Bathroom Status Indicator Lights and Automatic Switch




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.

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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 proximityswitches 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.

Step 2: Relays - Control Box

This box is located in the attic.  It receives the inputs from the proximity switches, and via relays, toggles the red/green light circuits and the - yet to be seen - door mounted fan.

The box contains two eight contact block relays and a 15 Amp breaker.

Step 3: Outputs - Lights and Fan

Once the relays are triggered from the closing of a door they break the green light hot lead, make the red light circuit, and - in the case of bathroom A - cut the power going to the door mounted exhaust fan.

Step 4: Enjoy

This is my first instructable; so, any advise is more than welcomed.  I have enjoyed this site and yall's projects for - so long - that I had to contribute.

Most of the hardware in this project is industrial grade leftovers, and I realize they are a little overkill for this application.  Please don't let that discourage you from a similar project; other cheaper but more-than-reliable-for-this-application hardware is available.  It could easily be duplicated with security magnetic break switches and some simple relays.

I look forward to updating this project as the questions come in.

Community suggested updates to be made:
option -- move more hardware into the attic to make installation less visible - jemivallo
info -- top down diagram of physical layout - jemivallo
info -- more detailed part descriptions - eli2k
info -- wiring diagram - eli2k
info -- more details on my relation to the building - lemonie
info -- advantages and disadvantages of used input - lowercase
option -- other forms of input and their advantages and disadvantages
  detecting door lock using microswitches - frollard
  motion sensors - pH_
  contact sensor working off a low voltage detection circuit - cornboy3
  read sensor and magnet to detect door position - Jeffrey G C
info -- the fan's purpose - iambarney155
option -- labels for light box - zoltzerino
option -- adding inputs and hardware to check for hand washing - monkeytoes
  use the water to makeup a low voltage detection circuit for water flow - seifpic
  use a momentary switch - pie ninja
  build a input into the soap dispenser - clickcolleen - clickcolleen
option -- replace light box with hotel vacancy sign - static
option -- one light vs. two light system - xavtek
option -- allow the door status to be checked remotely via webserver - drsquirrel - joe

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    63 Discussions


    1 year ago

    A way to substantially reduce the cost is to use the little magnetic door switches that are used for alarm systems. They are only a few dollars, are very light and can be mounted with double stick tape so no holes are drilled in the dorm room. By the look of the prox switch it is something that you had lying around so use what you have but if buying new look for it.


    Reply 9 years ago on Introduction

    Do-able - I need a way to detect whether or not he sink has been run since the door cycled.  Sensing actual water flow might be tricky... maybe I can detect the turn of the knob with a physical limit switch.

    I don't think I can execute the logic check easily with relays - though.  It might take a PLC (Programmable Logic Controller) to handle it.

    I love some Far Side - by the way :) 


    Reply 9 years ago on Introduction

    how about a combination of sensors, to make it harder to fool them.  and a timer to make sure they leave the water on for more than an instant.

    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.  like if someone is brushing their teeth, or just using the mirror.  then when someone needs to go really badly they can ask them to step out for a second.


    Reply 9 years ago on Introduction

    Actually, water conducts electricity. Just use a transistor and you're good to go... Nice Instructable by the way.

    Pie NinjaMr.Nelson

    Reply 9 years ago on Introduction

    You could try putting a momentary switch under the tap where the water comes out to detect the water flow.


    8 years ago on Step 4

    You should try using an airline indicator sign next time. I think it might be a little funnier haha. Just a suggestion.

    1 reply

    Reply 7 years ago on Introduction

    add a no smoking sign and a seatbelt sign as well, and make the seatbelt sign turn on and off at random intervals


    9 years ago on Introduction

    Read one of the edge lighting instructables and make a little light-up sign instead of just a plain circle of LEDs. Cool work!

    1 reply

    9 years ago on Introduction

    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! ! 

    1 reply

    Reply 9 years ago on Introduction

    Thanks.  Others have mentioned using a micro switch, but I like your direct approach.  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.