Honest ETA Device

by emily_littlebits

Published on February 11, 2015

This project was made using the Popular Science Super Bundle, our most powerful bundle.

Make an honest ETA device that lets your housemate [parent, significant other, roommate] know when you are on the way home and likely to arrive.
This cloud-connected progress meter tracks your proximity to home by reading your location from your smartphone and displaying it on a bargraph module in your house.  If arriving home first, you can text your housemate with the press of a button to let him/her know that you got home first.

*Note: This project works as a circuit setup, so you can make it with just Bits! If you like, you can follow further instructions for adding extra features and constructing the “housing”.

How it works:

This project uses a GPS enabled smartphone, and a few IFTTT recipes, the cloudBit, and a bargraph to visually display information about your proximity to home. The IFTTT recipes are set up using the location channel. This channel triggers when you enter or exit a location radius that you set. Because there are 5 LEDs on the bargraph, we set up 5 radii, each with recipes related to entry and exit so you can track someone as they come and go. When you leave the office, your smartphone will notify the cloudBit as you get closer to home and start lighting up the LEDs on the bargraph. The closer to home you are, the more LEDs will be lit up.

Additional features:
With a threshold, MP3 player and speaker, you can add an audio cue that lets your roommate know when you’ve left the building. The threshold is set to trigger when the bargraph moves to the 2nd LED.

Make it home first? With the addition of a button and an IFTTT SMS recipe, you can have the cloudBit send a text to your roommate to let him/her know you made it home first and that you'll start dinner. 

Build it out! Turn this circuit into an interactive wall piece that both displays your progress and holds your wallet. With a small hinged platform that sits directly on top of the button, the act of placing your wallet inside the case will automatically press the button, sending a text message. You can also add some acrylic edge lighting to the bargraph for nice visual effect.


How To Make It


Set up your cloudBit if you haven’t done so already. Instructions for setting up the cloudBit can be found here.


Connect your circuit. We will start with the most basic circuit for this project and then build on for more features. Click here for the circuit diagram.


Create an account on IFTTT (If This Then That) and activate the littleBits channel if you haven’t done so already. For more information about using the cloudBit with IFTTT, check out our cloudBit + IFTTT Tips & Tricks.


Set up IFTTT location recipes. These recipes will talk to the cloudBit and output specific voltages to the bargraph based on the GPS location of your smartphone. Make 10 recipes that track when you enter and exit a series of location radii [You can determine the scope of the radii in IFTTT] and set the output voltages to the cloudBit accordingly. The more voltage you send, the more LEDs on the bargraph will illuminate. Diagram: Click here to see how we set up our IFTTT recipes with the cloudBit and bargraph.


Now that the IFTTT recipes are set up, the main part of the project should be functioning. When you enter and leave the zones that you determined in IFTTT, the bargraph should display a corresponding number of LEDs, showing your proximity to home. Test it out with a friend. Take a walk while your friend stays with the circuit to make sure it is working. You could stop here, but if you want to add more features, continue reading.


Add a sound clip to notify your roommate [or family members] that you are on the way home. We chose to trigger the sound clip when entering Zone 2. To do this, we added a threshold + mp3 player + speaker after the bargraph. We set the threshold to 35 to correspond with the second LED on the bargraph. This means that the sound clip will only trigger when the voltage sent is over 35%. Because the IFTTT recipe says to send 40% “forever”, and all the next voltages sent while on your way home are above 40% [“forever”], the signal won’t drop below the threshold level until you enter Zone 1 again. To learn how to set the threshold module, check out the Threshold Tips & Tricks

You will also need to load .mp3 files onto your MP3 player module. To learn how to do this, check out the MP3 Player Tips & Tricks. Once your sound files are loaded, switch your mp3 player into “once” mode.


The next feature you can add is a text notification that lets your roommate [or family members] know when you’ve actually made it home. This is good for a scenario in which you are the first home and want to let the others know. In your circuit, place the button in between the power module and the cloudBit. You will also need to set up another IFTTT recipe here. It should read: IF littleBits button is pressed, THEN send an SMS text to your roommate.


The next steps will cover how to turn this circuit into an interactive wall piece that both displays your progress and holds your wallet. For the wall piece, check out the final circuit on the circuit diagram. You will notice that we added a split to make the circuit more flexible, and a fork + a second bargraph for extra illumination.


Time to make some fancy edge lighting! Edge lighting is acrylic that you place over the bargraph to diffuse the light from the LEDs and make a nice visual display for the progress meter. To make the edge lighting, you need 5 pieces of clear ⅛” acrylic, and 6 pieces of opaque 1/16” material (we used acrylic here too). If you have access to a laser cutter, use the templates provided to cut out your material. If not, use the templates to trace onto the acrylic and then cut out the shapes using a dremel. Once the pieces are cut, you will want to rough up the outer edges (except the sections that touch the bargraphs) with sand paper. This will help to diffuse the light better. Stack the the acrylic pieces alternating between opaque and clear. Two opaque pieces should flank the ends. Now you will want to glue all the pieces together. You can use acrylic glue or epoxy to do this. Then, place the edge lighting over your bargraphs and test it out! Pretty cool huh!


Build the enclosure. There are two parts of the enclosure, and inner box and an outer box. Cut out the pieces using the templates provided and glue them up. You can also make your own enclosure! What materials do you have around? Perhaps you have a box you can repurpose. On the inner box, we carefully glued 4 nuts to the inside of the back panel using epoxy. The nuts will line up with the screws you use when connecting the inner and outer boxes in upcoming steps.


Place the Bits in the smaller box. See how we laid them out in the images above. We used a few adhesive shoes to hold the circuit down and a mounting board (mounted with double sided tape) on the back panel to hold the bargraphs. Here, if you are using our template, you will want to make sure that the bargraphs are placed directly below the rectangular cutout in the outer enclosure. You will also want to pull the speaker off the board and disconnect the JST connection.


Slide the smaller box into the outer enclosure. Secure them together in the back with screws in the holes provided. You might want to countersink the holes in the back panel so the screws lie flat.


Place the speaker in from the front of the square cut out until it fits snugly. On the inside, grab the JST connection and reconnect it with the speaker board. If you can fit your hand inside, try using pliers. Then, you should be able to slide your edge lighting through the rectangular hole on the right and fit it snugly over the bargraphs. If you want to ensure that it doesn’t fall out, you can place a small bolt through the hole in the center of the acrylic, which will lock the edge lighting in place from the back.


The final touch for this build is to add a small hinged platform that sits on top of the button. You will then be able to press the button by simple placing your wallet on the platform. Glue or screw two small hinges to the platform and then place over the button. Determine the best height for triggering the button with the platform, and then fix the other side of the hinge to the outer case.


You are ready to rock! Plug it in and hang on the wall by your door. Boom! No more missed dinner dates!

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