Error opening serial post (COM) when ground is connected to Arduino board

Hi

My team is currently using an Arduino MKR1000 with a SPARKFUN BREAKOUT - ACS723 LOW CURRENT SENSOR and a WINGONEER VOLTAGE DIVIDER. The system is designed to measure current, voltage and strain in three directions using three quarter Wheatstone bridges. Each Wheatstone bridge uses two 100 ohm resistors and one 200 ohm variable resistor. Before we added the Wheatstone bridges the system was working and we could plug in the Arduino and upload sketches, once we added the bridges and specifically when we connect the ground wire into the Arduino ground port, we receive error “Error opening serial port ‘COM7’”, looking at Device Manager shows my computer doesn’t recognize the board (the Arduino is not simply on another port).

I think it has something to do with using VCC or the Ground port in the Arduino. Is it possible that using the 3.3 volts from VCC for the three Wheatstone Bridges and the Current sensor overloads or causes an issue? Once the Wheatstone bridges are unplugged, we no long receive the error.
Thank you for any help.

phystical Assembly 2.JPG

Wiring Diagram.pdf (59.1 KB)

"Is it possible that using the 3.3 volts from VCC for the three Wheatstone Bridges and the Current sensor overloads or causes an issue? Once the Wheatstone bridges are unplugged, we no long receive the error."
Yes, more than likely. The 3.3V regulator can only support 150mA.
Measure the 3.3V line - does it drop below 3.3V when all the stuff is connected?
If yes, than it's time to change to an external regulator.

A voltmeter shows 3.3 v and 60mA. I found a short in the wire bundle leaving the Wheatstone Bridges (the short is not pictured).

Thanks for the response CrossRoads.

Hi,
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom.. :slight_smile: