Help with a Bug - AC Voltage and Current Reading on a Teensy 3.6

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mendez

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Hello,

I'm measuring the current and voltage of an AC Motor with a Teensy 3.6 (see image below). The Voltage sensor requires 5V; and I'm using the Teensy 5V to power it (USBHost_t36.h Library). The diagram works, however, when I turn the motor ON, I can log the data well; but as soon I turn the motor OFF (from switch); the USB port gets disconnected.

What I'm doing wrong?

I thought it was a bad ground; but then, If I disconnect everything (gnd, analog and +5V) from the teensy, and run the motor again- It still disconnects from the USB as soon I turn the motor off. I try with 2 teensys 3.6 and 2 different pcs and the problem still exists.

Any help or tips will be very helpful.

Diagram.jpg
 
Motors generate a lot of electrical noise on the lines, and a lot of EM emissions too. Maybe when the motor is switched off, a spike occurs and disconnects the USB port.
See if you can figure an RC filter to protect the lines from spikes and noise.
 
Does the current sensor have a resistor built in? Some of those current transformers output a pure current and require a resistor to convert to a voltage which can be measured by Teensy. Without the resistor, it could risk damage to the Teensy.
 
Does the current sensor have a resistor built in? Some of those current transformers output a pure current and require a resistor to convert to a voltage which can be measured by Teensy. Without the resistor, it could risk damage to the Teensy.

Hi Paul, yes; that current sensor has a built in resistor. The diagram works well on a teensy; except that it will disconnect the USB when I turn the Switch off. Do you think that USB Isolator helps?
 
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