Controller board for illuminated signage or decorative LED letters.
Each output appears intended to switch one 12 V LED letter/load.
Bluetooth control is provided by an ESP32 module.
What the Device Should Do
Accept a 12 V DC input.
Generate 5 V and 3.3 V logic rails.
Use an ESP32-WROOM-32 module for Bluetooth control.
Drive 24 low-side switched LED outputs labeled Letter 1 through Letter 24.
Provide a mode pushbutton connected to the ESP32.
Main Features
24 switched 12 V LED outputs.
ESP32 Bluetooth logic/control.
MCP23017 I/O expander for 16 additional outputs over I2C.
Direct ESP32 GPIO outputs for remaining LED channels.
12 V input protection/fusing shown in the reference.
System Architecture
Diagram
Hardware Subsystems
Power Input and Protection
Reference shows a 12 V input connector, fuse, and diode/protection element.
The image appears to show a 15 A fuse, but this must be confirmed.
5 V Regulator
Reference shows LM2596S-5.0 switching regulator.
Visible support parts include an inductor, Schottky diode, and input/output capacitors.
Exact values are partly readable but should be verified against the regulator datasheet before implementation.
3.3 V Logic Regulator
Reference shows AMS1117-3.3 from 5 V to 3.3 V.
Input/output capacitors are shown; exact values should be verified against the regulator datasheet.
Controller
Reference shows ESP32-WROOM-32.
Bluetooth control assumed; WiFi may be available but not required unless user requests it.
I/O Expansion
Reference shows MCP23017-E/SP I/O expander.
Connected over I2C to the ESP32.
Pull-up resistors on SDA/SCL are shown, likely 10 kOhm, but value confirmation is needed.
LED Output Drivers
Reference shows 24 low-side drivers, apparently AOD408 MOSFETs or similar logic-level N-channel MOSFETs.
Each gate has a series resistor, likely 100 ohm, and each output connects to a terminal labeled Letter 1 to Letter 24.
Loads appear powered from +12 V and switched to ground by MOSFETs.
User Input
One mode pushbutton shown connected to an ESP32 GPIO, with a pull-down or pull-up arrangement.
Exact ESP32 GPIO must be confirmed from the image or selected during schematic recreation.
Interfaces and Connections
12 V DC power input connector.
24 LED letter output connectors.
ESP32 Bluetooth interface.
I2C bus between ESP32 and MCP23017.
Mode pushbutton.
Power and Runtime Expectations
Input: 12 V DC.
Logic rails: 5 V and 3.3 V.
Output load current: reference notes appear to say approximately 20 A total max and 3 A per output max, but this must be confirmed before selecting power-path parts and trace widths.
Power Tree and Power Budget
Table
Rail / Path
Source
Loads
Current Assumption
Status
+12 V
External DC input
24 LED letters
TBD; image suggests high current
Needs confirmation
+5 V
LM2596S-5.0 buck
AMS1117-3.3 input and possibly auxiliaries
TBD
Needs datasheet sizing
+3.3 V
AMS1117-3.3
ESP32, MCP23017, pull-ups
TBD
Needs datasheet sizing
Manufacturing and Assembly Expectations
Reference mixes through-hole style components/connectors with module-style ESP32.
User appears beginner-level; through-hole connectors and serviceable parts may be preferred unless compact assembly is required.
High-current output routing will require careful copper width, pours, and connector ratings.
Firmware-Relevant Hardware Requirements
ESP32 firmware should map 24 logical letter channels to GPIO/MCP23017 pins.
I2C initialization required for MCP23017.
Button input required for mode selection.
Bluetooth control protocol not specified yet.
Physical Design Expectations
Not specified yet.
ESP32 antenna area must be kept clear if using ESP32-WROOM-32.
High-current 12 V output connectors should be placed along board edges for wiring access.
Important Design Decisions
Use low-side N-channel MOSFET switching for 12 V LED loads.
Use MCP23017 to expand ESP32 GPIO count.
Use a buck converter for 12 V to 5 V, then an LDO for 3.3 V logic.
Assumptions and Items Needing Confirmation
Confirm that you want me to recreate this schematic in Flux from the image.
Confirm exact power requirement: total LED current and current per output.
Confirm whether the MOSFET part is AOD408 or a different part number.
Confirm the output connector type/current rating and preferred pitch.
Confirm whether the original reference should be followed exactly or improved for reliability/manufacturing.
Confirm board size, shape, and whether the design should be hand-solderable.
Confirm Bluetooth-only control or Bluetooth plus WiFi.
Change Notes
Initial draft created from uploaded reference image.
Project renamed from the random draft name to Bluetooth 24-Letter LED Controller.