SV241-Unbound Telescope Power Controller

This is a replacement firmware for the Svbony SV241 Pro. DISCLAIMER: This firmware is provided "as-is" without any warranty. Use it at your own risk. The author is not responsible for any damage to your device.

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This is a hobby project. If you find it useful and would like to support a good cause, consider donating via betterplace.org—all donations go directly to Doctors Without Borders.

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Table of Contents

• Project Overview
• Quick Start Guide
  • 1. Install the ASCOM Alpaca Proxy
  • 2. Flashing the Firmware
  • 3. Connecting from Astronomy Software
• The ASCOM Alpaca Proxy
• Advanced: Serial Command Interface
• Troubleshooting

Project Overview

This project consists of two main components:

1. Custom Firmware: A replacement firmware for the ESP32-based Svbony SV241 Pro controller. It unlocks advanced control over power outputs and dew heaters.
2. ASCOM Alpaca Proxy: A standalone application that runs on your computer. It connects to the controller via USB and exposes its functions as standard ASCOM devices. It should work with any ASCOM Alpaca compatible astronomy software (tested with NINA, validated with Conform Universal). For software without native Alpaca support, the installer includes a helper script to register a classic ASCOM driver (see Driver Installation).

Firmware Features

• Control for 5 DC outputs, 2 USB groups, and 1 adjustable voltage output (0-15V, powered by a Southchip SC8903 buck-boost converter).
• Advanced dew heater control:
  • Manual Mode: Variable 0-100% PWM control.
  • PID Mode: Automatic temperature regulation using a lens temperature sensor and configurable target temperature above dew point.
  • Ambient Tracking: Sensorless power adjustment based on ambient temperature and humidity.

PID Mode - How It Works

In PID Mode, the controller automatically adjusts heater power to maintain the lens temperature at a safe level above the dew point:

• Lens Temp: The current temperature of the lens, measured by an external sensor.
• Target Temp / Minimum Temp: The desired temperature offset above the ambient dew point. A typical value is 3-5°C.

The controller calculates the dew point from ambient temperature and humidity, adds the target offset, and adjusts heater power to maintain that temperature.

Important: The lens temperature sensor (labeled TEMP on the SV241) must be positioned under or adjacent to the dew heater strap. This ensures the sensor measures the heated area and provides accurate feedback for the PID controller.

• On-board sensor suite for monitoring power, ambient temperature/humidity, and lens temperature. The firmware is resilient to sensor failures.
• Experimental automatic drying cycle for the SHT40 humidity sensor.
• Configuration persistence across reboots.
• A powerful JSON-based serial command interface for direct control and integration.

Quick Start Guide

Follow these steps to get up and running quickly.

1. Install the ASCOM Alpaca Proxy

1. Download the latest installer (SV241-AscomAlpacaProxy-Setup-x.x.exe) from the project's releases page.
2. Run the installer. It's recommended to allow the proxy to start automatically with Windows.
3. Once running, an icon will appear in your system tray. Right-click it and select "Open Setup Page" to access the web interface.

2. Flashing the Firmware

Note: The web flasher requires a modern browser with Web Serial API support (Chrome or Edge).

On first startup, the proxy will display a First-Run Wizard that guides you through the firmware installation:

1. Connect the SV241 controller to your computer via USB.
2. The wizard will automatically check for compatible firmware.
3. If no firmware is detected, click "Flash Firmware" to open the integrated web flasher.
4. Select the correct COM port and follow the on-screen instructions.

Warning: Make sure you select the correct COM port! If you have other ESP32 devices connected, their firmware will be overwritten without further confirmation.

Alternative: Use the standalone SV241-Unbound Web Flasher directly.

3. Connecting from Astronomy Software

1. Open your ASCOM-compatible astronomy software (e.g., NINA).
2. Go to the equipment or hardware section.
3. When choosing a Switch or ObservingConditions device, open the ASCOM chooser.
4. You should see "SV241 Power Switch" and "SV241 Environment" listed under the Alpaca section. Select them.

You can now control the power outputs and read sensor data directly from your main software!

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The ASCOM Alpaca Proxy

The proxy application is a crucial part of the system, translating the device's serial commands into standard ASCOM Alpaca APIs. It runs on your computer, connects to the controller via USB, and exposes its functions to astronomy software.

It includes features like auto-detection and custom ASCOM actions.

Key Features:

• Rich Web Interface: A modern, responsive dark-themed dashboard for full control and configuration.
• Telemetry History: Built-in interactive charts for analyzing power and environmental data over time.

For detailed information on its features, configuration, and usage, please see the dedicated documentation:

ASCOM Alpaca Proxy Documentation

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Advanced: Serial Command Interface

Click to expand the detailed Serial Command Reference

The controller communicates over serial at 115200 baud. Commands are sent as JSON strings, terminated by a newline character (\n).

