flatpanel/WIRING.md

ESP32 FlatPanel – Wiring & BOM

What to buy

Item	Purpose	Notes
IRLZ44N N-channel MOSFET × 2	LED brightness + dew heater control	Logic-level: 3.3 V gate from ESP32 is sufficient. One per load.
100 Ω resistor × 2 (1/4 W)	MOSFET gate current limiting	One per MOSFET
10 kΩ resistor × 2 (1/4 W)	MOSFET gate pull-down	Ensures loads are off at boot
White LED strip or panel (12 V)	Flat-field illumination surface	High-CRI (Ra > 90) recommended. Size to scope aperture.
Frosted acrylic sheet	Light diffuser	3 mm thick, cut to scope outer diameter
Dew heater element (12 V, ~5-10 W)	Prevents flat panel misting up	Nichrome wire mat, resistive heating tape, or commercial dew strap cut to fit. ~24 Ω for 6 W at 12 V.
LM2596 or MP1584 buck converter module	12 V → 5 V for servo	Set output to 5.0 V before connecting
12 V DC power supply (≥ 4 A)	Powers everything	LED 2 A + dew heater 0.5 A + servo 1 A peak
1N4007 diode	Optional: reverse-polarity protection on 12 V input
Prototype / strip board	Assembly
JST connectors or screw terminals	Clean connections
Aluminium or 3D-printed enclosure	Mechanical housing

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Component roles

Component	Role
Arduino Nano ESP32	Main controller: WiFi, Alpaca server, PWM, servo
MG995 servo	Rotates the flat panel lid in / out of the telescope light path
SG90 micro servo	Spare / future use (e.g., secondary aperture cover)
28BYJ-48 stepper	Spare / future use (e.g., precision ND-filter wheel for extra dimming)
IRLZ44N MOSFET	Controls LED strip power via PWM from ESP32

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Wiring diagram

12 V PSU ──────────────────────────────────────────── 12 V rail
          │                                               │
          │   LM2596 buck (set to 5 V)                   │
          ├──[IN+]──[OUT+]──────────────── 5 V rail       │
          │   [IN-]──[OUT-]─────────────── GND rail       │
          │                                               │
          └── GND ──────────────────────── GND rail       │
                                                          │
  ┌─────────── Arduino Nano ESP32 ───────────────────┐   │
  │  VIN ◄──── 5 V rail                              │   │
  │  GND ◄──── GND rail                              │   │
  │                                                  │   │
  │  D9  ──────────────────────────► MG995 Signal    │   │
  │  5 V rail ─────────────────────► MG995 VCC (5V)  │   │
  │  GND ──────────────────────────► MG995 GND       │   │
  │                                                  │   │
  │  D3 ──[100 Ω]──► MOSFET-A Gate (LED)            │   │
  │  GND ──[10 kΩ]──► MOSFET-A Gate (pull-down)     │   │
  │                    MOSFET-A Source ──► GND rail  │   │
  │                    MOSFET-A Drain  ──► LED-      │   │
  │                                                  │   │
  │  D5 ──[100 Ω]──► MOSFET-B Gate (dew heater)    │   │
  │  GND ──[10 kΩ]──► MOSFET-B Gate (pull-down)     │   │
  │                    MOSFET-B Source ──► GND rail  │   │
  │                    MOSFET-B Drain  ──► Heater-   │   │
  └──────────────────────────────────────────────────┘   │
                                                          │
  LED strip/panel:  LED+ ◄────────────────── 12 V rail ──┤
                    LED- ◄────────────────── MOSFET-A Drain
                                                          │
  Dew heater:   Heater+ ◄────────────────── 12 V rail ───┘
                Heater- ◄────────────────── MOSFET-B Drain

MOSFET pinout (IRLZ44N TO-220, flat face towards you)

  Gate | Drain | Source
   1       2       3

Connect:

• Gate (1) → 100 Ω → D3, with 10 kΩ from Gate to GND
• Drain (2) → LED strip negative lead
• Source (3) → GND rail

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Servo signal cable colours (standard)

Colour	Signal
Brown / Black	GND
Red	VCC (5 V)
Orange / Yellow / White	Signal (PWM)

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Pin summary

ESP32 pin	Function	Config define
D9	MG995 servo signal	SERVO_PIN
D3	LED PWM (MOSFET-A gate)	LED_PWM_PIN
D5	Dew heater PWM (MOSFET-B gate)	DEW_HEATER_PIN

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Dew heater element sizing

12 V supply	Resistance	Power	Suitable for panel size
48 Ω	3 W	Up to 3″ aperture
24 Ω	6 W	4-6″ aperture (recommended)
12 Ω	12 W	8″+ aperture

Use nichrome wire, resistive heating tape, or a commercial dew strap wound flat under the acrylic diffuser. The MOSFET PWM keeps average power proportional to the 0-100 % setting — you do not need to match exact resistance; just aim for 5-10 W at 12 V.

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Choosing between WiFi and USB mode

	WiFi (Alpaca)	USB Serial (Alnitak)
Cable required	No	Yes (USB-A to USB-C)
Works with	ASCOM Remote, our INDI driver	N.I.N.A. built-in, SGPro, APT, indi_flipflat, our INDI driver
Dew heater control	Via Alpaca Action (our driver)	Via custom T/U serial commands (our driver only)
Debug output	Set SERIAL_DEBUG true	Set SERIAL_DEBUG false
Discovery	mDNS + UDP broadcast	COM port / /dev/ttyUSBx

For USB mode, edit config.h and set SERIAL_DEBUG false before flashing, then open the COM port at 9600 baud in your software.

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First-time setup checklist

1. Set LM2596 output to 5.0 V (measure with multimeter) before connecting servo.
2. Edit firmware/src/config.h — set WIFI_SSID, WIFI_PASSWORD.
   • For USB-only use: also set SERIAL_DEBUG false.
3. Adjust SERVO_OPEN / SERVO_CLOSED angles for your mechanical setup.
4. Flash firmware via PlatformIO: pio run -t upload.
5. WiFi mode: open Serial Monitor (9600 baud) — note the printed IP address, then browse to http://<IP>:11111/management/v1/configureddevices.
6. USB mode: connect to the COM port at 9600 baud and send >P000 — you should receive *P19000.

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ASCOM setup (Windows)

1. Install ASCOM Platform 6.6+.
2. Install ASCOM Remote (acts as Alpaca → COM bridge).
3. In ASCOM Remote, add a CoverCalibrator device pointing to http://esp32-flatpanel.local:11111.
4. In your imaging software (N.I.N.A., SGPro, APT) select the "ASCOM Remote CoverCalibrator" driver.

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INDI setup (Linux / Raspberry Pi)

# Build dependencies
sudo apt install libindi-dev libcurl4-openssl-dev nlohmann-json3-dev cmake

# Build
cd flatpanel/indi-driver
cmake -B build -DCMAKE_INSTALL_PREFIX=/usr
cmake --build build -j$(nproc)
sudo cmake --install build

# Run (KStars/Ekos will load it automatically once installed)
# Or manually:
indiserver indi_esp32_flatpanel

In KStars → Ekos, select ESP32 FlatPanel in the Aux device drop-down.

• WiFi mode: select "WiFi / Alpaca" in the Connection Mode switch, enter the host (esp32-flatpanel.local) and port (11111), then connect.
• USB mode: select "USB Serial (Alnitak)", enter the serial port (/dev/ttyUSB0 or /dev/ttyACM0), then connect. The dew heater slider is available in both modes.

Alternative for USB mode (no custom driver needed): The existing indi_flipflat driver (ships with INDI) speaks standard Alnitak and will control brightness and cover. It will not control the dew heater — use our driver for that.

indiserver indi_flipflat
# Select port /dev/ttyUSB0, baud 9600