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Apparently you can't run 7.4V servos through this.

Anyone know what chip I blew up? Trying to work out if I can fix it or need to buy another PCA9685.

Thanks

enter image description here

djb
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  • Probably the big one in the middle, unless there are some on the other side. – Hearth Sep 30 '22 at 18:45
  • New chip: almost 4€. New board: almost 7€. – RemyHx Sep 30 '22 at 18:48
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    For that price, buy a new board. – hacktastical Sep 30 '22 at 18:49
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    I wouldn't recommend driving motors with this in general anyway--the PCA9685 is an LED driver. You can get proper motor drivers for not that much money. – Hearth Sep 30 '22 at 19:29
  • @Hearth RC servos use a special kind of a PWM signal. The board would just be called upon to output logic level pulses. OPs mistake was connecting the servo power instead of a a lower voltage such as 3.3V or 5V to Vcc on the board. – Spehro Pefhany Oct 01 '22 at 03:09

2 Answers2

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Most likely both the PCA9685 and the SOT23 P-channel reverse-protection MOSFET (which is looking quite toasted). In terms of what happened, the PCA9685 probably failed short first, which caused excessive voltage drop across the MOSFET and the resulting power dissipation killed it dead.

Given the prices of such modules, you're probably better off just replacing it.

In the Adafruit schematic the transistor is an AOD417. This will be something else, such as an AO3401A, since AOD417 is in a TO252 package.

Spehro Pefhany
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It's the sot 23 package up by the silk screen marked power. My guess is it's either a mosfet for a pull-up or a voltage regulator supplying a specific voltage on the board.

You'll need to find out what the part markings are on it to replace it.

The best thing to do would be to find out what voltage is the parts needs and supply the correct voltage and see if you're getting the correct voltage to the Vcc pins on each part

Voltage Spike
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