Important: All JSON commands must be sent as a single, continuous line of text without any line breaks, followed by a single newline character (\n) to execute the command.

Get Sensor Data

• Request: {"get": "sensors"}
• Response: A JSON object with the latest sensor readings.
  • v: Input Voltage (V), i: Input Current (mA), p: Input Power (W)
  • t_amb: Ambient Temp (°C), h_amb: Ambient Humidity (%), d: Dew Point (°C)
  • t_lens: Lens Temp (°C), pwm1/pwm2: Heater Power (%)
  • hf, hmf, hma, hs: Heap memory statistics (Bytes)

Get Power Status

• Request: {"get": "status"}
• Response: A JSON object with the on/off state (1/0) of all outputs.
  • Example: {"status":{"d1":1,"d2":1,"d3":0,...},"dm":[0,1]}
  • dm: Dew heater modes array (0: Manual, 1: PID, 2: Ambient Tracking, 3: PID-Sync, 4: Min Temp, 5: Disabled)

Set Power State

• Request: {"set": {"<output_name>": <state>, ...}}
• <output_name>: d1-d5, u12, u34, adj, pwm1, pwm2, or all.
• <state>: 1 or true for ON, 0 or false for OFF.
• Response: The new power status JSON, reflecting the state after the change has been applied.

System Commands

• Reboot: {"command": "reboot"}
• Factory Reset: {"command": "factory_reset"}
• Manual Sensor Drying: {"command": "dry_sensor"}
  • Triggers the SHT40 internal heater to remove condensation. This is a blocking operation.
• Get Firmware Version: {"get": "version"}
  • Response: A JSON object containing the firmware version (e.g., {"version": "1.0.0"}).

Get/Set Full Configuration

• Get Config Request: {"get": "config"}
• Set Config Request: {"sc": { ... }}
• Response (for both): The complete configuration JSON, reflecting the state after the change has been applied.

Configuration Object Structure

• Parameter Breakdown: The body of the request is a JSON object containing one or more of the following top-level keys. You only need to send the keys for the settings you wish to change.

For numerical parameters without explicit ranges, typical values are expected. Refer to the firmware's source code for precise limits if needed.

Key	Description	Value Type
so	Sensor Offsets: Sets calibration offsets for sensor readings.	object
ui	Update Intervals: Sets the update frequency for sensors.	object
ps	Power Startup: Defines the on/off state of outputs at boot.	object
ac	Averaging Counts: Controls the samples for the median filter.	object
av	Adjustable Voltage: Sets the preset voltage for the converter.	float
ad	Auto Dry: Configures the automatic sensor drying feature.	object
dh	Dew Heaters: Configures the two dew heaters.	array

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so (Sensor Offsets)

Sub-Key	Description	Value Type
st	SHT40 Temperature offset (°C)	float
sh	SHT40 Humidity offset (%)	float
dt	DS18B20 Temperature offset (°C)	float
iv	INA219 Voltage offset (V)	float
ic	INA219 Current offset (mA)	float

ui (Update Intervals)

Sub-Key	Description	Value Type
i	INA219 (Power) interval (ms)	unsigned long
s	SHT40 (Ambient) interval (ms)	unsigned long
d	DS18B20 (Lens) interval (ms)	unsigned long

ps (Power Startup States)

Sub-Key	Description	Value Type
d1-d5	Startup state for DC Outputs 1-5	boolean
u12	Startup state for USB Group 1/2	boolean
u34	Startup state for USB Group 3/4/5	boolean
adj	Startup state for the Adjustable Voltage Converter	boolean

ac (Averaging Counts)

Sub-Key	Description	Value Type
st	Sample count for SHT40 temperature	int
sh	Sample count for SHT40 humidity	int
dt	Sample count for DS18B20 temperature	int
iv	Sample count for INA219 voltage	int
ic	Sample count for INA219 current	int

ad (Auto Dry)

Sub-Key	Description	Value Type
en	Enable the auto-dry feature (true/false).	boolean
ht	Humidity Threshold: The humidity (%) above which the trigger timer starts (e.g., 99.0).	float
td	Trigger Duration: The time in seconds the humidity must stay above the threshold to trigger the heater (e.g., 300 for 5 minutes).	unsigned long

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dh (Dew Heaters)

This is an array that can contain up to two heater configuration objects. To update a specific heater, you place its configuration object at the corresponding index (0 for PWM1, 1 for PWM2).

