Product Specifications

Product Overview

BTsplitter is a microcontroller-based intelligent automotive lighting converter that splits combined brake/turn signal inputs into three separate outputs: left turn, right turn, and brake. Unlike passive diode-based splitters, BTsplitter provides intelligent timing control, noise immunity, and professional-grade current handling.

Input: Two wires (left brake/turn combined, right brake/turn combined)
Output: Three separate signals (left turn, right turn, brake)
Power: Dedicated switched 12V input (must turn off with ignition)

Core Components

Professional-grade electronics selected for automotive reliability

ESP32-C3 Microcontroller

Model: Seeed Studio XIAO ESP32-C3
Processor: 32-bit RISC-V single-core @ 160MHz
Memory: 400KB SRAM, 4MB Flash
Connectivity: WiFi 802.11b/g/n, Bluetooth 5.0 LE
Note: WiFi/BT reserved for future features

IRF9540 Power MOSFETs

Type: P-Channel Power MOSFET
Quantity: 3 (one per output)
Continuous Current: 23A @ 25°C
Peak Current: 92A pulsed
Voltage Rating: 100V drain-source
On-Resistance: 0.117Ω @ Vgs=-10V

PC817 Optocouplers

Type: Photodarlington Optocoupler
Quantity: 2 (one per input)
Function: Electrical isolation
LED Current: ~10.8mA (1KΩ limiting resistor)
Isolation: 5000V RMS

2N7000 Gate Drivers

Type: N-Channel MOSFET
Quantity: 3 (one per output)
Function: Drive IRF9540 power MOSFETs
Interface: 3.3V logic to 12V gate drive

Complete Technical Specifications

Electrical Specifications

Input Voltage

12V DC automotive (10.5-14.5V operating range)

Logic Voltage

3.3V regulated (internal)

Current Draw

~100mA idle (ESP32-C3 operation)

Output Current Capacity

23A continuous, 92A peak per channel

Input Logic

Active-LOW with INPUT_PULLUP

Output Logic

Active-HIGH (HIGH = LED ON)

Pin Configuration

Input Pins (with Pull-ups)

GPIO 3: Left turn signal input (LTS_IN)
GPIO 4: Right turn signal input (RTS_IN)

Output Pins (Active-HIGH)

GPIO 6 (D4): Left turn signal output (LT_OUT)
GPIO 7 (D5): Stop/Brake light output (S_OUT)
GPIO 12 (D6): Right turn signal output (RT_OUT)

8-Pin Deutsch Connector Pinout

The BTsplitter uses an 8-pin Deutsch connector for all power, input, and output connections. The male connector pinout is as follows:

Pin	Function	Direction	Description
1	+12V SWITCHED	IN	Switched 12V power (must turn off with ignition)
2	Right Turn Signal OUT	OUT	To right turn signal LED
3	Brake Light OUT	OUT	To brake/stop light LED
4	Left Turn Signal OUT	OUT	To left turn signal LED
5	Left Turn Signal / Brake IN	IN	From vehicle's left turn / brake combined
6	Right Turn Signal / Brake IN	IN	From vehicle's right turn / brake combined
7	Not Used	-	Reserved for future use
8	GND	IN	Ground (common ground)

Important: Pin 1 must be connected to switched 12V (not constant power) to prevent battery drain when vehicle is off.

Firmware Features

Current Version

v1.0.7

Brake Persistence

2000ms (configurable in firmware)

Input Debouncing

50ms (configurable in firmware)

Refresh Interval

10ms output refresh rate

Serial Debug

115200 baud real-time state output

Updates

USB firmware updates via Arduino IDE/CLI

Physical Specifications

PCB

FR4, Version 1.0

Mounting Holes

4 holes, M6 metric or 1/4" SAE compatible

Mounting Ear Thickness

8mm (0.325")

Enclosure Dimensions

115mm x 75mm x 35mm (4.5" x 3.0" x 1.4")

Weight

185g (6.5oz) including enclosure and wiring

Wire Lengths

300mm (12") pre-soldered, color-coded leads

Enclosure

Professional 3D printed housing with integrated mounting

Environmental

Operating Temperature

-20°C to +70°C (ESP32 specification)

Storage Temperature

-40°C to +85°C

Environment

Designed for 12V automotive electrical systems

Wire Color Reference (v1.0 Board)

Standard wire colors used on production boards

Connection	Wire Color	Notes
+12V Power	Red	Must be switched 12V
Ground	Black	Common ground
Left Turn Input	Gray	From vehicle's left turn / brake combined
Right Turn Input	White	From vehicle's right turn / brake combined
Left Turn Output	Green	To left turn signal LED
Right Turn Output	Blue	To right turn signal LED
Brake Output	Yellow	To brake/stop light LED

Operating Modes

State machine logic for intelligent signal processing

Mode 1: Normal Operation

Condition: Single turn signal input active

Behavior: Only the corresponding turn signal output is activated. Brake light remains off.

Example: Left turn signal → Left turn output ON, all other outputs OFF

Mode 2: Brake Mode

Condition: Both turn signal inputs active simultaneously

Behavior: Brake light output activates immediately. Both turn signal outputs deactivate. 2-second persistence timer starts.

Example: Both inputs active → Brake output ON, turn signal outputs OFF

Mode 3: Timer/Persistence Mode

Condition: After brake mode detected, brake released but timer still active

Behavior: Brake light stays on for 2 seconds. Turn signals use inverted logic (input LOW → output LOW) allowing blinking to show through brake light.

Example: Brake released + left turn signal → Brake stays on, left turn can blink through

BTsplitter Technical Specifications