Hello! I'm new to electronics, and there doesn't seem to be a clear answer on Google. I'm planning to use a pca9685 16-channel I2C driver to control 13 servos, but I don't know a light, compact external power source to use. Any suggestions? Thanks!
(I'm using sg90 servos)
If you drive them simultaneously, you need quite beefy "power brick" style supply.
Define light and compact.
Welcome to the forum
The question in the title of this topic does not make any sense
How would you use a capacitor to power a servo, let alone 13 of them ?
An sg90 servo could draw around 300ā400 mA under typical loaded motion and higher near stall (600ā650 mA).
So multiplying 13 servos by around 0.35ā0.4 A suggests a supply capable of roughly 5 A to 6 A at 5 V to avoid voltage droop when multiple servos operate simultaneously.
is that battery powered or from main ?
Hello! Thanks for replying.
To Kmin: They won't drive simultaneously, each at only certain (varied) intervals at a time. "Light and compact" for me is something within the range (or a bit outside the range) of a space 1 in by 2.5 in.
To UKHeliBob: Sorry for the unclear title! What I meant was that some of the power sources I found required a capacitor to prevent energy bursts (or regulators to regulate the voltage), especially for so many servos.
To Jackson: That's a good question! I should have specified that. It should be battery powered.
That doesn't matter. The power supply MUST be able to provide the total current for all servos, 13 times the start/stall current (0.7 Amperes for SG90, 2.5 Amperes for MG996R).
Servos briefly draw the start/stall current every time they start moving, regardless of load, and if the power supply is inadequate, you will end up with a twitching mess of spastic servos.
Also, the PCA9685 circuit board cannot handle such large currents, so you will have to break up the servos into groups of 4 to 6, each group with its own PCA9685.
This is not a simple problem.
So only one servo runs/starts at the time?
About 2-4 servos would run at the same time.
Sorry about the confusion, but from what I've heard, one pca9685 should be able to control at most 16 servos. How come it cannot handle currents from 13 servos?
Answer is in post 7
It can control them, but to pass power for all of them can be hard time for pcb traces.
Why. The PCA9685 has no problems handling 16 servos signals.
The only problem is servo power.
A solution is to beef up the power/GND traces of the PCA board.
And bypass the tiny mosfet (if your board version has one).
This has been done many times on this forum.
Try a search in the field on top of this page.
Adafruit should start making a higher power version of these PCA9685 boards, with fatter traces and/or heavier copper, since this is a common problem.
Leo..
As I clearly stated.
Your suggestion is also a possibility.
Consider powering the servos separately from the PCA9685, but still use the PCA9685 outputs to control them. Be sure the grounds are connected.