Connect your first servo and LED. Check the controller pins and the separate servo power supply.
The Raspberry Pi connects to the PCA9685 via I2C and powers its logic at 3.3 V. A separate 5 V power supply powers the servo. The LED connects to CH15 on a module with a built-in series resistor.
Colour helps you trace a wire. Pin labels determine the connection.
| Signal | From | To |
|---|---|---|
| GND | Raspberry Pi · pin 6 (GND) | PCA1 · GND (left connector)Common ground for logic and servo power. |
| VCC | Raspberry Pi · pin 1 (3.3 V) | PCA1 · VCC (left connector) |
| SDA | Raspberry Pi · pin 3 (GPIO2 / SDA1) | PCA1 · SDA (left connector) |
| SCL | Raspberry Pi · pin 5 (GPIO3 / SCL1) | PCA1 · SCL (left connector) |
| GND | Power supply · − (GND) | PCA1 · GND terminal |
| V+ | Power supply · +5 V | PCA1 · V+ terminalV+ powers the servos, not the PCA9685 logic. |
| PWM | PCA1 · CH0 PWM | Servo · signal |
| V+ | PCA1 · CH0 V+ | Servo · +5 V |
| GND | PCA1 · CH0 GND | Servo · GND |
| PWM | PCA1 · CH15 PWM | LED · anode (+)No additional resistor. The diagram assumes a module with a series resistor on the PWM output. |
| GND | LED · cathode (−) | PCA1 · CH15 GND |
Use physical pins on the 40-pin header: 1 (3.3 V), 3 (GPIO2 / SDA1), 5 (GPIO3 / SCL1) and 6 (GND). A GPIO number is not its position on the header. Check the location of pin 1 on your board. This circuit is not for Raspberry Pi Pico or early boards with a 26-pin header.
Connect module VCC to Raspberry Pi 3.3 V. SDA and SCL may only be pulled up to 3.3 V. Do not connect VCC to V+ or the Pi's 5 V pins. Power servos separately via V+ and connect the grounds. A dedicated power supply powers the Raspberry Pi through its power socket. The PWM signal is at 3.3 V, so the servo must support it.
Run sudo raspi-config, choose Interface Options, then I2C and Yes. A module without address jumpers has address 0x40. In the control software, select bus I2C1 and the module's address. These are electrical wiring instructions; control requires software supporting PCA9685 on Raspberry Pi.
The diagram assumes a module with 220 Ω resistors on its PWM outputs. The LED connects directly to CH15 and GND. The output is at 3.3 V; check the LED current and forward voltage. If there is no built-in resistor, add an external one. Set PWM according to the servo requirements, usually around 50-60 Hz. All channels share the frequency, so a dimmed LED may flicker.
Disconnect both power supplies. Check GPIO numbering, LED polarity and servo wires. OE may remain unconnected only on a module with a factory-fitted pull-down resistor; otherwise connect OE to GND according to the module documentation.
Pinouts and connection rules have been checked against manufacturer documentation.