This project uses proximity switches and relays to control a bank of indicator lights.  The lights convey the occupancy status of two bathrooms.

Problem: Two single user bathrooms - in a dorm style house - are shared by multiple people, but the bathroom doors are not visible from the main hallway. This results in many failed trips down the hallway, only to find the one containing all of your toiletries or both (depending on what the need may be) are already occupied.

Solution: A centrally located visual indicator to convey the use status of the bathrooms.

Step 1: Inputs - Detecting Door Status

An assumption must be made to simplify the act of determining if the bathrooms are avaliable or unavailable.  This determination will be based on the condition of the door.  If a bathroom door is open, the bathroom is avaliable.  If a bathroom door is closed, the bathroom is unavailable.  The input I used for detecting the status of the door are inductive proximity switches.

Inductive proximity switches sense objects by generating a magnetic field.  When a metal object reaches a certain distance from the sensors head, it will open or close a circuit (depending on the model).  By placing a screw in the door, the sensor can be triggered when the door is closed.
A future enhancement could be a beacon if someone didn't wash their hands.&nbsp; <br />
Do-able - I need a way to detect whether or not he sink has been run since the door cycled.&nbsp; Sensing actual water flow might be tricky... maybe I can detect the turn of the knob with a physical limit switch.<br /> <br /> I don't think I can execute the logic check easily with relays - though.&nbsp; It might take a PLC (Programmable Logic Controller) to handle it.<br /> <br /> I love some Far Side - by the way :)&nbsp; <br />
someone here in 'ibles did it with a piezo
You cold use a flow sensor.<br /> <a href="http://www.flowmeterdirectory.com/" rel="nofollow">en.wikipedia.org/wiki/Flow_sensor</a><br /> <a href="http://www.flowmeterdirectory.com/" rel="nofollow">www.flowmeterdirectory.com/</a>
how about a combination of sensors, to make it harder to fool them. &nbsp;and a timer to make sure they leave the water on for more than an instant.<br /> <br /> and you could add a yellow light tied to a motion sensor to show when someone is in the bathroom, but left the door open. &nbsp;like if someone is brushing their teeth, or just using the mirror. &nbsp;then when someone needs to go really badly they can ask them to step out for a second.
Actually, water conducts electricity. Just use a transistor and you're good to go... Nice Instructable by the way.
So you would have two leads near or in the fixture.&nbsp; I can see it. Thanks<br />
You could try putting a momentary switch under the tap where the water comes out to detect the water flow.<br />
Great 'ible by the way, 5 stars.<br />
Thanks<br />
You should try using an airline indicator sign next time. I think it might be a little funnier haha. Just a suggestion.<br>
add a no smoking sign and a seatbelt sign as well, and make the seatbelt sign turn on and off at random intervals
Is Mr. Nelson in someway associated with a Terry Whaley?
I'm not familiar with a Terry Whaley, but I'm terrible with names.
Read one of the edge lighting instructables and make a little light-up sign instead of just a plain circle of LEDs. Cool work!
That would be a nice modification. Thanks
one improvement on this project would be to eliminate the over-enginerred door triggered switch and just screw an elbow joint to the top of the door frame, and a momentary switch to the door, so when the door closes, the switch will be closed by the elbow joint, in turn illuminating the light. but other than that, i really liked your instructable! !&nbsp;<br />
Thanks.&nbsp; Others have mentioned using a micro switch, but I like your direct approach.&nbsp; Using a small attachment to the door to trigger a micro switch would be allot easier than mounting it in the latch receiver --- slightly more visible, but micro switches are small. <br />
This is what happens when necessity collides with invention so hard it makes art...I&nbsp;give 5 stars, especially for the hardcore-industrial utilitarian look. I&nbsp;would totally do this....<br />
Thank You<br />
KUDOS to you my friend. Truly inspiring...seeing as I have been thinking of a way to do this myself and making it look half decent/professional lol. Yours is outstanding. 5 *'s from me!<br />
Thanks<br />
I really like the industrial look.&nbsp; And you did an outstanding job making it all very solid and professional.&nbsp; 5 stars.
Thank You<br />
&nbsp;Some would call it lazy, I call it innovative.
My thoughts exactly.&nbsp; It seems most innovation is driven by a desire to do less work and make our lives easier.<br />
Although it is always good to have more people. Because, after innovating, the innovator may become to used to less work (and therefore become lazy and no longer innovate).<br />
Great one! I gave it five stars!<br />
Thanks<br />
Fit an AVR&nbsp;webserver to it, so people can see if it's available from their computer/desk/phone etc :D<br />
This is great, we also just completed a handwash sensor for a Physical Computing project at the School of Visual Arts-complete with EWWW!&nbsp;output if someone didn't wash his/her hands...Watch our video!<br /> <br /> http://www.youtube.com/watch?v=qTF9-j_y7zU<br />
Nice!&nbsp; My first thought was to use the water flow as an indication of hand washing.&nbsp; Your soap trigger ensures a more appropriate job was done.<br />
I don't like the fact that a green light is always on to tell that the bathroom is available, it's kind of lost of energy where you could only have shown the status busy by lightning the red light. <br /> Also, what if someone leaves the bathroom and closes the door&nbsp;? status will be inacurate. I think people are most likely to switch the light on and off (that you can detect with a light sensor) than leaving the door closed when gone when.&nbsp;<br /> Otherwise, i find the system very nice and usefull :)<br />
