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Trouble with my second 16-channel PWM servo driver
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Trouble with my second 16-channel PWM servo driver

by grizzlyprototypes on Thu Feb 15, 2018 6:50 pm

Hello,
I recently purchased and assembled my second servo driver (Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C interface - PCA9685), and am having a bit of trouble with it, not sure what is going wrong. I am able to apply power to the board (green led is on and the servo is engaged), but am unable to run any code, including the example code. My other one works perfectly, and the setup seems to be the same.

Here are some notes on the setup:
-ground-->arduino ground, vcc--> arduino 5v
-SDA --> arduino A4, SCL-->arduino A5 (i tried flipping these, did not work)
-5v 3amp power supply to driver
-using a micro servo connected to port 0 on driver board (same as my other board, brown wire facing away from power input)
-all solder connections seem to be good
-I have tried multiple sets of wires

Perhaps I overlooked something simple, any advice is appreciated! (I can try to provide more information if needed)

grizzlyprototypes
 
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Re: Trouble with my second 16-channel PWM servo driver

by adafruit_support_bill on Thu Feb 15, 2018 7:02 pm

Please post some photos showing your soldering and connections to the board.

Also, please run the i2c scanner and post the results here:
https://playground.arduino.cc/Main/I2cScanner

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Re: Trouble with my second 16-channel PWM servo driver

by grizzlyprototypes on Thu Feb 15, 2018 7:39 pm

here is the output:

I2C Scanner
Scanning...
No I2C devices found

(and it repeats)

just to be thorough, i tested this with the same wiring on 2 different versions of the arduino uno (a new R3 and a much older uno)

My soldering isn't super pretty, but I made sure that every pin was fully connected to the solder point.

Thank you so much for the speedy reply!
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grizzlyprototypes
 
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Re: Trouble with my second 16-channel PWM servo driver

by adafruit_support_bill on Thu Feb 15, 2018 7:47 pm

There are a few suspect solder joints there - notably VCC, as well as the GND pin on the channel 0 header. On these joints, the solder does not appear to have flowed onto the solder pad surrounding the pin.

Ideally, the solder joint should have a cross-section similar to the diagram below. A marginal joint may measure fine with a multimeter, because the pressure from the probe makes it more conductive.

This guide has some tips on identifying and fixing common soldering problems:
http://learn.adafruit.com/adafruit-guid ... n-problems


Image

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Re: Trouble with my second 16-channel PWM servo driver

by grizzlyprototypes on Thu Feb 15, 2018 9:07 pm

Again, thank you very much for taking the time to help.

I ended up putting a new set of output pins on the other side of the board to do a fresh solder job, and it looks like the solder is fully in on each of the pins. One other detail is that the green LED on the driver turns on just when the arduino is connected (without the power supply), however when i ran the 12C scanner, it does not find the driver.

Any other ideas? is there a debugging/re-flashing program that might help?
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Re: Trouble with my second 16-channel PWM servo driver

by adafruit_support_bill on Thu Feb 15, 2018 9:14 pm

The new solder looks excellent. If it is still not seen by the i2c scanner, then we can try replacing it. Please contact support@adafruit.com with a link to this thread.

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Please be positive and constructive with your questions and comments.