Help! I keep killing Arduinos- 16 ch servo shield best pract

[carladiana]

I'm working with the 16-channel 12 bit PWM servo shield https://www.adafruit.com/product/1411 on a MacBook Pro running 10.13.6 and Arduino IDE 1.8.5 with the Arduino Uno R3 (and also one R2).

Something I'm doing during the programming stages seems like it is killing the Serial communication with my Arduino. It doesn't show up in the Port menu on the Arduino IDE, nor does it show up as a USB device in the Mac System Report. I've tried both USB ports on the Mac. I've managed to do this to 4 boards so far, so I'm anxious to sort out the problem to avoid it in the future. After the first one went, I tried to remove the shield every time I flash new code onto the Arduino, but eventually started leaving the shield on, but disconnecting the external power supply. That seemed to avoid the problem *I think* but I managed to do it again and generally feel unsure about what best practices are when using the shield. In each case the green light on the Arduino is on and the L light is solid. I have a 1000µF cap on the shield. (I have also used the same USB cable with different boards and they are recognized, so I don't think it's the cable.)

Is it necessary to remove power from the shield before flashing the board? The IDE doesn't seem to be able to upload when I have the shield on and powered.
Is this where I'm going wrong as removing the shield's power then leaves the servo to draw power from the Arduino?
Should I disconnect the servo before flashing? I'm thinking that maybe I have blown the diode by having too high a load on the board
Is it best to remove the shield altogether before flashing the board?
Is there something else I might be doing here that I haven't considered?
Any suggestions regarding what might be going on?

I found one suggestion online which was to restart the computer with the board connected. That seemed to work once, but then I lost the board again and couldn't get it back.

Thanks in advance for any help!

Addendum: I'm trying to see if I can salvage the board by programming it with an FTDI cable. The board shows up but I get a "board not responding" error.

[adafruit_support_carter]

In general, you should be OK to leave the shield attached.

Let's first focus on just the UNOs. It sounds like they can no longer be programmed? Even if you remove the shield and everything else?

[carladiana]

Yes, the Arduino Uno is no longer recognized via USB. In other words there’s no USB port showing up in the ports menu, even when I pull off the shield and have nothing else connected.

[adafruit_support_carter]

OK, so it's more than just not being able to program. It sounds like the UNOs are being damaged somehow. Let's check your hardware setup, starting with just the shield. Can you post photos showing both sides of the servo shield.

[carladiana]

Screen Shot 2019-03-15 at 6.44.27 PM.png (808.47 KiB) Viewed 205 times

Screen Shot 2019-03-15 at 6.44.47 PM.png (700.69 KiB) Viewed 205 times

Screen Shot 2019-03-15 at 6.44.51 PM.png (606.79 KiB) Viewed 205 times

[carladiana]

I'm powering the shield with the 5V 10 A power supply from Adafruit and using a 6V 1.5A power supply for the Arduino.

Screen Shot 2019-03-15 at 6.44.55 PM.png (669.67 KiB) Viewed 205 times

Screen Shot 2019-03-15 at 6.44.59 PM.png (447.81 KiB) Viewed 205 times

[carladiana]

I wanted to provide an update that I've been more careful about managing power in my setup and haven't repeated the issue. I believe the problem came when in the midst of testing I plugged the Arduino in to USB with the servo attached (and the power for the shield detached). I now make sure that either:
1. The servo is disconnected if the shield isn't powered
2. The shield has power when making any changes to the setup

This seems to be avoiding the problem.

Two of the four boards I thought I lost have also come back online as ports. (Two are still gone.)

[adafruit_support_carter]

Thanks for the photos. Nothing obviously wrong. That failure mode seems odd. Not sure why simply powering the UNO via USB without the shield powered would cause an issue. The servo power is separate from the logic power. So it should essentially work, you could still talk to the PCA9685 which creates the PWM signal for the servos, but the servos wouldn'r move since they have no power.

[carladiana]

Hmm. Okay, if I have any other insights as to what was going on I will share them. I had an issue last night where the Arduino port was lost when I pulled power out of the shield with the system plugged in to USB, but it came back after a reboot of the computer.