Unexpected power drainage

This unit is connected to a POWERTECH MP-3750 via the usb (for a power supply to the UNO board)
The voltage divider is connected to the POWERTECH 'load side' positive and negative so I can read the voltage
The ACS is in series with the 'battery connection' positive of the POWERTECH to read the amps.

When I disconnect the usb the OLED display and board is still 'ON' The OLED display then dims to about half illuminance.

My question is where is it draining power from?

A better description

What are the resistor values of the voltage divider.
If too low, then the divider could phantom-power the Uno through the analogue pin.


A circuit diagram would be easier to understand your project.

If the USB is the ONLY power source to your entire project, do the LED eventually go out?

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

1 Like

The values are as follow:
R1=910 & R2=470

No, as WAWA suggested, I think it's a back feed from the battery. I'll increase the resistor values and see if that solves the issue.

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