others are totally stupid, for example in the USA guns are fairly common place (probably far too much so), but in the UK only the criminals are allowed to have guns!.

Even registered gun clubs are no longer allowed to use handguns, except for muzzle loaded black powder weapons.

 

[gerty]

whoop s

 

[gerty]

Nigel they're called wirenuts.. what do they use over there?

 

[kybert]

Holy sh** dude, in the US you still use these "wirenuts" ???

Over here (UK) we have to use block connectors or junction boxes!

 

[gerty]

Modern technology ,ain't it wunnerfull.. :shock:

 

[Exo]

Nigel: I think here in the US there is something in the Bill of Rights that protects people's right to be electrocuted however they see fit - including crappy household wiring :wink: .

Yes, it's just the opposite over here - you're not allowed to do loads of things - some are fairly sensible (like the electrical regulations). But others are totally stupid, for example in the USA guns are fairly common place (probably far too much so), but in the UK only the criminals are allowed to have guns!.

Even registered gun clubs are no longer allowed to use handguns, except for muzzle loaded black powder weapons.

Same over here, if a criminal enters your house you are only allowed to defend yourself (knock him KO) if he first knocks you out...

find the logic :roll: