KK2.1.5 Quad Power Distribution Board, a ESP32 project

The KK2.1.5 Quad Power Distribution Board is a passive PCB that distributes battery power from a 3S LiPo pack to four ESCs while breaking out all control and sensor signals from a KK2.1.5 flight controller. Heavy copper traces handle high current delivery to each ESC independently, while a regulated 5 V UBEC safely powers the flight controller and its peripherals.

This guide provides a complete wiring diagram, parts list, and step-by-step assembly instructions for building a quad-rotor power system. The project covers connector installation, socket placement, signal routing, and critical pre-flight checks to ensure safe operation before the first battery connection.

Wiring diagram

Gather all the parts

Qty	Component
1	KK2.1.5 Quad Power Distribution and Full-Pin Breakout PCB 2-layer, 2 oz copper; 60 A XT60 input; 30 A minimum per ESC branch; full KK2.1.5 2.54 mm socket map A custom heavy-copper board that splits one 3S LiPo supply to four ESCs and provides a complete plug-in socket and breakout for a KK2.1.5 flight controller.
1	XT60 Male Panel/PCB Connector XT60 male, 60 A A yellow two-pole high-current connector that accepts the 3S LiPo battery's XT60 female plug.
1	2-Pole High-Current ESC Terminal ≥30 A, 5.08 mm pitch A two-position high-current terminal that carries battery power to ESC 1.
1	2-Pole High-Current ESC Terminal ≥30 A, 5.08 mm pitch A two-position high-current terminal that carries battery power to ESC 2.
1	2-Pole High-Current ESC Terminal ≥30 A, 5.08 mm pitch A two-position high-current terminal that carries battery power to ESC 3.
1	2-Pole High-Current ESC Terminal ≥30 A, 5.08 mm pitch A two-position high-current terminal that carries battery power to ESC 4.
1	3S LiPo Battery Pack with XT60 Female Plug 3S, 11.1 V nominal / 12.6 V full, XT60 female A three-cell lithium-polymer battery pack that provides the main power for the four ESCs.
1	5 V Switching UBEC 5 V, ≥3 A switching UBEC A regulated power module that converts the 3S battery voltage into safe 5 V power for the KK2.1.5 controller and receiver.
1	KK2.1.5 Flight Controller KK2.1.5; complete 2.54 mm connector footprint The plug-in flight controller whose complete connector layout is duplicated by the central socket footprint.

Assemble it in 6 steps

1. Order the board with heavy copper

Have pdb_pcb_1 made as a two-layer board with 2 oz copper, a wide positive copper area, a wide ground copper area, and short equal-width branches to the four ESC terminals. Keep the battery and ESC copper clear of the central 2.54 mm KK2.1.5 socket area so the controller is never exposed to battery voltage.

Put the XT60 at one board edge and place one ESC terminal pair toward each arm of the quadcopter.
Use generous copper pours and several stitched vias wherever a high-current path changes sides of the board.
Thin signal-sized tracks can overheat under motor current and can cause a fire or loss of aircraft control.

2. Fit the battery and ESC power connectors

Solder xt60_male_1 into the BAT+ and BAT− pads on pdb_pcb_1. Fit esc_terminal_1 through esc_terminal_4 into the four labelled ESC1 through ESC4 pad pairs; every V+ terminal goes to its matching positive pad and every GND terminal goes to its matching negative pad.

Use a high-current connector or solder pads rated for at least the maximum current of the ESC on that arm.
Mark the board clearly: BAT+, BAT−, ESC1 V+/GND, ESC2 V+/GND, ESC3 V+/GND, and ESC4 V+/GND.
Do not swap V+ and GND — a reversed 3S LiPo connection can instantly damage an ESC, the flight controller, or the battery wiring.
Never plug in the battery while soldering or checking continuity.

3. Install the KK2.1.5 socket footprint

Solder the 2.54 mm female header sockets into the central footprint on pdb_pcb_1 in the same row positions and orientation as every connector row on kk21_5_controller_1. Label every row exactly as printed on the controller: receiver inputs and OUT1 through OUT8. Route each signal socket straight through to a labelled breakout pad; route only the 5 V and ground bus as described below.

