👋 [Sept 2024] I’ve made lots of improvements to both the service (now hosted as an Azure Function) and the ESP module programming (using an esphome config). Read this post and then check out these updated links!

This past Christmas I set out to make a DIY “lovebox” as a gift. These devices come in pairs - each device at a different location. When one person performs some trigger, the peer device lights up. It’s a fun and passive way to let your partner know you’re thinking of them.

I thought it would be fun (and way cheaper!) to try and build the product myself. Below are the steps and associated code if you’d like to create one yourself!

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Parts

  • 2x ESP8266 boards (I used these) because they were a good size and required minimal soldering.
  • LEDs to solder onto the boards (I used red)
  • Some kind of transparent film to place over the hearts (the material I had wasn’t great, open to suggestions!)
  • 3D printed box (see below)
  • Soldering iron

Quickstart

If you to try the project for yourself:

  • Pull ghcr.io/joshspicer/lovebox and start the docker container
  • Update the variables.h file, setting the first unit as me=1 and peer=2 (and vice versa for the second box)
  • Flash sketch.ino to your boards that have an LED soldered onto the correct pin.

Hardware and 3D Model

For the 3D model, I had in mind a “companion cube” from Portal. I found a model by mooraayeelz online that fit the bill perfectly! I printed two on my Ender 3 with default PLA settings. I printed the base separately in a different color for some contrast.

As shown in the parts list, I used ESP8266 boards. I soldered the LEDs to GPIO pin 2 on the boards with a resistor appropriate for the LEDs I had on hand. I used a hot glue gun and some screws to attach things in place. I also snaked through a USB cable that sneaks out the back of the box for power.

Software

Each box is assigned an identifier (1 or 2) and a peer (the other box). The boxes are programmed to listen for a message from the peer and turn on the LED when a message is received.

#include <Arduino.h>

const char *ssid = "<TODO>";
const char *password = "<TODO>";
String me = "1";
String peer = "2";
String baseAddress = "http://<TODO>:3000";

String getMeAddress = baseAddress + "/?user=" + me;
String provisionMeAddress = baseAddress + "/provision?user=" + me;
String postPeerAddress = baseAddress + "/?user=" + peer;

I wrote a simple node server to run in the cloud and coordinate the “on” and “off” states. Each device is programmed to retrieve configuration at /provision startup from the coordination server with its id.

The simple state machine is maintained in-memory:

if (userObj.enable === 1 && userObj.ack === 0) {
    console.log(`[+] User '${userObj.id}' ack. Queuing disable for '${enableDurationInSeconds}' seconds.`);
    userObj.ack = 1;
    setTimeout(() => {
        console.log(`[*] Disabling user ${userObj.id}`)
        userObj.enable = 0;
        userObj.ack = 0;
    }, enableDurationInSeconds * 1000);
} else if (userObj.enable === 1 && userObj.ack === 1) {
    console.log(`[no-op] User '${userObj.id}' is already active.`)
} else {
    console.log(`[no-op] User '${userObj.id}' is not enabled.`);
}

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Simple, yet effective! I’ve also provided commented sections in the sketch where a Basic authentication header can be added to the HTTP requests. For example, running these services in an Azure Function and hardcoding in the shared secret would be a good way to secure the endpoints.

Triggering with a Siri Shortcut

I wanted to be able to trigger the box with a Siri Shortcut to trigger the partner’s device! I then added the shortcut to my home screen and added it to my home screen. These are easily shared though text - a great way to share with the gift’s recipient!

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Conclusion

The full source code can be found at https://github.com/joshspicer/lovebox. Thanks for reading!