Common Heater Properties:

Key	Description	Value Type
n	Name of the heater (e.g., "PWM1"). This is read-only.	string
en	Enabled on startup: true to enable the heater on boot.	boolean
m	Mode: Sets the control mode for the heater (0: Manual, 1: PID, 2: Ambient Tracking, 3: PID-Sync, 4: Minimum Temperature, 5: Disabled).	int

Mode-Specific Properties:

• Mode 0: Manual

  Key	Description	Value Type
  mp	Manual Power (0-100%).	int (0-100)

• Mode 1: PID (Lens Sensor)

  Key	Description	Value Type
  to	Target Offset: Desired temperature difference above the dew point (e.g., 3.0 for 3°C warmer).	float
  kp	Proportional gain: Reacts proportionally to the current temperature error. Higher values lead to a stronger, faster reaction.	double
  ki	Integral gain: Accumulates past errors to correct small, constant offsets over time. Helps eliminate steady-state errors.	double
  kd	Derivative gain: Reacts to the rate of temperature change. Helps to dampen overshoot and oscillations.	double

• Mode 2: Ambient Tracking (Sensorless)

  Key	Description	Value Type
  sd	Start Delta: Temp difference (Ambient - Dew Point) at which heating begins.	float
  ed	End Delta: Temp difference at which the heater reaches its maximum configured power.	float
  xp	Max Power (0-100%): The maximum power the heater is allowed to use in this mode.	int (0-100)

• Mode 3: PID-Sync (Follower) This mode allows a heater (the "follower") to mirror the power output of another heater running in PID mode (the "leader"). It is ideal for a guidescope heater that should follow the main scope's heater without needing its own sensor.

  Key	Description	Value Type
  psf	PID Sync Factor: A multiplier for the leader's power (e.g., 0.8 means the follower runs at 80% of the leader's power).	float

• Mode 4: Minimum Temperature This mode works like PID mode, but ensures the lens temperature never drops below a configured minimum, regardless of the dew point.

  Key	Description	Value Type
  to	Target Offset: Desired temperature difference above the dew point (same as PID mode).	float
  mt	Minimum Temperature: The absolute minimum lens temperature to maintain (e.g., 5.0 for 5°C).	float
  kp, ki, kd	PID tuning parameters (same as Mode 1).	double

• Mode 5: Disabled This mode completely disables the heater output and hides it from the ASCOM interface. Useful if you don't use one of the heater channels.

• Examples:

  • Change Adjustable Converter Voltage:

    {"sc": {"av": 9.5}}

  • Set Heater 1 (PWM1) to Manual 50% power:

    {"sc": {"dh": [{"m": 0, "mp": 50}]}}

    (Note: [{"m":...}] targets the first heater. The array index matters.)

  • Configure Heater 2 (PWM2) for Ambient Tracking:

    {"sc": {"dh": [null, {"m": 2, "sd": 6.0, "ed": 1.5, "xp": 75}]}}

    (Note: null is used as a placeholder to indicate that Heater 1's configuration should not be changed.)

  • Comprehensive Example: Change multiple settings at once: This example sets the startup state for DC1 to ON, changes the voltage preset, and configures Heater 1 for PID control.

    {"sc":{"ps":{"d1":true},"av":8.5,"dh":[{"m":1,"to":2.5,"kp":150}]}}

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Using PowerShell for Direct Serial Communication

You can send commands directly to the controller via PowerShell without the proxy. Replace COM9 with your actual COM port.

Generic Template:

$port = New-Object System.IO.Ports.SerialPort "COM9", 115200
$port.Open()
$port.WriteLine('{"get": "sensors"}')  # Your command here
Start-Sleep -Milliseconds 200
$port.ReadExisting()
$port.Close()

Example: Read Sensor Data

$port.WriteLine('{"get": "sensors"}')
# Response: {"v":12.8,"i":802,"p":10.3,"t_amb":18.5,"h_amb":65,...}

Example: Turn DC1 On

$port.WriteLine('{"set": {"d1": true}}')
# Response: {"status":{"d1":1,"d2":0,...}}

Example: Set Heater 1 to Manual 50%

$port.WriteLine('{"sc": {"dh": [{"m": 0, "mp": 50}]}}')
# Response: Full config JSON

Tip: For interactive testing, use a serial terminal like PuTTY (115200 baud) or the Arduino IDE Serial Monitor.

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Hardware SV241 Pro

Microcontroller Specifications

• Model: ESP32-PICO-D4 (Espressif Systems)
• Architecture: Xtensa LX6 Dual-Core up to 240 MHz
• Flash Memory: 4 MB Embedded
• Connectivity: Wi-Fi / Bluetooth (Hardware capability only; software uses USB-only communication)

GPIO Pinout Mapping

GPIO	Function	Description
12	DC2	12V Switched Output
13	DC1	12V Switched Output
14	DC3	12V Switched Output
18	USB 3/4/5	USB-A Ports
19	USB-C 1/2	USB-C Ports
21	I2C SDA	Data Line (Sensors)
22	I2C SCL	Clock Line (Sensors)
23	OneWire	DS18B20 Lens Sensor
25	Adj. Voltage	PWM for Southchip SC8903 (Adjustable Output)
26	DC5	12V Switched Output
27	DC4	12V Switched Output
32	PWM2	Dew Heater 2
33	PWM1	Dew Heater 1