My Arduino is still working after unplugging it

So recently I have started a project, I'm using an Arduino nano, 2 digital servos, and a senso, which has a built-in battery and and two output wires, SIGN and GND.
So I connected the the servos communication wires to D5 and D8 and the SIGN wire from my sensor to the A4.
This sensor give DC signals between 0-3.4 and the plan was that these signals would turn my two servos like when you do it with a potentiometer.
Instead of it, it does nothing and after I unplug the Arduino from its battery and the servos from their battery (the sensor, the Arduino nano and the servos are powered from separated sources), the sensor powers it with low voltage and it still does nothing.

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The sensor is from the spider, and I printed a Bionic arm, and I wanted to control the servos using the spider's motherboard as a sensor.

Attach a wiring diagram. Those Shakespeare wirings don't show the system. I will not make diagrams out of Your text.
If the Arduino runs after power is removed, then it's back powered from an other device having power. That can be very bad for circuits.

Welcome to the forum.

Please read the post at the start of any forum , entitled "How to use this Forum".

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: