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ASI585MC Peltier Cooler Controller

This project is an ESP32-based thermoelectric cooler controller designed for a ZWO ASI585MC planetary camera.

Status: this project is still under active development. Hardware, firmware, control strategy, and integrations are not yet final.

Purpose

The goal is to turn a non-cooled ASI585MC camera into a temperature-controlled cooled camera using:

  • a Peltier cell
  • an ESP32 controller
  • PWM power control through a MOSFET
  • closed-loop PID temperature regulation
  • dew-point protection to reduce condensation risk

Main Hardware Platform

  • Board: Wemos / LOLIN D32 Pro
  • MCU: ESP32
  • Connectivity: WiFi + Bluetooth Low Energy

Main Components

Cooling System

  • Peltier / TEC module Used to cool the camera body or cold finger assembly.

  • Logic-level MOSFET Used to modulate the Peltier power with PWM from the ESP32.

  • Hot-side heatsink and fan Required to remove heat from the hot side of the Peltier.

  • Cold finger / thermal interface Mechanical part that transfers cooling from the TEC to the camera body.

Sensors

  • NTC 10K B3950 cold-side thermistor Measures the controlled cooling point temperature.

  • NTC 10K B3950 hot-side thermistor, optional Protects the TEC and heatsink by shutting down PWM if the hot side overheats.

  • BME280 Measures ambient temperature and relative humidity.

  • INA219 Measures Peltier current and bus voltage.

Control Features

  • PID loop for cold-side temperature regulation
  • target temperature control
  • dew point calculation from ambient temperature and humidity
  • dew-point override so the effective target does not drop below a safe margin
  • hot-side thermal protection when the optional hot thermistor is enabled
  • current monitoring for power diagnostics

Network and User Access

  • Web dashboard for live status and configuration
  • BLE JSON service
  • BLE structured service with dedicated characteristics
  • AP fallback for onboarding
  • captive portal for first WiFi setup
  • persistent network settings page
  • mDNS support with .local

Stored Settings

The controller stores settings in non-volatile memory, including:

  • WiFi SSID and password
  • hostname
  • DHCP or static IP configuration
  • PID parameters
  • cooler target and limits
  • sensor calibration offsets
  • saved cooling presets

Default Pin Mapping

  • GPIO25: Peltier PWM output
  • GPIO34: cold-side NTC input
  • GPIO35: hot-side NTC input
  • GPIO21: I2C SDA
  • GPIO22: I2C SCL

Suggested Electrical Notes

  • Use a proper external power supply for the TEC
  • Do not power the Peltier directly from the ESP32 board
  • Use adequate wiring, grounding, and fuse protection
  • Add a MOSFET gate pulldown and, if needed, a gate driver stage
  • Ensure the hot side has enough thermal dissipation before extended testing

Suggested Mechanical Notes

  • Insulate the cold side to reduce condensation and thermal losses
  • Use thermal paste or suitable thermal pads where needed
  • Avoid stressing the camera body mechanically
  • Test gradually with limited duty cycle before using aggressive cooling targets

Development Note

This repository currently represents a development-stage prototype.

That means:

  • wiring may still change
  • firmware behavior may still evolve
  • the user interface and onboarding flow may still be refined
  • the Alpaca bridge is currently focused on cooler control only
  • full long-term hardware validation is still pending

Recommended Validation Before Real Use

  1. Verify sensor readings with the Peltier disabled.
  2. Verify current readings and PWM control at low duty cycle.
  3. Verify hot-side temperature protection.
  4. Verify dew-point protection in humid conditions.
  5. Run longer tests before attaching the final assembly to the camera.