&nbsp;I agree with xavtek, It's a waste of power to have the green light always on. I would set it up so that a red light comes on when the bathroom is&nbsp;occupied. And a lot of people close the bathroom door when they leave. Maybe you should have a motion detector wired in series with the door sensor. <br /> <br /> Great idea but you need to dress it up more. You can get a low profile door sensor on ebay, and instead of using flex conduit, just run a 4 conductor speaker cable, they're low profile.
I am unsure how much power motion sensors use in relation to LEDs, but the number of light indicators could defiantly be called a design choice.&nbsp; <br /> <br /> The people of this house were easily convinced to habitually leave the doors open upon exciting.&nbsp; The rooms are not in close enough in proximity to be easily effected by temporary unpleasant odors, and the central-air-vent-less hall depends on the thermal flow from the bathrooms to appropriately dictate the hall thermostat.<br /> <br /> The appearance is as a design choice.&nbsp; I went heavy on the industrial look. This could be done with a cleaner, less visible appearance.<br /> Thanks for the feedback.<br />
I contemplated a one light system, but I didn't like the trade off.&nbsp; One light would give you enough information to determine the condition of the bathroom's door - excluding the event of a dead light, tripped breaker, or other system failure.&nbsp; In any of these events, a two light system would quickly convey that a problem had occurred.&nbsp; (Not that this system is anywhere near as vital, but visualize a traffic signal that only has a red light.)&nbsp; The downside to the two light system is the larger upfront cost of more hardware, and the long term cost of increased power consumption.&nbsp; I considered the overall cost justifiable; LEDs are very efficient.&nbsp; Also - in my mind - a green light signifying go, and red light signifying stop -- more clearly convey the appropriate actoin.&nbsp; The absence of a light would require recalling the default status indication of the light, and seems slightly less direct.<br /> <br /> Interesting suggestion.&nbsp; Would the light switch be a better indication of occupancy?&nbsp; I think this would depend on the habits of the users in question, but I don't believe so - in the case of this location.&nbsp; It would be easier and cheaper to use the switch position in place of the proximity switches - though.&nbsp; Thanks for the idea of a diff rent input option.<br />
&nbsp;Ya need to scrounge up some old motel neon no vacancy or vacancy signs. That or make them out of LEDs for low power consumption, and low key light levels
I like it.&nbsp; The ones where the &quot;no&quot; toggles depending on condition.&nbsp; I even want it where it blinks and hums as the &quot;no&quot; turns on.<br /> <br /> I ran across images of LED versions - already in production - as I looked for the classic.&nbsp; Nice idea.<br />
I noticed that you have a proximity sensor, im not sure if this would simplify things, but try using a reed sensor and a magnet,&nbsp; the advantage to this is that you can put the reed sensor int the door frame, and the magnet in the door.&nbsp; when you close the door, the magnet should come very close to the reed sensor, completing the circuit, <br /> <br /> on another note, good instructable, i like this idea<br />
I was thinking of the same hardware when I talked about being able to use &quot;security magnetic break switches&quot;.&nbsp; Thanks for the vocab.<br /> <br /> After browsing the net briefly, I can defiantly say that it would reduce the sensor's costs, be allot easier to hide from site, and reduce the size and cost of the associated wiring.&nbsp; Thank you for the input.<br />
<br /> &nbsp;Those are some heavy-duty industrial housing and lights.,<br /> IP-67 rated?&nbsp; <br />
I had to look &quot;IP&quot; up.&nbsp; To be honest - I don't know, but being a betting man - I bet they are.&nbsp; Thanks for the new standards info.<br />
&nbsp;Excellent, only thing I could suggest to improve is to label the indicators - 'A' and 'B' and also 'Vacant' an 'Engaged'.
You make a good point.&nbsp; I meant to label it, but it slipped further and further down my to do list.<br /> <br /> It's also a good laugh when someone moves in and - about 3 months later - I realize I forgot to mention what the lights represent, when they ask &quot;what in the world are those lights there for&quot;?<br /> <br /> You've got to leave a little mystery in the world :)<br />
&nbsp;Very cool but somewhat extensive considering you could just use some aluminum tape and have the same effect.
I don't fully follow.&nbsp; If you mean using aluminum tape on the door and frame, and when you close the door they make contact -- that means I would have to have a low voltage detection circuit.&nbsp; A different model relay could allow for the low voltage to pickup the 120V going to the the lights and fan.&nbsp; OK - I can see how that could work.<br /> <br /> If I had to build this system 'from scratch' - without proximities that opperate on and output 120V - that would be a great idea.&nbsp; Thanks<br />
That makes sense now but isn't it incredibly unsafe to have 120v floating above your head when you don't need to?
Not when it is properly insulated and shielded.&nbsp; You usually have 120V circuits allot more exposed and within reach with your standard wall socket.<br /> <br /> But - you have a point - if this system were going to be mass produced, I can easily see you comment driving the design process.&nbsp; I don't think it is inherently unsafe to use a line voltage system, but if a low volt detection circuit could be used for a little more or the same price -- why not add that extra layer of safety.<br />
&nbsp;it is a very good idea but i dont get the fan why do i need a fan?
You're right - I didn't explain the need for the fan.&nbsp; This house was built in 1926, and it has gone through many partial renovations.&nbsp; When this bathroom was renovated, they sealed and covered the window to install a larger shower.&nbsp; This caused a ventilation problem, and - despite an in wall vent fan - moisture reeks havoc on the walls and trim.&nbsp; To keep the damage and mold growth down (college students don't get around to cleaning a bathroom too often) I put this fan in to pull out the hot moist air that rises from the shower.&nbsp; The sensor allows it to run when it would be effective; when the door is open.<br />

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