🔥 STRETCH Fire

A cozy LED fireplace that throws sparks every time someone books a class.

The real thing in the studio. Full 35 second video (MP4, 8 MB).

Built for STRETCH, a yoga studio in Vancouver's Chinatown.

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What is it?

A strip of warm lights that glows and flickers like a real wood fire. It sits quietly in the studio all day. When someone books a class online, the fire flares up and sends a shower of sparks up the strip, then settles back down.

No screens, no beeps, no dashboards. Just a little moment of celebration that everyone in the room can feel: someone new is coming to practise with us.

🪵 Looks like a real fire	Embers glow and fade on their own, with the odd draught dimming the flames, in warm ember-to-amber colours.
✨ Sparks for every booking	One booking, one burst. Three bookings in a row? Three bursts, one after another, so you can count them.
🏠 Part of the smart home	Turn it on and off, dim it, or change the style from your phone with Home Assistant.
🔌 Set and forget	Plug it in and it lights up. Updates arrive over Wi‑Fi, no cables needed.

How does a booking become a spark?

flowchart LR
    A["🧘 Someone books<br/>a class"] --> B["📧 The booking system<br/>sends an email"]
    B --> C["📬 The inbox spots it<br/>and taps a webhook"]
    C --> D["🏠 Home Assistant<br/>presses 'Spark'"]
    D --> E["🔥 The fire<br/>throws sparks"]

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1. Someone books a class. STRETCH uses Momence, which emails the studio for every new booking.
2. The inbox spots the email. A rule in the shared inbox (Missive) watches for emails titled "New booking for…" and instantly pings Home Assistant over the internet.
3. Home Assistant presses the Spark button on the fire.
4. The fire flares. The whole thing takes a second or two.

Tip

Not using Momence or Missive? Almost any booking system can do this. If it emails you about bookings, or offers webhooks or Zapier, you can point it at Home Assistant. See the booking trigger guide.

What's inside

Part	What it does	Rough cost
ESP32 dev board	The brains. A tiny Wi‑Fi computer that runs the fire effect.	~$10
60 LED strip (WS2812B, 1 m)	The fire itself. Every light can be its own colour.	~$20
74AHCT125 chip	A translator so the 3.3 V board can talk clearly to the 5 V lights.	~$2
5 V power supply, 2 to 3 A	Powers everything.	~$15
330 Ω resistor + 1000 µF capacitor	Protects the lights from spikes.	~$1
Something to diffuse the light	Frosted tube, paper lantern, a jar, a log-shaped shade...	your call

About $50 in parts, plus an afternoon. Full instructions are in the build guide.

Build your own

1. Wire it up following the diagram above (step by step).
2. Install the software with ESPHome. It's one command once your Wi‑Fi details are filled in (how).
3. Add it to Home Assistant. It's usually found automatically (how).
4. Connect your bookings so each one presses the Spark button (how).

Something not right? See troubleshooting.

🛠️ For the technically curious

• Firmware: ESPHome on ESP-IDF, using the esp32_rmt_led_strip light platform. Config in esphome/stretch-fire.yaml.

• Effects: two custom addressable_lambda effects in esphome/fire_effects.h:

  • Hearth: two octaves of smooth value noise per pixel, a contrast stretch, random "gusts" that dim the whole fire and recover exponentially, and a floor so the coals never go fully dark.
  • Fire2012: Mark Kriegsman's classic rising-flame simulation, for strips mounted vertically.
  • Both map "heat" through a warm palette (black, ember, red, orange, amber, pale yellow, never blue or white), and scale each frame to stay under a 2 A power budget.

• Sparks are an overlay, not an effect, so a booking never resets the fire. Each burst brightens the whole strip toward amber, decaying over about a second, and spawns 8 to 14 near-white sparks that drift along the strip and cool to orange. Bursts queue (up to 20) and play back to back.

• Home Assistant gets a light (with Hearth and Fire2012 effects), a Spark button, a spark action that takes a count, plus Wi‑Fi signal, uptime and restart.

• Trigger: an HA webhook automation in queued mode, so simultaneous bookings each get a burst.

• Original sketch: the project started as an Arduino/FastLED sketch with a serial command interface and lots of diagnostics. It's kept in arduino/fire_flicker for anyone who wants a standalone fire with no smart home.

• The rendered demo GIF below is produced by tools/render_demo.py, a Python port of the same effect maths, so you can see the spark overlay without the hardware.

  

Credits

• Fire2012 effect by Mark Kriegsman, from the FastLED project.
• Built on ESPHome and Home Assistant.
• Made with care at STRETCH, 180 E. Pender St, Vancouver. Come practise with us. 🧡

_{MIT licensed. Build one for your studio, café, shop or living room.}