Powering Sensor Expansion Shield with External Power

Other Hardware 3rd Party Boards
1

Hi everyone,

I'm currently trying to control multiple servos (maximum 12) using an Arduino Mega, and I found this breakout board that I was hoping would allow me to easily plug in servos without dealing with messy wiring. Link is here: Amazon.com: HiLetgo MEGA2560 ATmega2560-16AU Sensor Shield Sensor Expansion Board V2.0 with Bluetooth SD Card APC220 Wireless RF Ultrasonic Sensor Communication Interface : Industrial & Scientific

I am using a 7.4V battery to power my servos, and I know the sensor board shorts the power to the Mega, so I removed the all the pins that interface the sensor board to the Mega except for the digital and analog pins. Here's what that looks like:

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However, when I plug in the Arduino to my USB hub and I flip my battery switch, my USB cable gets really hot and I'm afraid that there may be a short in the circuit. But I've already removed any pins that could be shorting the battery power to the Arduino. Does anyone know if there's any other pins I need to remove?

I would really appreciate any help with this, thank you!

2

You cable salad photo is of little help. Please draw a circuit diagram with labels on all boxes and pins or wires.

Please provide a link to the sensor board data sheet.

3

Get your multimeter out and disconnect the shield. To which pins is red connected; blue (5V) or green (Vin)?

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If it's 5V you are feeding 7.4V into the 5V pin and you might have damaged your Mega and be in the process of blowing up your PC.

4

Yea so the red box (Vcc) is connected to the 5V pin, which I agree would cause a short from my 7.4V power supply into the Arduino 5V pin. However, I made sure to snap off the 5V pin on the backside of the shield, so it doesn't actually connect to the Arduino and therefore doesn't cause a short.

When testing, I actually found the issue was that the shield has a couple pins (the power select pins) which actually touch the USB port of the Arduino Mega. This is because the pins stick out too much on the bottom side of the board. When I put electrical tape around the USB port of the Mega, the USB wire stopped getting so hot. So I think this is just a weird defect of these expansion boards. Thanks everyone for the help!

5

An Adafruit PCA9685 servo board is a much better solution.
It moves all the servo processing to that chip, so the Mega is free to do other things.
You can plug the servos onto the headers and the board also comes in the form of a shield.
Leo..