Wireless Bathroom Vacancy Sign

by littleBits

Published on April 23, 2014

To avoid lines in our busy office, we made a central bathroom vacancy sign that indicates whether the bathrooms are available or not. Two wireless transmitters and a wireless receiver (along with a couple motion triggers and servos) make this system possible. Otherwise we might have needed more than 50 wire modules!

Credits: Bathroom pictogram by Igor Piskunov from The Noun Project

How To Make It


Build the circuit first. This project consists of 3 separate circuits - two transmitter circuits (one for each bathroom) and one receiver circuit for the display. The transmitter circuits sense if a person is in one of the bathrooms and send out the signal to the receiver (the display). The receiver grabs the signal and displays the availability of each bathroom by changing the servo’s orientation, thus changing the color of our vacancy graphics. For the first transmitter: power + motion trigger + RGB LED + wireless transmitter. For the second transmitter: power + motion trigger + RGB LED + wireless transmitter. Although the components that we use for the two transmitter circuits are exactly same, the configuration is different. On the wireless modules, you will see that there are 3 channels (labeled 1, 2, and 3). You will want to make sure that each bathroom transmitter is on a different channel. For the first transmitter circuit, the RGB LED should connect to channel 1 on its wireless transmitter. For the second transmitter circuit, the RGB LED should snap to channel 3 on its wireless transmitter. It is very important to make sure that you use two different channels so as not to mix them up. Also, because this project is a permanent installation in our office, we connected the power modules to power adapters instead of batteries. Check the circuit diagram to see how to set up the receiver circuit. This receiver circuit is a permanent installation in our office and also eats up a lot of power, so we used a power adaptor rather than a battery.


Place your circuit on mounting boards. Each transmitter circuit should fit on one mounting board. The receiver circuit will need two. Try to place the bright leds in the center of each mounting board on the receiver. This way you can evenly light up your graphics on the display. Also, make sure that the screw holes on the mounting boards are not blocked.


Lasercut all the plywood parts. You can download the template file from this page. Glue the the center pieces together to make one thick piece. We did some spackle work after cutting and painted the wood white. The thin layer of paint affects the tightness of the parts assembly, so use masking tape if needed.


Cut out the acrylic discs in the template file. Attach the round servo arm to the middle of the each disc with steel wire.


Cut a clear 4” diameter plastic pipe to 200mm in length (7.87”). Glue an acrylic disc to one end of the pipe. The servo arm should be positioned facing into the pipe.


Cut slide guides (bearings), using the laser cutter, out of ¼” acrylic board. Slot them in into the notches and screw down to the plywood backbone board. You need to drill screw holes on them before.


Make two pictogram signs. You can use our file or make your own. The bathroom graphics we used come from Igor Piskunov of the Noun Project. Add a piece of white paper behind the cutout as a diffuser for the bright LEDs.


Assemble all the plywood parts.Use 4 wood screws to connect the centerpiece and the base board firmly.


Attach the paper graphics and the mounting boards (with circuits) to the backbone board using M3 screws. Before you cover the circuit with the paper graphics, set the timeout appropriately (ours is set to ~30 seconds) and organize the wires so not to make any shadows on your graphics.


Place servos into their positions on the plywood and screw them down. You will need to make screw holes at the end of the backbone board before that.


Cut red plastic film and place it in the plastic tube. Position the film so that it covers up the light-up graphics when the bathroom is occupied and the servo turns. Gluedots are a good way to attach the film to the tube.


After fixing the position of the plastic film, attach the plastic pipe parts to the servos by connecting to their corresponding arm attachments Use the servo screws to hold them in place.


Place each of your transmitter circuits in the two bathrooms and place the receiver in an appropriate location where everyone can see. You can use gluedots to stick the transmitters to the wall, but the receiver should be fixed very firmly because it has moving parts and is heavy. We used cable ties to hold it on the air duct on our ceiling.


Never wait in a bathroom line again! Just sit in your chair and let littleBits notify you when the bathroom is free.

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