PCA9685 Burnout Question

Using Arduino Motors, Mechanics, Power and CNC
1

Wondering if anyone can help diagnose a problem.

I am using a PCA9685 servo driver to control 5 MG90S servos.

It is powered by a 5V, 10A power supply adapter from Amazon. The item is listed as: "100-240V to DC 5 Volt 10amp 50W Switching Power Converter 5V/10A100-240V to DC 5 Volt 10amp 50W Switching Power Converter 5V/10A."

The control board is an Arduino Uno.

The software I am using is Bottango.

I had a PCA9685 burnout on me 2 days back (burning, smoke, the whole 9 yards) and just received a replacement today.

Even after hooking up the new PCA9685 everything is still dead.

I double and triple checked the wiring.

Any ideas?

Is my power supply appropriate for what I require it to do?

Can a PCA9685 burnout kill the Arduino as well?

Thanks in advance!

2

A PCA9685 breakout board has two independent power circuits (with a shared ground).

  1. The PCA9685 itself is powered from the 5volt pin of the UNO.
  2. The servos are powered from the external 5volt supply, through to the screw terminal.

The power that burned out the PCA chip could only have come from the Arduino, assuming you have hooked it up right. So how did you power the Arduino.

Post a picture and/or diagram of the setup.
Leo..

3

Hi, @mattframe1
Welcome to the forum.

Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.

Thanks... Tom... :smiley: :+1: :coffee: :australia:

1 Like
4

The Arduino itself is powered by desktop USB cable and the PCA is powered by a 5v 10a power supply.

The mosfet on the PCA is the component that burned out.

Will post a pic of my setup as soon as I am able.

Thanks!

5

If you're using one of the old Adafruit boards, or a clone board, it likely has a tiny SOT23 MOSFET that could only handle something like 4A. Later Adafruit boards switched to a larger MOSFET that could handle 20A+ because the little ones tended to go poof, let the magic smoke out and make a bad smell.

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6

+1
Some boards don't even have that fet.
The mosfet is an "ideal diode", for reverse polarity protection. If you're never going to connect that servo supply with the wrong polarity, then you don't need that fet.
Just short source and drain of the fet with a piece of wire.
Leo..

1 Like
7

Fascinating. Is the root cause of the MOSFET burnout an Arduino or power supply thing?

8

Neither.
If you have the board with a tiny fet, then the designer of the board was cutting corners.
The fet is in the servo supply line.
Leo..

1 Like
9

Last question. I was using a dremel (I was drilling) on the same circuit as the power supply for the PCA when the Mosfet began to smoke. Is this just coincidental or could that be the onus for the crappy knockoff mosfet to give up the ghost?

10

Probably unrelated, unless you were drilling into the PCA9685 board :slight_smile:
Leo..

1 Like
11

Awesome thanks Wawa :slight_smile:

12

You were using the power supply that was on the PCA as the power supply for the Dremel?
If so where did you have the Dremel connected to the power supply, was the Dremel load current flowing through the PCA?

Tom.... :smiley: :+1: :coffee: :australia:

13

No they were plugged into the same powerbar when the PCA started it's death smoking...