Stoplight

🚥 Stoplight

Features

• TMC2209 Stepper Driver
• 1 Ω Sense Resistors (tuned for small motors)
• HUSB238 PD Controller for dynamic Voltage Control
• On-board temperature sensing
• Made for ESPHome
• Matter Accessory via rs-matter

Stoplight is a Xiao shield for operating small stepper motors. It is designed specifically for 28-BYJ48, although it may work with other small (0.225 RMS Amps or less) steppers as well. It aims to provide utility all around the home, and is especially useful when working with blinds and knobs.

Commercial stepsticks have sense resistors that are not properly sized for 'smaller' motors, making it more difficult to take advantage of TMC2209's features, including stallguard.

StopLight brings reliable stall sensing to commodity/low cost, high torque motors.

Stoplight seeks to remedy these issues, while also providing software selectable voltage control and temperature measurement in a package that works well with HomeAssistant/ESPHome.

For those not using HomeAssistant, StopLight can be used as a Matter accesory in your Apple/Google/WhatEver home.

Todo

• TVS Protection
• Change C14 to same as C18 (BOM Consolidation)
• Consider removing DIAG and just using UART events instead
• Consider reconnecting fan port
• Address DS18B20U reading high
• Test fit in mini blind housing
• Dim LED brightness
• Test StallGuard tuning
  • ✅ works very well at 12v+
  • ⚠️ 9v is untested
  • 🚦 5v is more finicky
• Add esphome sample yaml's
• Rewrite as Matter accessory

Homing

Fabrication

Use the production files to upload to jlc. Or first run available here.

You'll need to swap the motor wires to a JST XH 4 pin housing. In addition to removing the red cable, you also must perform the bipolar mod on your steppers.

Example HomeAssistant Config

The build sometimes fails, but can usually be completed by repeatedly pressing 'Retry', or switching to 'arduino' framework. If your ESPHome builds are failing, you may need to allocate more RAM, especially if you're running in a VM.

Tuning

substitutions:
  name: "stoplight"
  friendly_name: "StopLight"
  board: "seeed_xiao_esp32c3"

# board/wifi/ota stuff
packages:
  device_base: !include .esp32.yaml

esp32:
  framework:
    type: esp-idf

logger:
  level: DEBUG

esphome:
  on_boot:
    - tmc2209.configure:
        direction: cw # or ccw
        microsteps: 1
        interpolation: True
        enable_spreadcycle: False
        tcool_threshold: 0

Wall Heater

substitutions:
  name: "heater"
  friendly_name: "Wall Heater"
  board: "seeed_xiao_esp32c3"

# board/wifi/ota stuff
packages:
  device_base: !include .esp32.yaml

esphome:
  on_boot:
    # - lambda: id(husb_01)->command_request_voltage(5);
    - tmc2209.configure:
        direction: cw # or ccw
        microsteps: 1
        interpolation: True
        enable_spreadcycle: False
        tcool_threshold: 0
        tpwm_threshold: 0
    - tmc2209.stallguard:
        threshold: 23
    - tmc2209.currents:
        standstill_mode: freewheeling
        run_current: 0.1375 # was 0.150

Blinds

substitutions:
  name: "blins03"
  blind_number: right
  friendly_name: "Right Blind"
  board: "seeed_xiao_esp32c3"
  delay: "1s"

# board/wifi/ota stuff
packages:
  device_base: !include .esp32.yaml

esphome:
  on_boot:
    - tmc2209.configure:
        direction: ccw # or ccw
        microsteps: 1
        interpolation: True
        enable_spreadcycle: False
        tcool_threshold: 0
        tpwm_threshold: 0
    - tmc2209.stallguard:
        threshold: 45 
    - tmc2209.currents:
        standstill_mode: freewheeling

Schematic

Reference

TMC2209 Calaulations Worksheet

BTT-TMC2209-v1.2

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