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Topic: INA219 voltage on VCC when not powered, Vin+ & Vin- attached to battery (Read 168 times) previous topic - next topic

sourceless

Hi,
 needed to monitor very small consumption but had an error with Voltage readings. Both through the INA & Arduino analog input(A0 - orange cable on my pic). It was showing 1V where the reading was 3.8V.

Figured out that I didn't connect the grounds of the INA & Arduino together like here:


my pic: https://imgur.com/LxZaWXU

Blue cable on my pic.
The difference is that in my circuit I have a battery in the place of the RGB (load) and in the place of power I have hooked up a 5V generator.


Now everything is ok. But I saw that while the Arduino was USB unplugged and added the missing ground connection, Arduino got powered up. So I'm a bit confused, should it work like this? The INA219 has like 3.3V on the VCC input when battery is connected to Vin+ & Vin-. Shall I put a diode to disallow this?

Thanks


agmotes

Is the orange jumper in your pick connected to A0 or Vin on the Arduino?

If so, it looks like your battery/generator high side voltage is being fed to Vin on the arduino, and so when you connect the arduino ground to the battery/generator low side voltage, you're supplying the minimum 3-ish volts to power up the arduino.

sourceless

my circuit/pic - https://imgur.com/LxZaWXU
Yes, orange cable is connected to A0 and Batt+ (which is Vin+ on the INA219, not Vcc). It was just to debug it.

Quote
high side voltage is being fed to Vcc on the arduino
Shall I do something about it? My guess is that this should not be happening.

agmotes

I'm having a hard time figuring out what you are doing here.

Is the battery powering something like a charge pump, or are you using a 5V generator to charge the battery?

I would suggest removing the connection to A0 for the time being and see if that helps. If you have a voltmeter, you may want to disconnect the arduino and the common ground (blue wire), and then check the voltage of the purple INA219 Vcc pin relative to the black battery GND pin. If there is some sort of current leakage from the battery, through the INA219 from V+/V- to VCC, then you could be feeding an unknown voltage to the arduino 5V bus through the arduino 5V pin.

Let us know if you can measure this with a voltmeter and what the value is.

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