Before soldering all pins, place the controller over the sockets without power to confirm that every three-pin row enters cleanly.
Use a square pad or printed arrow to mark the signal end of every three-pin row.
A one-column offset or reversed three-pin row can put power onto a signal contact and damage the controller or connected receiver.

4. Wire only one regulated 5 V supply to the controller

Connect bec_5v_1 VIN+ to pdb_pcb_1 BAT+ (power) and VIN− to BAT− (ground). Connect the UBEC VOUT+ to FC_5V_IN (regulated 5 V power) and VOUT− to FC_GND (ground). Plug the KK2.1.5 into its socket footprint only after checking that this supply measures 5 V, not battery voltage.

Feed the KK2.1.5 and receiver from this one UBEC, or alternatively use exactly one ESC BEC; remove or insulate the red 5 V wires from all other ESC servo plugs.
Keep the 5 V traces separate from the 3S battery copper except at the UBEC input.
A fully charged 3S pack is 12.6 V. Connecting it to any KK2.1.5 5 V header pin will destroy the controller.
Paralleling the 5 V outputs of multiple ESC BECs can make the regulators fight each other and overheat.

5. Connect the four ESCs and control signals

For each ESC, connect its red battery wire to its matching V+ terminal and its black battery wire to the matching GND terminal: ESC 1 to esc_terminal_1, ESC 2 to esc_terminal_2, ESC 3 to esc_terminal_3, and ESC 4 to esc_terminal_4. Connect the signal lead from each ESC to the matching KK output breakout: OUT1 to M1_SIG (signal), OUT2 to M2_SIG (signal), OUT3 to M3_SIG (signal), and OUT4 to M4_SIG (signal); connect every ESC signal ground to FC_GND (ground).

Use the motor order shown in the KK2.1.5 mixer screen; terminal number and physical motor position are not automatically the same.
Keep motor power leads short and twist each positive and negative pair together where possible to reduce electrical noise.
Remove propellers for all first power-up, receiver checks, motor-order checks, and ESC calibration. A configuration mistake can start a motor unexpectedly.

6. Check before the first battery connection

With lipo_3s_1 disconnected, use a meter to confirm BAT+ has no short to BAT−, each ESC V+ terminal has continuity to BAT+, each ESC GND terminal has continuity to BAT−, and FC_5V_IN measures isolated from BAT+. Then plug lipo_3s_1 into xt60_male_1 and confirm the UBEC output is a steady 5 V before installing the controller.

Use a smoke stopper or current-limited first connection if you have one.
Secure the battery connector and UBEC so vibration cannot pull on solder joints.
Stop immediately if a wire, connector, or board becomes warm without motors running — disconnect the battery before investigating.

Review all connections

1. Connections between "xt60_male_1" and "ESP32"

Function	xt60_male_1	ESP32
`power`	POSITIVE → KK2.1.5 Quad PDB and Breakout Shield PCB BAT+	EXT
`ground`	NEGATIVE → KK2.1.5 Quad PDB and Breakout Shield PCB BAT-	EXT

