PCA9685 servo board... how to use external power?

[rainfern]

I'm using a PCA9685 servo board, a version that I can basically just stick onto the 40 pins on the pi(4). My servos need 12V, so I connected an external power source to the external power connectors on the 9685. However, its output pins (that should go to the servo) still read 5V. What am I doing wrong?

A 5V servo works fine with the board as is.

Connecting the V/GND pins on the 12V servo directly and using only the signal channel from the board does not work either.

[joan]

The output pins are for control, not power. They will be 5V as that is what the PCA9685 chip generates. Perhaps 5V is not seen as a logic high to your 12V servos?

[pcmanbob]

You will also need a ground connection from the servo to the PCA9685 servo board if you are using an external 12V and ground connected directly to the servo.

[rainfern]

Thanks much for your replies. I should clarify:

I expected the power pins on the board (black/red) to change voltage when connecting external power (green terminal). They remain at 5V. If that is normal behavior I do not understand why that external power terminal would be there at all?

I assume that by control you mean the PWM pin (yellow), or do you mean that each servo will need its own GND/V connection from the board?

[pcmanbob]

Is there a voltage regulator on the board , to supply the board with 5V from what ever voltage you connect to the power terminals

I mean connect all grounds like this

[rainfern]

This is how I have it wired up. Does not work using 5V servo (for testing). Using the same servo on the board directly ("as intended") works.

The board takes 5V from the pi for logic.

According to Adafruit manual for that board:
V+ - This is an optional power pin that will supply distributed power to the servos. If you are not using for servos
you can leave disconnected. It is not used at all by the chip. You can also inject power from the 2-pin terminal
block at the top of the board. You should provide 5-6VDC if you are using servos. If you have to, you can go
higher to 12VDC, but if you mess up and connect VCC to V+ you could damage your board!

So I expected that supplying higher voltage to that V+ pin of the board would bring that to the servo. It does not. Neither does supplying external power to servos directly (as in your diagram). Very mysterious!

[pcmanbob]

I can't comment on the servo board and using it to provide 12V to your servos as I don't have one to test.

But I can see why you can use the servo board to provide the PWM signal and use an external power supply.

The board can't know were the12V is coming from , nor can the servo.

Your quote even says you don't need to connect a power supply if you are not using it for servos.