Connecting multiple PCA9685 servo drivers

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,

i would like to control 18 servo motors (ds3225) with ESP32 or arduino.
I found it will be easiest to use PCA9685 boards.

I decided to use 3 of them, because despite of them being able to run 16 servos the current will be to high.
Stall current on each servo ist 2A, co as a rule of thumb I assume 6A for each 6 servos running should be fine.

i found this schematic on internet :

obraz_2026-01-12_142628858
obraz_2026-01-12_1426288581850×984 242 KB

and my questions are:

-is this schematic correct ? i found another one, where V+ betwen boards were connected also, but this one looks better for me

-how to power ESP/Arduino with this power source ? should i made another branch from power supply and connect it directly to GND and +5V pins on board ?

-what do you think is the realistic power compsumption for 6 servos ?

2

Power consumption for 6 servos is 6 x (read the label to get power for one)
Your first line of the OP says 18 servos, so why 6?

3

there is only stall current (1.9A) and idle current (4mA) for running it with 5V.

6 servos, because each of three 9685 board will have 6 servos connected to them. I dont want to Burn it.

Max current for 6 servos will be 12A (36A overall in all robot if all servos stall, but i think its not possible to stall all 18 servos at once.)

4

Ok, then for one multiplexer 6x1.9 is close enough to 12. So 3 power supplies of maybe 15A each, or one big one of 40A.
Read the specs re the V+ connector,

5

There are three types of PCA9685 boards, one without the MOSFET, one with the small MOSFET (that burns out) and one with the big MOSFET. Also some have the big capacitor and some don't.

Which do you have?

6

with big capacitor but probably without mosfet

7

Sounds like a famous last sentence,

More serious, you might add an ACS712 current sensor in the loop and monitor your actual usage. Depending on the current you might decide to switch off some servo’s or not start new ones.

Furthermore you could have a global counter in your code that tracks hoe many servo’s are moving at a given moment. (or a counter per PCA9685 board). Such a counter could be a “first line” to detect big currents.

8

The worst variety boards are the ones with smd mosfet.
A tiny 3-pin part next to the capacitor.

You could also join/connect V+ between boards, to spread the current.
V+ is the servo motor supply after a possibly included mosfet.
Leo..

9

Before you go any further you should find out for sure.
Adafruit claims their board can handle up to 8A.

10

The mosfet (if fitted) and the circuit board traces are the only limitations.