2. Connections between "pdb_pcb_1" and "ESP32"

Function	pdb_pcb_1	ESP32
`power`	ESC1+ → 2-Pole High-Current ESC Terminal V+	EXT
`ground`	ESC1- → 2-Pole High-Current ESC Terminal GND	EXT
`power`	ESC2+ → 2-Pole High-Current ESC Terminal V+	EXT
`ground`	ESC2- → 2-Pole High-Current ESC Terminal GND	EXT
`power`	ESC3+ → 2-Pole High-Current ESC Terminal V+	EXT
`ground`	ESC3- → 2-Pole High-Current ESC Terminal GND	EXT
`power`	ESC4+ → 2-Pole High-Current ESC Terminal V+	EXT
`ground`	ESC4- → 2-Pole High-Current ESC Terminal GND	EXT
`power`	FC_5V_IN → KK2.1.5 Flight Controller 5V_LOGIC_BUS	EXT
`ground`	FC_GND → KK2.1.5 Flight Controller GROUND_BUS	EXT
`digital`	M1_SIG → KK2.1.5 Flight Controller OUT1_SIGNAL	EXT
`digital`	M2_SIG → KK2.1.5 Flight Controller OUT2_SIGNAL	EXT
`digital`	M3_SIG → KK2.1.5 Flight Controller OUT3_SIGNAL	EXT
`digital`	M4_SIG → KK2.1.5 Flight Controller OUT4_SIGNAL	EXT
`digital`	M5_SIG → KK2.1.5 Flight Controller OUT5_SIGNAL	EXT
`digital`	M6_SIG → KK2.1.5 Flight Controller OUT6_SIGNAL	EXT
`digital`	M7_SIG → KK2.1.5 Flight Controller OUT7_SIGNAL	EXT
`digital`	M8_SIG → KK2.1.5 Flight Controller OUT8_SIGNAL	EXT
`digital`	AIL_SIG → KK2.1.5 Flight Controller AIL_SIGNAL	EXT
`digital`	ELE_SIG → KK2.1.5 Flight Controller ELE_SIGNAL	EXT
`digital`	THR_SIG → KK2.1.5 Flight Controller THR_SIGNAL	EXT
`digital`	RUD_SIG → KK2.1.5 Flight Controller RUD_SIGNAL	EXT
`digital`	AUX_SIG → KK2.1.5 Flight Controller AUX_SIGNAL	EXT
`analog`	VMON+ → KK2.1.5 Flight Controller VMON_POSITIVE	EXT
`ground`	VMON- → KK2.1.5 Flight Controller VMON_GROUND	EXT
`digital`	BUZZ+ → KK2.1.5 Flight Controller BUZZER_POSITIVE	EXT
`ground`	BUZZ- → KK2.1.5 Flight Controller BUZZER_GROUND	EXT
`spi`	ISP_MOSI → KK2.1.5 Flight Controller ISP_MOSI	EXT
`spi`	ISP_MISO → KK2.1.5 Flight Controller ISP_MISO	EXT
`spi`	ISP_SCK → KK2.1.5 Flight Controller ISP_SCK	EXT
`digital`	ISP_RST → KK2.1.5 Flight Controller ISP_RESET	EXT
`power`	ISP_5V → KK2.1.5 Flight Controller ISP_5V	EXT
`ground`	ISP_GND → KK2.1.5 Flight Controller ISP_GROUND	EXT

3. Connections between "lipo_3s_1" and "ESP32"

Function	lipo_3s_1	ESP32
`power`	POSITIVE → XT60 Male Panel/PCB Connector POSITIVE	EXT
`ground`	NEGATIVE → XT60 Male Panel/PCB Connector NEGATIVE	EXT

4. Connections between "bec_5v_1" and "ESP32"

Function	bec_5v_1	ESP32
`power`	VIN+ → KK2.1.5 Quad PDB and Breakout Shield PCB BAT+	EXT
`ground`	VIN- → KK2.1.5 Quad PDB and Breakout Shield PCB BAT-	EXT
`power`	VOUT+ → KK2.1.5 Quad PDB and Breakout Shield PCB FC_5V_IN	EXT
`ground`	VOUT- → KK2.1.5 Quad PDB and Breakout Shield PCB FC_GND	EXT

Deploy the firmware

main.cppOpen in Schematik

/*
 * This project is a passive power-distribution and KK2.1.5 breakout PCB.
 * The KK2.1.5 supplies its own flight firmware; this ESP32 workspace entrypoint
 * has no control role and intentionally does not drive any hardware.
 *
 * PCB net map:
 * - XT60 BAT+ / BAT-: 3S LiPo input, 12.6 V maximum.
 * - ESC1..ESC4 V+ / GND: four parallel high-current battery branches.
 * - KK 2.54 mm sockets: AIL, ELE, THR, RUD, AUX; OUT1..OUT8;
 *   battery monitor; buzzer; and 2x3 ISP, all reproduced as labelled breakouts.
 * - Only the 5 V UBEC feeds the KK 5 V rail. Never feed 3S battery voltage
 *   into a KK header.
 */

void setup() {
  // Passive PCB: no microcontroller I/O is used.
}

void loop() {
  // Passive PCB: no recurring work is required.
}